《浅议粉沙质海岸的建港模式》
关键词:粉沙;波浪掀沙;沿堤水流;航道淤积;港口平面布置
1 引言
在研究港口回淤计算以及港口平面布置等问题时,目前一般把海岸划分为两类,一类是淤泥质海岸,一类是沙质海岸,如我国《海港水文规范》对此就有比较明确的规定[1]。淤泥质海岸的港口航道回淤主要考虑细颗粒泥沙悬沙落淤,目前已经提出了相当多的计算方法和公式[2-4]。根据多年来对淤泥质海岸的研究,双堤环抱式平面布置方案已成为淤泥质海岸港口建设广泛认可的模式,这种港口布置型式可以有效减少淤泥质海岸的港口淤积,天津新港即为典型实例[5]。对于沙质海岸,一般认为造成港口航道淤积的主要原因是波浪引起的沿岸输沙,因此针对沿岸输沙的主方向拦截上游来沙的单突堤或者不阻碍沿岸输沙的栈桥-岛堤式布置成为解决港口淤积的主要方案,我国援建的毛里塔尼亚友谊港即是这方面的典型实例[6]。实际上,根据近年来我国的工程实践和随着泥沙运动特性研究的深入,粉沙质海岸的概念逐渐受到人们的关注。
刘家驹和喻国华将淤泥质海岸航道回淤公式推广到粉沙质海岸[7],张庆河等从泥沙水力特性和运移特征角度对粉沙质海岸进行了界定[8],曹祖德等进一步对粉沙质海岸的定义、泥沙运动推悬比及淤积分析计算等进行了研究[9-11]。另外一些工作结合实际工程对粉沙质海岸泥沙运动规律进行了分析[12-13]。从目前的研究结果看,粉沙质海岸泥沙粒径范围基本可以定义在d50为0.03～0.12 mm左右。粉沙质海岸之所以受到关注,在于粉沙质海岸的港口回淤有其特殊性,骤淤就是其中比较显著的现象之一。近年来,随着经济的发展,在粉沙质海岸建港已成为比较迫切的要求,一些粉沙质海岸已经建港、正在筹备建港或扩建。但粉沙质海岸一些已建港口不同程度地存在回淤特别是骤淤现象,使人们对粉沙质海岸的港口建设产生疑虑,采取何种港口布置型式能够有效减少粉沙质海岸港口淤积,已建港口如何整治最为经济有效,成为工程建设急需回答的问题。虽然最近罗刚和杨希宏[14]、孔令双等[15]以及杨华和麦苗[16]先后对粉沙质海岸港口布置问题进行了讨论,但一些问题仍有待深入认识,为此,本文将在分析粉沙质海岸泥沙运动和航道回淤成因的基础上,探讨粉沙质海岸的建港模式,以期为粉沙质海岸港口设计和港口减淤整治措施提供必要的依据。
2 粉沙质海岸港口回淤成因分析
大多数粉沙质海岸具有海滩比较平缓的特点,如京唐港附近海岸为典型的粉沙质海岸,泥沙粒径在0.08 mm左右,海滩坡度在1/400～1/700左右[17];东营港泥沙粒径在0.1 mm左右,也为典型粉沙质海岸,其岸滩坡度在1/1 000～3/1 000左右[16];黄骅港附近海岸虽然从岸滩沉积物的整体特性和粘土颗粒的总量来说,属于淤泥质海岸,但从其海床表层泥沙的粒径(0.03 mm左右)和运动特性来看,应归属于粉沙质淤泥海岸[12],其岸滩坡度在1/2 000左右。在上述平缓的粉沙质海岸修建港口,为了避免近岸剧烈泥沙运动造成港口航道淤积,大多数港口选择了从岸线开始
修建较长的双环抱堤或单引堤加双环抱堤的平面布置型式。虽然这些港口具有较长的防沙堤,但从近年来的工程实践看,港口外航道仍然可能发生较严重的淤积。我们将从以下几个方面对粉沙质海岸的回淤机理进行分析。
2.1 波浪的作用
在相当多的粉沙质海岸,波浪作用构成了航道回淤的主要诱因。京唐港出现的几次较为严重的回淤均与大风浪过程有关,如1992年11月,一次东北向大风过程造成防沙堤堤头段航道出现较为严重的集中淤积现象,最大淤厚达到3.2 m; 1993年12月发生的强风浪过程造成外航道集中淤积,最大淤厚达2.5 m[11, 18]。2003年10月出现的长达两天多的强风暴过程,使京唐港外航道最大淤强超过4 m。就黄骅港近年来的回淤现象而言,强浪作用下大量表层粉沙质泥沙的悬扬落淤,构成了黄骅港航道淤积的主要模式[12],例如2001年2月、2003年10月等多次强风浪过程均造成了黄骅港外航道的较严重淤积,每次风暴过程造成的外航道淤积总量均达200万m3以上,风暴过程最大骤淤甚至超过600万m3,最大淤厚超过3.5 m。从上述现象可以得知,粉沙质海岸强淤或骤淤是由波浪引起泥沙大量悬扬所决定的。另外,黄骅港和京唐港在夏季无风浪时不出现航道淤积现象也从反面证明了上述结论。
2.2 近岸水流的作用
虽然波浪作用是航道淤积的主要诱因,但近岸水流运动往往对航道淤积分布起着十分重要的作用。图1显示了我们利用2维ADCIRC潮流模型计算得到的无风情况下落潮过程中黄骅港流场情况,图2、3分别显示了8级NE向风作用下2维ADCIRC模型和SWAN模型耦合计算得到的综合考虑了风、浪(辐射应力)、潮影响后黄骅港落潮和京唐港涨潮过程的流场情况。由图1可见,港口工程修建后,由于建筑物与水流的相互作用,黄骅港北侧形成了沿建筑物向外的水流运动,该水流运动使得中等风浪天气时浅水区(如-2 m等深线以内)由波浪掀起的泥沙向外运动输送到航道内,产生航道淤积。
由图2和图3可见,在风暴作用期间,受各种动力因素影响,粉沙质海岸港口建筑物附近出现明显的沿海岸建筑物流动的水流,可以简称为沿堤水流。这种沿堤水流运动可以使近岸浅水区高浓度泥沙大量向深水区输送,并与航道相交,从而使航道局部位置产生比较强烈的淤积。
港口建筑物附近水流运动十分复杂,对不同海岸,各种动力因素所起的作用不尽相同。例如,黄骅港附近海岸岸滩极为平缓,潮流与风吹流对港口建筑物附近的沿堤流起着决定性作用,而京唐港附近海岸岸滩坡度则较陡一些,潮流与波浪引起的沿岸流对港口建筑物绕流起着决定性作用。从以上分析可以得知,对于粉沙质海岸的航道淤积,港口建筑物附近的水流运动对航道淤积起着十分重要的作用。
