西南交通大学基础工程课程设计
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Foundation Design
姓名 马德林
学号 20100193
班级 2010级土木茅1班
西南交通大学土木工程学院
2013年5月
CONTENTS
Problem --------------------------------------------------------------------- 2 Design ---------------------------------------------------------------------- 4
Chapter one Unit conversion ------------------------------------------------ 4
Chapter two Design load calculation ---------------------------------------- 4
Chapter three Geotechnical designing --------------------------------------- 4
Step 1 to Step 9 Allowable bearing pressure method ---------------------- 4
Step 10 Checking moment load --------------------------------------------- 8
Chapter four Stnjctural designing ------------------------------------------ 8
Part A Determine required thickness based on a two-way shear analysis—8
Check one-way shear ---------------------------------------------- 9
Part B Design the flexural steel ------------------------------------------- 9
Chapter five Sketch of the designed footing ---------------------------------- 11
Figure 2 Thickness and effective depth ------------------------------------ 11
Figure 3 Dimensions and reinforcing steel --------------------------------- 11
Figure 4 Inner block and outer block -------------------------------------- 12
Figure 5 Stmctural show --------------------------------------------------- 12Problem:
Design for Practice
A proposed office building is to be constnjcted at the site with a geologic profile showed in
figure 1. The ground table is at 5.5 ft. The shallow strata are very soft・ The data for these
strata maybe used in foundation design were obtained from a series in-situ tests and laboratoiy
tests, and showed in table 1・ In the table, Su is undrained shear strength; b巾 is preconsolidation
stress・
12-ft .......................................................................................
Silty Clay (CL)
23-ft ■ .............................. = ............ ................................
Medium Sand (Dr=60%)
Fig. 1 geologic section for the constniction site
The design columns of the proposed office building will carry the following loads: dead
vertical load range 30-100 k, live vertical load range 20-75 k, and dead load moment range 0-50
ft-k. These columns are to be supported on spreading footings.
A sketch of an interior column and its spreading footing is given in figure 2. If such an interior carrying a 50k dead vertical load, a 50k live vertical load, and a dead load moment 20 ft-High Plastic Clay (CH) GWT @ 5.5-ft k・ Try to determine the spreading footing of this column・ The design task should including
followings,
Table 1 data for different strata
Depth
Range (ft) Soil
Description Ytotal (PCf) Su(psf) Cc/(1 +e。) Cr/(1+eo)
Q'm(PSf)
0-12 CH 105 1280 0.15 0.02 2600
12-23 CL 112 1800 0.11 0.015 3000
23-27 Med. Sand 120 - 0.006 0.002 -
>27 CL 118 2600 0.08 0.01 6000
(1) Unit conversion
Before beginning your design, please convert the data in the figures and tables from English
to SI, and please use SI in your designing・
(2) Design load calculation
There are two methods of expressing and working with design loads: the allowable stress design
(ASD) and resistance factor design (LRFD). Calculate both of them.
(3) Geotechnical designing
Select a suitable type of the spreading footing, determine the footing depth, determine allowable
bearing pressure, and determine the required base dimensions for the footings of the column in
Figure 2.
Fig. 2 A sketch of the typical interior column and its footing
(4) Structural designing
Determine the materials using in the designed footings, determine the thickness of the footing,
and determine the reinforcing steel of the footing.
(5) Sketch of the designed footing
Show your design in a sketch. A proposed design
Chapter one Unit conversion
To Convert To Multiply by
ft m 0.3048
psf kPa 0.04787
pef kN/n? 0.1571
Data for different strata (SI)
Depth
Range(m) Soil
Description 我） S “伙Pd) %5)
◎(kPa)
0-3.657 CH 16.495 61.274 0」5 0.02 124.462
3.657-7.010 CL 17.595 86.166 0.11 0.015 143.610
7.010-8.229 Mcd.Sand 18.852 - 0.006 0.002 -
>8.229 CL 18.538 124.462 0.08 0.01 287.220
Tips: to convenient, English units will be used in the designing.
Chapter two Design load calculation
The allowable stress design (ASD):
P = 50£ + 50k = 100£ (Pmin=50k 也=175k )
M=20ft-k (旳叭=50〃7)
Resistance factor design (LRFD):
Pu = 1.4x 50k + 1.7 x 50k = 155k
M(i=\.4x20ft-k = 2Sft-k
Chapter three Geotechnical designing
Step 1一一 per TABLE 8.1 (P = 50k + 50k = 100/;)
Use an estimated D of 2 ft (24 in)
Step 2——The ground water table is at 5.5 ft .and is not a concern at this site
Step 3——per Figure 6.11 (Soil Type: Clay Design F with Typical Range)
