土木工程专业毕业设计外文翻译
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forced concrete structure reinforced with an overviewRein Since the reform and opening up, with the national economy's rapid and sustained development of a reinforced concrete structure built, reinforced with the development of technology has been great. Therefore, to promote the use of advanced technology reinforced connecting to improve project quality and speed up the pace of construction, improve labor productivity, reduce costs, and is of great significance.Reinforced steel bars connecting technologies can be divided into two broad categories linking welding machinery and steel. There are six types of welding steel welding methods, and some apply to the prefabricated plant, and some apply to the construction site, some of both apply. There are three types of machinery commonly used reinforcement linking method primarily applicable to the construction site. Ways has its own characteristics and different application, and in the continuous development and improvement. In actual production, should be based on specific conditions of work, working environment and technical requirements, the choice of suitable methods to achieve the best overall efficiency.1、steel mechanical link1.1 radial squeeze linkWill be a steel sleeve in two sets to the highly-reinforced Department with superhigh pressure hydraulic equipment (squeeze tongs) along steel sleeve radial squeeze steel casing, in squeezing out tongs squeeze pressure role of a steel sleeve plasticity deformation closely integrated with reinforced through reinforced steel sleeve and Wang Liang's Position will be two solid steel bars linkedCharacteristic: Connect intensity to be high, performance reliable, can bear high stress draw and pigeonhole the load and tired load repeatedly.Easy and simple to handle, construction fast, save energy and material, comprehensive economy profitable, this method has been already a large amount of application in the project.Applicable scope : Suitable for Ⅱ , Ⅲ , Ⅳ grade reinforcing bar (including welding bad reinforcing bar ) with ribbing of Ф 18- 50mm, connection between the same diameter or different diameters reinforcing bar .1.2must squeeze linkExtruders used in the covers, reinforced axis along the cold metal sleeve squeeze dedicated to insert sleeve Lane two hot rolling steel drums into a highly integrated mechanical linking methods.Characteristic: Easy to operate and joining fast and not having flame homework , can construct for 24 hours , save a large number of reinforcing bars and energy. Applicable scope : Suitable for , set up according to first and second class antidetonation requirement -proof armored concrete structure ФⅡ , Ⅲ grade reinforcing bar with ribbing of hot rolling of 20- 32mm join and construct live.1.3 cone thread connectingUsing cone thread to bear pulled, pressed both effort and self-locking nature, undergo good principles will be reinforced by linking into cone-processing thread at the moment the value of integration into the joints connecting steel bars.Characteristic: Simple , all right preparatory cut of the craft , connecting fast, concentricity is good, have pattern person who restrain from advantage reinforcing bar carbon content.Applicable scope : Suitable for the concrete structure of the industry , civil building and general structures, reinforcing bar diameter is for Фfor the the 16- 40mm one Ⅱ , Ⅲ grade verticality, it is the oblique to or reinforcing bars horizontal join construct live.conclusionsThese are now commonly used to connect steel synthesis methods, which links technology in the United States, Britain, Japan and other countries are widely used. There are different ways to connect their different characteristics and scope of the actual construction of production depending on the specific project choose a suitable method of connecting to achieve both energy conservation and saving time limit for a project ends.钢筋混凝土结构中钢筋连接综述改革开放以来,随着国民经济的快速、持久发展,各种钢筋混凝土建筑结构大量建造,钢筋连接技术得到很大的发展。
土木工程和工程管理专业外文翻译Risk Analysis of the International Construction ProjectBy: Paul Stanford KupakuwanaCost Engineering Vol. 51/No. 9 September 2009ABSTRACT:This analysis used a case study methodology to analyse the issues surrounding the partial collapse of the roof of a building housing the headquarters of the Standards Association of Zimbabwe (SAZ). In particular, it examined the prior roles played by the team of construction professionals. The analysis revealed that the SAZ’s traditional construction project was generally characterized by high risk. There was a clear indication of the failure of a contractor and architects in preventing and/or mitigating potential construction problems as alleged by the plaintiff. It was reasonable to conclude that between them the defects should have been detected earlier and rectified in good time before the partial roof failure. It appeared justified for the plaintiff to have brought a negligence claim against both the contractor and the architects. The risk analysis facilitated, through its multi-dimensional approach to a critical examination of a construction problem, the identification of an effective risk management strategy for future construction projects. It further served to emphasize the point that clients are becoming more demanding, more discerning, and less willing to accept risk without recompense. Clients do not want surprise, and are more likely to engage in litigation when things go wrong.KEY WORDS: Arbitration, claims, construction, contracts, litigation, project and risk The structural design of the reinforced concrete elements was done by consulting engineers Knight Presold (KP). Quantity surveying services were provided by Hawkins, Leshnick & Bath (HLB). The contract was awarded to Central African Building Corporation (CABCO) who was also responsible for the provision of a specialist roof structure using patented “gang nail” roof trusses. The building construction proceeded to completion and was handed over to the owners on Sept. 12, 1991. The SAZ took effective occupation of the headquarters building without a certificate of occupation. Also, the defects liability period was only three months.The roof structure was in place 10 years before partial failure in December 1999. The building insurance coverage did not cover enough, the City of Harare, a government municipality, issued the certificate of occupation 10 years after occupation, and after partial collapse of the roof.At first the SAZ decided to go to arbitration, but this failed to yield an immediate solution. The SAZ then decided to proceed to litigate in court and to bring a negligence claim against CABCO. The preparation for arbitration was reused for litigation. The SAZ’s quantified losses stood at approximately $ 6 million in Zimbabwe dol lars (US $1.2m).After all parties had examined the facts and evidence before them, it became clear that there was a great probability that the courts might rule that both the architects and the contractor were liable. It was at this stage that the defenda nts’ lawyers requested that the matter be settled out of court. The plaintiff agreed to this suggestion, with the terms of the settlement kept confidential.The aim of this critical analysis was to analyse the issues surrounding the partial collapse of the roof of the building housing the HQ of Standard Association of Zimbabwe. It examined the prior roles played by the project management function and construction professionals in preventing/mitigating potential construction problems. It further assessed the extent to which the employer/client and parties to a construction contract are able to recover damages under that contract. The main objective of this critical analysis was to identify an effective risk management strategy for future construction projects. The importance of this study is its multidimensional examination approach.Experience suggests that participants in a project are well able to identify risks based on their own experience. The adoption of a risk management approach, based solely in past experience and dependant on judgment, may work reasonably well in a stable low risk environment. It is unlikely to be effective where there is a change. This is because change requires the extrapolation of past experience, which could be misleading. All construction projects are prototypes to some extent and imply change. Change in the construction industry itself suggests that past experience is unlikely to be sufficient onits own. A structured approach is required. Such a structure can not and must not replace the experience and expertise of the participant. Rather, it brings additional benefits that assist to clarify objectives, identify the nature of the uncertainties, introduces effective communication systems, improves decision-making, introduces effective risk control measures, protects the project objectives and provides knowledge of the risk history. Construction professionals need to know how to balance the contingencies of risk with their specific contractual, financial, operational and organizational requirements. Many construction professionals look at risks in dividually with a myopic lens and do not realize the potential impact that other associated risks may have on their business operations. Using a holistic risk management approach will enable a firm to identify all of the organization’s business risks. This will increase the probability of risk mitigation, with the ultimate goal of total risk elimination.Recommended key construction and risk management strategies for future construction projects have been considered and their explanation follows. J.W. Hinchey stated that there is and can be no ‘best practice’ standard for risk allocation on a high-profile project or for that matter, any project. He said, instead, successful risk management is a mind-set and a process. According to Hinchey, the ideal mind-set is for the parties and their representatives to, first, be intentional about identifying project risks and then to proceed to develop a systematic and comprehensive process for avoiding, mitigating, managing and finally allocating, by contract, those risks in optimum ways for the particular project. This process is said to necessarily begin as a science and ends as an art.According to D. Atkinson, whether contractor, consultant or promoter, the right team needs to be assembled with the relevant multi-disciplinary experience of that particular type of project and its location. This is said to be necessary not only to allow alternative responses to be explored. But also to ensure that the right questions are asked and the major risks identified. Heads of sources of risk are said to be a convenient way of providing a structure for identifying risks to completion of a participant’s part of the project. Effective risk management is said to require a multi-disciplinary approach.Inevitably risk management requires examination of engineering, legal and insurance related solutions.It is stated that the use of analytical techniques based on a statistical approach could be of enormous use in decision making. Many of these techniques are said to be relevant to estimation of the consequences of risk events, and not how allocation of risk is to be achieved. In addition, at the present stage of the development of risk management, Atkinson states that it must be recognized that major decisions will be made that can not be based solely on mathematical analysis. The complexity of construction projects means that the project definition in terms of both physical form and organizational structure will be based on consideration of only a relatively small number of risks. This is said to then allow a general structured approach that can be applied to any construction project to increase the awareness of participants.The new, simplified Construction Design and Management Regulations (CDM Regulations) which came in to force in the UK in April 2007, revised and brought together the existing CDM 1994 and the Construction Health Safety and Welfare (CHSW) Regulations 1996, into a single regulatory package.The new CDM regulations offer an opportunity for a step change in health and safety performance and are used to reemphasize the health, safety and broader business benefits of a well-managed and co-ordinated approach to the management of health and safety in construction. I believe that the development of these skills is imperative to provide the client with the most effective services available, delivering the best value project possible.Construction Management at Risk (CM at Risk), similar to established private sector methods of construction contracting, is gaining popularity in the public sector. It is a process that allows a client to select a construction manager (CM) based on qualifications; make the CM a member of a collaborative project team; centralize responsibility for construction under a single contract; obtain a bonded guaranteed maximum price; produce a more manageable, predictable project; save time and money; and reduce risk for the client, the architect and the CM.CM at Risk, a more professional approach to construction, is taking its place along with design-build, bridging and the more traditional process of design-bid-build as an established method of project delivery.The AE can review the CM’s approach to the work, making helpful recommendations. The CM is allowed to take bids or proposals from subcontractors during completion of contract documents, prior to the guaranteed maximum price (GMP), which reduces the CM’s risk and provides useful input to design. The procedure is more methodical, manageable, predictable and less risky for all.The procurement of construction is also more business-like. Each trade contractor has a fair shot at being the low bidder without fear of bid shopping. Each must deliver the best to get the projec. Competition in the community is more equitable: all subcontractors have a fair shot at the work.A contingency within the GMP covers unexpected but justifiable costs, and a contingency above the GMP allows for client changes. As long as the subcontractors are within the GMP they are reimbursed to the CM, so the CM represents the client in negotiating inevitable changes with subcontractors.There can be similar problems where each party in a project is separately insured. For this reason a move towards project insurance is recommended. The traditional approach reinforces adversarial attitudes, and even provides incentives for people to overlook or conceal risks in an attempt to avoid or transfer responsibility.A contingency within the GMP covers unexpected but justifiable costs, and a contingency above the GMP allows for client changes. As long as the subcontractors are within the GMP they are reimbursed to the CM, so the CM represents the client in negotiating inevitable changes with subcontractors.There can be similar problems where each party in a project is separately insured. For this reason a move towards project insurance is recommended. The traditional approach reinforces adversarial attitudes, and even provides incentives for people to overlook or conceal risks in an attempt to avoid or transfer responsibility.It was reasonable to assume that between them the defects should have been detected earlier and rectified in good time before the partial roof failure. It did appear justified forthe plaintiff to have brought a negligence claim against both the contractor and the architects.In many projects clients do not understand the importance of their role in facilitating cooperation and coordination; the design is prepared without discussion between designers, manufacturers, suppliers and contractors. This means that the designer can not take advantage of suppliers’ or contractors’ knowledge of build ability or maintenance requirements and the impact these have on sustainability, the total cost of ownership or health and safety .This risk analysis was able to facilitate, through its multi-dimensional approach to a critical examination of a construction problem, the identification of an effective risk management strategy for future construction projects. This work also served to emphasize the point that clients are becoming more demanding, more discerning, and less willing to accept risk without recompense. They do not want surprises, and are more likely to engage in litigation when things go wrong.References[1]Madan L.Arora, “Project Management: One Step Beyond”[M], Civli Engineering, October 1996,pp67-68[2]Matthys Levy and Mario Salvadori, Why Buildings Fall Down, New York:[J] W.W.Norton, 1992[3]Louis Berger, “Emerging Role of Management in Civil Engineering"[M], Journal of Managementin Engineering, Vol.12, No.4, July 1996[4] Hagerty D J, Peck R B. H eave and Lateral Movements Du e to Pile Driving [J]. Journal of the SoilMechanics and Foun dations Division, 1997国际建设工程风险分析保罗斯坦福库帕库娃娜工程造价卷第五十一期2009年9月9日摘要:此次分析用实例研究方法分析津巴布韦标准协会总部(SAZ)的屋顶部分坍塌的问题。
