Seismic Performance Of Cluster Reinforced Prefabricated Concrete Columns With Grouting-anchor Connections

Since the 21st century,with the acceleration of industrialization process,the prefabricated buildings have become one of the most dominating construction methods due to its characteristics of standardization of design,industrialization of production and assembly of site construction.In September 2016,the State Council promulgated the“Guiding Opinions on Developing Prefabricated Buildings Vigorously”,which set the target proportion of prefabricated building for new buildings in the next ten years,and encourage the qualified regions to boldly carry out the research on prefabricated buildings.Since then,guidance documents have been issued throughout the country,and policy support and incentives have been given.The prefabricated concrete frame structure is a commonly used structural system,in which the column,as the main vertical bearing member,bears all the vertical load and the additional load caused by the horizontal forces.It’s one of the most important seismic defense lines,whose seismic performance directly affects the safety of the whole structure.Therefore,in the new era of the development of prefabricated buildings,it is of great theoretical significance and engineering application value to carry out research on the seismic performance of prefabricated concrete column members.Supported by the national "13th Five-Year Plan" key research project "Efficient Reinforcement and Performance-based Design Theory of Precast Concrete Members"(2016YFC0701402),this paper mainly adopts the method of experimental research,numerical simulation and theoretical analysis to study the seismic performance of prefabricated concrete columns in the form of grouting-anchor connection and cluster reinforcement.The main work and achievements are as follows:(1)Considering the three factors of axial compression ratio,lap length and lap spacing,and three levels of each factor,seven prefabricated concrete columns with cluster reinforcement and three cast-in-situ columns were designed and manufactured,and the failure process and hysteretic curve of each specimen were recorded through low-cycle reciprocating loading test.The results show that all the specimens have experienced the processes of the initial cracks,crack development,vertical cracks,the foot concrete crushing,showing the bending failure mode,which is ductile failure.During the test,only some initial cracks appear at the joints of the prefabricated specimens,and the joints remain intact during the later loading process.(2)On the basis of the experiment,the seismic performance indexes such as skeleton curve,ductility and energy consumption are analyzed,and the influencing factors of the seismic performance of the cluster reinforced precast columns are analyzed by using the finite element analysis software ABAQUS.The results show that in the form of cluster reinforcement,the prefabricated concrete column specimens and the cast-in-situ specimens have comparable seismic performance;increasing the lap length within 30d(d is the diameter of the longitudinal reinforcement)can improve the seismic performance indexes,while further increasing has slight effect on it;the seismic performance indexes changes a little under different lap space.(3)Based on the experimental research and finite element expansion analysis,and referring to the calculation method of seismic flexural capacity of cast-in-situ concrete columns,the calculation formula of seismic flexural capacity of cluster reinforced prefabricated concrete columns is established,which can be used as reference for engineering design.(4)Based on the hysteresis curves measured,the three-line restoring model of cluster reinforced concrete columns were proposed by fitting the formulas of skeleton curve and the empirical formulas of unloading stiffness,which can be used as reference for relevant theoretical research.