Effects of Lateral Constraints and Geometrical Characteristics on Deformation Capacity of the Persian Historic Unreinforced Masonry Shear Walls under Uncertainty Conditions

In the most structural codes, deformation capacity of the unreinforced masonry shear walls is estimated based on their structural behavior(failure mode) and aspect ratio. In this paper, deformation capacity was determined for the Persian historic brick masonry walls by considering the effects of various parameters such as lateral constraints, aspect ratio and thickness. Also, to take into account the uncertainties in material and geometry of the walls in their deformation capacity, partial factor γdu was proposed, somehow, deformation capacity of shaer wall is determined by multiplying this factor in the computed deformation. Accordingly, the in-plane behavior of 48 different specimens of masonry walls with four lateral constraint configurations (contribution of transverse walls and also top slab), four distinct aspect ratios(height to length) of 0.5, 0.75, 1.0 and 1.5, three traditional wall thicknesses of 0.20, 0.35 and 0.50 m, under pre-compression load of 0.10 MPa were computed using nonlinear pushover analyses. Then, the obtained force-deformation curves were idealized by bilinear curves (linear elastic – perfectly plastic) to make them easier for comparison objectives as well as to be more adopted in practical purposes. The latter results indicated that deformation capacity of the shear walls decreases by stiffer lateral constraints, more thickening; and decrease in height-to-length aspect ratio. In addition, it was observed that the transverse walls (vertical constraints on two sides, and at two ends of the base shear walls) were more efficient in reducing deformation capacity than the top slab (horizontal constraint).  As a result, according to the numerical calculations, the ultimate drift value for the Persian historic brick masonry walls determined between 1.3% and 2.7%. Eventually, the partial factor of γdu to consider uncertainty in modulus of elasticity and thickness assessment in deformation capacity of the Persian historic masonry shear walls achieved in the range of 1.3 to 1.7.