钢-混凝土组合梁扭转的组合作用分析

在试验及理论分析的基础上,对开口截面钢-混凝土组合梁在扭转中的组合作用进行研究。组合梁在扭转中,即使是纯扭作用下,截面上仍存在组合作用,分析时不能忽略混凝土翼板和钢梁间的相互约束作用,否则会低估组合梁的抗扭能力。钢梁自身的抗扭作用很小,钢梁对组合梁扭转的贡献在于,它向混凝土翼板提供了纵向约束。在钢筋混凝土变角软化桁架模型(RA-STM)的基础上,通过引入平截面假定,以考虑组合梁扭转中的组合作用,建立适于分析开口截面钢-混凝土组合弯扭性能的三维桁架模型:在弯扭作用下,组合梁截面各单元分别处于一维应力状态(体系1)和二维应力状态(体系2),体系1用来抵抗由弯矩和扭矩引起的截面纵向应力,体系2用来抵抗由扭矩引起的截面剪应力,两者通过截面的纵向应变协调和内力平衡条件联系起来。所分析内容充分满足平衡条件、变形协调条件和材料本构方程。计算结果与试验结果吻合良好。此外还简要评价了现有的组合梁极限扭矩计算公式的不足。

ANALYSIS OF COMPOSITE ACTIONS IN STEEL-CONCRETE COMPOSITE BEAMS SUBJECTED To TORSION

A study was conducted to investigate the composite action in steel-concrete composite beams subjected to torsion.Tests and analysis showed that the composite action definitely existed under torsion.It would underestimate the torsional strength of composite beams if the interaction was neglected between steel beams and concrete flanges.Steel beams play a vital role in restraining concrete flanges from deforming longitudinally.A three-dimensional behavioral truss model capable of analyzing composite beams sections subjected to combined bending and torsion is presented.It is based on the rotating-angle softened truss model(RA-STM) and assumes that plane sections remain plane to account for composite actions.In this model,the section is assumably subjected to one-and two-dimensional stresses separately.The former is resisting the longitudinal stresses due to bending and torsion,while the latter is resisting the shear stresses due to torsion.Links between the two systems are compatibility of strains and equilibrium of stresses in the longitudinal direction.It satisfies the equilibrium equations,compatibility equations and the constitutive laws of materials.Through analyzing several specimens available in the literature the results predicted by this method are in good agreement with those obtained from tests.In addition,a reported formula is appraised.