Research On Behavior Of Lightweight Aggregate Concrete Filled Thin-walled Steel Tube Columns Under Compression

Lightweight aggregate concrete filled thin-walled steel tube(LACFTST)is a special composite structure formed with the development of building materials.This structural system has many advantages,such as lightweight-high strength,fine plasticity and toughness,excellent economic benefits and so on.Therefore,this structure system has a broad application prospect in engineering practice,especially in multi-low-rise buildings.But so far,the research on lightweight aggregate concrete filled thin-walled steel tube is still less and related specification or regulation have not been completed.Therefore,it is necessary to carry out experimental and theoretical research on the mechanical properties of this structural system.Mechanics analysis of lightweight aggregate concrete filled thin-walled circular steel tube columns under compression is carried out by experimental method and finite element numerical simulation in this paper,which is summarized as follows.In this paper,four LACFTST axially compressed short columns,twelve LACFTST eccentrically loaded short columns and four axially compressed medium long columns were designed by using steel ratio,strength of core lightweight aggregate concrete,confinement index,slenderness ratio and eccentricity as the basic parameters.The failure process and failure mode of each specimen are analyzed by experiments.The load-deformation curves and load-longitudinal(circumferential)strain curves of specimens are studied.Discuss the influencing factors of strength enhancement coefficient of core lightweight aggregate concrete.The factors which affect the ultimate bearing capacity of specimens were analysed.Discuss the applicability of relevant literature and code for concrete filled steel tubular(CFST)at home and abroad for calculating the ultimate bearing capacity of LACFTST columns.It is found that the existence of core lightweight aggregate concrete delays the local buckling deformation of thin-walled steel tube during the compression process of thin-walled circular steel tube lightweight aggregate concrete columns,and thin-walled steel tube can also improve the compressive performance and brittleness characteristics of lightweight aggregate concrete.The failure modes of the axially compressed and eccentrically compressed short columns are strength failure,while those of the axially compressed medium-long columns are elastic-plastic instability failure.In addition,in this paper,the load-strain relationship and load-displacement relationship curves of some specimens were numerically simulated by finite element analysis software ABAQUS.Then the influence of strength grade of core lightweight aggregate on the mechanical properties of thin-walled steel tube lightweight aggregate concrete columns is analyzed.The longitudinal displacement,lateral displacement,ultimate bearing capacity,stress of thin-walled steel tube and principal compressive stress of lightweight aggregate concrete obtained by numerical calculation are compared with the corresponding test results,the applicability of ABAQUS to study the mechanical properties of lightweight aggregate concrete filled thin-walled steel tube columns is verified.