Experimental Study on Influence of a Grout Layer Between an End-Plate and a Column on Seismic Behavior of End-Plate-Connection RCS Joints

To study the influence of a grout layer between an end-plate and a column on seismic behavior of end-plate-connection RCS joints, we conducted a test in which four end-plate-connection RCS joints were put under cyclic loads with grout layers of different thicknesses and strengths between an end-plate and a column with pretension in a bolt.Based on experimental data, we analyzed failure modes, hysteresis behavior, bearing capacity, stiffness degradation law, ductility, energy dissipation capacity, and deformations of the joints.The test results indicate that end-plate-connection RCS joints that are designed according to the strong column-weak beam concept show a typical plastic-hinge failure mode at the end of the steel beam.Partial crushing of the grout layer was observed during the test.Throughout the test period, the connection among the end-plate, grout layer, and column was tight and no slippage was observed.The connection and transmission forces of the end-plate-connection RCS joints were reliable and showed good structural behavior.Each specimen exhibited good seismic behavior and had shuttle-shaped hysteresis curves.The plastic-hinge deformation at the end of the beam resulted in good energy dissipation capacity.The accumulation of damage to the grout layer between the end-plate and the column under cyclic loads resulted in reduced ductility and energy dissipation at the joints, and when damage to the ground layer was considerably serious, the ductility and energy dissipation of the joints decreased rapidly.Stiffness degradations of each specimen were almost the same, and the accumulation of damage to the grout layer accelerated the stiffness degradation of the joints.Deformations of the joints were mainly caused by the steel beam, and the rotation of the end-plate was small throughout the test period.When rotation failures occurred in specimens RCS1, RCS3, and RCS4, the ratios of the deformation caused by the rotation of the end-plate to the total deformation were 1.5%, 1.8% and 2.7%, respectively.The bending moment-rotation curves of each specimen show obvious nonlinear characteristics. Specimens RCS1-RCS4 are categorized as having semi-rigid connections.The initial rotational stiffness of joints improves when the thickness of the grout layer increases, but the range of improvement is limited. © 2020, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.