Repair of masonry arch bridges with respect to longitudinal cracking and load assessment

This paper outlines a case study on the rehabilitation of a masonry arch bridge on Woodhouse Estate, Co. Waterford, Ireland. The main structural defect with this bridge is longitudinal cracking, which has led to lateral spread of the spandrel walls. Different repair techniques are discussed and the most suitable repair technique for longitudinal cracking is identified. The resulting information is used to define a set of guidelines for repair of masonry arch bridges with respect to longitudinal cracking. A procedure is also developed for load assessment of a masonry arch bridge, based on Heyman's classic line of thrust assessment. Microsoft Excel's 'Solver' is used as an optimisation tool, to determine the maximum allowable imposed load on a masonry arch. These values can then be used in conjunction with Coulomb's analysis to identify the limits on the horizontal thrust under varying axle loads and under pre-repair and post-repair bridge conditions.