Experimental Study On Shear Behavior Of Recycled Concrete T-beams

In recent years,with the development of urbanization process,the speed of building renewal has accelerated,and the demolition of a large number of old buildings and the construction of new buildings have caused the amount of construction waste to increase day by day.The promotion and use of recycled concrete can reduce environmental pollution problems while recycling waste concrete,which has extremely important practical engineering application value and huge social and economic benefits.In practical engineering,the frame beam is the component supporting the upper structure of the building,and at the same time it plays the role of bearing and transferring all the loads on the floor.It is one of the most important parts of the upper structure of the building.However,the beams with oblique sections subjected to shear failure in the structure are brittle failure without obvious warning.Due to the initial micro-cracks and large porosity of recycled coarse aggregates,the brittleness characteristics of recycled concrete beams will be more severe when shear failure occurs.Obviously,the safety of the structure is poor.Therefore,the application of recycled aggregates in actual structural engineering needs to be further studied.At present,the research on the shear performance of recycled concrete beams mainly focuses on the experimental research on the shear performance of recycled concrete rectangular beams and steel fiber partially replacing recycled concrete rectangular beams.There are still few studies on the shear performance of recycled concrete T-beams.In this paper,five recycled concrete T-shaped cross-section beams were designed,and monotonic loading tests were carried out on them under six working conditions.The failure mode and shear performance of recycled concrete T-section beams were analyzed taking recycled aggregate replacement rate,steel fiber and hoop ratio as the main parameters.Based on codes and existing theories,a modified calculation method for the inclined section shear capacity of recycled concrete beams was proposed.And compared with the results of the test results and other existing test datas,the accuracy of the modified calculation method was verified.The non-linear finite element model of each specimen was established by using ABAQUS finite element software,and its rationality was verified by comparison with test datas.The main conclusions of this thesis are as follows:(1)The use of recycled coarse aggregate did not affect the failure type of the beam.Its failure mode and crack development law were similar to those of ordinary concrete beams,and all specimens eventually showed shear failure characteristics.(2)Compared with ordinary concrete specimens,the stiffness of recycled concrete specimens was reduced,the ductility was relatively poor,but the bearing capacity did not change significantly.When the replacement rate of recycled coarse aggregate was 50%,the stiffness and deformation capacity of the specimen decreased significantly.After the ultimate load,the bearing capacity of the specimen decreased quickly,and the brittle failure characteristics was more obvious.(3)Using steel fiber or increasing the hoop ratio can improve the shear performance of recycled concrete beams significantly.The addition of steel fiber can delay the appearance and development of oblique cracks in specimens,widen the maximum oblique crack width to a certain extent,and effectively improving the brittle failure characteristics of recycled concrete specimens.With the increase of the stirrup ratio,the stiffness of the specimen increased significantly,and there was a longer load-holding stage when the load was close to the peak load,and the bearing capacity and deformability of the specimen were improved.(4)Compared with the experimental value,the error of the shear capacity calculated by the modified calculation method was small,which can provide a reference for the shear design of recycled concrete beams.At the same time,it is applicable to the shear design of ordinary concrete rectangular beams.(5)The analysis results of the finite element model established on the ABAQUS platform were in good agreement with the experiment,indicating that ABAQUS can better simulate the shear performance of recycled concrete beams.