EFFECTIVENESS OF SEISMIC STRENGTHENING TECHNIQUES FOR MASONRY BUILDINGS

The effectiveness of various seismic-strengthening techniques of stone masonry buildings is assessed through linear elastic finite element analyses. The strengthening methods examined are (1) Reinforced concrete tie beams at the floor and roof levels, (2) replacement of wood floors by reinforced concrete slabs; (3) reinforced concrete tie-columns at all junctions of load-bearing walls, (4) shotcrete jackets over the entire external and/or internal wall surface, (5) horizontal prestressing of the spandrels; and (6) vertical prestressing of the piers. Combinations of methods, such as 1 and 2, 2 and 3, 5 and 6, etc., are also studied. The criterion for the effectiveness of a technique is the mean reduction of principal elastic tensile stresses in the masonry wall relative to the unstrengthened building for the combination of gravity loads with a seismic loading representative of the maximum expected earthquake loading in the building's conventional lifetime. Results are given separately for the walls normal to or parallel to the seismic action, for each story, and for the building as a whole. The most effective strengthening is the two-sided shotcrete jackets, followed hy the easy-to-construct combination of RC slabs and a RC tie-beam at the top