Abstract: One morning, upon discovering severe slab cracking, visible deflection, and a partially collapsed slab, the owner of a Northern California parking garage contracted with us to investigate and determine a course of action. Originally constructed in the early 1970s, the L-shaped garage has two parking levels?one a slab-on-ground and the other a roof slab. The upper level is constructed of cast-in-place, sand-lightweight concrete and is post-tensioned with paper-wrapped unbonded tendons. The slab is 4 in. (100 mm) thick and spans between transverse post-tensioned concrete beams spaced at 18 ft (5.4 m) on center (Fig. 1). The cracking and deflection occurred in only one wing of the L. The partial collapse resulted in a 4 x 5 ft (1.2 x 1.5 m) hole in the slab (Fig. 2), but the failure did not rupture the tendon strands.
Parking Structure Damage: Investigation and Repair Restores Structure to Service
October 30, 2009
Publication: Concrete International, ACI v 31 n 10 p 29-32
Services: Structural Investigation