拱墙结构平面外失稳机理与设计研究

拱墙是一种由拱、立柱、横梁组合而成的竖向平面结构，横梁上的竖向平面内荷载通过立柱传递到大跨度拱体中。为研究拱墙结构的失稳机理，采用有限元分析方法，对拱墙模型在弹性和弹塑性条件下的稳定性能进行了研究。分析结果表明：立柱侧向刚度及横梁侧向支撑刚度是影响拱墙稳定性能的主要因素，当横梁侧向支撑刚度小于其门槛刚度时，拱墙的屈曲模式表现为拱墙整体平面外失稳；当横梁侧向支撑刚度大于其门槛刚度而立柱的侧向刚度小于其门槛刚度时，拱墙的屈曲模式表现为拱体的平面外失稳；当横梁侧向支撑和立柱的侧向刚度均大于各自的门槛刚度时，拱墙的屈曲模式表现为拱墙整体平面内失稳。结合某火车站站房工程，建立了横梁位置施加侧向弹簧支撑和带纵向桁架的两种拱墙模型，分析了该拱墙结构的平面外稳定承载力。结果表明，纵向桁架为拱墙横梁提供的平面外支撑刚度远大于拱墙的侧向支撑门槛刚度，提高拱墙的平面外稳定承载力需通过增大立柱的侧向刚度和加强立柱两端的可靠连接实现。

Out-of-plane buckling behavior and design of arch wall

Arch wall is a vertical plane structure which combines pure arch, columns and beam together. The applied in-plane vertical loads on the beam will reach the large span arch through columns. For studying the stability of arch wall, the elastic and inelastic mechanical properties of arch wall were discussed in this paper by finite element method. It is shown that lateral bracing stiffness of beam and column stiffness are the key factors which affect the stability of arch wall: if the lateral bracing stiffness is less than its threshold stiffness, the arch wall shows a global out-of-plane buckling mode; if the bracing stiffness is greater than its threshold stiffness and column stiffness is less than its threshold stiffness, the pure arch shows an out-of-plane buckling mode; if both of the bracing stiffness and column stiffness are greater than their threshold stiffness, the arch wall shows an in-plane buckling mode. After that, two analytical models of arch wall from a practical engineering structure were proposed for predicting the ultimate out of plane strength of arch wall. One analytical model reflects only the arch wall laterally braced by equivalent lateral spring resulting from lateral trusses, and the other is a combination of arch wall with longitudinal trusses. The result points out that the lateral bracing stiffness of beam supplied by longitudinal trusses is much larger than the threshold stiffness, the bearing capability of arch wall can be improved only by increasing the stiffness of column or strengthening the reliable connection of column ends.