Rationalising assessment approaches for masonry arch bridges

Abstract

2Masonry arch bridges, most of which have far exceeded modern design lives, have demonstrated themselves to be sustainable structures with low life-cycle costs. However, increased traffic loading and material deterioration over time necessitate periodic reassessment of these structures. There are numerous different analytical methods available for the assessment of masonry arch bridges. The expectation is that for increasing levels of assessment complexity an increase in load capacity converging on the ultimate capacity would be achieved. In this paper it is demonstrated that this is not always the case. This has cost implications for both the bridge assessment itself and for costs associated with load restrictions and strengthening measures. Five different assessment methods were selected to assess a set of 11 single-span bridges, ranging in span from 2?4 m to 15?2 m, with the objective of reviewing and rationalising current assessment guidelines for masonry arch bridges. The bridges chosen are a representative sample of the stone arch bridges on the Irish National Roads network. It was found that there is a significant variation in assessed capacity depending on the assessment method used. Limit state analysis methods were found to generally result in higher ratings for segmental bridges while elastic methods resulted in higher ratings for three-centred or semi-circular bridges. Assessment ratings found using the Military Engineering Experimental Establishment (MEXE) method were difficult to rationalise across the bridge set considered in this study. Following a review of the origins of the MEXE method and its current form as set out in the assessment guidance, it is recommended that its use as the predominant tool in a simplified assessment procedure is not appropriate and that a more rational approach is required for a more realistic and reliable calculation of bridge capacity. The development of an improved assessment methodology is being considered as part of the current study.

A review of experimental investigations and assessment methods for masonry arch bridges

“…Furthermore, for a numerical model to adequately represent the behaviour of a real structure, both the constitutive model and the input material properties must be selected carefully to represent the non-linear response of masonry. It should also be expected that different methods should lead to different results depending on the adequacy of the approach and the information available, and not always an increase of the level of complexity leads to a more refined estimate of the actual load-carrying capacity (Gibbons and Fanning, 2012). Preferably, the approach selected to model masonry arch bridges should provide an acceptable degree of accuracy and within sustainable time and cost efforts.…”

“…A comprehensive comparison between the available methods for the structural analysis of masonry arch bridges is provided by Annex A of UIC Code 778-3R, while a comparison between them for applications to stone arch bridges is presented in (Gibbons and Fanning, 2012).…”

Numerical study on the structural response of a masonry arch bridge subject to flood flow and debris impact

“…Many existing studies have focused on the behaviour of the masonry arch barrel itself under vertical loading using mesoscale modelling approaches including simplified micro-modelling of the arch barrel and macro-modelling of the spandrel walls and backfill without consideration of the transverse behaviour of the bridge [70,71]. Since the present study seeks to investigate the global behaviour of the entire bridge, a macro-modelling approach for all structural components is adopted [48,58,61] with a focus of brickwork masonry. In the forthcoming section, a brief description of the methodology used in this study is detailed.…”

Winchelsea masonry arch bridge, Australia: first major maintenance

“…It was quick and easy to use, and has remained popular among bridge assessment engineers to this day . The modified MEXE method (Highways Agency, 2001) is mandated as an initial analysis in the UK, but there are growing concerns Winchelsea masonry arch bridge, Australia: first major maintenance Morris that the modified MEXE method of assessment has significant limitations and it is difficult to rationally advocate its continued use (Gibbons and Fanning, 2012). …”