Static Response of Fiberglass Pretensioned Beams

This paper presents results from an experimental study to determine the static response of fiberglass pretensioned beams. Three sets of underreinforced pretensioned beams 8‐ft span with cross sections of $6\mathrm{in}\text{.}\times 8\mathrm{in}\text{.}(0.15m\times 0.2m$, $6\mathrm{in}\text{.}\times 10\mathrm{in}\text{.}(0.15m\times 0.25m)$, and $6\mathrm{in}\text{.}\times 12\mathrm{in}\text{.}(0.15m\times 0.3m)$ were tested under two‐point loading. The beams were pretensioned using three $3/8\mathrm{in}\text{.}$ (9.5 mm) S‐2 glass/epoxy strands. For comparison, three identical beams pretensioned to the same effective prestress by two $3/8\mathrm{in}\text{.}$ (9.5 mm) steel strands were also tested. The results from the study indicate that the precracking response of these fiberglass pretensioned beams was near identical to the steel pretensioned beams, but its postcracking response was more flexible. Failure of some of the fiberglass pretensioned beams was accompanied by slip. Nonlinear finite‐element analysis showed good correlation with the test results. Tentative equations for estimating the failure stress and criteria for designing underreinforced beams are proposed.