Seismic Performance Of The Precast Concrete With Debonded Longitudinal Reinforcements

With the development of the industrialization of the precast building and the urbanization process,the precast low or multistory buildings are in an important role on the construction of the urbanization.The independent foundations connected with the grouted precast concrete columns used corrugated sleeves can be popular used as one of the most popular foundation types in the low or multistory buildings.In addition,it is important for the improvement of the ductility and energy dissipation of the precast concrete columns by the debonding of the longitudinal reinforcements of the precast columns,with the reason that the debonding of the precast column longitudinal reinforcements can change the distribution of the strains of the concrete and inforcements on the plastic hinges.However,there are little information about the researches on the seismic performances of the precast concrete columns with debonded longitudinal reinforcements,which grouted in the independent foundations with the corrugated sleeves.In this paper,the researches on the influences of the seismic performances of the precast concrete columns by the debonded longitudinal reinforcements on the independent foundations were conducted.The main efforts and results are listed as following:(1)10 precast concrete columns grouted in the independent foundation with the corrugated sleeves were designed to conduct the test of the seismic performance under low cycle loads.The failure modes of the precast concrete columns with the debonded longitudinal reinforcements on the independent foundations were investigated.The results of the test indicate that the crack damange of the foundation were mainly occurred on the specimens that the lengths of the grouted connections are 10 d.However,the flexural damage of the columns was occurred on the other specimens.The development of the cracks of the footing of the column was decreased with the increase of the debonded length of the longitudinal reinforcements.In addition,the development of the cracks was less when the debonding location of the longitudinal reinforcements is on the top of the interface of the foundation than the other debonding locations.(2)The seismic performance in terms of the hysteretic loop,ductility,energy dissipation,flexural deformation,and residual deformation of the columns with debonded longitudinal reinforcements were analyzed,considering the parameters of the axial index,the grouted length of the longitudinal reinforcements,the debonding length of the longitudinal reinforcements and the debonding location of the longitudinal reinforcements.The results of the test indicate that the improvement of the ductility and flexural deformation are larger when the axial index is smaller or the debonding location is in the top of the interface of the foundation.However,it is smaller for the improvement of the energy dissipation.Besides,with the increase of the length of the debonded longitudinal reinforcements or the length of the grouted longitudinal reinforcements,the residual deformation is increased,but the flexural deformation is little influenced.Compared with the other debonded locations,the residual deformation is largest when the debonded location is on the half of the interface of the foundation.(3)The mechanical model of the region of the grouted connection on the climacteric states,which the independent foundation will be cracked,was created,and the analized methods and calculated formula of the climacteric length of the grouted connection were proposed,which had been proved by the test results in its applicability.Besides,the influence of the climacteric length of the grouted connection by some parameters were studied in theory.