Title:
Effect of Sustained Load and Environment on Long-Term Tensile Properties of Glass Fiber-Reinforced Polymer Reinforcing Bars
Author(s):
Gilbert Nkurunziza, Brahim Benmokrane, Ahmed S. Debaiky, and Radhouane Masmoudi
Publication:
Structural Journal
Volume:
102
Issue:
4
Appears on pages(s):
615-621
Keywords:
load; polymer; strain
DOI:
10.14359/14566
Date:
7/1/2005
Abstract:
This paper describes a research effort to evaluate the creep behavior of glass fiber-reinforced polymer (GFRP) bars in different environments under sustained load. Twenty GFRP bars (E-glass in vinylester matrix) 9.5 mm in diameter in four series have been tested for over 417 days (10,000 h) 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 and 38% of guaranteed tensile strength while being surrounded by either alkaline solution (pH 12.8) or de-ionized water (pH 7.0). The initial strain applied to the bars varied between 4000 and 6000 microstrain, which are 2.9 and 4.3 times the maximum allowable sustained strain given by ACI 440.1R-03 (20% eu). ACI 440.1R-03 allowable sustained strain is limited by both environmental and creep rupture considerations. Axial strain in the central conditioned part of the bars was monitored with time to evaluate the creep behavior. Following the extended creep test, the GFRP bars were tested in axial tension until failure for residual tensile strength, elastic modulus, and axial strain. The experimental results obtained showed that the tested GFRP bar performed very well under these extreme loading and environmental conditions. The average residual tensile strength was found to be 139 and 144% of the design tensile strength for bars conditioned in de-ionized water at 25 and 38% stress level, respectively. In alkaline solution, this range was 126 and 97%. More importantly, no significant change in the elastic modulus was observed under the stress levels and environmental conditions used. The entire group of bars had a residual modulus ranging from 38.5 to 42.9 GPa, which is almost in the range of the original elastic modulus.