2.3 回淤现象的综合分析
根据上述结论和近年来黄骅港、京唐港等粉沙质海岸的工程实践,我们有以下基本认识:在非常平缓的粉沙质海岸上,如黄骅港,在中等风浪天气下,港口也会发生一定的淤积。由于港口口门位置在-2.5 m等深线处,该处在中等风浪天气下基本无泥沙悬扬,因此,造成航道淤积的泥沙主要是-2.0 m等深线以内受波流作用掀起的泥沙,由沿堤水流携带并在航
道落淤而造成的。对于风级较大且持续时间较长的大风暴过程,大浪作用使水深较大的区域(口门以外)就有大量泥沙悬扬,沿堤水流作用的相对重要性反而有所降低。对于岸滩坡度稍陡一些的粉沙质海岸,如京唐港,由于口门水深较大,无论小或大风暴过程中,口门以外直接由波浪掀起的泥沙量都较小,航道的淤积均和沿堤水流有关。从黄骅港与京唐港的淤积分布上也可以证实这一点,黄骅港在小或中等风暴过程作用下,淤积分布主要集中于口门以外8 km以内,而在大风暴作用下,则容易形成外航道的全线回淤;京唐港无论波浪作用大小,其淤积主要集中在口门附近。综合以上分析结果可以认为,波浪作用是造成粉沙质海岸泥沙悬扬运动的主要因素,近岸水流作用,特别是沿堤水流对航道淤积起着十分重要的作用。
沙质海岸港口平面布置的讨论
3.1 粉沙质海岸港口建设的平面布置型式
根据上述粉沙质海岸的回淤成因分析,粉沙质海岸的港口平面布置方式应该遵循以下原则:(1)口门最好选择在一般波浪条件甚至中等风暴过程不能使泥沙产生大量悬扬的水深处,(2)港口平面布置应避免出现沿堤水流携带大量泥沙向外输送的现象。因此,对于粉沙质海岸拟建港口,选用如图4、5所示的两种平面布置型式是较为合理的:图4为港口建在较深水域中的栈桥-岛堤方案;图5为栈桥与双堤环抱式布置方案。第一种方案将码头建在水深较大(如-10 m以上)处,尽量避免航道开挖,因此从根本上避免了航道回淤问题,但由于粉沙质海岸坡度十分平缓,这种方案存在掩护性差、港口利用率较低,码头距岸线过远,一次性投资较大等缺点。第二种方案则承继了单引堤加双堤环抱方案的优点[19],可将港口口门布置在中等风暴不能掀起大量泥沙的等深线处,但将单引堤改为透空式栈桥,避免近岸地区形成沿堤流向外输送泥沙所造成的航道淤积。我们认为,第二种方案在很多情况下是一种值得推荐的方案。图6 (a)、(b)图分别显示了黄骅海岸采用栈桥-双堤环抱式布置后在无风天和8级NE向风作用下的近岸流场。(a)图、(b)图分别与图1、2相比较(对应流场相位分别相同)可知,栈桥-导堤式布置方案的沿堤水流运动现象明显减弱,因此,由沿堤水流输送泥沙所造成的淤积必然会减小。
需要指出的是,上述栈桥-双堤环抱式方案可以有效避免中等风浪造成的航道淤积;对于岸滩坡度较陡的粉沙质海岸,也可以基本解决大风暴造成的航道回淤问题;但对于岸坡十分平缓的粉沙质海岸,大风暴引起的航道非掩护段的淤积仍是难以避免的,因为这时口门外除了沿堤向外的泥沙输送外还有波浪本身的大量掀沙。
3.2 关于粉沙质海岸已建港口的整治
对于未来粉沙质海岸的港口建设,考虑本文3.1中推荐的布置型式是合理的,但对于目前已经建成的粉沙质海岸港口,如果舍弃已建港口而采用上述推荐布置方案,则相当于港口重建,其经济效益比较显然是不合理的。为了进一步减小港口回淤,在现有港口建筑物的基础上进行整治工程建设是更为合理的选择。一般来说,延长防沙堤对于港口减淤起着决定性作用,防沙堤延长虽然不能解决沿堤流问题,但近岸泥沙在随沿堤流运动过程中会逐渐落淤,从而可以减小非掩护段航道淤积。在延长防沙堤时有两个问题有待深入研究: (1)如何延长防沙堤,在延长防沙堤
的同时是否需要建造以及建造何种辅助性建筑物(如横向挡沙堤),需要结合港口具体情况来确定; (2)根据目前所了解的粉沙质海岸泥沙运动特性,在防沙堤顶高程的选择上,潜堤或顶高程在平均水位附近的中水堤在降低防沙堤费用的同时,也可能取得可观的减淤效果,但这方面还需要更深入的研究,特别是大量现场观测来证实。
4 结语
本文根据近年来国内对粉沙质海岸泥沙运动规律的研究、大量港口工程实践和流场数值模拟结果,分析了粉沙质海岸港口发生淤积的原因,指出了波浪掀沙是港口回淤的主要诱因,而近岸复杂水流运动,特别是沿堤水流运动携带泥沙在航道落淤对航道淤积起着重要作用。针对粉沙质海岸港口淤积特点,提出了粉沙质海岸修建港口时的合理平面布置型式,即栈桥加双堤环抱的港口平面布置可能是粉沙质海岸修建港口的合理选择。另外,也对粉沙质海岸已建港口的减淤措施进行了讨论,指出了延长防沙堤是港口整治的合理方案。
需要指出的是,本文所讨论的粉沙质海岸,主要是针对波浪作为主要动力掀沙而潮流作用不能使泥沙大量悬扬的粉沙质海岸而言的。实际上,我国还存在一部分潮流动力作用很强的粉沙质海岸河口,如江苏如东海岸等,对这些海岸的港口平面布置,还需要进一步研究。
参考文献:
[1] JTJ213-98,海港水文规范[S].
[2]Liu Jiaju, hang Jingchao. The channel of muddy coast, sedimentation calculation method and its application [ J]. Wat er conservancy water research,1993, (4):301-320.
[3] 罗肇森.河口航道开挖后的回淤计算[J].泥沙研究, 1987,(2): 13-20.