土木工程毕业设计中英文翻译附录:中英文翻译英文部分:LOADSLoads that act on structures are usually classified as dead loads or live loads.Dead loads are fixed in location and constant in magnitude throughout the life of the ually the self-weight of a structure is the most important part of the structure and the unit weight of the material.Concrete density2varies from about 90 to 120 pcf (14 to 19 )for lightweight concrete,and is about 145 pcf (23 KN/m2)for normal concrete.In calculating the dead load of structural concrete,usually a 5 pcf (1 KN/m2)increment is included with the weight of the concrete to account for the presence of the KN/mreinforcement.Live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic forces.They may be either fully or partially in place,or not present at all.They may also change in location.Althought it is the responsibility of the engineer to calculate dead loads,live loads are usually specified by local,regional,or national codes and specifications.Typical sources are the publications of the American National Standards Institute,the American Association of StateHighway and Transportation Officials and,for wind loads,the recommendations of the ASCE Task Committee on Wind Forces.Specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be exceeded.It is oftern important to distinguish between the specified load,and what is termed the characteristic load,that is,the load that actually is in effect under normal conditions of service,which may be significantly less.In estimating the long-term deflection of a structure,for example,it is the characteristic load that isimportant,not the specified load.The sum of the calculated dead load and the specified live load is called the service load,because this is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.StrengthThe strength of a structure depends on the strength of the materials from which it is made.Minimum material strengths are specified incertain standardized ways.The properties of concrete and its components,the methods of mixing,placing,and curing to obtain the required quality,and the methods for testing,are specified by the American Concrete Insititue(ACI).Included by refrence in the same documentare standards of the American Society for TestingMaterials(ASTM)pertaining to reinforcing and prestressing steels and concrete.Strength also depends on the care with which the structure isbuilt.Member sizes may differ from specified dimensions,reinforcement may be out of position,or poor placement of concrete may result in voids.An important part of the job of the ergineer is to provide proper supervision of construction.Slighting of this responsibility has had disastrous consequences in more than one instance.Structural SafetySafety requires that the strength of a structure be adequate for all loads that may conceivably act on it.If strength could be predicted accurately and if loads were known with equal certainty,then safely could be assured by providing strength just barely in excess of the requirements of the loads.But there are many sources of uncertainty in the estimation of loads as well as in analysis,design,andconstruction.These uncertainties require a safety margin.In recent years engineers have come to realize that the matter of structural safety is probabilistic in nature,and the safety provisions of many current specifications reflect this view.Separate consideration is given to loads and strength.Loadfactors,larger than unity,are applied to the calculated dead loads and estimated or specified service live loads,to obtain factorde loads that the member must just be capable of sustaining at incipient failure.Loadfactors pertaining to different types of loads vary,depending on the degree of uncertainty associated with loads of various types,and with the likelihood of simultaneous occurrence of different loads.Early in the development of prestressed concrete,the goal of prestressing was the complete elimination of concrete ternsile stress at service loads.The concept was that of an entirely new,homogeneous material that woukd remain uncracked and respond elastically up to the maximum anticipated loading.This kind of design,where the limiting tensile stressing,while an alternative approach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full service load,is called partial prestressing.There are cases in which it is necessary to avoid all risk of cracking and in which full prestressing is required.Such cases include tanks or reservious where leaks must be avoided,submerged structures or those subject to a highly corrosive envionment where maximum protection of reinforcement must be insured,and structures subject to high frequency repetition of load where faatigue of the reinforcement may be a consideration.However,there are many cses where substantially improved performance,reduced cost,or both may be obtained through the use of a lesser amount of prestress.Full predtressed beams may exhibit an undesirable amount of upward camber because of the eccentric prestressing force,a displacement that is only partially counteracted by the gravity loads producing downward deflection.This tendency isaggrabated by creep in the concrete,which magnigies the upward displacement due to the prestress force,but has little influence on the should heavily prestressed members be overloaded and fail,they may do so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.This is important from the point of view of safety,because suddenfailure without warning is dangeroud,and gives no opportunity for corrective measures to be taken.Furthermore,experience indicates that in many cases improved economy results from the use of a combination of unstressed bar steel and high strength prestressed steel tendons.While tensile stress and possible cracking may be allowed at full service load,it is also recognized that such full service load may be infrequently applied.The typical,or characteristic,load acting is likely to be the dead load plus a small fraction of the specified liveload.Thus a partially predtressed beam may not be subject to tensile stress under the usual conditions of loading.Cracks may from occasionally,when the maximum load is applied,but these will close completely when that load is removed.They may be no more objectionablein prestressed structures than in ordinary reinforced.They may be no more objectionable in prestressed structures than in ordinary reinforced concrete,in which flexural cracks always form.They may be considered a small price for the improvements in performance and economy that are obtained.It has been observed that reinforced concrete is but a special case of prestressed concrete in which the prestressing force is zero.Thebehavior of reinforced and prestressed concrete beams,as the failure load is approached,is essentially the same.The Joint European Committee on Concrete establishes threee classes of prestressed beams.Class 1:Fully prestressed,in which no tensile stress is allowed in the concrete at service load.Class 2:Partially prestressed, in which occasional temporary cracking is permitted under infrequent high loads.Class 3:Partially prestressed,in which there may be permanent cracks provided that their width is suitably limited.The choise of a suitable amount of prestress is governed by avariety of factors.These include thenature of the loading (for exmaple,highway or railroadbridged,storage,ect.),the ratio of live to dead load,the frequency of occurrence of loading may be reversed,such as in transmission poles,a high uniform prestress would result ultimate strength and in brittle failure.In such a case,partial prestressing provides the only satifactory solution.The advantages of partial prestressing are important.A smaller prestress force will be required,permitting reduction in the number of tendons and anchorages.The necessary flexural strength may be provided in such cases either by a combination of prestressed tendons and non-prestressed reinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than the prestressing force isless,the size of the bottom flange,which is requied mainly to resist the compression when a beam is in the unloaded stage,can be reduced or eliminated altogether.This leads in turn to significant simplification and cost reduction in the construction of forms,as well as resulting in structures that are mor pleasing esthetically.Furthermore,by relaxing the requirement for low service load tension in the concrete,a significant improvement can be made in the deflection characteristics of a beam.Troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestress force selected primarily to produce the desired deflection for a particular loading condition.The behavior of partially prestressed beamsm,should they be overloaded to failure,is apt to be superior to that of fully prestressed beams,because the improved ductility provides ample warning of distress.英译汉:荷载作用在结构上的荷载通常分为恒载或活载。
Issues in Sustainable Architecture andPossible SolutionsFatima Ghani, Member COA (India), Member IIIDAbstract—The growing concern with environmental and ecological conditions have led to the discussion/search for ‘energy conscious’, ‘Eco friendly’, ‘energy efficient’ building designs. For the better growth of the future, keeping in view the environment related issues, the first objective of the designer is sustainable development i.e. environmentally compatible building designs. Sustainable architecture also referred as green architecture is a design that uses natural building materials e.g. earth, wood, stone etc (not involving pollution in its treatment) that are energy efficient and that make little or no impact on the nature of a site and its resources. This paper discusses issues related to Sustainable/environmental architecture. It also considers possible solutions related to these issues.Index Terms—Sustainable, Green, Architecture, Building, Design. Efficiency.I. I NTRODUCTIONThe words "Green", "Ecological" and "Sustainable" are terms used by environmentalists to indicate modes of practice. From global economics to household features these practices minimize our impact on the environment and generate a healthy place of living. In a deeper sense the words involve as to what can be done to heal and regenerate the earth's ability to bear life[1-4].A.Principles of Environmentally Oriented DesignIn Architecture there are many ways a building may be "green" and respond to the growing environmental problems of our planet. Sustainable architecture can be practiced still maintaining efficiency, beauty, layouts and cost effectiveness. There are five basic areas of an environmentally oriented design. They are Healthy Interior Environment, Energy Efficiency, Ecological Building Materials, Building Form and Good Design.• Healthy Interior Environment: It has to be well insured that building materials and systems used do not emit toxic unhealthy gases and substances in the built spaces. Further extra cars and measures are to be taken to provide maximum levels of fresh air and adequate ventilation to the interior environment.• Energy Efficiency: It has to be well ensured that the building's use of energy is minimized. The various HV AC systems and methods of construction etc. should be so designed that energy consumption is minimal.• Ecological Building Materials: As far as possible the use of building materials should be from renewable sources having relatively safe sources of production.• Building Form: The building form should respond to the site, region, climate and the materials available thereby generating a harmony between the inhabitants and the surroundings.