问题 问答题 简答题

简述随着配筋率的变化,梁的破坏形式的变化及各自的破坏特征。

答案

参考答案:

随着配筋率的增大,出现少筋、适筋、超筋三种破坏形式,少筋梁的破坏特征为一旦出现裂缝,裂缝迅速开展,构件即宣告破坏;适筋梁的破坏特征为受拉钢筋先屈服,后压区混凝土被压碎,为塑性破坏,破坏前有预兆;超筋梁的破坏特征为受压区混凝土被压碎,此时受拉钢筋尚未达到屈服强度,少筋和超筋破坏均为脆性破坏。

阅读理解

阅读理解。

    When the world was very young, people lived only in hot places. They did not live in

cold places because they could not keep warm there.

    At first men do not know how to make a fire. Sometimes trees were hit by lightning.

Then a fire was started. People took some of the fire near their homes. A fire was very

important for three reasons. It kept them warm. Wild animals were frightened when they

saw it. And when food was cooked, it tasted much better.

    But men did not know how to make a fire. When they had a fire, they did not let it

stop burning. If it went out (熄灭), they could not start it again. They had to wait for

lightning to start another fire. Sometimes they had to wait for years.

    Later, they learned how to make a fire. But it was not easy to make something burn. 

    Now we have matches. We can carry them in our pockets and make a fire when we want

to.

1. "When the world was very young" means "_____". [ ]

A. before liberation (解放)

B. in the following years

C. before long

D. millions of years ago

2. People found that _____. [ ]

A. the cooked food tasted better than the uncooked food

B. the uncooked food tasted much better than the cooked food

C. wild animals enjoyed the cooked food

D. wild animals kept warm near the trees

3. People didn't let a fire stop burning because _____. [ ]

A. they were not able to make a fire

B. they liked to wait for lightning

C. it rained now and then

D. they didn't like to make a fire

4. Now we can make a fire _____. [ ]

A. by lightning

B. if it is necessary

C. for three reasons

D. in our pockets

单项选择题