Experimental Study On Dynamic Response And Protection Of Compressed Steel Tubular Members Under Lateral Impact Load

Steel members are widely used in various fields because of their high strength,high ratio of strength to weight,good plasticity and toughness.As the simplest section form of steel members,steel tubes are widely used.Compared with the traditional concrete members,the steel members have lighter self weight,once they are damaged by impact,the damage degree will be more serious.At present,most of the impact tests of steel members do not consider the follow-up effect of axial pressure on the failure process of members,the influence of preload on impact failure is considered in a few experimental studies.Therefore,it is very important to study the dynamic response and protection of steel members and their derivatives under the impact load.In this paper,the test method is used to study the dynamic response and protection of compressed steel tubular members under lateral impact load.In order to achieve the follow-up effect of the axial pressure in the impact process,the impact device,axial pressure device and guide device needed for the test are designed,the parts of each device are supervised and manufactured,the test platform is installed and built,the test scheme is formulated,and the pendulum impact test is carried out.In this paper,the dynamic response of the compressed steel tube under the transverse impact load is studied;the energy consumption effect of the compressed steel tube with XPS board and wood board composite structure is compared with that of the unprotected compressed steel tube;the energy consumption mechanism of the concrete filled steel tube under the transverse impact load is analyzed.The main research results of this paper are as follows:1、From the process,phenomenon and results of three groups of tests,it can be found that the designed platform can better achieve the follow-up effect of axial pressure in the process of specimen impact.The experimental results show that the failure effect of axial pressure in the process of specimen impact can not be ignored.2、During the manufacture and installation of the specimen,there are defects such as welding residual stress and initial eccentricity.When the impact energy is small,the specimen does not lose stability under the action of axial pressure;when the impact energy is increased,the eccentric bending moment is generated under the action of axial pressure.When the eccentric bending moment exceeds the ultimate bending moment of the specimen,the specimen is crushed,and the instability occurs,and the plastic hinge will be formed instantly.The failure of the specimen shows in-plane instability.3、In this paper,the dynamic response of compressed steel tube under lateral impact load is studied.The results show that:The ultimate failure deformation of the specimen is the result of the combined action of impact energy and axial pressure,but the effect can be divided into primary and secondary.When the axial pressure is small,the ultimate failure of the specimen is mainly determined by the impact energy,followed by the axial pressure;when the axial pressure is large,the ultimate failure of the specimen is mainly determined by the axial pressure,followed by the impact energy,the critical value of axial pressure is between 30%and 40%of Eulerian load.In the process of impact,the axial pressure will produce violent fluctuation.Under the same axial pressure,the greater the impact energy is,the greater the amplitude and duration of the fluctuation of the axial pressure is,and the fluctuation of the axial pressure lags behind the fluctuation of the impact force.4、The experimental study on the protective effect of XPS board and wood board composite structure as protective measures is carried out.The results show that:Compared with the test piece without protection,the test piece with the protection of XPS board and wood board composite structure is better than the test piece without protection,the deflection deformation of the specimen with the protection is reduced by 13%～47%,the maximum impact force is reduced by 27%～3 5%,the maximum strain is reduced by 29%～3 8%,the order of magnitude of the maximum strain rate is reduced from 107με/s to 105με/s,the duration of impact is prolonged by 1～5 times,and the amplitude of axial pressure fluctuation of the specimen is significantly reduced.5、The dynamic response of concrete filled steel tubular(CFST)specimens under lateral impact load is studied.The results show that:Compared with the steel tube,the dynamic data of the concrete-filled steel tube is obviously larger than that of the steel tube under the same conditions,but its deflection is reduced by 16%～37%;compared with the specimens protected by XPS board and wood board composite structure,the effect of concrete-filled steel tube is worse under small impact energy and better under large impact energy.