• Good Design: Structure & Material and Aesthetics are the basic parameters of defining design. They should be so integrated that the final outcome is a well built, convenient and a beautiful living space.These principles of environmentally oriented design comprise yet another meaningful and environmental building approach called Green or Sustainable design. Architects should use their creativity and perception to correlate these principles to generate locally appropriate strategies, materials and methods keeping in mind that every region should employ different green strategies [5-7].B. DefinitionSustainability means 'to hold' up or 'to support from below'. It refers to the ability of a society, ecosystem or any such ongoing system, to continue functioning into the indefinite future (without being forced into decline through exhaustion of key resources).Sustainable architecture involves a combination of values: aesthetic, environmental, social, political and moral. It's about one's perception and technical knowledge to engage in a central aspect of the practice i.e. to design and build in harmony with the environment. It is the duty of an architect to think rationally about a combination of issues like sustainability, durability, longevity, appropriate materials and sense of place [8-10].The present environmental conditions have led to the discussion/search for ‘energy conscious’, ‘Eco friendly’,‘energy efficient’ building designs. For the better growth of the future, keeping in view the environment related issues, the first objective of the designer is a sustainable development i.e. environmentally compatible. This paper discusses issues related to Sustainable/environmental architecture. The main focus of the paper is on sustainable architecture - its need, solutions and impact on the future.II. N EEDS AND I SSUESThe ecological crisis today is very serious and till date much of the debate still focuses on the symptoms rather than the causes. As a result there is an urgent need to emphasize and workout the best possible approach towards environmental protection thereby minimizing further degradation. Architecture presents a unique challenge in the field of sustainability. Construction projects typically consume large amounts of materials, produce tons of waste, and often involve weighing the preservation of buildings that have historical significance against the desire for the development of newer, more modern designs. Sustainable development is one such measure, which presents an approach that can largely contribute to environmental protection. A striking balance between Environmental protection and Sustainable development is a difficult and delicate task. Sustainable design is the thoughtful integration of architecture with electrical, mechanical, and structural engineering. In addition to concern for the traditional aesthetics of massing, proportion, scale, texture, shadow, and light, the facility design team needs to be concerned with long term costs: environmental, economic, and human as shown in Figure 1.III. CONCEPT AND RELEV ANCE OF SUSTAINABLE ARCHITECTUREIn the present day scenario the idea and concept of Sustainable Architecture/Development is relevant in the light of the following two aspects:a) Ecological and Environmental crisisb) Imminent disasters and their managementSome of the major causes, which greatly contribute to these two aspects, can be listed as:• Rapid Urbanization and Industrialization:The consequences of this can further lead to Population explosion, Geological deposits of sewage and garbage, Unsustainable patterns of living & development, Environmental degradation (pollution of air, water, soil etc, food web disruption). Thus sustainable urban development is crucial to improve the lives of urban populations and the remainder of the planet. Both people and ecosystems impacted upon by their activities.• Natural Calamities:Natural calamities like volcanic eruptions, earthquakes, flood, famine etc. which are being further aggravated by mankind add to the list of other ill effects like atomic explosion, green house effect, ozone depletion etc. Sustainable design attempts to have an understanding of the natural processes as well as the environmental impact of the design. Making natural cycles and processes visible, bring the designed environment back to life.• Depletion of Non-renewable sources:Rapid depletion of non-renewable sources is leading to serious issues related to energy & water conservation etc. Thus the rational use of natural resources and appropriate management of the building stock can contribute to saving scarce resources, reducing energy consumption and improving environmental quality.IV. SOLUTIONSA. Sustainable ConstructionSustainable construction is defined as "the creation and responsible management of a healthy built environment based on resource efficient and ecological principles". Sustainable designed buildings aim to lessen their impact on our environment through energy and resource efficiency. "Sustainable building" may be defined as building practices, which strive for integral quality (including economic, social and environmental performance) in a very broad way. Thus, the rational use of natural resources and appropriate management of the building stock will contribute to saving scarce resources, reducing energy consumption (energy conservation), and improving environmental quality.Sustainable building involves considering the entire life cycle of buildings, taking environmental quality, functional quality and future values into account environmental initiatives of the construction sector and the demands of users are key factors in the market. Governments will be able to give a considerable impulse to sustainable buildings by encouraging these developments. Further the various energy related issues during the different phases in the construction of buildings can be understood with respect to the chart shown in Figure2.B. Environmentally Friendly HousesFollowing the five basic principles of environmentally oriented design can lead to the construction of what can be called as Environmentally Friendly House. An environmentally friendly house is designed and built to be in tune with its occupants, nature, environment and ecosystem. It is designed and built according to the region it is located in, keeping in mind the climate, material, availability and building practices. The basic areas of design need to be considered at this stage can be listed as:• Orientation• Reduce Energy Gain or Loss• Lighting• Responsible Landscaping• Waste Management• External VentilationC. Green BuildingA green building places a high priority on health, environmental and resource conservation performance over its life cycle. These new priorities expand and complement the classical building design concerns: economy, utility, durability and delight. Green design emphasize a number of new environmental, resource and occupant health concerns:• Reduce human exposure to noxious materials.• Conserve non-renewable energy and scarce materials.• Minimize life cycle ecological impact of energy and materials used.• Use renewable energy and materials that are sustainable harvested.• Protect and restore local air, water, soil, flora & fauna• Support pedestrian, bicycles, mass transit and other alternatives to fossil-fueled vehicles.Most green buildings are high quality buildings they last longer, cost less to operate and maintain and provide greater occupant satisfaction than standard development.D. Green Roofs & Porous PavementsAs already discussed the rapid urbanization and industrialization is resulting in extensivedeforestation as a result the green areas are being covered with pavements and concrete. The rainwater that naturally seeps through land covered with vegetation and trees now just runoff, thereby leading to a major environmental imbalance in terms of groundwater. This problem can be solved to a great extent with the help of the construction of Green Roofs and Porous Pavements. Green roofs & porous pavements present a unique method of ground water conservation. Vegetation to hold water on rooftops, and pavement that lets it percolate in the ground are some of the latest ways that can save water tables. Visually what might come across may be a roof sprouted with plants and a parking lot that drains water like a sieve-probably the latest in groundwater conservation.E. Building MaterialsTons of materials including timber go into building construction. There are three principal approaches to improve the material efficiency of building construction:• Reducing the amount of material used in construction.• Using recycled materials that otherwise would have been waste.• Reducing waste generation in the construction process.Further as far as possible sustainable harvested building materials and finishes should be used with low toxicity in manufacturing and installation.V. CONCLUSIONSSustainability often is defined as meeting the needs of the present without compromising the ability of future generations to meet their own needs. A growing number of people are committed to reaching this goal by modifying patterns of development and consumption to reduce demand on natural resource supplies and help preserve environmental quality. Achieving greater sustainability in the field of construction is particularly important, because building construction consumes more energy and resources than any other economic activity. Not only does a home represent the largest financial investment a family is likely to make, but it also represents the most resource- and energy-intensive possession most people will ever own. Making homes more sustainable, then, has a tremendous potential to contribute to the ability of future generations to meet their own needs. Sustainable housing design is a multifaceted concept, embracing:• Affordability• Marketability• Appropriate design• Resource efficiency• Energy efficiency• Durability• Comfort• HealthAs a developed society we should not undermine our resource base, the assimilative capacity of our surroundings or the biotic stocks on which our future depends. As a sustainable society our efforts should consist of a long-term and integrated approach to developing and achieving a healthy community. We should realize that the problems associated with sustainable development are global as a result the issues need worldwide attention. If we work together we can bring change faster.R EFERENCES[1] Bruntland, G. Our Common Future: The World Commission on Environment and Development, edited by Bruntland, G., Oxford University Press, Oxford., 1987[2] /sustaindev.html[3] http://arch.hku.hk/research/BEER/sustain.htm#1.1[4] [5] Jani , V., Architecture Time Space & People, V ol. 3, Issue 4, 2003, pp32.[6] Jani , V., Architecture Time Space & People, V ol. 3, Issue 1, 2003, pp34.[7] Bergstrom , B., Architecture Time Space & People, V ol. 3 Issue 1, 2002, pp40.[8] Sinha , S..B., Architecture Time Space & People, V ol. 2, Issue 12, 2002, pp22.[9] Walker , S. , Sustainable Design Explorations in Theory and Practice by, Earthscan , 2006.[10] Datschefski , E. , The Total Beauty of Sustainable Products , Rotovision ,May 2001.可持续建筑的问题和可能的解决方案法蒂玛·加尼,会员COA(印度),会员IIID摘要:越来越多地关注环境和生态条件已经引起了人们对“节能意识”、“友好生态”、“高效节能”的建筑设计的讨论和探索。
Tall Building StructureTall buildings have fascinated mankind from the beginning of civilization, their construction being initially for defense and subsequently for ecclesiastical purposes. The growth in modern tall building construction, however, which began in the 1880s, has been largely for commercial and residential purposes.Tall commercial buildings are primarily a response to the demand by business activities to be as close to each other, and to the city center, as possible, thereby putting intense pressure on the available land space. Also, because they form distinctive landmarks, tall commercial buildings are frequently developed in city centers as prestige symbols for corporate organizations.Further, the business and tourist community, with its increasing mobility, has fuelled a need for more, frequently high-rise, city center hotel accommodations.The rapid growth of the urban population and the consequent pressure on limited space have considerably influenced city residential development. The high cost of land, the desire to avoid a continuous urban sprawl, and the need to preserve important agricultural production have all contributed to drive residential buildings upward.Ideally, in the early stages of planning a building, the entire design team, including the architect, structural engineer, and services engineer, should collaborate to agree on a form of structure to satisfy their respective requirements of function, safety and serviceability, and servicing.It is difficult to define a high-rise building . One may say that a low-rise building ranges from 1 to 2 stories . A medium-rise building probably ranges between 3 or 4 stories up to 10 or 20 stories or more .Although the basic principles of vertical and horizontal subsystem design remain the same for low- , medium- , or high-rise buildings , when a building gets high the vertical subsystems become a controlling problem for two reasons . Higher vertical loads will require larger columns , walls , and shafts . But , more significantly , the overturning moment and the shear deflections produced by lateral forces are much larger andmust be carefully provided for .The vertical subsystems in a high-rise building transmit accumulated gravity load from story to story , thus requiring larger column or wall sections to support such loading . In addition these same vertical subsystems must transmit lateral loads , such as wind or seismic loads , to the foundations. However , in contrast to vertical load , lateral load effects on buildings are not linear and increase rapidly with increase in height . For example under wind load , the overturning moment at the base of buildings varies approximately as the square of a buildings may vary as the fourth power of buildings height , other things being equal. Earthquake produces an even more pronounced effect.When the structure for a low-or medium-rise building is designed for dead and live load , it is almost an inherent property that the columns , walls , and stair or elevator shafts can carry most of the horizontal forces . The problem is primarily one of shear resistance . Moderate addition bracing for rigid frames in“short”buildings can easily be provided by filling certain panels without increasing the sizes of the columns and girders otherwise required for vertical loads.Unfortunately , this is not is for high-rise buildings because the problem is primarily resistance to moment and deflection rather than shear alone . Special structural arrangements will often have to be made and additional structural material is always required for the columns , girders , walls , and slabs in order to made a high-rise buildings sufficiently resistant to much higher lateral deformations .As previously mentioned , the quantity of structural material required per square foot of floor of a high-rise buildings is in excess of that required for low-rise buildings . The vertical components carrying the gravity load , such as walls , columns , and shafts , will need to be strengthened over the full height of the buildings . But quantity of material required for resisting lateral forces is even more significant .With reinforced concrete , the quantity of material also increases as the number of stories increases . But here it should be noted that the increase in the weight of material added for gravity load is much more sizable than steel , whereas for wind load the increase for lateral force resistance is not that much more since the weight of a concrete buildingshelps to resist overturn . On the other hand , the problem of design for earthquake forces . Additional mass in the upper floors will give rise to a greater overall lateral force under the of seismic effects .In the case of either concrete or steel design , there are certain basic principles for providing additional resistance to lateral to lateral forces and deflections in high-rise buildings without too much sacrifire in economy .