Abstract
Axial force has a great influence on the dynamic behavior and the impact resistance of concrete-filled steel tubular (CFST) members. Based on numerical simulation and theoretical analysis, the impact response and deflection calculation method for axially loaded CFST members subjected to lateral impact are investigated in this paper. The nonlinear numerical model of an axially loaded CFST member considering the strain rate effects has been established, and the simulation accuracy has been validated by comparing with existing test results. The contrastive investigation is carried out to illustrate the influence of axial load on the variation pattern of impact force for CFST members under various structural and impact parameters, and its result indicates that the impact force-time histories for CFST members with different axial loads are mainly characterized by rectangular pulse and triangular pulse. Moreover, a simplified calculation method considering the effect of axial force is proposed based on the equivalent single degree of freedom (SDOF) method, devoted to predicting the deflection of axially loaded CFST members subjected to lateral impact. The comparisons with the numerical simulation prove that the deflection calculation method has a reasonable accuracy; thus, the proposed method can be utilized in the damage assessment and anti-impact design for CFST members subjected to lateral impact and axial load.
Highlights
Concrete-filled steel tubular (CFST) members exhibit mechanical benefits of high strength and favorable ductility; they have been widely applied to high-rise and longspan engineering structures [1,2,3]
In [10], the authors carried out a series of drop weight tests on CFST members through a DHR9401 drop hammer test machine, as shown in Figure 2. e support restraint device provided the boundary constraints for the CFST member, and the loading device of the axial force applied the axial pressure for the CFST member. e weight of the drop hammer mc was 229.8 kg, and the different impact energy was obtained by changing the impact height (H)
When the CFST members encounter high impact energy, even within the small range of axial load ratio, the impact force will unload without experiencing a stable platform stage and the axial force will significantly weaken the impact resistance of CFST members
Summary
Concrete-filled steel tubular (CFST) members exhibit mechanical benefits of high strength and favorable ductility; they have been widely applied to high-rise and longspan engineering structures [1,2,3]. Erefore, a more reasonable and feasible way is to modify the differential equation and resistance function of the equivalent SDOF model to reflect the effect of axial force on CFST members subjected to lateral impact. To address these issues described above, the impact response and deflection calculation method for axially loaded CFST members subjected to lateral impact are investigated in this paper. A deflection calculation method of CFST members under lateral impact is established based on the equivalent SDOF method, and it reflects the effect of axial force by modifying the differential equation and the resistance function of the equivalent SDOF model. A deflection calculation method of CFST members under lateral impact is established based on the equivalent SDOF method, and it reflects the effect of axial force by modifying the differential equation and the resistance function of the equivalent SDOF model. e general calculation flow of the proposed method is summarized for obtaining the deflection of axially loaded CFSTmembers subjected to lateral impact, and the simulation results are utilized to validate and analyze the accuracy of the deflection calculation method
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