Construction of a concrete segmental arch bridge over a railway

Abstract

This paper describes the modelling of the behaviour of a large precast concrete segmental arch structure during construction over a main line railway. The main aim of the modelling was to accurately predict the deflections of the segmental arch during construction and to set trigger levels to prevent another failure similar to that which occurred at Gerrards Cross, UK. The failure at Gerrards Cross, reported in 2005, demonstrated the importance of controlling the backfill and carefully controlling and monitoring the deflections of the arch during construction. To enable accurate predictions, finite-difference analysis of the precast segmental structure was utilised, which takes account of the soil–structure interaction effects covering structure and soil stiffness. Many sensitivity analyses were necessary to predict lower and upper bounds using predominant parameters that influenced the behaviour and included the movement of the arches on the piled foundations. Observations taken on site of movements of the arch during construction showed that actual deflections matched the predicted movements to a very high degree.