建筑工程技术-力学试题3.图示简支梁为矩形截面,许用应力〔a〕=10Mpa,试校核梁的强度

最大应力在梁中间处,最大弯矩：
Mmax =q(L^2)/8 = (4kN/m)x(6m^2)/8 = 18kNm
对z轴抗弯截面模量：
Wz = b(h^2)/6 =(0.2m)x(0.3m^2)/6 =0.003m^3
最大拉应力：
σmax = Mmax/Wz = 18kNm/0.003m^3 = 6000kPa =6MPa < 10MPa
答：梁的抗弯强度足够.