Impact Factor for High-Speed Railway Bridge Structures

India’s need for sustainable and resilient transportation infrastructure has led to the development of high-speed railway (HSR) corridors to improve connectivity and promote economic growth. The first HSR corridor on viaducts and bridge structures is being constructed between Mumbai and Ahmedabad. However, designing HSR bridges poses a significant challenge due to the dynamic interaction between the high-speed trains and bridge deck and the need for codal provisions to incorporate the same in the analysis and design. The Estimation of impact factors for HSR bridges is a critical issue requiring immediate attention. Existing codal provisions only provide impact factors for speeds up to 160 km/h, which are not applicable for higher speeds. Railway bridges must adhere to stringent serviceability criteria such as passenger safety and comfort at high speeds. Correct estimation of impact factor is critical to ensure safe design and serviceability performance of these bridge structures. This paper presents a numerical study on estimating the impact factor of HSR bridge structures through the finite element method. The effect of multiple moving loads is considered through multi-point contact modeling. The dynamic interaction between the deck and the moving train is considered. The effects of span length, axle spacing, and number of wheels on the impact factor are investigated. The impact factor value obtained using the finite element analysis is validated against simplified analytical formulations and compared with the existing codal provisions. It was found that the existing codal provisions valid for lower speeds, overestimate the impact factor value. Also, the impact factor is increased with span length for a given speed, whereas an increase in axle spacing increases the resonating speed. Finally, impact factor is recommended for typical rake configuration and bridge spans being used in the Mumbai-Ahmedabad HSR corridor.