A NEW RETROFITTING TECHNIQUE FOR MASONRY BRIDGES

Retrofitting of masonry bridges usually applies the basic concepts of r.c. to this kind of masonry structure. The results are that often that the retrofitting works are almost ineffective and, always, the historical value of the bridge is largely lost. A series of tests on reduced properly scaled models (see other papers in this Conference) show that the actual load carrying structure is an arch with reduced span in comparison with its geometric appearance. The actual span depends on the fill material (stiffness and strength) at the springing. Besides, the fill does not distribute the load, applied on its surface, on the arch extrados close to the ultimate load. Based on these two issues, a new retrofitting technique is discussed: selective injection of the fill, limited to the part close to the springing, may reduce the effective arch span, thus increasing the l.c.c. of the bridge as a whole. This issue is discussed through a test on a 4m-span model.