| Unreinforced masonry is a common construction system for low-rise commercial buildings. It is often used as load-bearing wall system in large low-rise buildings such as malls, warehouse and industrial buildings. Failure of such construction type is prevalent during severe windstorm events such as tornadoes, hurricanes and severe thunderstorms.; Resistance of masonry construction to wind depends on the out-of-plane strength of the exterior walls. Out-of-plane strength of unreinforced masonry walls depends mainly on the wall modulus of rupture (MOR). The statistical analysis of previously published investigations gives a mean value of the MOR of 55.5 psi with a COV of 26%. Wind-induced load is probability-based and involves variables of wind speed, terrain exposure, building enclosure type, and pressure direction. The Monte Carlo Simulation using 1,000 observations of the MOR and the wind-induced loads is used to determine the probability of failure of walls. For a wall of 10-in. thickness and 15-ft height of a partially enclosed building located in terrain exposure C in Lubbock, Texas, the probability of failure is 94% in 50-year life of the building.; A target probability of failure of 1.5% in a 50-year life is ascertained from the current practice of masonry wall design. Failure strength of intermittently reinforced walls is determined using yield-line theory analysis. A mathematical methodology to relate the target probability of failure to the intermittent reinforcement spacing is introduced. It is found that a wall with intermittent reinforcement placed at a spacing equal to the wall height would survive in areas with design wind speeds up to 120 mph. |
