S.K. SUMON Transport Research Laboratory

The introduction of the 40T lorries on I January 1999 by the European Commission Directive means that many of the 40,000 masonry arch highway bridges will need urgent attention. According to 1993 figures it is estimated that 1 % of the stock will need replacing, strengthening or repairing each year. This will lead to an annual bill of over £23M. Five model arch bridges have been tested to failure at the Transport Research Laboratory to investigate the effectiveness of a number of strengthening methods. The arches were of nominally identical construction. One was built with ring-separation, and two others were strengthened using sprayed concrete and a concrete saddle, respectively. The ring-separated arch was loaded to failure, reprofiled and strengthened using a propriety method, Masonry Arch Repairs and Strengthening (MARS) and tested again. Sprayed concrete and the concrete saddle increased the strength of the arch by factors of 3.72 and 2.90, respectively. Compared with Arch 1 (control model) the ring-separated arch model gave a significant reduction in load bearing capacity, but when strengthened using MARS gave an increase in capacity of 1.14.