The extraction powder quality, and the coast of port mode
Keywords:powder; Lift the sand with the waves. Along the dike flow; Channel sedimentation; Port layout
1 the introduction
Back silting computing in the study of port and port layout, is generally the coast is divided into two categories, one kind is muddy coast, one kind is sandy coast, such as the \"guidelines for seaport hydrology\" in our country have had more clear rules [1]. Muddy coast port channel back silting main consideration fine sediment suspended sediment deposition, has been put forward quite a lot of calculation method and formula [2-4]. According to over the years, the research of muddy coast, the double dike surrounded muddy coast port construction layout scheme has become a widely accepted model, the port arrangement type can effectively reduce aggradations of the muddy coast port, tianjin xingang as typical examples [5]. For sandy coast, generally considered the main cause of the port channel siltation caused waves of coastal sediment, so in view of the main direction of river sediment intercept sediment from upstream single jetty or don't hinder the sediment pier - island off the coast dam type is decorated become main solutions to port sedimentation, Mauritania friendship port built in our country is a classic example of the [6]. In fact, according to the engineering practice in our country in recent years and with the deepening of the sediment movement characteristics research, the concept of silty sand quality, and the coast gradually get the attention of people.
Liu Guju muddy coast and YuGuoHua will back silting formula is extended to the waterway silt coast [7], Zhang Qinghe etc, from the Angle of sediment hydraulic characteristics and migration characteristics of silt coast is defined [8], such as Cao Zude further definition of silt coast quality, sediment movement suspension and deposition analysis and calculation are studied, such as [9-11]. Other work combined with practical engineering of silt coast sediment motion is analyzed [12-13]. Look from the current study results, silt coast sediment particle size range of the basic can be defined in the d50 is about 0.03 ~ 0.12 mm. Silt coast is concern, is that qualitative silt coast port back silting has its particularity, sudden deposition is one of the more significant phenomenon. In recent years, with the development of economy, built on silty sand mass coast port has become more urgent requirements, some powder mass has built off the coast of Hong Kong, is planning to build or expand. But some existing port silt mass coast back silting especially sudden sedimentation phenomenon exist in different degrees, in silt coast port construction quality suspicious, what port arrangement type can effectively reduce silt coast port sedimentation, established port how to punish the most economic and effective, as engineering construction need answer. Although recent Luo Gang and Yang Xihong [14], Kong Lingshuang etc. [15], and Yang hua and wheat seeding [16] on silty sand coast port layout problems are discussed, but some problems still need further understanding, therefore, this article
on the analysis of the silt coast sediment movement and channel back silting cause, on the basis of the discussion on the mode of silt coast quality building, in order to silt coast port design and sedimentation reduction quality control measures to provide the necessary basis.
2 silt coast port back silting cause analysis
Most of the silt coast has the characteristics of beach is gentle, such as the coast near jingtang for typical silty sand coast, sediment particle size of about 0.08 mm, the slope beach around 1/400 ~ 1/700 [17]; Dongying port of sediment grain size in 0.1 mm or so, also for typical silty sand coast, along the slope around 1/1 ~ 3/1 000 000 [16]. Although oil drilling near coast from the overall characteristics of sediment and the amount of clay particles, belongs to muddy coast, but from the seabed surface sediment particle size (0.03 mm) and movement characteristics, should belong to [12] in silty sand silt coast, along the slope in 1/2 around 000. In the flat above the silt coast build ports, in order to avoid the near-shore sediment movement caused severe port channel siltation, chose the most ports from coast started to build a long double surrounded by dike or single quote dike to add double unbroken dike layout pattern. Although these ports have long groin, but looked from the engineering practice in recent years, outside the port channel may still happen serious sedimentation. We will from the following several aspects of silty sand coast back silting mechanism is analyzed.
2.1 the waves
In a considerable amount of silt coast, wave action constitutes the main reasons for back silting in the waterway. Jingtang appeared several times more severe back silting are associated with heavy weather process, such as in November 1992, a northeast to the weather process of sand dike head appear channel serious silting phenomenon, the maximum silting thickness is 3.2 m; In December 1993, by the strong wind processes outside the channel siltation, maximum silting thickness of 2.5 m (11, 18). In October 2003 for more than two days of strong storms process, makes the jingtang channel maximum silting stronger more than 4 m. For oil drilling back silting phenomenon in recent years, under the action of strong wave of surface sediment of suspended silt Yang sedimentation, constitute the main mode of oil drilling channel siltation [12], for example in February 2001 and October 2003 times of strong wind, which caused the oil drilling outside channel more severe siltation, every time a tempest process caused by the channel siltation volume are more than 2 million m3, sudden silt largest storm process even more than 6 million m3, maximum silting thickness more than 3.5 m. Can learn from the above phenomenon, powder quality, and the strong coastal silt or sudden sedimentation are caused by the wave and sediment of a suspension Yang. In addition, oil drilling and jingtang harbour in the summer not appear when no wind channel sedimentation phenomenon also proved this conclusion from the opposite side.
2.2 the role of the nearshore currents
Although the wave action is the principal cause of channel sedimentation, but nearshore currents tend to channel siltation distribution plays a very important role. Figure 1 shows we use 2 d ADCIRC tidal current model calculated without wind oil drilling flow field in the process of ebb tide, figure 2, 3 respectively shows the magnitude 8 NE to 2 d ADCIRC model under the action of wind and the SWAN model coupling calculated considering the wind, wave radiation (stress), oil drilling ebb after tide impact, and jingtang flow field in the process of flood situation. From figure 1 shows, port engineering construction, due to interaction with the flow of the buildings, oil drilling on the north side formed along the building outward flow movement, shallow water when the water flow movement makes medium rough weather (such as 2 m isobath) outward by the waves of the sediment transport in the channel, the channel siltation.
From figure 2 and figure 3 shows, in effect during the storm, influenced by all kinds of incentive factors, silt mass coast port structures appear along the coast near flowing water, can be referred to as the dam water flow. This can make the shallow waters high concentration sediment moving along the dike flow to deep water area in great quantities, and fellowship with the channel, so that the channel deposition in local position is strong.
Port buildings near the water flow movement is complex, with different coast, the role of the various dynamic factors is not the same. Oil drilling near coast along, for example, is very gentle, tide and wind flow on port nearby buildings along the dike flow plays a decisive role, and jingtang near the coast along the slope is steep, tide and wave caused by coastal current flow around on the port structures play a decisive role. From the above analysis, for silt coast channel siltation, the flow in the vicinity of the port building movement plays a very important role to the channel siltation.
