Mozart wrote his first opera _____ the a

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问题选择题

Mozart wrote his first opera _____ the age of 14.[ ]

A. in

B. at

C. on

答案

单项选择题

某框架柱，柱截面尺寸为500mm×500mm，计算长度l₀=4500mm；混凝土强度等级C20，纵向钢筋采用828HRB335级钢筋，钢筋的保护层厚度为30mm，见图7-10-1。考虑结构侧移引起的二阶效应附加弯矩及构件挠曲轴向压力产生的附加弯矩影响，构件控制截面内力设计值为：M_y=166kN·m，M_x=98kN·m，N=243kN。