Experimental and numerical studies on composite structures under lateral cyclic loading: precast l-plate encased composite columns and wide U beam-column joints

Due to several advantages like the requirement of less construction time and labor works for installation and removal of formworks, enhanced quality of construction etc., composite structural components are being used extensively by the construction industry. Composite structures in this study refer to structures comprising precast components that will later be infilled with cast-in-place concrete. The precast components perform as the permanent formwork while casting the cast-in-place concrete and become parts of the final structural component of the system after the cast-in-place concrete is hardened. Two composite structural systems were studied: L-shaped precast plate encased composite column and post-tensioned composite wide U beam-column joint systems. In this research, a study on the seismic behavior of composite structures was performed based on numerical simulations and experimental studies. The study on selecting a suitable concrete material model and contact algorithm was performed to depict composite structures' behavior by simulating the composite columns available in the research database. With the verified modelling concept, the performance of the L-shaped precast plate encased composite column was investigated. Also, some modifications were suggested to enhance the interface shear strength between the outer precast encasement and inner cast-in-place core concrete to achieve composite action. The modelling concept verified from the numerical study of composite columns was also adopted to study the behavior of full-scale L-shaped precast plate encased composite column and modified wide beam-column exterior and interior joint systems. Extensive numerical studies were performed to investigate the effects of spandrel beam and confining transverse tendons on seismic upgrading of composite full-scale wide beam-column exterior and interior joints.Moreover, this study reports an experimental investigation performed to explore seismic performance comparison of two half-scale wide beam-column interior joint systems. The two tested interior joints include one control and another modified, of which the latter is an improvement of the control with the addition of spandrel reinforcement in the joint core and confining transverse tie bars. Hence, the seismic behavior of composite structures comprising of a composite column and composite wide beam-column joint was studied in this research. Finally, the seismicity of Thailand was explored, and an L-shaped precast plate encased composite column, and precast wide U beam-column joint systems which are suitable for all seismic zones of the country were proposed. From the simulation results, continuous surface cap (MAT_159) and kinematic plasticity (MAT_003) material models were found suitable to model concrete and reinforcement for analyzing the behavior of RC structures subjected to lateral cyclic loading. Moreover, a numerical model using the tied with failure (tiebreak) contact algorithm could capture the test results of the tested composite columns with satisfactory accuracy. With this modeling approach, numerical studies of the L-shaped precast plate encased composite columns and the full-scale wide beam-column joint systems were performed. The numerical model could capture the test results of the L-shaped precast plate encased composite columns and the half-scale wide beam-column joints. Hence, depending on the severity of the seismic hazard and soil site conditions in various regions, the proper L-shaped precast plate encased composite columns and wide beam-column joint models proposed in this study are suggested for each location in Thailand. The composite control column and joint model were found to be safe only in regions with very low seismicity, even on soft soil sites. However, the modified composite column and joint models could be adopted depending upon the levels of seismicity and soil site conditions. Therefore, it can be concluded that the proposed modified composite columns and wide beam-column joint systems can be used for all seismic zones in Thailand.