铝合金桁架桥梁大偏心节点连接受力性能分析与设计优化

Mechanical Performance Analysis and Design Optimization of Large Eccentric Joints of an Aluminum Alloy Truss Bridge

为研究铝合金桁架桥梁大偏心节点连接受力性能,以一座大偏心节点连接的铝合金人行桁架桥为例,结合有限元模拟和理论计算方法,研究节点大偏心对桥梁结构位移、构件应力及节点连接承载力的影响。结果表明:偏心次弯矩的存在导致桥梁结构位移增大15.9%,节点各连接构件的应力均大幅增加,其中近梯道处的桁架节点受到构件连接偏心次应力的影响较大,最大增加101.8%。节点处各连接构件的应力理论值与节点偏心模型计算结果较吻合。依据规范验算桁架桥连接节点的承载能力,发现节点大偏心和连接件截面及螺栓直径会导致4处节点的螺栓抗剪验算和孔壁承压验算不满足规范要求。通过节点设计优化对比分析,发现大偏心连接节点采用减小节点偏心措施可使其节点设计达到规范要求,而增大螺栓直径和连接构件截面可有效提高螺栓抗剪和构件承压承载力。

To study the mechanical performance of large eccentric joints of aluminum alloy truss bridges,an aluminum alloy pedestrian truss bridge with large eccentric joints was taken as an example to analyze the effect of large eccentricity of joints by use of finite element method and theoretical method.Structural displacement,stress of connecting members,and bearing capacity of joints were all studied.The results show that the effect of eccentric secondary bending moment leads to a 15.9%increase in the structural displacement of the bridge.The stress of each connecting member of joints increase significantly,with the maximum increase of 101.8%in the truss joint near the stairway.The theoretical stress of each connecting member at the joints is in accordance with the calculation results of finite element model.Bearing capacity of the connection joint was checked according to the Chinese code,and it was found that the bolt shear bearing capacity and hole wall bearing pressure of 4 joints did not meet the requirements under design loads.Through comparison and analysis of joint design optimization,it is found that the joint design can meet the code requirements by adopting measures to reduce the joint eccentricity,while increasing the bolt diameter and the cross section of the connecting members can effectively improve the bolt shear resistance and member bearing capacity.