Lateral Deflection Analysis And Damage Assessment Of Concrete Filled Steel Tube Columns Subjected To Blast Loading

Typical major explosion accidents have caused serious loss of personnel and property.As a special kind of disaster,explosion,on the one hand,produces debris and huge shock wave which will directly cause casualties,on the other hand,explosion shock wave will lead to building damage or even collapse,so the explosion resistance of building structure has become an important part of structural design.Concrete filled steel tube(CFST)has many advantages,such as good bearing capacity and ductility under axial compression,excellent explosion resistance and so on,which has been used more and more in protective engineering.The main contents of research and analysis on anti-explosion capability of structure are two points.The first is dynamic response analysis of structure after being subjected to blast,such as displacement,failure mode,etc.The second is damage characteristic analysis of structural column as structure frame after being subjected to blast.In view of the above problems,the main research contents are as follows:(1)By using ANSYS/LS-DYNA finite element software to analyze the CFST column explosion test completed by research group,finite element model of the whole process of CFST column explosion under explosive load was established.The established finite element model is corrected by used the displacement time-history,overpressure time-history and impulse timehistory of typical components in explosion test,and the errors are all within a reasonable range,which indicates that the whole process numerical simulation can effectively simulate the whole process of explosion test.(2)The explosion impulse with 90% guaranteed rate at each proportional distance was obtained by statistical method,and the relationship curve was fitted.The equivalent single-degree-of-freedom(SDOF)system based on explosive impulse was used to analyze the dynamic response of square and circular CFST columns under explosive load.The maximum deflection of undamped SDOF system under triangular impulse load is obtained by ductility coefficient.The accuracy of theoretical analysis was verified by comparison with experiments.The results show that simplified theoretical analysis method can accurately calculate the maximum deflection in column,and calculation results are safer than test results.Given characteristic parameters of any CFST column,the lateral deflection of column members under explosive load can be accurately obtained by theoretical analysis and prediction formula.The results of parameter analysis show that stiffness and strength of CFST columns can be increased by increasing the axial compression ratio properly.The axial compression ratio,hoop coefficient and proportional distance have significant effects on explosion resistance of CFST columns.(3)Pressure-impulse(P-I)curves of circular CFST column members are established by numerical simulation and equivalent single-degree-of-freedom method based on damage assessment criterion of bearing angular displacement.The effects of various parameters on P-I curves,overpressure asymptotes and impulse asymptotes are analyzed.The results show that evaluation criterion of bearing angle can effectively reflect the damage degree of CFST column under blast load.The results show that both the CONWEP algorithm and equivalent SDOF method can obtain the P-I curve of CFST under blast load,but the P-I curve obtained by numerical simulation method rises to the upper right near impulse asymptote.The P-I curve obtained by SDOF method has higher safety redundancy in lower left of numerical simulation method.The height of CFST column is inversely proportional to asymptotes,that is,with the increase of column height,overpressure asymptotes and impulse asymptotes become smaller and smaller;with the increase of axial compression ratio of CFST column,overpressure asymptotes and impulse asymptotes first increase and then decrease rapidly;the wall thickness,steel strength and concrete strength of CFST column are proportional to asymptotes,that is,with the increase of each parameter,overpressure asymptotes become larger.