Strength Performance of Prestressed Glass Fiber-Reinforced Polymer, Glued-Laminated Beams

This article focuses on assessing the strength performance of glued-laminated (glulam) beams with E-glass fiber reinforced polymer (GFRP) prestressing (prestressed GFRP-glulam beams) through bending tests and cross-sectional analysis. In addition to fifteen 6.7-m-long prestressed glulam beams, 15 GFRP-reinforced glulam beams and 15 unreinforced glulam control beams with nominally identical layups and 6.7-m lengths were tested to failure in four-point bending to provide direct performance comparisons. Load-displacement data and strains in the prestressed GFRP were monitored. The results of the tests show that the prestressed GFRP-glulam beams exhibited a 38 percent increase in allowable bending stresses compared with reinforced GFRP-glulam beams without prestress and an approximately 95 percent increase compared with unreinforced glulam beams. Both the prestressed and reinforced specimens exhibited an 8 percent increase in stiffness relative to the control specimens. Loss of prestress due to creep was examined for one specimen by monitoring GFRP strains over a 12-day period following fabrication. The total loss of prestress over this 12-day period was less than 2 percent, and the rate of prestress loss decreased during monitoring. The GFRP stresses predicted by a cross-sectional moment-curvature analysis of the prestressed and reinforced beams agree well with stresses inferred from measured strains. The results of this study show that prestressed GFRP reinforcement of glulam beams shows significant promise for practical applications.