Study On Mechanical Properties Of Improved Discontinuous Reinforced Joints

With the implementation of the important western strategy and the construction of the external traffic corridor,it is urgent to build the transportation infrastructure in the high(high altitudes,high latitudes)and cold areas.The natural environment in the high and cold regions is relatively poor,the average temperature of the whole year is generally low,the time for construction is limited,and the frequent domestic strong earthquakes in recent years have suffered serious damage to the traffic lifeline.Therefore,the construction of the precast concrete joint system with rapid construction characteristics and good mechanical properties is expected to provide a new way for the rapid repair of the bridge in the high and cold areas and the disaster relief and disaster relief projects.In this paper,the design steps and the configuration criterion and the strength checking method of the strut-and-tie models are introduced,the concept of improved discontinuous reinforced joint with rapid construction characteristics for connecting prefabricated components is proposed.And a strut-and-tie models which can reflect the mechanical properties of improved discontinuous reinforced joints is established.Static bending tests are carried out for six specimens of discontinuous reinforced joints with different structural parameters.Based on the data of ultimate bearing capacity,curvature,deflection and reinforcement strain,the optimal improved discontinuous reinforced joint parameters are determined.The finite element numerical model is used to analyze the test model,and the results of the strut-and-tie models and the finite element numerical simulation and the test are verified and analyzed.On the basis of validating the finite element numerical model,parametric analysis is carried out.The analysis shows that the strut-and-tie models can truly reflect the mechanical properties of discontinuous regions,and the calculation result is the lower limit value of the ultimate bearing capacity of the discontinuous structure,and it is safe and reliable.The structural performance of improved discontinuous reinforced joints is related to the laplength and spacing of reinforcement.The shorter the reinforcement spacing,the smaller the lap length can provide enough anchorage bearing capacity,and can significantly improve the ultimate bearing capacity.The improved discontinuous reinforced joints with 152 mm length and spacing is the best parameter,which can meet the structural bearing capacity and ductility requirement.The strength grade of the joint,the structure of reinforcing bar and joint type have little influence on the mechanical properties and failure modes of the prefabricated component,and the double-layer transverse lap reinforcement can significantly increase the ultimate bearing capacity,but it has no effect on the cracking load.The improved discontinuous reinforced joints can provide sufficient ultimate flexural capacity to ensure effective load transfer between adjacent prefabricated components,and provide a improved connection system for the precast concrete structures with rapid construction characteristics.