基于塑性分析的钢筋混凝土箱梁悬臂板横向受力有效分布宽度

Plastic analysis of the lateral effective width of cantilever slabs of reinforced concrete box-girders

目前国内外相关设计规范中关于行车道板横向受力有效分布宽度的取值是基于弹性理论分析结果确定的,不能体现塑性阶段行车道板横向受力特点。通过对2个钢筋混凝土箱梁模型上的4块悬臂板进行荷载试验,得出悬臂板极限荷载和塑性铰线分布形式,并运用塑性分析方法,推导钢筋混凝土箱梁悬臂板在局部荷载作用下塑性有效分布宽度的计算公式。试验结果和理论分析比较表明:悬臂板的塑性有效分布宽度与荷载作用位置及单位板宽正、负极限弯矩值相关;满足构造配筋要求的箱梁悬臂板进行极限状态设计时,建议采用简化的三折线破坏模式进行塑性横向有效分布宽度计算,取正铰线扩散角为45°,负铰线扩散角为60°;荷载作用于悬臂板边缘时基于塑性的横向有效分布宽度是基于弹性分析的1.58倍。

According to the current design code specifications home and abroad, the values of effective width are mostly based on the results of elasticity theory, which cannot represent the characteristics of effective width in the plastic stage. The ultimate load capacity of cantilever slab and the distribution form of plastic yield-lines were acquired through loading experiments of four cantilever slabs of two reinforced concrete box-girders. The formula for calculating the effective width of the slabs under patch load was derived from plastic analysis. By comparing the experimental results with that of theoretical analysis, it is found that the plastic effective width depends on the load-bearing position and both the positive and negative values of ultimate moment, in addition, the simplified tri-linear mode could effectively determine the ultimate strength and plastic effective width of the slabs with at least the minimum reinforcement, and the desirable calculation plastic spread angle is 45~ for the positive yield-line, 60~ for the negative yield-line. The suggested plastic effective width is about 1.58 times of the result of elastic analysis when the concentrated load on the edge of the cantilever slab.