问题 单项选择题

为了减小钢筋混凝土梁弯曲产生的裂缝宽度,下列所述措施中哪种措施无效()。

A.提高混凝土强度等级

B.加大纵向钢筋用量

C.加密箍筋

D.将纵向钢筋改成较小直径

答案

参考答案:C

解析:

根据《混凝土规范》第8.1.2条规定,受弯构件考虑裂缝宽度分布的不均匀性和荷载长期效应组合的影响,其最大裂缝宽度按下式计算:

式中,符号可见规范第8.1.2条,σsk计算可见规范第8.1.3条。从规范中可看出,加密箍筋对减小裂缝宽度无效。

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Trees are useful to man(人类)in three very important ways. The first important way is that they provide man with food, wood and other products. Trees provide not only man with food, but also many animals with food. Without trees many animals could not live on the earth. It's not easy for man to live on the earth, either.

The second important way is that trees give us shade. On a hot summer day, people are eager(渴望)to have a rest under the shade of a tree after they have walked a long way. You can imagine how important the shade of a tree is to man and to animals.

The third important way is that trees help to prevent drought(干旱)and floods(洪水). However, in many parts of the world, man has not realized the third important way. He has cut trees down in large numbers. In the end he finds that he has lost the best friends he had.

小题1:Trees are important to man in       ways.

A.2

B.3

C.4

D.5小题2:Which sentence is true?

A.Trees give food to both man and animals.

B.Trees only provide animals with food.

C.Trees give food to neither man nor animals.

D.Trees only provide man with food小题3:On a hot summer day,        .

A.people are eager to have a rest

B.people usually walk a long way

C.animals don't need shade

D.the shade of a tree is very important to man and to animals小题4:In many parts of the world, man has not realized that trees help to          

A.give us food

B.give us shade

C.prevent drought and floods

D.give us wood小题5:In this story the underlined word "He" means       .

A.farmer

B.man

C.worker

D.boy

判断题