2.3 back silting phenomenon of comprehensive analysis
According to the above conclusions, and in recent years, oil drilling, jingtang silt coast engineering practice, we have the following basic understanding: in a very gentle silt coast, such as oil drilling, under medium rough weather, port will occur certain sedimentation. Due to the position at the entrance of the port at 2.5 m depth contour, the basic no sediment suspension in medium rough weather, therefore, the main sediment siltation in the waterway is within 2.0 m depth contour by the wave function of the sediment flow, the along the dike flow carry and falls in waterway silting. For longer big storm wind scale is larger and the duration of the process, the wave function to make deeper water area at the entrance of the () there is a lot of sediment suspension and along the dike flow function instead of the relative importance of reduced. For a little steep slope along the silt coast, such as jingtang, due to the water depth is larger, at the entrance of the process, whether small or big storm outside the entrance directly by the waves of the sediment loads are smaller, the channel siltation and along the dike flow. From the deposition distribution of oil drilling and jingtang can also confirmed this, oil drilling under the effect of small or medium storm process, the deposition distribution mainly concentrates on the outside
at the entrance of the 8 km, and under the action of a big storm, siltation of all is easy to form the outside; Jingtang regardless of the size of the wave action, the deposition mainly concentrated near the entrance. Comprehensive the above analysis results can be thought of, wave action is the main factors of coastal sediments suspended silt uplift movement, nearshore currents, especially on channel siltation along the dike flow plays a very important role.
Sandy coast port layout of the discussion
3.1 powder mass coastal port layout of the construction of the model
According to the silt coast back silting cause analysis, qualitative silt coast port layout should follow the following principles: (1) the best choice in general at the entrance of the wave conditions even moderate storm process cannot make produce a large number of suspended silt Yang water depths, (2) the port layout should avoid outward along the dike water carry a lot of sediment transport. So for silt coast land port, chooses as shown in figure 4, 5, two kinds of layout pattern is reasonable: figure 4 for the port construction in deep waters in the dam pier - island; Figure 5 surrounded by pier and double barrier type layout. The first scheme will dock built in deeper water (such as more than 10 m), try to avoid channel excavation, thus avoided channel back silting problem fundamentally, but because of the silt coast very gentle slope, this solution is cover port utilization rate is low, and the terminal from the coast too far, shortcomings and so on one-time investment is larger. The second scheme is inherited the single quote dike with dual advantages of dike surrounded scheme [19], can be in port layout at the entrance of the medium storm cannot bring about a large amount of sediment depth contour, but change the single quote dike to openwork pier, avoid inshore areas along the dike flow caused by the sediment transport channel siltation. We believe that the second scheme in many cases is a recommended plan. Figure 6 (a) and (b) the figure shows the respectively in huanghua coast after the pier - double dike surrounded type decorates breezeless and 8 NE nearshore flow field under the action of the wind. Figure (a) and (b), respectively, compared with figures 1, 2 (corresponding to the flow field were the same phase), the pier - jetty type layout along the dike flow phenomenon is significantly weakened, therefore, caused by along the dike flow transporting sediment deposition will decrease.
It should be pointed out that the pier with double dike surrounded type scheme can effectively avoid the secondary waves caused by the channel deposition; For along slope steep silt coast, also can solve the basic channel back silting problems caused by the big storm; But for the bank slope is gentle silt coast, big storm caused by the passage not cover period of sedimentation is still difficult to avoid, because the mouth outside besides outward along the embankment of sediment transport and wave itself
a lot of lift.
3.2 about silt mass has built off the coast of port regulation
For future silt coast port construction, consider the arrangement type are recommended in this article 3.1 is reasonable, but to have been built in silt coast port,
if give up already built port and the scheme of the recommended layout is equivalent to port reconstruction, its economic benefit is obviously unreasonable. In order to further reduce the port back silting in the existing port on the basis of the engineering construction building is a more reasonable choice. Generally speaking, the extension of the groyne sedimentation reduction plays a decisive role for the port, groyne extended although cannot solve the problem of flow along the dike, but nearshore sediment along the dike flow movement in the process will gradually fall deposition, which can reduce the cover period of channel siltation. In the extension of the groyne are two problems to be further study: (1) how to extend the groyne, the extension of the groyne and whether you need to build and build what kind of supporting structures, such as horizontal block sand dike, need to be connected with specific circumstances to determine; (2) according to the current know silt coast sediment movement characteristics, on the choice of sediment control edterminationof elevationof, submerged jetty or near the average level of the elevation of water in the dam in reducing the costs of groin at the same time, also can achieve significant sedimentation reduction effect, but also need further research, especially a large number of field observation to confirm.
4 conclusion
Based on the sediment transport of silt coast quality in our country in recent years in the research, a large number of port engineering practice and flow field numerical simulation results, alluvial silt mass coast port are analyzed, the reason, pointed out the wave lift sand is the main reasons for back silting in the port, and nearshore complex water flow movement, especially along the dike flow carry falls in waterway silting plays an important role in channel siltation. For silt coast port sedimentation characteristics, puts forward the powder quality and the reasonable layout pattern built off the coast of port, the pier plus double dike surrounded the port layout may be built off the coast of silt mass of rational choice. In addition, also existing on silty sand coast port sedimentation reduction measures are discussed, pointed out the extension of the groyne is reasonable scheme of port regulation.
It should be pointed out that, this paper discussed the silt coast, mainly for wave as a main engine lift sand and tide effect can't make a lot of silt suspension Yang powder in terms of quality, and the coast. In fact, in our country there is a part of the strong tide force silt coast estuarine, such as jiangsu, such as the east coast to the coastal port layout, further research is needed.
References:
JTJ213-98 [1], the seaport hydrology specification [S].
[2] Liu Jiaju, The channel of muddy squadron, sedimentation calculation method and its application [J]. Water conservancy Water research, 1993, (4) : 301-320.
[3] Luo Zhaosen. Siltation after excavation of estuary calculation [J]. Journal of sediment research, 1987, (2) : 13-20.
