第5章 受压构件的截面承载力(gai)专用课件.ppt

It suggests that compression bars do not yield. Assuming x=2as’，taking the moment about the point of As’. Additionally ，assuming As’=0 to compute the As. ?ei e? ?1fc fyAs ?s?As? As As? b as? x h0 h as N 12 As=As’=？ 3、Design of small eccentric compression member Formulas Steel bars are under tension or compression and do not yield. Depth of compression is impossible to exceed h, so Example formulas ★ ★ （1） ★ （2） According to Eqs.(3) and (4) to compute ξ Example 4、Section analysis Formulas (1) Know b×h、strength of materials、reinforcements, N; Determine M Example ★ Distinguish the type of eccentric compression member ★ Compute x or ξ ★ Compute e0 （1）The type of eccentric compression cannot be directly distinguished. Assume it is large eccentric compression member (2) Know b×h、strength of materials、reinforcements, e0; Determine N (N and M) Formulas Example ★ If ，, compute Nu based on large eccentric compression formula. Formulas ★ If ?ei e? ?1fc fyAs ?s?As? As As? b as? x h0 h as N compressive steel bars do not yield. ★ If ，recalculate ξ based on small eccentric compression formula Formulas 5、Check the load-bearing capacity of column in the plane perpendicular to the bending plane y N x N N Bending plane Plane perpendicular to bending plane 5.7 Design method of eccentric rectangular compression member----symmetrical reinforcements 1、Distinguish type of eccentric compression Balance failure： Know：Dimension of section，strength of materials，e0，N; Determine As=As’ Large eccentric compression Small eccentric compression example formulas （1）Compute ?； 2、Design of large eccentric compression member （2）Compute area of reinforcements and check the minimum reinforcement ratio Formulas If ?2a?s/h0 Compressive reinforcements do not yield. 3、 Design of small eccentric compression member Formulas （1）Compute ?； （2）Compute area of reinforcements and check the minimum reinforcement ratio Conclusion 偏心受压构件正截面承载力计算 弯矩作用平面内的偏压计算 垂直于弯矩作用平面的轴压验算 大偏压 小偏压 适用条件： 适用条件： 5.9