ABSTRACT: This paper describes a research effort to evaluate the creep behaviour of Glass FRP (GFRP) bars in different environments under sustained load. Twenty (20) GFRP bars (E-glass in Vinyl ester matrix) 9.5 mm in diameter in four series have been tested for over 417 days (10,000 hours) under combinations of different sustained load levels and surrounding mediums in ambient temperature. The bars were subjected to two levels of sustained tensile stress at 25 to 38% of ultimate short-term ultimate tensile strength while being surrounded by either alkaline solution (pH of 12.8) or de-ionized water (pH of 7.0). The initial strain applied to the bars varied between 4900 to 6530 µε, which is 3.5-4.7 times the maximum allowable strain for sustained loads given by the ACI 440.1R-03. Axial strain in the central conditioned part of the bars was monitored with time to evaluate the creep behaviour. Following the extended creep test, the GFRP bars were tested in axial tension till failure for residual tensile strength, elastic modulus, and axial strain. The obtained experimental results shown that the tested Glass FRP bar performed very well under these extreme loading and environmental conditions. The residual tensile strength was found to be between 138 to 144% of the allowable design stress for bars conditioned in de-ionized water at 25 and 38% stress level, respectively. In alkaline solution this range was 129 to 97%. Also, no significant change in the elastic modulus was observed under the conditions used. |
