如图所示柱基础底面尺寸为1.8m×1.2m，作用在基础底面的偏心荷载Fk+Gk=300kN，偏心距e=0.2m，基础底面应力分布最接近下列哪个选项？（）
A.A
B.B
C.C
D.D
参考答案：A
解析：
偏心距
。
基底压力计算公式为
利用问题的特殊性，本题也可以这样判断：
答案B和D对应的是三角形荷载，合力作用点在三分点处，由此可以得到荷载的偏心距为
，与偏心距e=0.2不等。所以B和D不是正确答案。
答案A和C的区别主要在荷载大小上，可以分别计算出两者对应的合力。答案A为(46.3+
，答案C为
。因此选A。
点评：本题的要点是记住相关公式，如果没有记住公式，也不要轻易放弃，利用排除法，根据力的平衡可以迅速得到答案。
| The idea of test-tube babies may make you either delighted at the wonders of modem medicine or irritated while considering the moral, or legal, or technological implications-of starting life in a laboratory. But if you’ve ever been pregnant yourself, one thing is certain: You wonder what it’s like to carry a test-tube baby. Are these pregnancies normal Are the babies normal The earliest answers come from Australia, where a group of medical experts at the Queen Victoria Medical Center in Melbourne have taken a look at the continent’s first nine successful invitro pregnancies. The Australians report that the pregnancies themselves seemed to have proceeded according to plan, but at birth some unusual trends did show up. Seven of the nine babies turned out to be girls. Six of the nine were delivered by Caesarean section. And one baby, a twin, was born with a serious heart defect and a few days later developed life-threatening problems. What does it all mean Even the doctors don’t know for sure, because the numbers are so small. The proportion of girls to boys is high, but until there are many more test-tube babies no one will know whether that’s something that just happened to be like that or something special that happens when egg meets sperm in a test tube instead of a fallopian tube. The same thing is true of the single heart defect. It usually shows up in only 15 out of 60,000 births in that part of Australia, but the fact that it occurred in one out of nine test-tube babies does not necessarily mean that they are at special risk. One thing the doctors can explain is the high number of Caesareans. Most of the mothers were older, had long histories of fertility problems and in some cases had had surgery on the fallopian tubes, all of which made them likely candidates for Caesareans anyway. The Australian researchers report that they are quite encouraged. All the babies are now making normal progress, even the twin with the birth defects. |
What does the word "invitro" underlined in Paragraph 2 most probably mean
A．Normal.
B．Test-tube.
C．Built-in.
D．Formal.