Fiber-Reinforced Polymer Strengthening of Two-Way Slabs

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Title: Fiber-Reinforced Polymer Strengthening of Two-Way Slabs

Author(s): U. Ebead and H. Marzouk

Publication: Structural Journal

Volume: 101

Issue: 5

Appears on pages(s): 650-659

Keywords: concrete; fibers; reinforcement; shear; slab; strength

Date: 9/1/2004

Abstract:
In this paper, the strengthening of two-way slabs using fiber-reinforced polymers (FRPs) is evaluated experimentally. Two different types of FRP materials were evaluated: carbon FRP strips and glass FRP laminates. The dominating failure mode for two-way slab, flexural, or punching shear is based on the slab steel reinforcement ratio. The reinforcement ratios were chosen to serve the purpose of demarcating the two possible modes of failure. The tested specimens were classified according to the purpose of strengthening into specimens strengthened in flexure and specimens strengthened in punching shear. Specimens strengthened in flexure had two steel reinforcement ratios: 0.35 and 0.5%. Results show that the flexural capacity of two-way slabs can increase to an average of 35.5% over that of the reference (unstrengthened) specimen. An increase of the initial stiffness was achieved for flexural specimens; however, an apparent decrease in the overall ductility was evident. FRP materials can be used to increase the flexural capacity of two-way slabs. However, an average decrease in the values of the energy absorption of approximately 30% for flexural strengthening specimens was observed. Specimens strengthened for punching shear have an original slab reinforcement ratio of 1.0%. A strengthening technique that combines the use of carbon FRP strips and steel bolts increases the strength of the slab by 9.0%. An analytical model for the analysis of FRP strengthening of two-way slabs under flexure or punching shear is introduced.