问题 单项选择题

某建筑物的地基基础设计等级为乙级,采用柱下桩基,工程桩采用泥浆护壁钻孔灌注桩,桩径d为650mm。相应于荷载效应标准组合时,由上部结构传至基础顶面的竖向力Fk为10000kN,力矩Mxk为1200kN·m,Myk为0;相应于荷载效应基本组合时,由上部结构传至基础顶面的竖向力F为13000kN,力矩Mx为1.560kN·m,My为0。基础及其上土的加权平均重度为20kN/m3,承台及方柱的尺寸、桩的布置以及各土层的地质情况见图2-17。
提示:根据《建筑桩基技术规范》(JGJ94—2008)作答。


试问,桩基承台受弯计算时的最大弯矩设计值Mmax(kN·m),与下列何项数值最为接近

答案

参考答案:D

解析: 根据《建筑桩基技术规范》(JGJ94—2008)5.9.2条,本题是计算承台内力的题目,为多桩锥形承台,受弯计算截面取在柱边,弯矩由3根桩的竖向净反力构成,由桩的中心至计算截面的距离为1.60m,竖向净反力由下式计算:
[*]
弯矩由下式计算:
[*]
故正确的答案是计算所得的弯矩最接近于7600kN·m。

判断题
单项选择题

D

American cities are similar to other cities around the world: In every country, cities reflect the values of the culture. American cities are changing, just as American society is changing.

After World War U , the population of most large American cities decreased ; however, the population in many Sun Belt cities increased. Los Angeles and Houston are cities where population shifts(转移) to and from the city reflect the changing values of American society. In the late 1940s and early 1950s, city residents (居民) became wealthier. They had more children so they needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs (郊区).

Now things are changing. The children of the people who left the cities in the 1950s are now adults. Many, unlike their parents, want to live in the cities. They continue to move to Sun Belt cities and older ones of the Northeast and Midwest. Many young professionals are moving back into cities. They prefer the cities to the suburbs because their jobs are there; or they just enjoy the excitement and possibilities that the city offers.

This population shift is bringing problems as well as benefits. Countless poor people must leave their apartments in the city because the owners want to sell the buildings or make apartments for sale instead of renting, In the 1950s, many poor people did not have enough money to move to the suburbs; now many of these same people do not have enough money to stay in the cities.

Only a few years ago, people though that the older American cities were dying. Some city residents now see a bright, new future. Others see only problems and conflicts. One thing is sure: many dying cities are alive again.

According to the 4th paragraph, a great many poor people in American cities().

A. are faced with housing problems

B. are forced to move to the suburbs

C. want to sell their buildings

D. need more money for daily expenses