Response Of Blind-bolted Angle Connections With Concrete-filled Steel-tubular Column Against Earthquake

As a new structure system,concrete-filled tube structure has the advantages of high bearing capacity,good anti-fire performance and convenient construction,and thus it has good application prospect in engineering.However,the difficulties associated with the lack of access for the installation of conventional bolts have often hamper the research and design of bolted connections to tubes.This requires the development of new bolts to connect the joints of the steel tube structure,thus resolving the problem of the traditional bolts needing to be tightened on both sides.Therefore,a special bolt system named blind bolt has provided the development of a new bolted connection alternative.However,the static performance and the seismic behavior of blind-bolted angle connections with concrete-filled steel-tubular column is still unknown,and it is an urgent need to study and develop the promotion of this new type of joint.In this paper,the static performance and seismic behavior of the blind bolted joints to concrete-filled steel tubular columns are examined by experimental and theoretical investigation.The failure modes of the connections under static and cyclic loading are revealed,and the main factors influencing the connection bearing capacity are analyzed.The main research work and conclusions are summarized as follows:(1)Four concrete filled steel tubular column-H steel blind-bolted and improved blind-bolted angle connections were tested under static loading.The influences of different parameters on static performance of the connections were investigated,including the type of bolt,angle thickness and addition of web angles.Meanwhile,the obtained experimental results are the basic data for the subsequent low cyclic loading tests.(2)Four concrete filled steel tubular column-H steel blind-bolted and improved blind-bolted angle connections were tested under low cyclic loading.The influences of different parameters on seismic behavior of the connections were investigated,including the type of bolt,angle thickness and addition of web angles.The key seismic performance indexes were studied by analyzing the flexural bearing capacity,strength degradation,stiffness degradation,ductility and energy dissipation.(3)Based on the component-based method,a three-parameters simplified model is presented for calculating the moment-rotation curves of blind-bolted and improvedblind-bolted configurations.The calculation results were in good agreement with the experimental results,which can provide reference for engineering practice.