钢筋混凝土梁受压区加固后新增混凝土高度分析

针对受压区增大截面加固后的组合截面受弯构件正截面承载力计算公式并没有对其新增混凝土高度的限制条件进行说明,对钢筋混凝土梁受压区加固后新增混凝土高度进行分析.考虑新增混凝土的应变超前效应,对加固后钢筋混凝土梁进行应力应变分析,得到界限破坏的3种形式.对每种界限破坏形式利用截面材料的应力应变关系,得出加固后的钢筋混凝土梁极限承载力计算公式.通过引入截面有效系数和承载力可提高系数以及程序得出新增混凝土高度对其承载力的影响,并进一步得出新增混凝土高度的限制条件.分析结果表明,原截面高度与加固后截面高度比尽量要超过0.8,这样避免原构件的截面受拉钢筋应力很快达到屈服状态,发生少筋脆性破坏的情况.

Analysis on Height of New Concrete on Compressive Region of Reinforced Concrete Beams after Reinforcement

According to the fact that no explanation of the limit condition of height of new concrete in the calculation formula of normal section ultimate bearing capacity of combined sectional bending component after enlarging sectional areas on compressive region, height of new concrete on compressive region of reinforced concrete beams after reinforcement was analyzed.With consideration of the effect of exceeded strain of new concrete, three limiting destruct forms were found out by analyzing stress-strain states of strengthened reinforced concrete beams.The calculation formularies for limiting bearing capacity of reinforced concrete beams were educed by stress-strain relation of different materials in different limiting destroy states.With introduction of the coefficient of effective section, the coefficient of improvable bearing capacity and relative program, the influence of height of new concrete on bearing capacity was found out, and the limit condition of height of new concrete was deduced.The analysis result shows that the ratio of height of original section to height of reinforced section should excess 0.8 to avoid the stress in original component yielding in short period and occurring brittle failure.