Experimental Research On Lap Length Of Steel Restraint Grouting-anchoring Lap Considering Corrugated Pipes

Restraint grouting-anchoring lap,which is a common method of precast concrete structure connection,belongs to an indirect connection.But the long lap length results in large connection area and removing the mandrel tube during production process of component resulting the bigger pore forming error and hard guarantee of construction quality.Therefore,this research group developed a new connection method applied in precast concrete structures,that is restraint grouting-anchoring lap considering the combination of corrugated tube.The author carried out quasi-static experiments of 4 precast shear wall specimens considering the combination of corrugated tube.Studied the influence of vertical rebar lap length in the corrugated tube on precast shear walls with indirect lap on vertical rebars from bearing capacity,ductility,etc.At the same time,shear wall specimens with different lap lengths are simulated by ABAQUS software.Study indicates that:(1)The failure modes of assembled shear wall specimans considering the combination of corrugated tube are basically the same,that is the vertical rebars of edge member are tensially yield and the bottom concrete crushed;There are some horizontal cracks above the corrugated tube and fully developed.The ultimate broken positions of the specimens are all above the bottom beams,which mean vertical steels with corrugated tubes of precast shear walls can transmit stresses effectively.(2)The bearing capacities of two specimens with 0.7 vertical lap lengths are basically the same with the specimens with 0.9 vertical lap lengths,which means the impact to reduce the lap length of corrugated tubes is negligible.(3)In test conditions,the limit displacement angles of precast shear walls with restraint grouting-anchoring lap considering the combination of corrugated tube meet rule in the GB50011-2010 code for "seismic design of buildings" that is the elastoplastic displacement angle need to be over 1/120 of shear wall structures under strong earthquakes,and ductility factors of precast shear wall specimans with corrugated tube are bigger than 4,which represents good ductility.Ductility factors of specimans with 0.7 lap lengths are bigger than the ones with 0.9 lap lengths under the same axial compression ratio.(4)The failure modes and the overall trends of skeleton curves of specimens are similar to test resaults,which prove the feasibility of the constitutive relation and simulation method.Therefore,simulation tests of lap length with expanded parameters have been done to study the influences of 0.4laE,0.5laE,0.6laE,0.7laE,0.9laE,1.1laE on seismic performances of precast shear walls.Comprehensive construction and safety factors to consider,consider corrugated pipe combination constraint pulp anchor bar connection of shear wall vertical connection 0.7 times the lap length recommended lap length is more appropriate.(5)Preliminarily determine the longitudinal reinforcement lap length expression by grouting anchor connection:l1,=?1?2laE,perfect the precast concrete structure design codes and provide a basis for the engineering application.