双幅桁架组合梁空间受力研究

Analysis of Spatial Mechanical Performance of Double-Span Truss Composite Beams

双幅桁架组合梁是通过横向联结系将A,B两个单幅桁架组合梁连接到一起组成新结构,为了了解该组合梁的受力性能、变形能力、破坏机理以及各个杆件的内力分布规律等,设计并制作试件,通过对试验梁A幅静力加载试验,分析其位移、沿截面高度纵向应变、混凝土板顶纵向应变、斜腹杆轴向应变以及横向联结系轴向应变随荷载的发展变化。通过ABAQUS有限元分析软件建立相同试件模型并且后处理,比较试验研究成果,验证模型的合理性。研究表明,施加单幅对称荷载时该组合梁具有良好的承载能力和变形能力;破坏形态为A幅弯曲破坏的同时伴随着受拉腹杆节点的冲剪破坏,B幅仅斜腹杆受轴力且影响较小;剪力滞系数在梁肋处达到峰值,说明梁肋处应力分布最不均匀,系数纵向影响范围只位于加载点附近,变形集中于中间区域;下弦杆除了承受轴向力,弯曲效应对杆件的受力影响较大,不容忽视。

A double truss composite beam is a new structure that connects two single truss composite beams A and B through a transverse connection system.In order to understand the mechanical performance,deformation capacity,failure mechanism and internal force of each member of the composite beam distribution rules,etc.Design and make test specimens.Through static loading test of A beam of test beam,its displacement,longitudinal strain along the cross-section height,longitudinal strain at the top of concrete slab,axial strain of oblique webs,and the axial direction of transverse coupling system were analyzed.Strain changes with load development.The same specimen model was established and processed by ABAQUS finite element analysis software,and the experimental research results were compared to verify the rationality of the model.The research shows that the composite beam has a good bearing capacity and deformation capacity when a single symmetrical load is applied;the failure mode is A-frame bending failure accompanied by punching and shear failure of the tensioned web rod nodes,and B-frame only oblique web rods receive the axis The force has a small effect;the shear lag coefficient reaches its peak at the ribs,indicating that the stress distribution at the beam ribs is the most uneven.The longitudinal influence range of the coefficients is only near the loading point,and the deformation is concentrated in the middle region.In addition to the axial force of the lower chord The bending effect has a greater influence on the force of the rod,which cannot be ignored.