Abstract
Shear failure is a common mode for bridge column collapse during a vehicle-column collision. In current design codes, an equivalent static load value is usually employed to specify the shear capacity of bridge columns subject to vehicle collisions. But how to consider the dynamic effect on bridge columns induced by impact load needs further research. The dynamic amplification factor (DAF) is generally used in the analysis and design to include the dynamic effect, which is usually determined using the equivalent single degree of freedom (SDOF) method. However, SDOF method neglects the effect of the higher-order modes, leading to big difference between the calculated results and the real induced forces. Therefore, a novel method to obtain dynamic response under concentrated impact load including the effect of higher-order modes is proposed in the paper, which is based on the modified Timoshenko beam theory (MTB) and the classical Timoshenko beam theory (CTB). Finite element models are conducted to validate the proposed method. The result comparisons show that the results from the proposed method have more accuracy compared with the results from the CTB theory. Additionally, the proposed method is employed to calculate the maximum DAF of shear forces for bridge columns under impact load. Parametric studies are conducted to investigate the effect on the DAF of shear forces including slenderness ratio, boundary condition, and shape and position of impact load. Finally, a simplified formula for calculating the maximum DAF of shear force is proposed for bridge column design.
Highlights
Vehicle-column collisions occurred occasionally for bridge columns in recent years
Shear failure should be avoided since it is a brittle failure and reduces the structural capacity to absorb energy [3]. e failure modes of reinforced concrete structures under impact loads are quite different from those under static loads
In a drop-weight test, for the reinforced concrete beams conducted by Saatci and Vecchio [4], the specimen subjected to shear failure under impact load even it was flexure-critical under static load. is is because the impact load excites highorder vibration modes resulting in internal force distribution different from the one under static load, which is the dynamic effect induced by the impact load [5]
Summary
Vehicle-column collisions occurred occasionally for bridge columns in recent years. Among them, bridge columns often collapsed with shear failure. To accurately obtain the dynamic response of bridge columns under impact load, a novel method is proposed based on both the CTB and MTB theories in the paper. Accurately achieve the dynamic responses of bridge columns under impact load, an improved method is proposed (IMCTB) based on the MTB and CTB theories, and the calculation process is as follows. E dynamic internal force response is mainly influenced by the first several modes, which means the CTB theory can produce large errors especially when the slenderness ratio is smaller It indicates that the DAF of shear force calculation using the IMCTB method shows good agreements with FE analysis results, especially for the columns with small slenderness ratios
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