Grand Parade, Bath: in situ load testing of a historic structure to avoid unnecessary intervention

摘要

All five sections of balustrade subject to testing were capable of resisting the applied loading with negligible deflections and no signs of impending failure. An acceptable deflection for a 1.1m high balustrade would be around 6mm (span/180); the maximum deflection achieved under the implied load was 0.2mm. The testing proved that the balustrade is capable of resisting more than four times the anticipated failure load through calculation alone. The elastic behaviour of the balustrade was unexpected as masonry is a non-ductile material and a brittle failure would have been expected. The load was applied over a 900mm long beam to the centre of each bay. It is likely that the balustrade is resisting the load through an arching mechanism and the resulting load spread. Should the load have been applied along the length of the balustrade, the same conclusion might not have been reached. When initially assessing the test load, it was deemed that it would be unlikely that the balustrade would be subject to 1.67kN/m (1.5kN/0.9m) along its entire length and that this load represents a localised peak force which may occur at only one or two locations on any occasion.