Strength and Seismic Performance Factors of Posttensioned Masonry Walls: Fid-Bau Portal

Strength and Seismic Performance Factors of Posttensioned Masonry Walls

Hassanli, Reza / ElGawady, Mohamed A. / Mills, Julie E.

In this study, the behavior of posttensioned masonry walls is investigated using a database of 31 tested walls. The accuracy of the current Masonry Standards Joint Committee (MSJC) in evaluating the strength of posttensioned masonry walls is studied using the available test results. Moreover, using the experimental results, the seismic performance factors including ductility, response modification factor, and displacement amplification factor are determined for different types of walls including fully grouted, partially grouted, ungrouted walls, walls with confinement plates, walls with supplemental mild steel, and walls with an opening. As a result of this study, it was determined that the MSJC underestimates the strength of fully grouted unbonded posttensioned walls by about 20%. Using the strain compatibility method to determine the flexural capacity of bonded masonry walls resulted in reasonable predictions of strength. Moreover, an average response modification factor of 4.27 to 7.76 and displacement amplification factor of 3.5 are estimated for posttensioned fully grouted masonry walls. The ductility and response modification factor for ungrouted and partially grouted walls and walls with an opening were much lower than those of fully grouted walls. It was found that the $R$ -factor of partially grouted walls can be estimated by linear interpolation between the $R$ -factors of ungrouted and fully grouted walls. This study also concluded that the axial stress ratio has a prominent effect on the ductility of posttensioned masonry walls. To provide a ductile response, based on the findings, it is recommended to limit the axial stress ratio to a value of 0.15.