Prestress losses in fibreglass pretensioned concrete compression members

Abstract

Fibreglass has been used recently as a prestressing material in concrete structures, and it has demonstrated some advantages over steel tendons especially in corrosive environments. An experimental estimation of the long term losses of concrete columns and piles pretensioned with fibreglass (S-2 glass) is presented in this paper. Three identical sets of steel and fibreglass specimens with nominal dimensions of 152 mm×102 mm×2.6 m (6 in ×4 in ×102 in) were instrumented and tested to evaluate prestress losses under axial compression loads at different stress levels. Results after 20 months show that prestress losses in fibreglass tendons are less than those in steel tendons. The effective prestress for fibreglass pretensioned specimens can be predicted accurately using the step-by-step method. The measured data were compared with several models. For a practical applied stress of 0.3fc′, the current ACI and Bazant equations for creep and shrinkage predicted the strain history, prestress losses, and effective prestress of fibreglass pretensioned concrete specimens with good accuracy.