Load and Ultimate Moment of Prestressed Concrete Action Under Overload-Cracking Load It has been shown that a variation in the external load acting on a prestressed beam results in a change in the location of the pressure line for beams in the elastic range.This is a fundamental principle of prestressed construction.In a normal prestressed beam,this shift in the location of the pressure line continues at a relatively uniform rate,as the external load is increased,to the point where cracks develop in the tension fiber.After the cracking load has been exceeded,the rate of movement in the pressure line decreases as additional load is applied,and a significant increase in the stress in the prestressing tendon and the resultant concrete force begins to take place.This change in the action of the internal moment continues until all movement of the pressure line ceases.The moment caused by loads that are applied thereafter is offset entirely by a corresponding and proportional change in the internal forces,just as in reinforced-concrete construction.This fact,that the load in the elastic range and the plastic range is carried by actions that are fundamentally different,is very significant and renders strength computations essential for all designs in order to ensure that adequate safety factors exist.This is true even though the stresses in the elastic range may conform to a recognized elastic design criterion. It should be noted that the load deflection curve is close to a straight line up to the cracking load and that the curve becomes progressively more curved as the load is increased above the cracking load.The curvature of the load-deflection curve for loads over the cracking load is due to the change in the basic internal resisting moment action that counteracts the applied loads,as described above,as well as to plastic strains that begin to take place in the steel and the concrete when stressed to high levels. In some structures it may be essential that the flexural members remain crack free even under significant overloads.This may be due to the structures’being exposed to exceptionally corrosive atmospheres during their useful life.In designing prestressed members to be used in special structures of this type,it may be necessary to compute the load that causes cracking of the tensile flange,in order to ensure that adequate safety against cracking is provided by the design.The computation of the moment that will cause cracking is also necessary to ensure compliance with some design criteria. Many tests have demonstrated that the load-deflection curves of prestressed beams are approximately linear up to and slightly in excess of the load that causes the first cracks in the tensile flange.(The linearity is a function of the rate at which the load is applied.)For this reason,normal elastic-design relationships can be used in computing the cracking load by simply determining the load that results in a net tensile stress in the tensile flange(prestress minus the effects of the applied loads)that is equal to the tensile strength of the concrete.It is customary to assume that the flexural tensile strength of the concrete is equal to the modulus of rupture of the
理工学院 毕业设计外文资料翻译 专业：计算机科学与技术 姓名：马艳丽 学号： 12L0752218 外文出处：The Design and Implementation of 3D Electronic Map of Campus Based on WEBGIS 附件： 1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文 基于WebGIS的校园三维电子地图的设计与实现 一．导言 如今，数字化和信息化是当今时代的主题。随着信息革命和计算机科学的发展，计算机技术已经渗透到科学的各个领域，并引起了许多革命性的变化，在这些科目，古代制图学也不例外。随着技术和文化的不断进步，地图变化的形式和内容也随之更新。在计算机图形学中，地理信息系统（GIS）不断应用到Web，制作和演示的传统方式经历了巨大的变化，由于先进的信息技术的发展，地图的应用已经大大延长。在这些情况下，绘图将面临广阔的发展前景。电子地图是随之应运而生的产品之一。随着计算机技术，计算机图形学理论，遥感技术，航空摄影测量技术和其他相关技术的飞速发展。用户需要的三维可视化，动态的交互性和展示自己的各种地理相关的数据处理和分析，如此多的关注应支付的研究三维地图。东北石油大学及其周边地区的基础上本文设计并建立三维电子地图。 二．系统设计 基于WebGIS的校园三维电子地图系统的具有普通地图的一般特性。通过按键盘上的箭头键（上，下，左，右），可以使地图向相应的方向移动。通过拖动鼠标，可以查看感兴趣的任何一个地方。使用鼠标滚轮，可以控制地图的大小，根据用户的需求来查看不同缩放级别的地图。在地图的左下角会显示当前鼠标的坐标。在一个div层，我们描绘了一个新建筑物的热点，这层可以根据不同的地图图层的显示，它也可以自动调整。通过点击热点，它可以显示热点的具体信息。也可以输入到查询的信息，根据自己的需要，并得到一些相关的信息。此外，通过点击鼠标，人们可以选择检查的三维地图和卫星地图。 主要功能包括： ?用户信息管理：检查用户名和密码，根据权限设置级别的认证，允许不同权限的用户通过互联网登录系统。 ?位置信息查询：系统可以为用户提供模糊查询和快速定位。
E---MARKETING (From:E--Marketing by Judy Strauss,Adel El--Ansary,Raymond Frost---3rd ed.1999 by Pearson Education pp .G4-G25.) As the growth of https://www.doczj.com/doc/112647211.html, shows, some marketing principles never change.Markets always welcome an innovative new product, even in a crowded field of competitors ,as long as it provides customer value.Also,Google`s success shows that customers trust good brands and that well-crafted marketing mix strategies can be effective in helping newcomers enter crowded markets. Nevertheless, organizations are scrambling to determine how they can use information technology profitably and to understand what technology means for their business strategies. Marketers want to know which of their time-ested concepts will be enhanced by the Internet, databases,wireless mobile devices, and other technologies. The rapid growth of the Internet and subsequent bursting of the dot-com bubble has marketers wondering,"What next?" This article attempts to answer these questions through careful and systematic examination of successful e-mar-keting strategies in light of proven traditional marketing practices. （Sales Promotion;E--Marketing；Internet；Strategic Planning ） 1.What is E--Marketing E--Marketing is the application of a broad range of information technologies for: Transforming marketing strategies to create more customer value through more effective segmentation ,and positioning strategies；More efficiently planning and executing the conception, distribution promotion,and pricing of goods,services,and ideas;andCreating exchanges that satisfy individual consumer and organizational customers` objectives. This definition sounds a lot like the definition of traditional marketing. Another way to view it is that e-marketing is the result of information technology applied to traditional marketing. E-marketing affects traditional marketing in two ways. First,it increases efficiency in traditional marketing strategies.The transformation results in new business models that add customer value and/or increase company profitability.
