Fiber composites: An economical alternative for retrofitting earthquake-damaged precast-concrete walls

A new approach for seismic retrofitting of lightly-reinforced precast-concrete walls is presented. The technique involves epoxy bonding the reinforcing material (composite fabric) to the exterior surface of the wall. The flexible light-weight fabrics are extremely strong in tension and can significantly increase the flexural and shear capacity of the member. The thin composite fabrics cause little increase in the weight and thickness of the wall, causing little change to the inertial loads and eliminating the need for strengthening of the footings. Following the January 17, 1994 Northridge earthquake, this technique was applied to a tilt-up concrete building in southern California. The method proved to be the most cost-effective alternative to repair this damaged building in a very short time. More than 20,000 ft.² of wall surface area were strengthened, making this project the largest reported application of this technique. This paper discusses some of the design considerations and the strengthening of the damaged building.