⒈Increase the effective width of the moment-resisting subsystems . This is very useful because increasing the width will cut down the overturn force directly and will reduce deflection by the third power of the width increase , other things remaining cinstant . However , this does require that vertical components of the widened subsystem be suitably connected to actually gain this benefit.⒉Design subsystems such that the components are made to interact in the most efficient manner . For example , use truss systems with chords and diagonals efficiently stressed , place reinforcing for walls at critical locations , and optimize stiffness ratios for rigid frames .⒊Increase the material in the most effective resisting components . For example , materials added in the lower floors to the flanges of columns and connecting girders will directly decrease the overall deflection and increase the moment resistance without contributing mass in the upper floors where the earthquake problem is aggravated .⒋Arrange to have the greater part of vertical loads be carried directly on the primary moment-resisting components . This will help stabilize the buildings against tensile overturning forces by precompressing the major overturn-resisting components .⒌The local shear in each story can be best resisted by strategic placement if solid walls or the use of diagonal members in a vertical subsystem . Resisting these shears solely by vertical members in bending is usually less economical , since achieving sufficient bending resistance in the columns and connecting girders will require more material and construction energy than using walls or diagonal members .⒍Sufficient horizontal diaphragm action should be provided floor . This will help to bring the various resisting elements to work together instead of separately .⒎Create mega-frames by joining large vertical and horizontal components such as two or more elevator shafts at multistory intervals with a heavy floor subsystems , or by use of very deep girder trusses .Remember that all high-rise buildings are essentially vertical cantilevers which are supported at the ground . When the above principles are judiciously applied , structurally desirable schemes can be obtained by walls , cores , rigid frames, tubular construction , and other vertical subsystems to achieve horizontal strength and rigidity . Some of these applications will now be described in subsequent sections in the following .Shear-Wall SystemsWhen shear walls are compatible with other functional requirements , they can be economically utilized to resist lateral forces in high-rise buildings . For example , apartment buildings naturally require many separation walls . When some of these are designed to be solid , they can act as shear walls to resist lateral forces and to carry the vertical load as well . For buildings up to some 20storise , the use of shear walls is common . If given sufficient length ,such walls can economically resist lateral forces up to 30 to 40 stories or more .However , shear walls can resist lateral load only the plane of the walls ( i.e.not in a diretion perpendicular to them ) . There fore ,it is always necessary to provide shear walls in two perpendicular directions can be at least in sufficient orientation so that lateral force in any direction can be resisted . In addition , that wall layout should reflect consideration of any torsional effect .In design progress , two or more shear walls can be connected to from L-shaped or channel-shaped subsystems . Indeed , internal shear walls can be connected to from a rectangular shaft that will resist lateral forces very efficiently . If all external shear walls are continuously connected , then the whole buildings acts as tube , and connected , then the whole buildings acts as a tube , and is excellent Shear-Wall Seystems resisting lateral loads and torsion .Whereas concrete shear walls are generally of solid type with openings when necessary , steel shear walls are usually made of trusses . Thesetrusses can have single diagonals , “X”diagonals , or“K”arrangements .A trussed wall will have its members act essentially in direct tension or compression under the action of view , and they offer some opportunity and deflection-limitation point of view , and they offer some opportunity for penetration between members . Of course , the inclined members of trusses must be suitable placed so as not to interfere with requirements for wiondows and for circulation service penetrations though these walls .As stated above , the walls of elevator , staircase ,and utility shafts form natural tubes and are commonly employed to resist both vertical and lateral forces . Since these shafts are normally rectangular or circular in cross-section , they can offer an efficient means for resisting moments and shear in all directions due to tube structural action . But a problem in the design of these shafts is provided sufficient strength around door openings and other penetrations through these elements . For reinforced concrete construction , special steel reinforcements are placed around such opening .In steel construction , heavier and more rigid connections are required to resist racking at the openings .In many high-rise buildings , a combination of walls and shafts can offer excellent resistance to lateral forces when they are suitably located ant connected to one another . It is also desirable that the stiffness offered these subsystems be more-or-less symmertrical in all directions .Rigid-Frame SystemsIn the design of architectural buildings , rigid-frame systems for resisting vertical and lateral loads have long been accepted as an important and standard means for designing building . They are employed for low-and medium means for designing buildings . They are employed for low- and medium up to high-rise building perhaps 70 or 100 stories high . When compared to shear-wall systems , these rigid frames both within and at the outside of a buildings . They also make use of the stiffness in beams and columns that are required for the buildings in any case , but the columns are made stronger when rigidly connected to resist the lateral as well as vertical forces though frame bending .Frequently , rigid frames will not be as stiff as shear-wallconstruction , and therefore may produce excessive deflections for the more slender high-rise buildings designs . But because of this flexibility , they are often considered as being more ductile and thus less susceptible to catastrophic earthquake failure when compared with ( some ) shear-wall designs . For example , if over stressing occurs at certain portions of a steel rigid frame ( i.e.,near the joint ) , ductility will allow the structure as a whole to deflect a little more , but it will by no means collapse even under a much larger force than expected on the structure . For this reason , rigid-frame construction is considered by some to be a “best”seismic-resisting type for high-rise steel buildings . On the other hand ,it is also unlikely that a well-designed share-wall system would collapse.In the case of concrete rigid frames ,there is a divergence of opinion . It true that if a concrete rigid frame is designed in the conventional manner , without special care to produce higher ductility , it will not be able to withstand a catastrophic earthquake that can produce forces several times lerger than the code design earthquake forces . therefore , some believe that it may not have additional capacity possessed by steel rigid frames . But modern research and experience has indicated that concrete frames can be designed to be ductile , when sufficient stirrups and joinery reinforcement are designed in to the frame . Modern buildings codes have specifications for the so-called ductile concrete frames . However , at present , these codes often require excessive reinforcement at certain points in the frame so as to cause congestion and result in construction difficulties 。
附录:中英文翻译英文部分:LOADSLoads that act on structures are usually classified as dead loads or live loads.Dead loads are fixed in location and constant in magnitude throughout the life of the ually the self-weight of a structure is the most important part of the structure and the unit weight of the material.Concrete density varies from about 90 to 120 pcf (14 to 19 2KN/m)for lightweight concrete,and is about 145 pcf (23 2KN/m)for normal concrete.In calculating the dead load of structural concrete,usually a 5 pcf (1 2KN/m)increment is included with the weight of the concrete to account for the presence of the reinforcement.Live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic forces.They may be either fully or partially in place,or not present at all.They may also change in location.Althought it is the responsibility of the engineer to calculate dead loads,live loads are usually specified by local,regional,or national codes and specifications.Typical sources are the publications of the American National Standards Institute,the American Association of State Highway and Transportation Officials and,for wind loads,the recommendations of the ASCE Task Committee on Wind Forces.Specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be exceeded.It is oftern important to distinguish between the specified load,and what is termed the characteristic load,that is,the load that actually is in effect under normal conditions of service,which may be significantly less.In estimating the long-term deflection of a structure,for example,it is the characteristic load that is important,not the specified load.The sum of the calculated dead load and the specified live load is called the service load,because this is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.StrengthThe strength of a structure depends on the strength of the materials from which it is made.Minimum material strengths are specified in certain standardized ways.The properties of concrete and its components,the methods of mixing,placing,and curing to obtain the required quality,and the methods for testing,are specified by the American Concrete Insititue(ACI).Included by refrence in the same documentare standards of the American Society for Testing Materials(ASTM)pertaining to reinforcing and prestressing steels and concrete.Strength also depends on the care with which the structure is built.Member sizes may differ from specified dimensions,reinforcement may be out of position,or poor placement of concrete may result in voids.An important part of the job of the ergineer is to provide proper supervision of construction.Slighting of this responsibility has had disastrous consequences in more than one instance.Structural SafetySafety requires that the strength of a structure be adequate for all loads that may conceivably act on it.If strength could be predicted accurately and if loads were known with equal certainty,then safely could be assured by providing strength just barely in excess of the requirements of the loads.But there are many sources of uncertainty in the estimation of loads as well as in analysis,design,and construction.These uncertainties require a safety margin.In recent years engineers have come to realize that the matter of structural safety is probabilistic in nature,and the safety provisions of many current specifications reflect this view.Separate consideration is given to loads and strength.Load factors,larger than unity,are applied to the calculated dead loads and estimated or specified service live loads,to obtain factorde loads that the member must just be capable of sustaining at incipient failure.Load factors pertaining to different types of loads vary,depending on the degree of uncertainty associated with loads of various types,and with the likelihood of simultaneous occurrence of different loads.Early in the development of prestressed concrete,the goal of prestressing was the complete elimination of concrete ternsile stress at service loads.The concept was that of an entirely new,homogeneous material that woukd remain uncracked and respond elastically up to the maximum anticipated loading.This kind of design,where the limiting tensile stressing,while an alternative approach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full service load,is called partial prestressing.There are cases in which it is necessary to avoid all risk of cracking and in which full prestressing is required.Such cases include tanks or reservious where leaks must be avoided,submerged structures or those subject to a highly corrosive envionment where maximum protection of reinforcement must be insured,and structures subject to high frequency repetition of load where faatigue of the reinforcement may be a consideration.However,there are many cses where substantially improved performance,reduced cost,or both may be obtained through the use of a lesser amount of prestress.Full predtressed beams may exhibit an undesirable amount of upward camber because of the eccentric prestressing force,a displacement that is only partially counteracted by the gravity loads producing downward deflection.This tendency is aggrabated by creep in the concrete,which magnigies the upward displacement due to the prestress force,but has little influence on the should heavily prestressed members be overloaded and fail,they may do so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.This is important from the point of view of safety,because suddenfailure without warning is dangeroud,and gives no opportunity for corrective measures to be taken.Furthermore,experience indicates that in many cases improved economy results from the use of a combination of unstressed bar steel and high strength prestressed steel tendons.While tensile stress and possible cracking may be allowed at full service load,it is also recognized that such full service load may be infrequently applied.The typical,or characteristic,load acting is likely to be the dead load plus a small fraction of the specified live load.Thus a partially predtressed beam may not be subject to tensile stress under the usual conditions of loading.Cracks may from occasionally,when the maximum load is applied,but these will close completely when that load is removed.They may be no more objectionable in prestressed structures than in ordinary reinforced.They may be no more objectionable in prestressed structures than in ordinary reinforced concrete,in which flexural cracks