长悬臂无梁板桥梁结构分析与设计优化

Structural Analysis and Design Optimization of Long Cantilever Beamless Slab Bridge

无梁板桥具有整体受力性能优越、构造灵活、适应性强、施工便捷和外形简洁美观等优点。一座位于崇明文化活动中心的桥梁,由于受到建设条件的限制而采用不规则支承长悬臂无梁板结构。通过对该结构进行板壳和块体有限元分析得知:长悬臂和不规则支承使得超过一半的单元横向弯矩比纵向弯矩超过15%,在桥墩立柱附近尤为明显;在同一个横截面内,内力沿板宽方向分布也不均匀;墩柱与板固结可以有效降低板的弯矩峰值;长悬臂效应不仅体现在整体受力,在轮载下板的局部受力也不符合初等梁理论。通过讨论板设计中的一些问题,提出方便合理的空间网格配筋法,并与其他结构的对比证明了无梁板桥的经济性。

The beamless slab bridge has advantages of favorable global mechanical behavior, flexible structural formation, good adaptability, easy and rapid construction as well as simple and elegant appearance. Restricted by the construction conditions, a bridge in the Chongming Cultural Activity Center is designed as a long cantilever beamless slab structure with irregular supports. From the plate and shell element and block element analysis made for the structure, it is known that owing to the long cantilever and the irregular supports, the transverse bending moment of more than one half of the elements is 15% greater than the longitudinal bending moment and the situation is particularly obvious close to the pier columns. In the same cross section, the internal force distribution along the slab width is also not uniform and the rigid fixity of the pier column with the slab may effectively reduce the peak value of the bending moment in the slab. The effect of the long cantilever is not in accord with the elementary beam theory not only in aspect of the global force condition, but also the local force condition of the slab subjected to wheel loading. After the study of some problems in the design of the slab, a convenient and rational method of spatial grid reinforcement layout is proposed and the cost-saving of the beamless slab bridge is also verified in comparison to other structures.