Effect of Concrete Strength on Bond Behavior Under Impact Loading

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Title: Effect of Concrete Strength on Bond Behavior Under Impact Loading

Author(s): C. Yan and S. Mindness

Publication: Special Publication

Volume: 149

Issue:

Appears on pages(s): 679-700

Keywords: bond; bond stress; fibers; fracture properties; impact; loading rate; loads (forces); polypropylene fibers; reinforcing steels; slippage; strength; Structural Research

Date: 10/1/1994

Abstract:
Bond reinforcing bars and concrete under impact loading were studied for both plain and steel fiber reinforced concretes. Experiments consisted of both pullout tests and push-in tests. The design compressive strengths of the concrete were 40 MPa (normal strength) and 75 MPa (high strength) at 28 days. The impact loading induced bond stress rates ranging from 0.5 x 10 -4 to 0.5 x 10 -2 MPa/sec. The bond under stress rates ranging from 0.5 x 10 -8 to 0.5 x 10 -4 MPa/sec was also studied for comparison. Each reinforcing bar was instrumented with five pairs of strain gages to monitor the actual strains during the bond-slip process. All test data were collected by a high-speed data acquisition system at a sampling rate of 200 sec. Stress distributions in both the steel and concrete, bond stresses and slips, bond stress-slip relationships, fracture energy in bond failure, and internal crack development were investigated. It was found that compressive strengths increased the bond-resistance capacity and fracture energy in bond failure, and therefore had a great influence on bond stress-versus-slip relationship. This effect was increased by high loading rates and steel fiber additions, especially for the push-in loading mode.