桩顶水平位移约束下的长桩等代柱法

Equivalent column method for long pile with top horizontal restriction

框架柱基为一柱一桩的基础形式往往难以保证柱子底部为理想刚接.设计人员一般在一柱一桩基础上设置双向拉梁来约束桩顶水平位移,以保证基础的侧向稳定性,但转角位移却不能避免.上部结构计算分析中,仍假定柱底为完全刚接,这样分析的结果必然与实际受力情况有较大出入.本文根据桩受水平荷载作用的m法,推导出弹性长桩在桩顶受水平位移约束条件下的抗弯刚度,将桩等代为一抗弯刚度相同、截面相同的两端刚接的柱子,从而可将桩基与上部结构以及基础梁一起进行共同作用分析,可得出比较符合实际情况的上部结构内力和拉梁内力,以及桩顶荷载.等代柱法概念明确,工程应用很方便,不失为一种考虑上部结构与基础共同作用的良好方法.

One column with one pile foundation can not ensure the bottom of frame to be rigid. Designers know it is necessary to connect single pile cap with base beams to ensure the stability of cap, but the rotation of cap is not avoidable. In upper frame analyse, we still assume the bottom of column is rigid, so the result is not quite responsible. By adopting the “m” method, the thesis gain the bending rigidity of elastic long pile which top is horizontally restricted. If we replace pile with a equivalent column which has the same bending rigidity, we can analyze upper frame together with pile, so get more reasonable internal force of frame and pile load. The equivalent column method is clear in concept, and easy to apply. It is a good way to consider the interaction of upper structure and foundation.