always form.They may be considered a small price for the improvements in performance and economy that are obtained.It has been observed that reinforced concrete is but a special case of prestressed concrete in which the prestressing force is zero.The behavior of reinforced and prestressed concrete beams,as the failure load is approached,is essentially the same.The Joint European Committee on Concrete establishes threee classes of prestressed beams.Class 1:Fully prestressed,in which no tensile stress is allowed in the concrete at service load.Class 2:Partially prestressed, in which occasional temporary cracking is permitted under infrequent high loads.Class 3:Partially prestressed,in which there may be permanent cracks provided that their width is suitably limited.The choise of a suitable amount of prestress is governed by a variety of factors.These include thenature of the loading (for exmaple,highway or railroad bridged,storage,ect.),the ratio of live to dead load,the frequency of occurrence of loading may be reversed,such as in transmission poles,a high uniform prestress would result ultimate strength and in brittle failure.In such a case,partial prestressing provides the only satifactory solution.The advantages of partial prestressing are important.A smaller prestress force will be required,permitting reduction in the number of tendons and anchorages.The necessary flexural strength may be provided in such cases either by a combination of prestressed tendons and non-prestressed reinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than the prestressing force is less,the size of the bottom flange,which is requied mainly to resist the compression when a beam is in the unloaded stage,can be reduced or eliminated altogether.This leads in turn to significant simplification and cost reduction in the construction of forms,as well as resulting in structures that are mor pleasing esthetically.Furthermore,by relaxing the requirement for low service load tension in the concrete,a significant improvement can be made in the deflection characteristics of a beam.Troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestress force selected primarily to produce the desired deflection for a particular loading condition.The behavior of partially prestressed beamsm,should they be overloaded to failure,is apt to be superior to that of fully prestressed beams,because the improved ductility provides ample warning of distress.英译汉:荷 载作用在结构上的荷载通常分为恒载或活载。
DESIGN AND EXECUTION OF GROUNDINVESTIGATION FOR EARTHWORKSABSTRACTThe design and execution of ground investigation works for earthwork projects has become increasingly important as the availability of suitable disposal areas becomes limited and costs of importing engineering fill increase. An outline of ground investigation methods which can augment ‘traditional investigation methods’ particularly for glacial till / boulder clay soils is presented. The issue of ‘geotechnical certification’ is raised an d recommendations outlined on its merits for incorporation with ground investigations and earthworks.1. INTRODUCTIONThe investigation and re-use evaluation of many Irish boulder clay soils presents difficulties for both the geotechnical engineer and the road design engineer. These glacial till or boulder clay soils are mainly of low plasticity and have particle sizes ranging from clay to boulders. Most of our boulder clay soils contain varying proportions of sand, gravel, cobbles and boulders in a clay or silt matrix. The amount of fines governs their behaviour and the silt content makes it very weather susceptible.Moisture contents can be highly variable ranging from as low as 7% for the hard grey black Dublin boulder clay up to 20-25% for Midland, South-West and North-West light grey boulder clay deposits. The ability of boulder clay soils to take-in free water is well established and poor planning of earthworks often amplifies this.The fine soil constituents are generally sensitive to small increases in moisture content which often lead to loss in strength and render the soils unsuitable for re-use as engineering fill. Many of our boulder clay soils (especially those with intermediate type silts and fine sandmatrix) have been rejected at the selection stage, but good planning shows that they can in fact fulfil specification requirements in terms of compaction and strength.The selection process should aim to maximise the use of locally available soils and with careful evaluation it is possible to use o r incorporate ‘poor or marginal soils’ within fill areas and embankments. Fill material needs to be placed at a moisture content such that it is neither too wet to be stable and trafficable or too dry to be properly compacted.High moisture content / low strength boulder clay soils can be suitable for use as fill in low height embankments (i.e. 2 to 2.5m) but not suitable for trafficking by earthwork plant without using a geotextile separator and granular fill capping layer. Hence, it is vital that the earthworks contractor fully understands the handling properties of the soils, as for many projects this is effectively governed by the trafficability of earthmoving equipment.2. TRADITIONAL GROUND INVESTIGATION METHODSFor road projects, a principal aim of the ground investigation is to classify the suitability of the soils in accordance with Table 6.1 from Series 600 of the NRA Specification for Road Works (SRW), March 2000. The majority of current ground investigations for road works includes a combination of the following to give the required geotechnical data:▪Trial pits▪Cable percussion boreholes▪Dynamic probing▪Rotary core drilling▪In-situ testing (SPT, variable head permeability tests, geophysical etc.)▪Laboratory testingThe importance of ‘phasing’ th e fieldwork operations cannot be overstressed, particularly when assessing soil suitability from deep cut areas. Cable percussion boreholes are normally sunk to a desired depth or ‘refusal’ with disturbed and undisturbed samples recovered at 1.00m intervals or change of strata.In many instances, cable percussion boring is unable to penetrate through very stiff, hard boulder clay soils due to cobble, boulder obstructions. Sample disturbance in boreholes should be prevented and loss of fines is common, invariably this leads to inaccurate classification.Trial pits are considered more appropriate for recovering appropriate size samples and for observing the proportion of clasts to matrix and sizes of cobbles, boulders. Detailed and accurate field descriptions are therefore vital for cut areas and trial pits provide an opportunity to examine the soils on a larger scale than boreholes. Trial pits also provide an insight on trench stability and to observe water ingress and its effects.A suitably experienced geotechnical engineer or engineering geologist should supervise the trial pitting works and recovery of samples. The characteristics of the soils during trial pit excavation should be closely observed as this provides information on soil sensitivity, especially if water from granular zones migrates into the fine matrix material. Very often, the condition of soil on the sides of an excavation provides a more accurate assessment of its in-situ condition.3. SOIL CLASSIFICATIONSoil description and classification should be undertaken in accordance with BS 5930 (1999) and tested in accordance with BS 1377 (1990). The engineering description of a soil is based on its particle size grading, supplemented by plasticity for fine soils. For many of our glacial till, boulde r clay soils (i.e. ‘mixed soils’) difficulties arise with descriptions and assessing engineering performance tests.A key parameter (which is often underestimated) in classifying and understanding these soils is permeability (K). Inspection of the particle size gradings will indicate magnitude of permeability. Where possible, triaxial cell tests should be carried out on either undisturbed samples (U100’s) or good quality core samples to evaluate the drainage characteristics of the soils accurately.Low plasticity boulder clay soils of intermediate permeability (i.e. K of the order of 10-5 to 10-7 m/s) can often be ‘conditioned’ by drainage measures. This usually entails the installation of perimeter drains and sumps at cut areas or borrow pits so as to reduc e the moisture content. Hence, with small reduction in moisture content, difficult glacial till soils can become suitable as engineering fill.4. ENGINEERING PERFORMANCE TESTING OF SOILSLaboratory testing is very much dictated by the proposed end-use for the soils. The engineering parameters set out in Table 6.1 pf the NRA SRW include a combination of the following:▪Moisture content▪Particle size grading▪Plastic Limit▪CBR▪Compaction (relating to optimum MC)▪Remoulded undrained shear strengthA number of key factors should be borne in mind when scheduling laboratory testing:▪Compaction / CBR / MCV tests are carried out on < 20mm size material.▪Moisture content values should relate to < 20mm size material to provide a valid comparison.▪Pore pressures are not taken into account during compaction and may vary considerably between laboratory and field.▪Preparation methods for soil testing must be clearly stipulated and agreed with the designated laboratory.Great care must be taken when determining moisture content of boulder clay soils. Ideally, the moisture content should be related to the particle size and have a corresponding grading analysis for direct comparison, although this is not always practical.In the majority of cases, the MCV when used with compaction data is considered to offer the best method of establishing (and checking) the suitability characteristics of a boulder clay soil. MCV testing during trial pitting is strongly recommended as it provides a rapid assessment of the soil suitability directly after excavation. MCV calibration can then be carried out in the laboratory at various moisture content increments. Sample disturbance can occur during transportation to the laboratory and this can have a significant impact on the resultant MCV’s. IGSL h as found large discrepancies when performing MCV’s in the field on low plasticity boulder clays with those carried out later in the laboratory (2 to 7 days). Many of the aforementioned low plasticity boulder clay soils exhibit time dependant behaviour with significantly different MCV’s recorded at a later date –increased values can be due to the drainage of the material following sampling, transportation and storage while dilatancy and migration of water from granular lenses can lead to deterioration and lower values.CBR testing of boulder clay soils also needs careful consideration, mainly with the preparation method employed. Design engineers need to be aware of this, as it can have an order of magnitude difference in results. Static compaction of boulder clay soils is advised as compaction with the 2.5 or 4.5kg rammer often leads to high excess pore pressures being generated – hence very low CBR values can result. Also, curing of compacted boulder clay samples is important as this allows excess pore water pressures to dissipate.5. ENGINEERING CLASSIFICATION OF SOILSIn accordance with the NRA SRW, general cohesive fill is categorised in Table 6.1 as follows:▪2A Wet cohesive▪2B Dry cohesive▪2C Stony cohesive▪2D Silty cohesiveThe material properties required for acceptability are given and the design engineer then determines the upper and lower bound limits on the basis of the laboratory classification and engineering performance tests. Irish boulder clay soils are predominantly Class 2C.Clause 612 of the SRW sets out compaction methods. Two procedures are available:▪Method Compaction▪End-Product CompactionEnd product compaction is considered more practical, especially when good compaction control data becomes available during the early stages of an earthworks contract. A minimum Target Dry Density (TDD) is considered very useful for the contractor to work with as a means of checking compaction quality. Once the material has been approved and meets the acceptability limits, then in-situ density can be measured, preferably by nuclear gauge or sand replacement tests where the stone content is low.As placing and compaction of the fill progresses, the in-situ TDD can be checked and non-conforming areas quickly recognised and corrective action taken. This process requires the design engineer to review the field densities with the laboratory compaction plots and evaluate actual with ‘theoretical densities’.6. SUPPLEMENTARY GROUND INVESTIGATION METHODS FOR EARTHWORKSThe more traditional methods and procedures have been outlined in Section 2. The following are examples of methods which are believed to enhance ground investigation works for road projects:▪Phasing the ground investigation works, particularly the laboratory testing▪Excavation & sampling in deep trial pits▪Large diameter high quality rotary core drilling using air-mist or polymer gel techniques▪Small-scale compaction trials on potentially suitable cut material6.1PHASINGPhasing ground investigation works for many large projects has been advocated for many years –this is particularly true for road projects where significant amounts of geotechnical data becomes available over a short period. On the majority of large ground investigation projects no period is left to ‘digest’ or review the preliminary fi ndings and re-appraise the suitability of the methods.With regard to soil laboratory testing, large testing schedules are often prepared with no real consideration given to their end use. In many cases, the schedule is prepared by a junior engineer while the senior design engineer who will probably design the earthworks will have no real involvement.It is highlighted that the engineering performance tests are expensive and of long duration (e.g. 5 point compaction with CBR & MCV at each point takes in exc ess of two weeks). When classification tests (moisture contents, particle size analysis and Atterberg Limits) are completed then a more incisive evaluation can be carried out on the data and the engineering performance tests scheduled. If MCV’s are perform ed during trial pitting then a good assessment of the soil suitability can be immediately obtained.6.2DEEP TRIAL PITSThe excavation of deep trial pits is often perceived as cumbersome and difficult and therefore not considered appropriate by design engineers. Excavation of deep trial pits in boulder clay soils to depths of up to 12m is feasible using benching techniques and sump pumping of groundwater.In recent years, IGSL has undertaken such deep trial pits on several large road ground investigation projects. The data obtained from these has certainly enhanced the geotechnical data and provided a better understanding of the bulk properties of the soils.It is recommended that this work be carried out following completion of the cable percussion boreholes and rotary core drill holes. The groundwater regime within the cut area will play an important role in governing the feasibility of excavating deep trial pits. The installation ofstandpipes and piezometers will greatly assist the understanding of the ground water conditions, hence the purpose of undertaking this work late on in the ground investigation programme.Large representative samples can be obtained (using trench box) and in-situ shear strength measured on block samples. The stability of the pit sidewalls and groundwater conditions can also be established and compared with levels in nearby borehole standpipes or piezometers. Over a prominent cut area of say 500m, three deep trial pits can prove invaluable and the spoil material also used to carry out small-scale compaction trials.From a value engineering perspective, the cost of excavating and reinstating these excavations can be easily recovered. A provisional sum can be allocated in the ground investigation and used for this work.7. CONCLUSIONS▪Close co-operation is needed between ground investigation contractors and consulting engineers to ensure that the geotechnical investigation work for the roads NDP can be satisfactorily carried out.