外文出处： 《Exploiting Software How to Break Code》By Greg Hoglund, Gary McGraw Publisher : Addison Wesley Pub Date : February 17, 2004 ISBN : 0-201-78695-8 译文标题： JDBC接口技术 译文： JDBC是一种可用于执行SQL语句的JavaAPI（ApplicationProgrammingInterface应用程序设计接口）。它由一些Java语言编写的类和界面组成。JDBC为数据库应用开发人员、数据库前台工具开发人员提供了一种标准的应用程序设计接口，使开发人员可以用纯Java语言编写完整的数据库应用程序。 一、ODBC到JDBC的发展历程 说到JDBC，很容易让人联想到另一个十分熟悉的字眼“ODBC”。它们之间有没有联系呢？如果有，那么它们之间又是怎样的关系呢？ ODBC是OpenDatabaseConnectivity的英文简写。它是一种用来在相关或不相关的数据库管理系统（DBMS）中存取数据的，用C语言实现的，标准应用程序数据接口。通过ODBCAPI，应用程序可以存取保存在多种不同数据库管理系统（DBMS）中的数据，而不论每个DBMS使用了何种数据存储格式和编程接口。 1．ODBC的结构模型 ODBC的结构包括四个主要部分：应用程序接口、驱动器管理器、数据库驱动器和数据源。应用程序接口：屏蔽不同的ODBC数据库驱动器之间函数调用的差别，为用户提供统一的SQL编程接口。 驱动器管理器：为应用程序装载数据库驱动器。 数据库驱动器：实现ODBC的函数调用，提供对特定数据源的SQL请求。如果需要，数据库驱动器将修改应用程序的请求，使得请求符合相关的DBMS所支持的文法。 数据源：由用户想要存取的数据以及与它相关的操作系统、DBMS和用于访问DBMS的网络平台组成。 虽然ODBC驱动器管理器的主要目的是加载数据库驱动器，以便ODBC函数调用，但是数据库驱动器本身也执行ODBC函数调用，并与数据库相互配合。因此当应用系统发出调用与数据源进行连接时，数据库驱动器能管理通信协议。当建立起与数据源的连接时，数据库驱动器便能处理应用系统向DBMS发出的请求，对分析或发自数据源的设计进行必要的翻译，并将结果返回给应用系统。 2．JDBC的诞生 自从Java语言于1995年5月正式公布以来，Java风靡全球。出现大量的用java语言编写的程序，其中也包括数据库应用程序。由于没有一个Java语言的API，编程人员不得不在Java程序中加入C语言的ODBC函数调用。这就使很多Java的优秀特性无法充分发挥，比如平台无关性、面向对象特性等。随着越来越多的编程人员对Java语言的日益喜爱，越来越多的公司在Java程序开发上投入的精力日益增加，对java语言接口的访问数据库的API 的要求越来越强烈。也由于ODBC的有其不足之处，比如它并不容易使用，没有面向对象的特性等等，SUN公司决定开发一Java语言为接口的数据库应用程序开发接口。在JDK1．x 版本中，JDBC只是一个可选部件，到了JDK1．1公布时，SQL类包（也就是JDBCAPI）
华北电力大学科技学院 毕业设计（论文）附件 外文文献翻译 学号：121912020115姓名：彭钰钊 所在系别：动力工程系专业班级：测控技术与仪器12K1指导教师：李冰 原文标题：Infrared Remote Control System Abstract 2016 年 4 月 19 日
红外遥控系统 摘要 红外数据通信技术是目前在世界范围内被广泛使用的一种无线连接技术，被众多的硬件和软件平台所支持。红外收发器产品具有成本低，小型化，传输速率快，点对点安全传输，不受电磁干扰等特点，可以实现信息在不同产品之间快速、方便、安全地交换与传送，在短距离无线传输方面拥有十分明显的优势。红外遥控收发系统的设计在具有很高的实用价值，目前红外收发器产品在可携式产品中的应用潜力很大。全世界约有1亿5千万台设备采用红外技术，在电子产品和工业设备、医疗设备等领域广泛使用。绝大多数笔记本电脑和手机都配置红外收发器接口。随着红外数据传输技术更加成熟、成本下降，红外收发器在短距离通讯领域必将得到更广泛的应用。 本系统的设计目的是用红外线作为传输媒质来传输用户的操作信息并由接收电路解调出原始信号，主要用到编码芯片和解码芯片对信号进行调制与解调，其中编码芯片用的是台湾生产的PT2262，解码芯片是PT2272。主要工作原理是：利用编码键盘可以为PT2262提供的输入信息，PT2262对输入的信息进行编码并加载到38KHZ的载波上并调制红外发射二极管并辐射到空间，然后再由接收系统接收到发射的信号并解调出原始信息，由PT2272对原信号进行解码以驱动相应的电路完成用户的操作要求。 关键字：红外线；编码；解码；LM386；红外收发器。 1 绪论
Journal of Industrial Textiles https://www.doczj.com/doc/112647211.html,/ Optimization of Parameters for the Production of Needlepunched Nonwoven Geotextiles Amit Rawal, Subhash Anand and Tahir Shah 2008 37: 341Journal of Industrial Textiles DOI: 10.1177/1528083707081594 The online version of this article can be found at: https://www.doczj.com/doc/112647211.html,/content/37/4/341 Published by: https://www.doczj.com/doc/112647211.html, can be found at:Journal of Industrial TextilesAdditional services and information for https://www.doczj.com/doc/112647211.html,/cgi/alertsEmail Alerts: https://www.doczj.com/doc/112647211.html,/subscriptionsSubscriptions: https://www.doczj.com/doc/112647211.html,/journalsReprints.navReprints: https://www.doczj.com/doc/112647211.html,/journalsPermissions.navPermissions: https://www.doczj.com/doc/112647211.html,/content/37/4/341.refs.htmlCitations: - Mar 28, 2008Version of Record >>
外文翻译 专业机械设计制造及其自动化学生姓名刘链柱 班级机制111 学号1110101102 指导教师葛友华
外文资料名称： Design and performance evaluation of vacuum cleaners using cyclone technology 外文资料出处：Korean J. Chem. Eng., 23(6), (用外文写) 925-930 (2006) 附件： 1.外文资料翻译译文 2.外文原文
应用旋风技术真空吸尘器的设计和性能介绍 吉尔泰金，洪城铱昌，宰瑾李， 刘链柱译 摘要：旋风型分离器技术用于真空吸尘器 - 轴向进流旋风和切向进气道流旋风有效地收集粉尘和降低压力降已被实验研究。优化设计等因素作为集尘效率，压降，并切成尺寸被粒度对应于分级收集的50％的效率进行了研究。颗粒切成大小降低入口面积，体直径，减小涡取景器直径的旋风。切向入口的双流量气旋具有良好的性能考虑的350毫米汞柱的低压降和为1.5μm的质量中位直径在1米3的流量的截止尺寸。一使用切向入口的双流量旋风吸尘器示出了势是一种有效的方法，用于收集在家庭中产生的粉尘。 摘要及关键词：吸尘器; 粉尘; 旋风分离器 引言 我们这个时代的很大一部分都花在了房子，工作场所，或其他建筑，因此，室内空间应该是既舒适情绪和卫生。但室内空气中含有超过室外空气因气密性的二次污染物，毒物，食品气味。这是通过使用产生在建筑中的新材料和设备。真空吸尘器为代表的家电去除有害物质从地板到地毯所用的商用真空吸尘器房子由纸过滤，预过滤器和排气过滤器通过洁净的空气排放到大气中。虽然真空吸尘器是方便在使用中，吸入压力下降说唱空转成比例地清洗的时间，以及纸过滤器也应定期更换，由于压力下降，气味和细菌通过纸过滤器内的残留粉尘。 图1示出了大气气溶胶的粒度分布通常是双峰形，在粗颗粒（>2.0微米）模式为主要的外部来源，如风吹尘，海盐喷雾，火山，从工厂直接排放和车辆废气排放，以及那些在细颗粒模式包括燃烧或光化学反应。表1显示模式，典型的大气航空的直径和质量浓度溶胶被许多研究者测量。精细模式在0.18?0.36 在5.7到25微米尺寸范围微米尺寸范围。质量浓度为2?205微克，可直接在大气气溶胶和 3.85至36.3μg/m3柴油气溶胶。
毕业论文外文文献翻译 毕业设计（论文）题目关于企业内部环境绩效审计的研究翻译题目最高审计机关的环境审计活动 学院会计学院 专业会计学 姓名张军芳 班级09020615 学号09027927 指导教师何瑞雄
