问题 单项选择题

某网状配筋砖砌体受压构件截面如图8-3 8-1所示,截面为370mm×750mm(厚度×长度),轴向力的偏心距e=0.1h(h为墙厚),构件的高厚比<16。采用MU10级烧结普通砖、M10级水泥砂浆砌筑,砌体施工重量控制等级为B级,结构重要性系数1.0。钢筋网竖向间距Sn=325mm,采用冷拔低碳钢丝Φb4焊接而成,其抗拉强度fy=430MPa,水平间距为@60mm×60mm。试问,该配筋砖砌体构件的承压承载力(kN),应与下列何项数值最为接近?()

提示:φn为高厚比和配筋率及轴向力的偏心距对网状配筋砖砌体受压构件承载力的影响系数。

A.500φn

B.610φn

C.700φn

D.750φn

答案

参考答案:B

解析:

(1)按照《砌体规范》第8.1.2条,体积配筋率:

(2)根据《砌体规范》第3.2.3条规定,确定砌体强度设计值的调整系数ya。

墙体面积A=370×750=277500mm2=0.278m2>0.2m2,按规范第3.2.3条2款,调整系数γa=1.0,由于砌体用水泥砂浆砌筑,对砌体抗压强度调整系数γa=0.9。

(3)查《砌体规范》表3.2.1-1,MU10烧结普通砖,M10水泥砂浆,抗压强度设计值f=1.89N/mm2

(4)fy=430MPa>320MPa,在计算中应取fy=320MPa。

(5)按《砌体规范》式(8.1.2-2)计算网状配筋砖砌体抗压强度设计值fn

(6)该配筋砖砌体构件的受压承载力:

N≤φnfnA=2.1959×277500φn=609362φnN=609.4φnkN

与B项最接近,与A、C、D三项均不接近。

[点评] 结构工程师应注意:

(1)规范第8.1.2条规定,当冷拔低碳钢丝的抗拉强度设计值大于320MPa时,只取320MPa。

(2)对采用水泥砂浆砌筑的砌体,按照规范第3.2.3条3款的要求,仅对砌体强度设计值厂乘以调整系数γa

(3)根据《砌体规范》第3.2.3条2款,对于配筋砌体,砌体构件截面积大于0.2m2时,不需要对砌体强度设计值进行调整。

阅读理解

The food we eat seems to have a great effect on our health. Although science has made big steps in making food more fit to eat, it has, at the same time, made many foods unfit to eat. Some research has shown that perhaps eighty percent of human illness is related to food and forty percent of cancer is related to food as well. That food is related to illness is not a new discovery. In 1945, some researchers realized that things commonly used to keep colour in meats and other food additives(添加剂)caused cancer.

Yet, these additives remain in our food, and it is difficult to know which things on the wrappings(包装)of foods are helpful or harmful. The additives which we eat are not all so direct. Farmers often give penicillin to their animals, and because of this, penicillin has been found in the milk of cows. Sometimes similar tings are supplied to animals not for their health, but just to make a profit.

The farmers are simply trying to fatten the animals in order to get a higher price on the market. Although some countries have tried to control such things, the practice continues.

小题1:Which of the following is not true?

A.Some wrappings of food are harmful.

B.Farmers try to make more money on the market by fattening their animals.

C.“The practice continues” means “things are still going on like that”.

D.We needn’t take care of what we eat.小题2:According to this passage, we can know      .

A.perhaps most of human illness is caused by what we eat

B.perhaps most kinds of cancer are related to what people eat

C.cancer was discovered in 1945

D.science has made food unfit to eat小题3:Things that are used to keep colours in meats are      .

A.harmful

B.useless

C.helpless

D.dangerous小题4:All the additives      .

A.are bright and colourless

B.are not bright and colourful

C.have indirect effects on our health

D.have direct effects on our health

判断题