Load Testing and Fiber-Reinforced Polymer Reinforcement of 1920s Vintage Chicago Public School Building

Abstract

The subject of this paper is the investigation, load testing, and repair of a 1920's vintage public school building located in Chicago, Illinois. This school is one of thirty-two similar schools that were the subject of substantial controversy at the time they were built. Shortly after construction was completed, selected portions of the reinforced concrete roof structure were shored with supplemental steel beams to address alleged design and construction defects. The roofs have since been plagued with recurring maintenance issues related to the supplemental steel beams.An engineering study of the existing roof framing and supplemental steel reinforcement was performed to determine if the existing reinforcement was necessary. Full scale load tests of various portions of the roof structure were performed to verify the capacity of the original concrete framing. Repairs were developed to address locations where deterioration was observed or additional capacity was required, which allowed the complete removal of the existing structural steel reinforcement in place. Fiber-reinforced polymer (FRP) reinforcement, used for the first time in the Chicago Public School System, was chosen to reinforce selected concrete beams and joists. This paper will review the investigation, structural analysis, load testing and the design and installation of the externally bonded FRP reinforcement. DESCRIPTION OF STRUCTUREThe school building is a two-story reinforced concrete structure with a basement. The floor and roof construction typically consists of one-way cast-in-place reinforced concrete joists. The concrete joists are primarily supported by reinforced concrete girders and, at some locations, by the exterior masonry walls. The girders are 1991 Structures Congress 2012