论现行规范中有关增大截面加固受弯构件的设计原理

Research about the Design Principle of Flexural Member Strengthened with Reinforced Concrete for Existing Codes

对现行规范有关增大截面加固钢筋混凝土受弯构件设计的部分计算原理进行了理论分析,并通过实桥加固设计数据,计算新增钢筋拉应力在主要设计参数变化时的影响。结果表明:计算截面受压边缘混凝土的压应变取极限压应变时,不能反映构件加固前后两阶段受力的影响,新增钢筋拉应变的计算没有意义,计算的承载能力不安全,混凝土的压应变建议取相应抗压强度设计值的应变;加固前计算截面的恒载内力应该取实际值而非组合设计值,加固后截面的相对界限受压区高度的计算应考虑二阶段受力的影响。

Theoretical analysis on partial calculation principles of reinforced concrete flexural members strengthened with reinforced concrete for existing codes is carried out, Influences of new steel reinforcement tensile stress is calculated with main design parameters changes and base on the design data of actual bridge reinforcement. The results show that when the compressive strain of compressed concrete edge of computation section take ultimate compressive strain, calculation cannot reflect two stages stress states of member fore- and-aft reinforcement. New steel reinforcement tensile strain calculation become meaningless and ultimate bearing capacity is unsafe. Therefore, the concrete compressive strain should take corresponding strain of the compressive strength design value. Before the reinforcement, the permanent load internal force of calculation section should take practical design value instead of combination design value. After the reinforcement, the calculation of the relative balanced depth of section compression zone should consider the influences of two-stage stress.