Title: Evaluation, Repair and Reinforcement of an Ultra-Thin, Two-Way Flat Slab With Drop panels

Author(s): Steven G. Provenghi and Gregg E. Brandow

Publication: Special Publication

Volume: 128

Issue:

Appears on pages(s): 1277-1292

Keywords: concrete panels; cracking (fracturing); flat concrete slabs; inspection; nondestructive testing; parking structures; post-tensioning; plastics, polymers and resins; reinforced concrete; repairs; strengthening; structural design; trusses; Design

Date: 11/1/1991

Abstract:
This is an actual case-study of a four-story reinforced concrete parking structure with ultra-thin, two-way flat slabs with drop panels. The slabs were 4.50 in. thick on bays as large as 27 x 27 ft with midspan deflections as much as 5.50 in. The evaluation included physical inspections to evaluate crack patterns as well as nondestructive tests to locate reinforcing steel and full-scale load tests per ACI recommendations to evaluate the strength of the structural slab. Recommendations for repair and strengthening were accomplished by a combination of external post-tensioning with king-post type trussing below the floor slabs and with a gravity-fed polymer repair of the structural cracks found within the slab.