拔出型试验钢筋与混凝土间滑移量的简化解法

Simplified solution of the slip between rebar and concrete based on pull-out test

为了求解钢筋与混凝土间滑移量,对黏结滑移基本方程进行了分析,导出了黏结应力-局部滑移相互关系的二阶微分方程.分别运用幂函数和线性局部黏结应力滑移本构关系,得出了黏结应力τ、滑移s、钢筋应变εs、混凝土应变εc的一般解.基于立方体拔出试验(GB50152—92)的边界条件,得出了特解及其适用条件.分析发现:现有混凝土结构设计规范(GB50010—2002)规定的锚固长度Ld低于闭合解临界长度Lth;基于幂函数本构关系只能得出复杂的级数形式解;基于线性局部黏结本构关系却可以得出较简单的闭合解,通过该闭合解可方便地估算钢筋各点滑移量s(x).试验结果验证了公式的适用性和基于线性本构关系求解最大滑移量的正确性.

In order to study the slip between rebar and concrete, the fundamental equations are analyzed and the 2nd order differential equation of the relation between bond stress and local slip are obtained. Based on the power function and linear local bond stress-slip relation, the common solution of bond stress τ, slip s, steel stress εs and concrete stress εc are deduced. According to the Chinese pull-out test of cubic specimens （GB 50152--92） as well as its boundary conditions, the particular solution and accommodated conditions are obtained. It is found that the anchorage length Ld prescribed by Chinese code for design of concrete structures （GB 50010--2002） is less than the critical length Lth. The power function can only produce a complex solution in series form. However, a simple closed solution can be obtained by the linear local bond stress-slip relation. The approximate slip s（x） of different rebar points can be reckoned by the simple closed solution. According to the test results, the adaptability and correctness of the maximum slip solution based on the linear bond stress-slip are testified.