Experimental study on force condition and seismic behavior of concrete columns confined with welded reinforcement grids and multi-layer longitudinal rebar
In order to study the seismic behavior of welded reinforcement grids(WRG)columns and WRG columns with multi-layer longitudinal rebar,six normal WRG columns and ten WRG columns with multi-layer longitudinal rebar are tested under vertical compression and cyclic lateral load respectively.This experiment shows the impact of the amount and distribution of inner longitudinal rebar on the columns'capacity and seismic behavior by comparing different columns.Test results indicate that the mechanism of WRG columns is identical to columns confined with conventional stirrups.WRG can reach the yield strain point and it takes full advantage of strength of stirrups.WRG column performs better under axial force and possesses better seismic behavior.WRG can support inner longitudinal rebar effectively and make full use of rebar compressive strength,so it can satisfy the requirement of seismic ductility.Based on experimental study,the calculation method of axial load ratio for WRG columns and suggested ratio limit are proposed.Axial compressive capacity of WRG column with multi-layer longitudinal rebar is higher than the value generated by the formula.The contribution of longitudinal rebar confined by inner grids to the compressive capacity of column can be taken into consideration in the calculation of axial load ratio.