No abstract

No 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.

In practice, bridge foundations and pier columns are usually constructed with cast-in-place concrete. Precast columns are currently widely used in highway bridges in China, which can save construction time and improve concrete quality. The connection between precast bridge columns and the foundation can affect how forces transfer from one to the other. This paper investigates using external sockets to form a connection between the bridge column and foundation. This method can accelerate the bridge construction time with the additional advantages of improving the orientation and creating a large erection tolerance. Two types of connections are presented and tested to investigate the behavior of the column-foundation connections and find a more suitable way to use external socket connections. The experimental results show that the column-foundation connection design satisfies the design requirements. The results also show that roughening the column surface within the external socket is more effective at connecting the column to the foundation when using an external socket compared to attaching a steel plate on the column. The experimental results are validated with a finite element analysis, resulting in a proposal regarding the column-foundation connection behavior as well as design recommendations for the external socket connection.

P‐I diagrams are widely used for structures subjected to blast loads. In the same manner, structures subjected to vehicle impact load, such as bridge columns, could potentially take advantages of the P‐I diagram if the dynamic characteristics of vehicle impact load and bridge columns are well considered. In the paper, the performance of bridge columns and hence the use of P‐I diagram is evaluated under vehicle impact load. The main tasks of the paper are (1) to determine the dynamic characteristics of vehicle impact load through finite element method, and three simplified load shapes are obtained including isosceles triangle, right triangle, and rectangular shapes; (2) to investigate structural failure modes under various shear‐bending ratios and impact loads; (3) to establish the damage index based on the residual axial capacity of bridge columns and to obtain P‐I diagrams at different damage levels of bridge columns under vehicle impact load; (4) to parametrically analyze the effects on the impulse asymptotic and the peak load asymptotic of P‐I diagrams, including column diameter, stirrup reinforcement ratio, longitudinal reinforcement ratio, and strength of the concrete. Finally, a simplified calculation method of P‐I diagrams is proposed to evaluate the performance of bridge columns under vehicle impact load.