Seismic Retrofitting for Chord Reinforcement for Unreinforced Masonry Historic Buildings with Flexible Diaphragms

Abstract

The existing wood-diaphragm-to-masonry-wall connections in unreinforced masonry (URM) buildings provided very little or insufficient resistance in past earthquakes. Recent strengthening techniques for the connections between URM walls and flexible diaphragms concentrate only on the installation of wall anchorages for out-of-plane tension forces and shear bolts for in-plane shear forces. Strengthened chord elements, however, are also essential parts of URM buildings to resist earthquakes. This paper proposes seismic rehabilitation techniques where steel angles are used as chord reinforcement. A practical design example is presented, where chord axial forces caused by in-plane diaphragm deflections and chord shear flows caused by transverse seismic forces are computed. The computed axial forces and shear flows are to be used in the design of the chord reinforcement and the chord shear connections, respectively.