组合钢板梁负弯矩区疲劳损伤效应试验研究

Experimental Study on Fatigue Damage Effect in Negative Moment Area of Steel-concrete Composite Girders

为研究组合钢板梁负弯矩区的疲劳损伤效应,基于某常规跨径组合梁桥结构形式设计了2根不同配筋率组合梁试验模型,在倒置状态下开展了模型梁的初始开裂加载、疲劳加载及极限破坏加载试验,对试件的裂缝发展、挠度、应变等指标进行了观测和分析。试验结果表明,配筋率对组合梁混凝土开裂荷载影响较小,但对后期疲劳裂缝发展速率和裂缝宽度影响较大;疲劳荷载作用下,组合梁挠度和应变响应在达到稳定发展之前,会经历复杂的内力重分布过程,高配筋率试件相比于低配筋率试件有更长的内力调整期;2×10^(6)次疲劳试验后,组合梁整体刚度有轻微地退化,但钢梁未出现疲劳开裂。钢梁应变数据的观测以及损伤分析表明,钢梁中性轴指标能较好地反映组合梁负弯矩区的疲劳累计损伤作用。

In order to study the fatigue damage effect in negative moment area of steel-concrete composite girders,two test specimens with different reinforcement ratios were designed based on the structural form of a small and medium span steel-concrete composite girder bridge.Static tests of initial cracking tests,fatigue tests and ultimate failure loading tests on specimens were carried out under inverted loading condition.The crack development,deflection and strain of specimens were observed and analyzed.The results show that the reinforcement ratio has small effect on the cracking loads of specimens,but has great effect on the crack growth rates and crack widths of concrete in the follow-up fatigue stage.In fatigue test stage,before the deflection and strain response reach a stable development state,the composite girders have gone through complex internal force redistribution process,and the specimen with high reinforcement ratio experiences longer cycles of internal force redistribution than that with low reinforcement ratio.After 2 million fatigue tests,there is a slightly deterioration in stiffness,but no fatigue cracks occur in steel girders.The ultimate static loading tests on two specimens both end up with the buckling failure of the steel girders,and their ultimate bearing capacities are close.The observation of strain data and the damage analysis of steel girders show that the neutral axis index of steel girders is closely correlated to the cumulative fatigue damage effect on the negative moment area of composite girders.