圆钢管混凝土柱-钢筋桁架组合梁节点抗连续倒塌机制及参数分析

Anti-progressive Collapse Mechanism and Parameter Analysis of Circular CFST Column and Steel Bar Truss Composite Beam Joint

为研究钢筋桁架组合梁对钢管混凝土结构抗连续倒塌性能的影响,采用ABAQUS建立圆钢管混凝土柱-钢筋桁架组合梁节点数值模型,分析中柱失效工况下该类节点的破坏机理和抗力计算曲线,以及钢筋桁架高度、混凝土强度、钢筋强度等主要参数对组合节点抗连续倒塌能力的影响。结果表明:相比钢管混凝土柱-RC组合梁节点,钢筋桁架组合梁节点的梁机制和悬链线机制峰值承载力分别提高了12.5%和10%;因钢筋桁架在下弦钢筋屈服后上弦钢筋仍可以提供拉力,使得钢梁下翼缘断裂后承载力可以继续提高,表现出良好的抗连续倒塌能力;钢筋桁架高度和钢筋桁架钢筋强度主要对节点梁机制峰值承载力与极限承载力提升较显著,对悬链线机制峰值承载力影响较小,楼板混凝土强度对节点各阶段的承载力影响较小,并且会降低节点延性;综合对比分析不同参数下节点的抗力指标和位移延性指标发现,增加钢筋桁架高度和钢筋强度对节点的抗连续倒塌极限承载力具有有利影响,在工程设计和应用中应予以考虑。

In order to study the influence of steel truss composite beam on the progressive collapse resistance of concrete-filled steel tubular(CFST)structure,ABAQUS was used to establish the numerical model of the joint of CFST column and steel bar truss composite beam.The failure mechanism and resistance calculation curve of the joint under the failure condition of middle column were analyzed,and the influences of main parameters such as the height of steel truss,concrete strength and steel strength on the progressive collapse resistance of composite joint were analyzed.The results show that compared with CFST column-RC composite beam joints,the peak bearing capacities of beam mechanism and catenary mechanism of reinforced truss composite beam joints increase by 12.5%and 10%,respectively.Since the steel bar truss can still provide tension after the yield of the lower chord steel bar,the bearing capacity of the lower flange of the steel beam can continue improving after the fracture,showing good progressive collapse resistance.The height of steel truss and the strength of steel truss mainly improve the peak bearing capacity and ultimate bearing capacity of joint beam mechanism,but have little effect on the peak bearing capacity of catenary mechanism.The strength of floor slab concrete has little effect on the bearing capacity of each stage of joint,and can reduce the ductility of joint.By comparing and analyzing the resistance index and displacement ductility index of joints under different parameters,it is found that the increases of height and strength of steel truss have beneficial effects on the ultimate bearing capacity of joints,which should be considered in engineering design and application.