Study On Mechanical Properties Of Residual Load After Lateral Impact Of Steel Reinforced Concrete Column

The embedded cross-sectional steel-concrete composite structure has been widely used in high-rise structures,bridges,subway platforms and other engineering structures because of its excellent load-bearing properties,high ductility and high energy consumption.In recent years,the research on the mechanical properties of embedded cross-sectional steel-concrete composite members has also received widespread attention from scholars.In addition to static loads and dynamic loads such as seismic and wind loads,such structures are subjected to incidental loads,including impact,during service.With the increasing popularity of transportation,accidents of impacting structures can be caused by aircraft,ships,vehicles and trains.As structural loadbearing columns,embedded cross-sectional steel and concrete members are also subject to impact,which can lead to collapse of the structure if the damage is severe.In the case of factories,laboratories and other structures,the impact of the elements on the structural columns can be caused by mishandling of the elements during lifting,but the impact is minor and usually ignored,but the damage to the structural columns will be accumulated in the long run,and the safety of the structure will be reduced if other natural loads such as earthquakes occur.Therefore,the evaluation of the residual bearing capacity damage of embedded cross section steel and concrete columns after impact is particularly important and of great significance to the engineering practice.The purpose of this paper is to investigate the mechanical characteristics of the embedded cross section steel and concrete composite column under lateral impact and its residual load carrying capacity after impact.The main work is as follows:(1)Lateral impact tests on steel and concrete specimens were carried out under a super heavy-duty drop hammer testing machine.Firstly,the test design of concrete members with embedded cross sections was carried out,followed by detailed analysis of the impact process,deformation pattern,force and displacement curves,energy dissipation curve and axial force curve during the test,and finally,the dynamic response of the impacted specimens under different factors(impact speed,boundary conditions and axial pressure ratio)was investigated.(2)Refined finite element modeling of concrete members with embedded crosssectional steel under falling hammer impact was established using the finite element software ANSYS/LS＿DYNA.Firstly,the effects of material rate effect,contact,mesh sensitivity analysis and boundary conditions on the test results are considered,secondly,a coupled axial force-impact model is established,and the reliability and feasibility of the numerical model of the article is verified by this test and other classical tests,and finally,the whole process of its impact,damage pattern and energy dissipation are specifically analyzed.The impact energy,axial pressure ratio,boundary conditions,material strength and impact location on the impact response are investigated using the numerical model,and the load holding process of the embedded section concrete specimen is also analyzed in detail.(3)Immediately after the impact test,an experimental study of the axial compression bearing performance was carried out.The calculation and acquisition of the residual bearing capacity after axial compression were analyzed,and the deformation pattern and residual bearing capacity-displacement curve of the specimen were obtained through experimental investigation with the impact energy,axial compression ratio and boundary conditions as parameters.Based on the finite element software,a finite element model of the residual bearing capacity of the concrete member with embedded cross section steel after impact with falling hammer is established.The model considers the effects of strain rate effect of material,contact,mesh sensitivity analysis,boundary conditions,etc.on the test results,and the reliability and feasibility of the numerical model of the article are verified by this test and other classical tests,and the effects of impact energy,axial pressure ratio,boundary conditions,material strength and The influence of impact energy,axial compression ratio,boundary conditions,material strength and impact location on the residual bearing capacity is investigated,and the formula for calculating the residual bearing capacity is proposed through multiple linear regression fitting.(4)On the basis of the study of first small size column,the effect of size effect on the load carrying performance is studied.Firstly,the finite element modeling of large size column is carried out by software,secondly,the deformation pattern,force curve,displacement curve and residual bearing capacity-displacement curve of large size column are analyzed,and finally,the damage evaluation criterion and damage evaluation level are proposed through the impact process study,which can quickly identify the damage of section steel and concrete column under lateral impact and whether it can continue to be used in the structure,and provide reference basis for other load-bearing members in engineering structure in This will provide a reference basis for the identification of damage and reinforcement maintenance of other load-bearing elements in engineering structures after lateral impact.