Shakedown and dynamic behaviour of masonry arch railway bridges

Masonry arch bridges form an integral part of our rail infrastructure network and their safety is important for the functioning of our society. Although, there have been several studies to understand the in-service condition of masonry arch bridges, these are mainly focusing on static analyses. However, it is well known that moving vehicles exert a dynamic force on bridges as they cross them. This paper investigates the shakedown and dynamic behaviour of railway masonry arch bridges under traffic load conditions. A nonlinear, mixed discrete-finite element numerical model was developed to investigate static and dynamic response on a masonry arch bridge. Each voussoir of the masonry arch was represented by a distinct block, while the mortar joints were modelled as zero thickness interfaces which can open and close depending on the magnitude and direction of the stresses applied to them. Both static and real dynamic analyses were carried out investigate the effects of moving traffic loads. In addition, investigations into the train to bridge interaction were undertaken and the dynamic amplification factors (DAFs) were estimated. From the evaluation of the results, it was shown that as the external load passes through the bridge, plastic deformations and residual stresses exist in the arch barrel. Also, the dynamic amplification depends on the magnitude of the external load. As the load increases, non-linearity in the structure is evident, which decreases the natural frequency of the bridge. Hence the critical speed is decreasing. Observations provided here reveal new insight into the residual and load carrying capacity of masonry arch bridges.

Automated summary

This study investigates the stability and dynamic behavior of railway masonry arch bridges under traffic load conditions using a nonlinear mixed discrete-finite element numerical model, exploring the effects of moving traffic loads and train to bridge interaction. It is shown that the external load passing through the bridge causes plastic deformations and residual stresses, with dynamic amplification factors depending on the magnitude of the external load. The presence of nonlinearity in the structure with increased load decreases the natural frequency of the bridge, ultimately impacting the critical speed.