Study On Mechanical Behavior Of The Joint Of Prefabricated Pier With Socket Connection

Based on the comparison and analysis of various connections schemes of the preassembled bridge substructure,it can be seen that the construction of the socket connection is allowed to have a larger error,the construction process is simple,and there is no need for special construction equipment compared with the sleeve grouting connection and prestressed connection.Socket connection has good seismic performance,and the construction period is similar to that of sleeve grouting.It has great application advantages and development potential.However,most of the current researches on socket connection are based on the connection between piers and spread foundation,piers and piles,and piers and strip foundation,with smaller pier section and larger ratio of depth to height(generally above 1.0).Therefore,in combination with the practical project,this thesis,by means of numerical simulation and theoretical analysis,puts forward the design method of the socket connection between pier and four pile caps with a small depth to height ratio,including the calculation of mutual force between pier and cap and the calculation of horizontal reinforcement of cap.The influence of horizontal stiffness of pier on bearing capacity of cap is also analyzed.The performance difference between socket connection and cast-in-place connection is compared.Finally,the influences of depth to height ratio,axial compression ratio,reinforcement ratio and shear span ratio on the mechanical characteristics of pier and cap are analyzed with 9 finite element models,and the design theory is verified.The main conclusions include:(1)The smaller the horizontal restraining effect of the pile on the cap,the greater the force on the steel bar at the bottom of the cap.For safety considerations,the horizontal restraining effect of the pile may not be considered when designing the reinforcement of the cap.(2)Compared with the cast-in-place connection system,the cap steel of socket connection system is more stressed,but the force displacement curves of the two are similar.It can be seen that as long as some steel bars are properly arranged in the cap of socket connection system,the socket-connecting pier columns and the integrally cast-in-place pier columns have the same mechanical performance.(3)When the depth to height ratio is 0.5,the horizontal stiffness of the pier decreases obviously,the damage degree of the cap and the joints deepens obviously,and the steel tension at the bottom of the cap increases obviously(that is,the amount of reinforcement increases),so the depth to height ratio should not be too small.Therefore,this thesis suggests that the depth to height ratio should be 0.7 and above.(4)By comparing the numerical simulation results with the theoretical calculation results,it can be seen that in most cases,the design theory proposed in this thesis is partial to safety,and the error is within the acceptable range of engineering,which has certain reference significance for engineering design.(5)The smaller the depth to height ratio or the greater the axial compression ratio or the reinforcement ratio of the pier,the greater the amount of reinforcement required by the cap.The influence of shear-span ratio on the amount of reinforcement is not obvious.