USING CONSTRUCTION HISTORY AS AN AID TO MASONRY BRIDGE ASSESSMENT

Masonry arch bridges form a critical part of the transportation system in Europe, with tens of thousands of such bridges still in service in each country. They are heavy duty bridges of any size and shape, from single arch bridges with less than 5 m span to viaducts with multiple tiers of arches. Difficulty is experienced in assessing arch structures and there is a need to improve the ability to analyse the behaviour and load carrying capacity of arch bridges. Some of the bridges deemed to be at risk may not have developed significant or noticeable signs of distress. Numerical analysis refers to a basic bridge type in which relevant parameters are modelled. However, one or more of these assumptions may not be correct and analytical calculations are sometimes too conservative with consequences of strategic and financial importance. Indeed there is a whole series of masonry arch bridge typologies, which are never considered when performing the load capacity calculations, because they are not well known or believed to be not relevant. Inner structural elements may contribute to a reserve of strength. For example: hollow spandrel wall construction, when present, may have the effect of stiffening the arch ring. The aim of this work is to review masonry bridge construction in Britain so as to refresh the memory of the array of bridges which the testing and assessment engineer can encounter. Some guidance is offered on how to recognise from visual inspection the different types of bridges, the age of construction, the likely internal arch and spandrel configuration (hollow or filled) and the materials used. Masonry arch bridges from different parts of Britain are considered, focusing on the period between 1720 and 1840, outlining the peculiarities of individual designers and specific regional areas. For the covering abstract see ITRD E122683.