The Finite Element Analysis On Cast In-situ Reinforced Concrete Frame Structure With Construction Joints

Construction joints require the setting location due to the stopping in the construction process of the concrete.The construction joint is usually a weak position,which impresses the horizontal seismic behavior.Therefore,it is extremely necessary to implement the experiment and theoretical studies for the frame structure with construction joints.Based on the project of Dalian Urban and Rural Construction Committee Scientific Item"Setting Location and Treating Methods of Cast in-situ Reinforced Concrete Frame Structure with Construction Joint,the structural laboratory of Dalian University of Technology has finished the pseudo static test of 13 frame columns with construction joints and monolithic cast columns.The pseudo static test presents the analyses with respect to the influence of the axial compression ratio and the construction quality of construction joints on the seismic behavior of columns.Additionally,the pseudo static test with respect to the two-storied and two-bay reinforced concrete frame with construction joints has also been completed,which investigates the influence of construction joints on the overall structure performance.According to the test of low reserved cyclic loads for the reinforced concrete,the nonlinear finite element method analysis of monolithic cast columns without construction joints and cast column by stages with construction joints are presented in this thesis.The tradition beam column construction contains a great quantity of concentrated reinforcements.Meanwhile,the separated simulation method used in the aforementioned structure is extremely complicated,and the monolithic-type modeling cannot extract the distribution of internal force for the single reinforcement.Based on the principle of the combined-type modeling as well as the second development for ANSYS,this thesis will present a combined-type modeling of reinforced concrete under consideration of the bond slip,the present model can be generated by using APDL language automatically.Comparing the numerical results and experimental results,the accuracy and reliability of the numerical analysis are verified,which involves the selection of the element and material constitutive,the constraint and load settings together with the modeling scheme of the reinforced concrete.Based on the nonlinear finite element method analysis of monolithic cast columns,the contact element is adopted to model the construction joint under low reserved cyclic loads in this thesis.The influence of the axial compression ratio and material parameters of joints on the seismic behavior of the single column has also been considered.Comparing the failure characteristics,hysteretic loop curves,stiffness degeneration of the single column with experimental results,the rationality and reliability of the selected construction joints element are verified.The nonlinear finite element method analysis of two frame structures based on the numerical analysis model and parameters of the single column,which one is constructed by the monolithic cast,the other is constructed by the staging cast with construction joints.The stirrup and Longitudinal bar are modeled by the monolithic-type modeling and the combined-type modeling respectively,and the bond slip between the Longitudinal bar and the concrete is considered.The hysteretic characteristics,strength and stiffness degradation for the overall structure as well as local stress,crack distribution,reinforcement slip and plastic development in the vicinity of construction joint are tested under low,medium,high axial compression ratio.Different treatments of construction joints can reflect by modifying the contact element parameters such as material cohesive force,interfacial friction coefficient etc.Moreover,the influence of different quality of the construction joint on the structural mechanical behavior are compared with the experimental results,which proves accuracy and reliability of the nonlinear finite element numerical modeling scheme.The present model can provide a reference for considering construction joints with different setting location,the numerical modeling of new-to-old concrete interface and the modeling of the reinforced concrete.by the staging cast with construction joints.The stirrup and Longitudinal bar are modeled by the monolithic-type modeling and the combined-type modeling respectively,and the bond slip between the Longitudinal bar and the concrete is considered.The hysteretic characteristics,strength and stiffness degradation for the overall structure as well as local stress,crack distribution,reinforcement slip and plastic development in the vicinity of construction joint are tested under low,medium,high axial compression ratio.Different treatments of construction joints can reflect by modifying the contact element parameters such as material cohesive force,interfacial friction coefficient etc.Moreover,the influence of different quality of the construction joint on the structural mechanical behavior are compared with the experimental results,which proves accuracy and reliability of the nonlinear finite element numerical modeling scheme.The present model can provide a reference for considering construction joints with different setting location,the numerical modeling of new-to-old concrete interface and the modeling of the reinforced concrete.