Experiment And Simulation On Mechanical Properties Of Reinforced Concrete Beams And Frames With Kinked Rebar And Weak Links

In the actual earthquake damage,it is found that due to the contribution of the floor slab to the bending capacity of the beam and the influence of the super reinforcement,the frame is often difficult to form the mechanism of "strong column and weak beam",which is easy to form the collapse of the structure.The kinked rebar is a new method of artificial plastic hinge designed by relevant researchers recently,and which is bent three times through the linear reinforcement to form an inverted "V" shape and is arranged at the reverse bending point of the frame beam.It can effectively weaken the flexural bearing capacity of the beam end and make the structure first form plastic hinge at the kinked section under earthquake to meet the requirements of "strong column and weak beam".At the same time,in the process of the kinked rebar straightening,the frame beam obtains greater rotational deformation capacity and shows better energy consumption capacity.However,due to the small bearing capacity at the initial elastic stage of the kinked rebar,it may be difficult to meet the requirements of "no damage in small earthquake" and limit the normal use of beam.At the same time,under the action of moderate earthquake,the plastic development of the wave initiation section is relatively large,which makes it difficult to strengthen and repair in the later stage.Therefore,the following research is made in this paper:The optimization design of the original kinked rebar is carried out.By welding a linear rebar which weaker than the straight section of kinked rebar and the relevant uniaxial tensile test results show that: the design can effectively improve the initial elastic stage of the kinked rebar and meets the requirements of " no damage in small earthquake" and the normal use at limit state;at the same time,through the constraint of weak link to the kinked rebar,improving the stress level of kinked rebar in the process of straightening and delaying its straightening speed,so that it can meet the requirements of "moderate earthquake repairable".The four point bending static loading test is carried out on reinforcement concrete beam with new type of kinked rebar.The results show that the new type of kinked rebar undergoes the whole process of weak link fracture and then kinked rebar straightening in the beam.The beam still has good rotational deformation ability,and the plastic hinge is still concentrated on the kinked section.By setting the weak link,the bearing capacity at the initial elastic stage of the beam can be improved,the initial crack generate later and the crack width can be reduced.At the same time,the growth rate of the deflection of the beam can be slowed down during the straightening process of the kinked rebar.ECC is applied to the beam with kinked rebar to change the distribution of the beam cracks.The test results show that the RC / ECC composite form can also improve the bearing capacity at the elastic stage.At the same time,the better crack dispersion ability of ECC is used to avoid the wide crack at the section of kinked rebar and decrease concentrated crack at several bending points of kinked rebar in the early stage and then it can meet the requirement to the width of crack at limit state of normal use.Through ABAQUS finite element software,the uniaxial tensile test and beam static load test of the new type of kinked rebar are analyzed,and the analysis of relevant influencing factors is supplemented.The results show that the finite element analysis results are relatively consistent with the test results,which has certain reference value.In the early stage,scholars mainly focused on the mechanical properties of the components with kinked rebar,but few on the dynamic characteristics of the structure with kinked rebar.In this paper,ABAQUS finite element software is used to build the frame model,and the dynamic elastoplastic analysis of the frame is carried out.The results show that the kinked rebar can realize the transfer of plastic hinge,making the structure easy to form "strong column and weak beam".At the same time,the energy consumption capacity of the structure is more excellent.