▪Many soils are too easily rejected at selection / design stag e. It is hoped that the proposed methods outlined in this paper will assist design engineers during scoping and specifying of ground investigation works for road projects.▪With modern instrumentation, monitoring of earthworks during construction is very straightforward. Pore water pressures, lateral and vertical movements can be easily measured and provide important feedback on the performance of the engineered soils.▪Phasing of the ground investigation works, particularly laboratory testing is considered vital so that the data can be properly evaluated.▪Disposal of ‘marginal’ soils will become increasingly difficult and more expensive as the waste licensing regulations are tightened. The advent of landfill tax in the UK has seenthorough examination of all soils for use in earthworks. This is likely to provide a similar incentive and challenge to geotechnical and civil engineers in Ireland in the coming years.▪ A certification approach comparable with that outlined should be considered by the NRAfor ground investigation and earthwork activitie▪土方工程的地基勘察与施工摘要:当工程场地的处理面积有限且填方工程费用大量增加时,土方工程的地基勘察设计与施工已逐渐地变得重要。
土木工程毕业设计英文翻译Civil Engineering Graduation Design English TranslationIntroductionIn this article, we will discuss the translation of a graduation design project in the field of civil engineering from Chinese to English. The translation process requires careful attention to technical terminology, ensuring accuracy and clarity while maintaining the overall structure and coherence of the original content. BackgroundCivil engineering graduation design projects are an integral part of the curriculum for civil engineering students. These projects allow students to apply their theoretical knowledge and practical skills to solve real-world engineering problems. The projects cover a wide range of topics, including structural design, transportation engineering, geotechnical engineering, and water resources management.Translation ChallengesTranslating a civil engineering graduation design project from Chinese to English presents several challenges. Firstly, technical terms specific to the field of civil engineering may not have direct equivalents in English. Secondly, the translation must accurately convey the intended meaning of the original content without losing any crucial information. Finally, maintaining the coherence and readability of the translated text is essential to ensure the understanding of the target audience.Translation StrategiesTo overcome the challenges mentioned above, the following translation strategies can be employed:1. Terminology Research: Extensive research on technical terms in both languages is crucial. This includes consulting specialized dictionaries, academic resources, and industry-standard glossaries. It is essential to find the most accurate and widely accepted translations for specific technical terms.2. Contextual Understanding: To maintain the overall coherence and meaning of the original content, it is important to understand the context in which the technical terms are used. This requires a thorough understanding of the civil engineering discipline and its specific concepts and principles.3. Adaptation and Explanation: In cases where there is no direct translation for a technical term, adaptation or explanation can be used. This involves finding alternative expressions or providing additional information to convey the intended meaning accurately. However, it is important to strike a balance between clarity and conciseness to avoid overwhelming the reader with excessive information.4. Proofreading and Editing: After the initial translation, it is crucial to proofread and edit the translated text. This helps to identify any errors, inconsistencies, or ambiguities and make necessary revisions to ensure the final translation is accurate and coherent.ConclusionTranslating a civil engineering graduation design project from Chinese to English requires careful consideration of technical terminology, context, and overall coherence. By employing effective translation strategies such as terminology research, contextual understanding, adaptation and explanation, and thorough proofreading and editing, a high-quality translation can be achieved. This ensures that the English version of the graduation design project accurately conveys the intended meaning and maintains its readability and comprehensibility for the target audience.。
144 Study on Construction Cost of Construction ProjectsHui LiAudit Department of Tianjin Polytechnic UniversityE-mail: lihui650122@AbstractChina is a country which has the largest investment amount in engineering construction in the world and which has the most construction projects. It is a significant subject for the extensive engineering managers to have effective engineering cost management in construction project management and to reasonably determine and control construction cost on the condition of ensuring construction quality and time limit.On the basis of the status quo of losing control in Chinese construction investment and of separation of technique and economy in engineering, and guided by basic theories of construction cost control, the author discusses control methods and application of construction cost, sets forth existing issues in construction cost control and influences of these issues on determination and control of construction cost, puts forward that construction cost control should reflect cost control of the entire construction process at the earlier stage of construction, and then introduces some procedures and methods of applying value project cost control at all stages of construction projects.Keywords: Construction cost, Cost control, Project1. Significance of the studyThe existing construction cost management system in China was formulated in 1950s, and improved in 1980s. Traditional construction cost managerial approach was one method brought in from the former Soviet Union based on unified quota of the country. It is characterized by the managerial approach of construction cost in the planned economy, which determines that it cannot adapt to requirements of the current market economy.Traditional construction cost managerial approach in China mainly includes two aspects, namely, determination approach of construction cost and control approach of construction cost. The traditional determination approach of construction cost mainly applied mechanically national or local unified quantity quota to determine the cost of a construction project. Although this approach has undergone reform of over 20 years, until now, influences of planned economy management mode have still been in existence in many regions. Control approach of our traditional construction cost is mainly to control settlement and alteration of construction cost, which is merely an approach to settle accounts after the event, and which cannot satisfy the purpose of saving resources and improving work. In recent years, requirements of developed countries on project investment have been to plan to control in advance and to control in the middle of an event, whose effects have proved to be effective. An actually scientific approach should be that construction cost control approach beforehand and after the event can eliminate or diminish labour in vain or poor efficiency and unnecessary resource degradation and methods applied in implementation of construction projects before or after the event.Considering the above situation, the academic circles put forward concept of cost management and control of the overall process as early as 1980s. They began to attach importance to prophase management of construction projects and take the initiative to conduct cost management. Afterwards, on July 1, 2003, implementation of <<Cost Estimate Norm for Bill of Quantity of Construction Works>> symbolized that cost estimate of China had entered a brand-new era that complied with development rules of market economy. From then on, concepts and approaches of Chinese cost management were really integrated with the international society.Losing control of construction project investment is a universal phenomenon in fixed investment field in China. A construction project consumes quite a lot of manpower, materials and machines, with large investment, long construction cycle, and strong synthesis, so it is related with economic interests of all construction parties and means a lot to national economy. Currently, in the field of Chinese project construction, there exists the status quo of separation of technique and economy. Most of engineers and technicians tend to regard construction cost as duty of financing andpreliminary budget personnel, and mistakenly believe that it has nothing to do with themselves. In the process of carrying out a project, they usually only focus on quality control and progress control, while they ignore control over investment in construction projects. If technicians ignore construction cost, and those who are in charge of construction cost have no knowledge in relevant technical construction connected with construction cost, then it is difficult for them to reasonably confirm and effectively control construction cost. Construction supervision investment control refers to managerial activities at the whole implementation state of the project, which attempts to guarantee realization of project investment targets with the premise of satisfying quality and progress. Investment targets are set at different stages with further progress of construction practice, and construction cost control runs through the entire process of project construction, but it should give prominence to the key points. Obviously, the key of construction cost control lies in investment decision-making and design stage before the construction, while after the investment decision is made, the key lies in the design. Life cycle of construction project includes construction cost and recurrent expenditure after the construction project is put into service, and discard and removal costs etc after usage period of the project. According to analysis of some western countries, usually design cost only amounts to less than 1% of life cycle of construction project. However, it is the cost of less than 1% that accounts for more than 75% of influences on construction cost. It is therefore obvious that, design quality is vital to benefits of the entire project construction.For a long time, construction cost control of the preliminary engineering of project construction has been ignored in China, while the primary energy of controlling construction cost has been focused upon auditing working drawing estimate, settling construction cost and settling itemized account during construction. Although this has its effect, after all, this had no difference from taking precautions after suffering a loss and getting half the result with twice the efforts. In order to effectively control construction cost, the emphasis of control should be firmly transferred to preliminary construction stage. At present, we should take all pains to grasp this significant stage so as to achieve maximum results with little effort.This article aims to analyze existing issues in cost control of the entire construction period through study on theoretical methods and practice of construction cost management. Especially, issues in cost control in the earlier period of construction deserve our research, so that we can explore corresponding reform measures to offer some references for construction project cost control.The situation of a construction project in which budgetary estimate exceeds estimation, budget exceeds budgetary estimate, and settlement exceeds budget, is a universal phenomenon in investment in fixed assets in China. Construction cost which is out of control adds to investment pressure, increases construction cost, reduces investment profit, affects investment decision-making, and, to a great extent, wastes the national finance, so it is likely to result in corruption or offence. Since the middle of 1950s, on the basis of summarizing practical experiences of fundamental construction battle line for several decades, we have conducted a series of reforms in construction field. Especially since May 1988, we have gradually implemented the system of construction supervision all over the country, which has had some positive effects upon reversing the phenomenon of losing control of a construction project in the implementation period. However, because that system is still in its starting stage, there hasn’t appeared a large batch of professional and socialized supervision teams. In addition, in projects in which construction supervision is carried out, there exist general phenomena, such as “emphasis on quality control at the construction stage and neglect of investment control”, and “emphasis on technical aspects of supervision and neglect of economic aspects of supervision”. In reality, rights of supervision tend to be confined to management of technical aspects, while management of economic aspects is firmly in control of proprietors. Meanwhile, lagging behind of existing construction cost management system is the primary cause for losing control of construction cost. Therefore, as a whole, the phenomenon of losing control over construction project cost is still quite serious, so it is necessary to conduct further study and make further analysis on major factors of current