最高审计机关的环境审计活动 1最高审计机关越来越多的活跃在环境审计领域。特别是1993-1996年期间，工作组已检测到环境审计活动坚定的数量增长。首先，越来越多的最高审计机关已经活跃在这个领域。其次是积极的最高审计机关，甚至变得更加活跃：他们分配较大部分的审计资源给这类工作，同时出版更多环保审计报告。表1显示了平均数字。然而，这里是机构间差异较大。例如，环境报告的数量变化，每个审计机关从1到36份报告不等。 1996-1999年期间，结果是不那么容易诠释。第一，活跃在环境审计领域的最高审计机关数量并没有太大变化。“活性基团”的组成没有保持相同的：一些最高审计机关进入，而其他最高审计机关离开了团队。环境审计花费的时间量略有增加。二，但是，审计报告数量略有下降，1996年和1999年之间。这些数字可能反映了从量到质的转变。这个信号解释了在过去三年从规律性审计到绩效审计的转变（1994-1996年，20％的规律性审计和44％绩效审计;1997-1999：16％规律性审计和绩效审计54％）。在一般情况下，绩效审计需要更多的资源。我们必须认识到审计的范围可能急剧变化。在将来，再将来开发一些其他方式去测算人们工作量而不是计算通过花费的时间和发表的报告会是很有趣的。 在2000年，有62个响应了最高审计机关并向工作组提供了更详细的关于他们自1997年以来公布的工作信息。在1997-1999年，这62个最高审计机关公布的560个环境审计报告。当然，这些报告反映了一个庞大的身躯，可用于其他机构的经验。环境审计报告的参考书目可在网站上的最高审计机关国际组织的工作组看到。这里这个信息是用来给最高审计机关的审计工作的内容更多一些洞察。 自1997年以来，少数环境审计是规律性审计（560篇报告中有87篇，占16％）。大多数审计绩效审计（560篇报告中有304篇，占54％），或组合的规律性和绩效审计（560篇报告中有169篇，占30％）。如前文所述，绩效审计是一个广泛的概念。在实践中，绩效审计往往集中于环保计划的实施（560篇报告中有264篇，占47％），符合国家环保法律，法规的，由政府部门，部委和/或其他机构的任务给访问（560篇报告中有212篇，占38％）。此外，审计经常被列入政府的环境管理系统（560篇报告中有156篇，占28％）。下面的元素得到了关注审计报告：影响或影响现有的国家环境计划非环保项目对环境的影响;环境政策;由政府遵守国际义务和承诺的10％至20％。许多绩效审计包括以上提到的要素之一。 1本文译自：S. Van Leeuwen.(2004).’’Developments in Environmental Auditing by Supreme Audit Institutions’’ Environmental Management Vol. 33, No. 2, pp. 163–1721
毕业设计（论文） 外文翻译 题目西安市水源工程中的 水电站设计 专业水利水电工程 班级 学生 指导教师 2016年
研究钢弧形闸门的动态稳定性 牛志国 河海大学水利水电工程学院，中国南京，邮编210098 nzg_197901@https://www.doczj.com/doc/112647211.html,，niuzhiguo@https://www.doczj.com/doc/112647211.html, 李同春 河海大学水利水电工程学院，中国南京，邮编210098 ltchhu@https://www.doczj.com/doc/112647211.html, 摘要 由于钢弧形闸门的结构特征和弹力，调查对参数共振的弧形闸门的臂一直是研究领域的热点话题弧形弧形闸门的动力稳定性。在这个论文中，简化空间框架作为分析模型，根据弹性体薄壁结构的扰动方程和梁单元模型和薄壁结构的梁单元模型，动态不稳定区域的弧形闸门可以通过有限元的方法，应用有限元的方法计算动态不稳定性的主要区域的弧形弧形闸门工作。此外，结合物理和数值模型，对识别新方法的参数共振钢弧形闸门提出了调查，本文不仅是重要的改进弧形闸门的参数振动的计算方法，但也为进一步研究弧形弧形闸门结构的动态稳定性打下了坚实的基础。 简介 低举升力，没有门槽，好流型，和操作方便等优点，使钢弧形闸门已经广泛应用于水工建筑物。弧形闸门的结构特点是液压完全作用于弧形闸门，通过门叶和主大梁，所以弧形闸门臂是主要的组件确保弧形闸门安全操作。如果周期性轴向载荷作用于手臂，手臂的不稳定是在一定条件下可能发生。调查指出:在弧形闸门的20次事故中，除了极特殊的破坏情况下，弧形闸门的破坏的原因是弧形闸门臂的不稳定;此外，明显的动态作用下发生破坏。例如:张山闸，位于中国的江苏省，包括36个弧形闸门。当一个弧形闸门打开放水时，门被破坏了，而其他弧形闸门则关闭，受到静态静水压力仍然是一样的，很明显，一个动态的加载是造成的弧形闸门破坏一个主要因素。因此弧形闸门臂的动态不稳定是造成弧形闸门(特别是低水头的弧形闸门)破坏的主要原是毫无疑问。
外文翻译 原文 Marketing Material Source：Marketing Management Author：Philip Kotler Marketing Channels To reach a target market, the marketer uses three kinds of marketing channels. Communication channels deliver messages to and receive messages from target buyers. They include newspapers, magazines, radio, television, mail, telephone, billboards, posters, fliers, CDs, audiotapes, and the Internet. Beyond these, communications are conveyed by facial expressions and clothing, the look of retail stores, and many other media. Marketers are increasingly adding dialogue channels (e-mail and toll-free numbers) to counterbalance the more normal monologue channels (such as ads). The marketer uses distribution channels to display or deliver the physical product or service to the buyer or user. There are physical distribution channels and service distribution channels, which include warehouses, transportation vehicles, and various trade channels such as distributors, wholesalers, and retailers. The marketer also uses selling channels to effect transactions with potential buyers. Selling channels include not only the distributors and retailers but also the banks and insurance companies that facilitate transactions. Marketers clearly face a design problem in choosing the best mix of communication, distribution, and selling channels for their offerings. Supply Chain Whereas marketing channels connect the marketer to the target buyers, the supply chain describes a longer channel stretching from raw materials to components to final products that are carried to final buyers. For example, the supply chain for women’s purses starts with hides, tanning operations, cutting operations, manufacturing, and the marketing channels that bring products to customers. This supply chain represents a value delivery system. Each company captures only a certain percentage of the total value generated by the supply chain. When a company acquires competitors or moves upstream or downstream, its aim is
华南理工大学广州学院 本科毕业设计（论文）外文翻译 外文原文名Marketing Strategy Adjustment and Marketing Innovation in the Experience Economy Era 中文译名体验经济时代的营销战略调整与营销创新 学院管理学院 专业班级2013级工商管理1班 学生姓名潘嘉谊 学生学号201330090184 指导教师罗玲苑讲师李巍巍 填写日期2017年5月19日
