A NEW RETROFIT TECHNIQUE TO IMPROVE SEISMIC RESISTANCE OF MASONRY WALLS UNDER OUT-OF-PLANE LOADS
Unreinforced Masonry (URM) walls are commonly used as interior partitions and/or exterior perimeters in building structures throughout the world. One of the most critical deficiencies of URM walls is the out-ofplane brittleness. This study proposes a new retrofit technique for improving the seismic performance of masonry walls in the out-of-plane direction. Geometric axial elongation of masonry walls under lateral deformation is focused and utilized as a source of passive compression in the proposed method. Applying tension rods to masonry walls to restrain the axial elongation, compression can be applied to wall crosssections under lateral deformation and therefore increases the flexural strengths. The mechanism of retrofit technique above is summarized in the paper. Application tests were conducted using brick wall specimens which were actually placed in an earthquake-damaged building in Indonesia. The wall specimens strengthened/un-strengthened by the proposed method were subjected to uniform out-of-plane loads using a new loading system developed in this study. Although shaking tables are usually implemented to investigate out-of-plane performance of URM walls subjected to inertial forces normal to the surfaces, it is occasionally difficult to observe failure behavior by optical inspections in dynamic tests. Therefore, in this study, a new static loading system was also developed using a rubber airbag which was adopted as a generator of uniform distribution loads, and implemented for evaluating out-of-plane performance of the specimens. As a result of the tests, it was found that the proposed retrofit technique improved the out-of-plane performance, namely deformation capacity as well as flexural strength of the brick wall specimen.