construction cost management and factors at all stages of a construction project that affect construction cost.2. Primary study contentAiming at the subject of “control of whole-process of construction project cost”, and based on lots of literature reviews about determination and control of construction project cost both at home and abroad, the author of this paper has collected extensively some relevant provincial and city reports and data after investigation. Afterwards, the author conducts the following work.1) To analyze formulation of construction project investment and to find out primary reasons for losing control over construction cost at all stages of a construction project.2) To study and analyze status quo and existing issues of current construction cost management, and study influences of these issues upon determination and control of a construction cost.3) To put forward effective approaches and methods as well application of value engineering of a construction project from its decision-making stage, design stage, construction stage to the final acceptance of construction stage.1454) To make clear significance, necessity and feasibility of cost control of a construction project so as to provide recommendations for improvement of construction cost management in China.2.1 Construction cost control theory and management mod eAccording to the new cost control theory, cost engineers are “professional persons who undertake cost estimate, cost control, marketing planning and scientific management”. Fields undertaken by cost engineers include such aspects as project management, project planning, progress management and profitability analysis etc of a project construction and its production process. Cost engineers offer service for control over life cycle expenditure, property facilities and production & manufacture of a construction project with their management technique with an overall cost.2.2 Current construction cost management model and theories in China2.2.1 Direct regulation and control of the governmentConsidering development process of quota, it can be discovered that quota has come into being, developed and become mature gradually with development of planned economy after foundation of PRC. Since China has carried out centralized management model of investment system for a long time, the government is not only a maker of macropolicy, but a participant of micro-project construction. Therefore, a unified quota with dense colour of planned economy is able to provide powerful methods and means for the government to carry out macro-investment regulation and control and micro-construction project management.2.2.2 Valuation basis for current construction costBasic materials for calculation of construction cost usually include construction cost quota, construction cost expense quota, cost index, basic unit price, quantities calculation rule and relevant economic rules and policies issued by competent departments of the government, etc. It includes index of estimate (budgetary estimate index), budgetary estimate quota, budgetary quota (comprehensive budgetary quota), expense quota (standard), labor quota, working-day norm, materials, budgetary price of facilities, direct price index of a project, material price index and cost index. And also included is valuation criterion of consumption quota and list of items in recent two years.2.2.3 Valuation model of current construction costValuation model is a basic aspect of construction cost management. Construction cost management is a governmental behavior, while valuation model is a means for a country to manage and control construction cost. There are two construction valuation models at present in China, namely, valuation model according to quota and one according to bill of quantities.2.2.3.1 Valuation model according to quotaValuation model according to quota is an effective model adopted during the transition period from planned economy to market economy. Determination of construction cost through valuation model according to quota prevents overrated valuation and standards and prices pressed down to some extent, because budgetary quota standardizes rate of consumption and a variety of documents stipulate manpower, materials, unit price of machines and all sorts of service fee norms, which reflects normativity, unitarity and rationality of construction cost. However, it has an inhibited effect upon market competition, and is not favorable for a construction enterprise to improve its technique, strengthen its management and enhance its labor efficiency and market competition.2.2.3.2 Valuation model according to bill of quantitiesValuation model according to bill of quantities is a construction cost determination model proposed recently. In this model, the government merely unifies project code, project name, unit of measurement and measurement rule of quantities. Each construction enterprise has its self-determination to quote a price according to its own situation in a tender offer, and price of building products is formed thereby in the process of bidding.2.3 Cost control in the process of implementationFor a long time, technique and economy has been separated in the field of project construction. Restrained by the planned economy, there lacks the economic concept in the minds of our engineers and technicians, because they regard reduction of construction cost as a duty of financial personnel which has nothing to do with themselves. However, the primary responsibility of financial and preliminary budget personnel is to act in accordance with financial system. Usually, they are not familiar with construction technique, and know little or even nothing about changes of various relations in project design, construction content and implementation of construction. Under such a circumstance, they have no choice but to mechanically work out or audit the expenditure from a financial perspective, which results in mutual separation of technique and economy. They just do what they do, which negatively reflects price of quantities of a project that has been completed, so it is difficult to control construction cost rationally and effectively.1462.4 Control of cost in the process of constructionImplementation stage of a construction project is a stage which requires the most assets in the whole process of a project construction, and is also a vital stage for pecuniary resources to transform into building entities. Cost control at the implementation stage refers to confine construction cost within a scheduled control scope through a scientific cost control theory and method on the condition of ensuring project quality and time limit. The process of generation of a building entity is inreversible, so if effective automatic control and precontrol cannot be conducted over construction cost, then economic loss might be caused that cannot be made up for.2.5 Analysis of major factors that affect construction cost at the stage of implementationImplementation stage of a project refers to the period from completion of construction documents design and examination and submission to the construction party to the final completion acceptance of the project and until it is put into use. According to the basic operation procedure of the implementation stage of a construction project, formation of a construction cost has to undergo such major aspects as bidding, contract signing and management, joint auditing of a shop drawing, investigation of a construction management plan, material management and completion settlement, etc. All these aspects affect construction cost settlement to different degrees. In that process, after evolving from budgetary price, price for successful bidding, refurbishing cost for a contract, the construction cost is finally determined in the form of settlement price for project completion. Factors affecting construction cost are various, but from the perspective of analysis of cost formation, there are primarily the following reasons.1) Influences of a project bidding. Bidding can determine price for successful bidding, while contract price is determined on the basis of price for successful bidding. If something goes wrong with bidding, then it might result in distortion of the price for bidding, and it is impossible to provide accurate and reliable foundation for cost control, and even result in losing control over the cost.2) Influences of contract signing and management. Determination of a contract price further makes precise target of cost control, and an initial draft of a contract term provides correct foundation and principles for cost control. After signing of a contract, contract items are regarded as foundation, which will have strict contract control over design changes at the construction stage, project measurement, payment of a construction debt, and construction compensation, etc, and which will ensure realization of a control target. Therefore, losing control over signing and management of a contract will necessarily result in losing control over construction cost.3) Influences of examination of construction management plan. Construction management plan is one of important foundations for determine a project bidding price and contract price. In the process of construction, adjustment of a contract price should also be determined according to construction management plan, because quality of construction management plan will directly affect quality and progress of a project. Therefore, losing control over examination of construction management plan will bring extremely unfavorable influences upon control over construction cost.4) Influences of material management. On one hand, material price is an important component of bidding price and contract price. On the other hand, material expense accounts for a large proportion in construction cost, because price of materials determine construction cost. Therefore, losing control over material management will necessarily result in losing control over construction cost.5) Influences of settlement, examination and verification of a project completion. Settlement, examination and verification is the final stage of a construction cost control at the implementation stage. A strict and meticulous settlement, examination and verification can ensure accuracy and authenticity of settlement cost of a project. According to previous analysis, we believe that all aspects of cost control can have effect upon formation of construction cost, among which bidding of a project, contract signing and management, examination of a construction management plan and management of materials all have decisive effects upon formation of construction cost, and are vital aspects in cost construction at the implementation stage of a project, so neglect of these four aspects is a direct cause for losing control over construction cost.In this paper, the author summarizes relevant issues in construction cost control at the decision-making stage of a construction project, at the design stage and construction stage, and puts forward principles or resolutions for handing such issues. Especially, as a method of combination of technique and economics, application of value engineering is elaborated at all stages, so that construction cost gets effective controlled. 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毕业设计(论文)外文文献翻译院系:土木工程与建筑系年级专业:姓名:学号:附件:盾构SHIELDSSHIELDS【Abstract】A tunnel shield is a structural system, used during the face excavation process. The paper mainly discusses the form and the structure of the shield. Propulsion for the shield is provided by a series of hydraulic jacks installed in the tail of the shield and the shield is widespread used in the underground environment where can not be in long time stable. The main enemy of the shield is ground pressure. Non-uniform ground pressure caused by the steering may act on the skin tends to force the shield off line and grade. And working decks inside the shield enable the miners to excavate the face, drill and load holes.【Keywords】shield hydraulic jacks ground pressure steering working decksA tunnel shield is a structural system, normally constructed of steel, used during the face excavation process. The shield has an outside configuration which matches the tunnel. The shield provides protection for the men and equipment and also furnished initial ground support until structural supports can be installed within the tail section of the shield. The shield also provides a reaction base for the breast-board system used to control face movement. The shield may have either an open or closed bottom. In a closed-bottom shield, the shield structure and skin provide 360-degree ground contact and the weight of the shield rests upon the invert section of the shield skin. The open shield has no bottom section and requires some additional provision is a pair of side drifts driven in advance of shield excavation. Rails or skid tracks are installed within these side drifts to provide bearing support for the shield.Shield length generally varies from1/2 to 3/4 of the tunnel diameter. The front of the shield is generally hooded to so that the top of the shield protrudes forward further than the invert portion which provides additional protection for the men working at the face and also ease pressure on the breast-boards. The steel skin of the shield may varyfrom 1.3 to 10 cm in thickness, depending on the expected ground pressures. The type of steel used in the shield is the subject of many arguments within the tunneling fraternity. Some prefer mild steel in the A36 category because of its ductility and case of welding in the underground environment where precision work is difficult. Others prefer a high-strength steel such as T-1 because of its higher strength/weight ratio. Shield weight may range from 5 to 500 tons. Most of the heaviest shields are found in the former Sovier Union because of their preference for cast-iron in both structural and skin elements.Propulsion for the shield is provided by a series of hydraulic jacks installed in the tail of the shield that thrust against the last steel set that has been installed. The total required thrust will vary with skin area and ground pressure. Several shields have been constructed with total thrust capabilities in excess of 10000 tons. Hydraulic systems are usually self-contained, air-motor powered, and mounted on the shield. Working pressures in the hydraulic system may range from 20-70 Mpa. To resist the thrust of the shield jacks, a horizontal structure member (collar brace) must be installed opposite each jack location and between the flanges of the steel set. In addition, some structural provision must be made for transferring this thrust load into the tunnel walls. Without this provision the thrust will extend