问题 单项选择题

混凝土徐变会对构件产生哪些不利影响()。 Ⅰ.增大混凝土结构的变形 Ⅱ.使大体积混凝土表面出现裂缝 Ⅲ.在预应力混凝土构件中引起预应力损失 Ⅳ.引起基础不均匀沉降

A.Ⅰ、Ⅱ、Ⅲ 

B.Ⅱ、Ⅲ、Ⅳ 

C.Ⅰ、Ⅲ 

D.Ⅱ、Ⅳ

答案

参考答案:C

解析:

徐变对结构的影响主要有:①徐变使结构的变形增大;②徐变使结构内部应力重新分布;③徐变将引起预应力混凝土结构中的预应力损失;④受拉徐变,会延缓混凝土收缩裂缝的出现及减少由于支座不均匀沉降产生的应力等。

解答题
阅读理解

阅读理解

     In 1963,former Senator Gaylord Nelson began to worry about our planet. Nelson knew that our world

was getting dirty and that many of our plants and animals were dying. He wondered why most people

weren't trying to solve these problems. He talked to other lawmakers and to the President. They decided

that the President would go around the country and tell people about these problems. He did, but still not

enough people were working on it.  

     Then in 1969, Senator Nelson had another idea. He decided to have a special day to teach everyone

about the things that needed changing in our environment. He wrote letters to all of the colleges and put a

special article in Scholastic Magazine to tell them about the special day he had planned.

     On April 22,1970, the first Earth Day meeting was held. People all over the country made promises to

help improve the environment. Since then, Earth Day has spread all over the planet. People all over the

world know that there are problems we need to work on and this is our special day to look at the planet 

and see what needs changing. Isn't it great? One person had an idea and kept working until everyone

began working together to solve it.

1. The passage mainly talks about _____.

A. the importance of Earth Day

B. the person who planned the Earth Day

C. the history of Earth Day

D. the first Earth Day

2. Why did  Senator Gaylord Nelson  worry about our planet?

A. The world was getting dirty

B. Many plants and animals were dying.

C. Few people cared about the earth

D. All of the above.

3. Nelson did all this to_____  

A. become famous  

B. make more laws  

C. change the environment

D. make people care about the environment

4. It took Nelson _____ years to get people pay much attention to the earth.

A. 10      

B. 7    

C. 6      

D. 15