Problem Assignment - Capacity Design of Reinforced Masonry Shear Walls
Two reinforced concrete masonry shear walls are attached to a continuous concrete floor slab, as shown in the figure below. Each wall is constructed with eight-inch blocks, is grouted fully, and is reinforced with one #8 vertical reinforcing bar at each end. Dead and live loads are applied uniformly over the wall length as shown.
Consider the floor slab to be rigid with respect to horizontal in-plane forces, but fully flexible in bending, and that the foundation has sufficient flexural strength and stiffness to react whatever forces are transmitted from each wall. Neglect the self weight of each wall and the slab, and assume that shear reinforcement is provided such that design of each wall be flexure controlled (i.e. shear strength is more than twice flexural strength). Neglect compressive reinforcement to simplify. Masonry compressive strength is 2500 psi. Type N Portland cement mortar is used.
Determine the following.
1. The percentage of the earthquake force, Heq, that will be attracted to each wall according to a linear analysis.
2. The design flexural strength of each wall.
3. The seismic force demand-to-capacity ratios for each wall, if the Heq force is equal to 100 kips.
4. The force capacity of the system, Hequ, based on strength design.
5. The force capacity of the system, Hequ, based on capacity design.
6. The displacement demand-to-capacity ratios for each wall, if the Heq force is equal to 100 kips. Consider each wall to be a specially reinforced masonry wall.
