Mq?18(gk?0.5qk)l0?218(20?6)62?117 KN?m
2
2
2
对于C25混凝土：Ec?2.8?104N/mm；Es?2.0?105 N/mm；ftk?1.78 N/mm
As?804 mm；h0?400?25?8?367mm
EsAsEcbh02.0?103.0?10542
?E???804200?367?0.0782
?te?AsAteM?8040.5?200?400144?106?0.0201
?sk?k?h0As?0.87?367?804?560.95 N/mm
2
ψ?1.1-0.65ftk?te?sk2?1.1?0.651.780.0201?560.953?0.997
Bs?EsAsh01.15ψ?0.2?6?E?Mkk?200?10?804?36721.15?0.997?0.2?6?0.07821312?1.19?1013N?mm2
B?Mq(??1)?M?144117?1446?1.19?10?6.57?10 N?mm2
f?5M48Bkl20?5144?10?6000486.57?10122?82?1200l0?30mm
不满足要求。
3．某屋架下弦杆按轴心受拉构件设计，截面尺寸为200mm×200mm，混凝土强度等级为C30，钢筋为HRB400级，4解：
18，环境类别为一类。荷载效应标准组合的轴向拉力Nk=160kN。试对其进行裂缝宽度验算。
；ftk?2.01 N/mm2
轴心受拉构件?cr?2.7；As?1017mm2
?te?AsAte?1017200?200?0.0254
deq?18mm
?sk?NkAs?1600001017ftk?157.33 N/mm2
ψ?1.1-0.65?te?sk?1.1?0.652.010.0254?157.33?0.773
wmax??crψ?skEs(1.9c?0.08deq?te)?2.7?0.773157.332.0?105(1.9?25?0.08180.254)?0.171mm〈wlim?0.2 mm
满足要求。
4．简支矩形截面普通钢筋混凝土梁，截面尺寸b×h=200 mm×500mm，混凝土强度等级为C30，钢筋为HRB335
级，4
16，按荷载效应标准组合计算的跨中弯矩Mk=95kN?m；环境类别为一类。试对其进行裂缝宽度验算，如不
满足应采取什么措施。 解：
对于C30混凝土：Ec?3.0?104N/mm2；Es?2.0?105 N/mm2；ftk?2.01 N/mm2
As?804mm；h0?500?25?8?466mm
EsAsEcbh02.0?103.0?10542
?E???804200?466?0.0575
?te?AsAteM?8040.5?200?50095?106?0.01608
?sk?k?h0As?0.87?466?804?291.4 N/mm
2
ψ?1.1-0.65ftk?te?sk?1.1?0.652.010.01608?291.4?0.82
deq?16mm；c?25mm；?cr?2.1
wmax??crψ?skEs(1.9c?0.08deq?te)?2.1?0.82291.42.0?105(1.9?25?0.08160.01608)?0.319mm〉wlim?0.2mm
不满足要求。可以采取增大截面高度的措施。