| Composite beam is an important component of prefabricated structure.Due to the existence of post-pouring composite surface,its force and damage are more complex than cast-in-place components.At present,there are relatively few research results on the damage mechanism of composite beams at home and abroad,so it is necessary to carry out special research on the damage mechanism and damage assessment.Through the static load test of composite beam and cast-in-place beam with different stirrup ratio,the effect of stirrups on the damage of composite beam is analyzed.The results show that compared with the cast-in-place beam,the yield load and peak load of the composite beam are reduced by more than 20%,and the shear failure occurs more easily.Once the composite beam is cracked,it is easy to produce penetrating cracks,and increasing the hoop ratio has no obvious effect on the bearing capacity of the composite beam.However,it can make the crack distribution of the steel bar at the bottom of the beam more uniform,reduce the maximum crack width,increase the later stiffness,and greatly improve the ductility at the same time.It is easy to cause shear failure that the strain of stirrups in composite beams is larger than that of cast-in-place beams.Due to the existence of composite surface,the strain at different positions of the same stirrups is also different,resulting in damage differences.The static load simulation of the composite beam is carried out by using Abaqus,and the numerical value and phenomenon of the simulation results can be compared with the test,and then the quasi-static simulation is carried out on the basis of this model.By quasi-static simulation with Abaqus,the damage of composite beam can be divided into three stages: elastic stage,elastic-plastic stage and plastic stage.As the cycle increases,the damage begins to accumulate,and the stiffness and bearingcapacity continue to decrease.Different structural forms are "consistent" with the degradation of stiffness and bearing capacity.The mechanical degradation and seismic behavior of composite beams with different stirrup ratio,reinforcement ratio and concrete strength are investigated.The results show that increasing the stirrup ratio mainly improves the ductility of members,increases the yield load,peak load and early stiffness,reduces the degradation rate of bearing capacity,and reduces the degradation coefficient during failure.Increasing the strength of concrete is less likely to increase the yield load and peak load,but advance the peak load.Modify the damage formula,calculate the damage value of each stage,and select the appropriate damage range as the damage evaluation of the composite beam,which can be used as a reference for the reinforcement work. |
