斜腹板钢箱组合梁负弯矩区非线性受力性能

通过模型试验研究了斜腹板钢箱组合连续梁中间支座处负弯矩区的非线性力学性能.测试了在不同荷载作用下沿纵向各部位的变形、不同截面的应变分布、混凝土板的裂缝分布、钢与混凝土之间的相对滑移以及整个结构的极限承载力等.试验表明,试件在加载初始阶段呈现线弹性,但由于混凝土裂缝较早出现,试件在大部分的加载过程中表现为非线性特征;此外,混凝土中钢筋配筋率对斜腹板钢箱组合梁受力的影响显著,配筋率较少时组合梁在混凝土开裂后刚度降低很快,并使得钢梁较早屈服,而配筋率适当的斜腹板钢箱组合梁表现出了较好的力学性能.试验结果与现行组合梁设计方法对比分析表明,规范规定采用简化折减刚度法计算斜腹板钢箱组合梁的整体变形是安全可行的,以混凝土裂缝宽度为0.2mm对应的承载能力作为斜腹板钢箱组合梁正常使用状态下的承载力具有较大的安全储备.

Non linear Behavior of Hogging Moment Zone of Inclined Web Steel box Composite Girder

Two experiments for inclined web steel box composite girder were carried out to investigate the non elastic behavior of the hogging moment zone at the intermediate supports of continuous girder. Tests were made of the deformation of the girder along the longitudinal direction, strains distribution on various sections, formation and propagation of concrete cracks, slips between steel girder and concrete and bearing capacities of these experimental specimens. Experiment results show the specimens behave non linearly most time though they behave linearly at the beginning of the loading. Additionally, the reinforcement ratio affected the mechanical behavior of the inclined web steel box composite girder significantly. The stiffness of the composite girder with less reinforcement ratio decreased rapidly and caused steel yield earlier, while excellent mechanical behaviors were presented in inclined web steel box composite girder with proper reinforcement ratio. Comparison between the testing results and relatively designing method of composite girder indicates that the simplified discounting stiffness method in code GB50017 2003 for calculating the deflection of inclined web steel box composite girder is safe and feasible. Large bearing capacity reservation exists in inclined web steel box composite girder when the bearing capacity with concrete crack width 0.2 mm is taken as its normal service state bearing capacity.