部分柱顶滑移钢筋混凝土结构的滑移柱P-δ效应

P-δ Effect of Sliding Columns in Reinforced Concrete Structures with Partial Columns Sliding at Upper Ends

为揭示部分柱顶滑移钢筋混凝土结构中滑移柱的P-δ效应,首先对该类柱的上端铰接简化模型的有效性进行了验证,在此基础上考察了不同情况下无侧移滑移柱因P-δ效应引发的二阶弯矩的特点,指出了需考虑二阶弯矩的界限条件,并就此提出了无侧移滑移柱弯矩增大系数的确定方法,然后通过参数修正初步考虑了混凝土非线性对前述结果的影响,最后给出了算例分析.研究表明:小震阶段采用普通铰对滑移柱顶部的摩擦支座进行近似处理是可行的;在某些情况下,无侧移滑移柱因P-δ效应引发的二阶弯矩对柱身最大弯矩有增大效应,此时只需利用无侧移滑移柱的一阶弯矩和弯矩增大系数,即可方便地确定其考虑P-δ效应后的柱身最大弯矩.

In order to reveal the P-δ effect of sliding columns in reinforced concrete structures with partial columns sliding at upper ends,the validity of a simplified model with upper end joints is verified.Then,the characteristics of the second-order moment of the sliding column without sidesway caused by the P-δ effect are investigated in different cases,the boundary condition considering the second-order moment is presented,and a method to determine the increment coefficient of the bending moment for the sliding column without sidesway is proposed.Moreover,the concrete nonlinearity is taken into account primarily by amending the parameters in the proposed method,and some examples are finally analyzed.It is found that the friction support located at the upper end of the sliding column under minor earthquakes can be approximately treated as a joint;and that,in some cases,the column 's maximum bending moment increases owing to the second-order moment of the sliding column without sidesway caused by the P-δ effect and that it can be easily determined by using the first-order moment of the sliding column without sidesway and the aforementioned increment coefficient.