Report - PEER - University of California, Berkeley

VsR= FRη phfyhAT (2)3 mdistance betweenbond beamsdistancebetween ≤tiecolumnsbond beam inparapets ≥ 500 mm4 m1.5HslabTie-columns atwall intersectionsH≤ 30tt ≥ 100 mmtie-columnsin parapetsHconfining elementsaround openingsThe efficiency factor η wasderived from experimentaldata (Aguilar 1996, Alcocer1996b, 1999). This factorcorresponds to that recordedat the allowable inelasticlateral drift discussed before.The upper limit on ph isrelated to the masonrycrushing strength. The lowerlimit corresponds to thepercentage of horizontal steelneeded to maintain thestrength at first diagonalcracking.Figure 2. Confined masonry requirements.3. ANALYTICAL MODEL FOR CONFINED MASONRYA hysteretic model intended to perform nonlinear dynamic analyses was developedand calibrated from tests carried out on full scale wall structures (Flores and Alcocer,1996). The model is applicable to confined masonry walls built with handmade claybricks and cement mortar, with or without horizontal reinforcement. The envelopecurve follows a tri-linear backbone curve where first inclined cracking, strength andultimate strength (and their corresponding drift angles) are key engineeringparameters in its definition. The hysteresis model follows stiffness decay rules for theloading and unloading branches. To obtain the best-fit curve, measured stiffness ofthe loading and unloading branches in the experimental hysteresis loops werenormalized by the measured initial stiffness.237