Report - PEER - University of California, Berkeley

1 / (Stiff / Init. Stiff.)8070605040302010Loading brancha (γ max) 4 + b γ max+ 1a = 1 x 10 9b = 100030252015105Unloading brancha (γ max) 4 + b γ max+ 1a = 1 x 10 8b = 600000 0,005 0,01 0,015 0 0,005 0,01 0,015Maximum drift ratio (γ max ) Maximum drift ratio (γ max )Figure 4. Normalized stiffness degradation curves for the loading and unloadingbranches.The serviceability limit state is associated to the onset of masonry inclinedcracking, which typically occurs at drift angle of the order of 0,15%. Such value isquite variable, depending upon the type of masonry unit, wall flexural-to-shearcapacity ratio, among other factors. Evidently, at this state, damage is minor. For thereparability limit state, it was decided to associate it to the formation of the fullinclined cracking, and the penetration of such cracking into TC ends. It has beenobserved in the lab that the residual crack width at such limit state is of the order of 2mm, and that a drift angle is approximately 0,25%. The safety limit state correspondsto wall shear strength, typically characterized by large masonry cracks (with aresidual width of 5 mm) and considerable damage at TC ends. Damage in TC occursin the form of yielding of TC longitudinal reinforcement due to shearing and onset ofcracking crushing and spalling.Performance criteria presented in Table 1 were developed keeping in mind theneed for repair of a masonry structure after a moderate-to-severe event (reparabilitylimit state). In this regard, three basic repair methods were considered: injection of anadhesive component (epoxy or Portland cement-based materials); jacketing (mortaroverlays reinforced with welded wire meshes, or composite overlays); and placementof additional horizontal reinforcing bars within mortar joints. Rehabilitationtechniques where made consistent with the damage and structural response (Fig. 5).239