外文原文版出处：.Marketing Strategy Adjustment and Marketing Innovation in the Experience Economy Era[J]. Contemporary Logistics,2012 (06) :230-267 译文成绩：指导教师（导师组长）签名： 译文： 体验经济时代的营销战略调整与营销创新 吴青学 摘要：从商品货物经济，到服务经济的的转移演化经历过程，经历了农业经济、工业经济，服务经济和体验经济。在服务经济时期，企业只是打包经验与传统的产品一起销售，而在促进经验经济的时期，企业要把最好产品为未来的潜在用户设计，让消费者心甘情愿支付购买产品。 关键词：体验经济；市场营销战略；营销创新 1 介绍 随着科学技术和信息行业的发展，人们的需要和欲望连同消费者支出模式开始发生转变，相应地对企业生产环境产生了一系列影响。经济社会发展由传统时期进入体验经济时期。从一个经济产品的转变，进而到经济体系经济模式的转变。由缓慢转变为激进经济模式。因此导致社会发展从一个经济时期到另一个经济时期，经济模式和经济体系的转变将不可避免地影响到交换关系的转化。这是关注体验的结果，是由人类社会的发展的规律所决定的生产水平的产物。一旦交流关系发生变化、营销模式必须做出相应的变化。 2 企业营销策略的选择方向 在体验经济时代，企业不仅要理性思考高瞻远瞩，从客户的角度实施营销活动，更要重视与沟通客户，发现在他们内心的期望。我们自己的产品和服务代表企业的形象，产品要指向指定的客户体验。在当今时代，体验营销已成为营销活动最强大的秘密武器因此，这是非常重要的。而传统的营销策略，包括调整经验营销都已经不适应当前发展需求，迟早要被时代所淘汰。 2.1 建立营销思想的观念要求提高客户体验 根据马斯洛需求层次理论，人的需要分为五个层次，分别是：生理的需要、安全的需要、归属于爱的需要、尊重的需要和自我实现的需要。随着经济的发展和消费者日益增强的购买能力变化，人们生理需求得到满足，个人需求将会上升心
xxxxxxxxx 毕业设计（论文）外文文献翻译 （本科学生用） 题目：Poduct Line Engineering: The State of the Practice 生产线工程：实践的形态 学生姓名：学号： 学部（系）: 专业年级: 指导教师：职称或学位： 2011年3月10日
外文文献翻译（译成中文1000字左右）： 【主要阅读文献不少于5篇，译文后附注文献信息，包括：作者、书名（或论文题目）、出版社（或刊物名称）、出版时间（或刊号）、页码。提供所译外文资料附件（印刷类含封面、封底、目录、翻译部分的复印件等，网站类的请附网址及原文】 Requirements engineering practices A precise requirements engineering process— a main driver for successful software development —is even more important for product line engineering. Usually, the product line’s scope addresses various domains simultaneously. This makes requirements engineering more complex. Furthermore, SPL development involves more tasks than single-product development. Many product line requirements are complex, interlinked, and divided into common and product-specific requirements. So, several requirements engineering practices are important specifically in SPL development: ? Domain identification and modeling, as well as commonalities and variations across product instances Separate specification and verification for platform and product requirements ? Management of integrating future requirements into the platform and products ? Identification, modeling, and management of requirement dependencies The first two practices are specific to SPL engineering. The latter two are common to software development but have much higher importance for SPLs. Issues with performing these additional activities can severely affect the product line’s long-term success. During the investigation, we found that most organizations today apply organizational and procedural measures to master these challenges. The applicability of more formal requirements engineering techniques and tools appeared rather limited, partly because such techniques are not yet designed to cope with product line evelopment’s inherent complexities. The investigation determined that the following three SPL requirements engineering practices were most important to SPL success. Domain analysis and domain description. Before starting SPL development, organizations should perform a thorough domain analysis. A well-understood domain is a prerequisite for defining a suitable scope for the product line. It’s the foundation for efficiently identifying and distinguishing platform and product requirements. Among the five participants in our investigation, three explicitly modeled the product line requirements. The others used experienced architects and domain experts to develop the SPL core assets without extensive requirements elicitation. Two organizations from the first group established a continuous requirements management that maintained links between product line and product instance requirements. The three other organizations managed their core assets’ evolution using change management procedures and versioning concepts. Their business did not force them to maintain more detailed links between the requirements on core assets and product instances. The impact of architectural decisions on requirements negotiations. A stable but flexible architecture is important for SPL development. However, focusing SPL evolution too much on architectural issues will lead to shallow or even incorrect specifications. It can cause core assets to ignore important SPL requirements so that the core assets lose relevance for SPL development. Organizations can avoid this problem by establishing clear responsibilities for requirements management in addition to architectural roles. The work group participants reported that a suitable organizational tool for balancing requirements and architecture is roundtable meetings in which requirements engineers,