二次受力下外粘钢板加固钢筋混凝土梁抗弯承载力

Bending Bearing Capacity of Reinforced Concrete Beams Strengthened with Steel Plates Considering the Effect of the Second Loading

基于条带法提出了考虑二次受力影响的外粘钢板加固钢筋混凝土梁抗弯承载力的两阶段接力计算方法。和已有试验结果的比较表明,该数值计算方法具有足够的精度。为考虑二次受力对不同加固梁的影响,设计了24根数值分析试件,采用建议的数值计算方法对每个试件在不同持荷水平下的承载力进行了计算,并和《混凝土结构加固设计规范》(GB 50367—2006)推荐方法算得的承载力计算结果进行了比较分析。结果表明,大多数情况下二次受力并不影响外粘钢板加固梁的抗弯承载力,只有当混凝土强度等级较低且持荷水平较高时需考虑二次受力对加固梁抗弯承载力的不利影响;规范方法对于计算受压面粘钢加固梁抗弯承载力及超筋破坏模式下梁的抗弯承载力会给出不安全的结果。

Based on the strip method,a relay numerical calculation method for the bending bearing capacity of reinforced concrete beams strengthened with externally bonded steel plates considering the effect of the second loading was proposed.Comparing the calculation results with the existing test results,it was verified that the numerical calculation method is accurate enough to be used to calculate the bending bearing capacity of strengthened reinforced concrete beams.To consider the effect of the second loading on the bending bearing capacity of the beams,24 numerical analysis specimens were designed.The bending bearing capacity for each beam strengthened under certain sustained load was calculated by using the proposed relay numerical calculation method,and it was compared with the corresponding value calculated by using the method recommended by the ＂Design code for strengthening concrete structures＂（GB50367-2006）.The results showed that in most cases the effect of the second loading on the bending bearing capacity of the beams can be neglected.However,in the cases that the strength of concrete is low and the sustained load level is high,the negative effect of the second loading on the bending bearing capacity of the beams should be taken into account.And the method recommended by the national code may overestimate the bending bearing capacity of a beam strengthened with steel plates in compression zone or whose damage mode is the crush of the concrete but the steel bars remain in elastic stage.