through the collar braces to the tunnel portal.An Englishman, Marc Brunel, is credited with inventing the shield. Brunel supposedly got his idea by studying the action of the Teredo navalis, a highly destructive woodworm, when he was working at the Chatham dock yard. In 1818 Brunel obtained an English patent for his rectangular shield which was subsequently uses to construct the first tunnel under the River Thames in London. In 1869 the first circular shield was devised by Barlow and Great Head in London and is referred to as the Great Head-type shield. Later that same year, Beach in New York City produced similar shield. The first use of the circular shield came during 1869 when Barlow and Great Head employed their device in the construction of the 2.1 in diameter Tower Subway under the River Thames. Despite the name of the tunnel, it was used only for pedestrian traffic. Beach also put his circular shield to work in 1869 to construct a demonstration project for a proposed NewYork City subway system. The project consisted of a 2.4 m diameter tunnel, 90 m long, used to experiment with a subway car propelled by air pressure.Here are some tunnels which were built by shield principle.Soft-ground tunneling Some tunnels are driven wholly or mostly through soft material. In very soft ground, little or no blasting is necessary because the material is easily excavated.At first, forepoling was the only method for building tunnels through very soft ground. Forepoles are heavy planks about 1.5 m long and sharpened to a point. They were inserted over the top horizontal bar of the bracing at the face of the tunnel. The forepoles were driven into the ground of the face with an outward inclination. After all the roof poles were driven for about half of their length, a timber was laid across their exposed ends to counter any strain on the outer ends. The forepoles thus provided an extension of the tunnel support, and the face was extended under them. When the ends of the forepoles were reached, new timbering support was added, and the forepoles were driven into the ground for the next advance of the tunneling.The use of compressed air simplified working in soft ground. An airlock was built, though which men and equipment passed, and sufficient air pressure was maintained at the tunnel face to hold the ground firm during excavation until timbering or other support was erected.Another development was the use of hydraulically powered shields behind which cast-iron or steel plates were placed on the circumference of the tunnels. These plates provided sufficient support for the tunnel while the work proceeded, as well as full working space for men in the tunnel.Under water tunneling The most difficult tunneling is that undertaken at considerable depths below a river or other body of water. In such cases, water seeps through porous material or crevices, subjecting the work in progress to the pressure of the water above the tunneling path. When the tunnel is driven through stiff clay, the flow of water may be small enough to be removed by pumping. In more porous ground,compressed air must be used to exclude water. The amount of air pressure that is needed increases as the depth of the tunnel increases below the surface.A circular shield has proved to be most efficient in resisting the pressure of soft ground, so most shield-driven tunnels are circular. The shield once consisted of steel plates and angle supports, with a heavily braced diaphragm across its face. The diaphragm had a number of openings with doors so that workers could excavate material in front of the shield. In a further development, the shield was shoved forward into the silty material of a riverbed, thereby squeezing displaced material through the doors and into the tunnel, from which the muck was removed. The cylindrical shell of the shield may extend several feet in front of the diaphragm to provide a cutting edge. A rear section, called the tail, extends for several feet behind the body of the shield to protect workers. In large shields, an erector arm is used in the rear side of the shield to place the metal support segments along the circumference of the tunnel.The pressure against the forward motion of a shield may exceed 48.8 Mpa. Hydraulic jacks are used to overcome this pressure and advance the shield, producing a pressure of about 245 Mpa on the outside surface of the shield.Shields can be steered by varying the thrust of the jacks from left side to right side or from top to bottom, thus varying the tunnel direction left or right or up or down. The jacks shove against the tunnel lining for each forward shove. The cycle of operation is forward shove, line, muck, and then another forward shove. The shield used about 1955 on the third tube of the Lincoln Tunnel in New York City was 5.5 m long and 9.6 m in diameter. It was moved about 81.2 cm per shove, permitting the fabrication of a 81.2 cm support ring behind it.Cast-iron segments commonly are used in working behind such a shield. They are erected and bolted together in a short time to provide strength and water tightness. In the third tube of the Lincoln Tunnel each segment is 2 m long, 81.2 cm wide, and 35.5 cm thick, and weighs about 1.5 tons. These sections form a ring of 14 segments that are linked together by bolts. The bolts were tightened by hand and then by machine.Immediately after they were in place, the sections were sealed at the joints to ensure permanent water tightness.Shields are most commonly used in ground condition where adequate stand-up time does not exist. The advantage of the shield in this type of ground, in addition to the protection afforded men and equipment , is the time available to install steel ribs, liner plates, or precast concrete segments under the tail segment of the shield before ground pressure and movement become adverse factors.One of the principle problems associated with shield use is steering. Non-uniform ground pressure acting on the skin tends to force the shield off line and grade. This problem is particularly acute with closed bottom shield that do not ride on rails or skid tracks. Steering is accomplished by varying the hydraulic pressure in individual thrust jacks. If the shied is trying to dive, additional pressure on the invert jacks will resist this tendency. It is not unusual to find shield wandering several feet from the required. Although lasers are frequently used to provide continuous line and grade data to operator, once the shield wanders off its course, its sheer bulk resists efforts to bring it back. Heterogeneous ground conditions, such as clay with random boulders, also presents steering problems.One theoretical disadvantage of the shield is the annular space left between the support system and the ground surface. When the support system is installed within the tail section of the shield, the individual support members are separated from the ground surface by the thickness of the tail skin. When steel ribs are used, the annular space is filled with timber blocking as the forward motion of the shield exposes the individual ribs. A continuous support system presents a different problem. In this case, a filler material, such as pea gravel or grout, is pumped behind the support system to fill the void between it and the ground surface.The main enemy of the shield is ground pressure. As ground pressure begins to build, two things happen, more thrust is required for shield propulsion and stress increases in the structural members of the shield. Shields are designed and function undera preselected ground pressure. Designers will select this pressure as a percentage of the maximum ground pressure contemplated by the permanent tunnel design. In some cases, unfortunately, the shield just gets built without specific consideration of the ground pressures it might encounter. When ground pressure exceeds the design limit, the shield gets “stuck”. The friction component of the ground pressure on the skin becomes greater than the thrust capability of the jacks. Several methods, including pumping bentonite slurry into the skin, ground interface, pushing heavy equipment, and bumping with dynamite, have been applied to stuck shields with occasional success.Because ground pressure tends to increase with time, the cardinal rule of operation is “keeping moving”. This accounts for the fracture activity when a shield has suffered a temporary mechanical failure. As ground pressure continues to build on the nonmoving shield , the load finally exceeds its structural limit and bucking begins. An example of shield destruction occurred in California in 1968 when two shields being used to drive the CarlyV.Porter Tunnel were caught by excessive ground pressure and deformed beyond repair. One of the Porter Tunnel shields was brought to a halt in reasonably good ground by water bearing ground fault that required full breast-boards. While the contractor was trying to bring the face under control, skin pressure began to increase. While the face condition finally stabilized, the contractor prepared to resume operations and discovered the shield was stuck. No combination of methods was able to move it, and the increasing ground pressure destroyed the shield.To offset the ground pressure effect, a standard provision in design is a cutting edge radius several inches greater than the main body radius. This allows a certain degree of ground movement before pressure can come to bear on the shield skin. Another approach, considered in theory but not yet put into practice, is the “watermelon seed” design. The theory calls for a continuous taper in the shield configuration; maximum radius at the cutting edge and the minimum radius at the trailing edge of the tail. With this configuration, any amount of forward movement would create a drop in skin pressure.Working decks, spaced 2.4 to 3.0 m vertically, are provided inside the shield. These working decks enable the miners to excavate the face, drill and load holes, if necessary, and adjust the breast-board system. The hydraulic jacks for the breast-board are mounted on the underside of the work decks. Blast doors are sometimes installed as an integral part of the work decks if a substantial amount of blasting is expected.Some form of mechanical equipment is provided on the rear end of the working decks to assist the miners in handing and placing the element of the support system. In large tunnels, these individual support elements can weigh several tons and mechanical assistance becomes essential. Sufficient vertical clearance must be provided between the invert and the first working deck to permit access to the face by the loading equipment.盾构【摘要】隧道盾构是一结构系统,通常用于洞室开挖。
1 2020年4月19日
土木工程专业毕业设计外文翻译 文档仅供参考
2 2020年4月19日
High-Rise Buildings Introduction It is difficult to define a high-rise building . One may say that a low-rise building ranges from 1 to 2 stories . A medium-rise building probably ranges between 3 or 4 stories up to 10 or 20 stories or more . Although the basic principles of vertical and horizontal subsystem design remain the same for low- , medium- , or high-rise buildings , when a building gets high the vertical subsystems become a controlling problem for two reasons . Higher vertical loads will require larger columns , walls , and shafts . But , more significantly , the overturning moment and the shear deflections produced by lateral forces are much larger and must be carefully provided for . The vertical subsystems in a high-rise building transmit accumulated gravity load from story to story , thus requiring larger column or wall sections to support such loading . In addition these same vertical subsystems must transmit lateral loads , such as wind or seismic loads , to the foundations. However , in contrast to vertical load , lateral load effects on buildings are not linear and increase rapidly with increase in height . For example under wind load , the overturning moment at the base of buildings varies approximately as 文档仅供参考 3 2020年4月19日
the square of a buildings may vary as the fourth power of buildings height , other things being equal. Earthquake produces an even more pronounced effect. When the structure for a low-or medium-rise building is designed for dead and live load , it is almost an inherent property that the columns , walls , and stair or elevator shafts can carry most of the horizontal forces . The problem is primarily one of shear resistance . Moderate addition bracing for rigid frames in“short”buildings can easily be provided by filling certain panels ( or even all panels ) without increasing the sizes of the columns and girders otherwise required for vertical loads. Unfortunately , this is not is for high-rise buildings because the problem is primarily resistance to moment and deflection rather than shear alone . Special structural arrangements will often have to be made and additional structural material is always required for the columns , girders , walls , and slabs in order to made a high-rise buildings sufficiently resistant to much higher lateral deformations . As previously mentioned , the quantity of structural material required per square foot of floor of a high-rise buildings is in excess of that required for low-rise buildings . The vertical components carrying the gravity load , such as walls , columns , and shafts , will need to be strengthened over the full height of the buildings . But quantity of 文档仅供参考 4 2020年4月19日
material required for resisting lateral forces is even more significant . With reinforced concrete , the quantity of material also increases as the number of stories increases . But here it should be noted that the increase in the weight of material added for gravity load is much more sizable than steel , whereas for wind load the increase for lateral force resistance is not that much more since the weight of a concrete buildings helps to resist overturn . On the other hand , the problem of design for earthquake forces . Additional mass in the upper floors will give rise to a greater overall lateral force under the of seismic effects . In the case of either concrete or steel design , there are certain basic principles for providing additional resistance to lateral to lateral forces and deflections in high-rise buildings without too much sacrifire in economy . 1. Increase the effective width of the moment-resisting subsystems . This is very useful because increasing the width will cut down the overturn force directly and will reduce deflection by the third power of the width increase , other things remaining cinstant . However , this does require that vertical components of the widened subsystem be suitably connected to actually gain this benefit. 2. Design subsystems such that the components are made to interact in the most efficient manner . For example , use truss