Engineering Model for Forecast of Stress Rupture Strength of Stressed Aramid Fiber Reinforced Polymer Bars Embedded in Concrete

Abstract

AFRP tensile elements (bars, strands, etc.) can be successfully applied for the pretensioning of precast concrete members, for post-tensioning tendons, ground anchors etc. In such applications, the AFRP may come into permanent contact with the alkaline pore solution of concrete or cementitious grout. Many tests prove that such aggressive environment may seriously damage the stressed AFRP and significantly abbreviate its lifetime due to premature stress rupture. The serviceability and safety of FRP is the relevant durability property to ensure the serviceability and safety of a structural concrete member during its service life. The stress rupture behavior is usually studied on stressed AFRP bars placed in aggressive solutions, etc. It is though evident that such severe environment does not realistically reflect the true environment of AFRP in dense concrete and grout. It was therefore the aim of the authors to develop - on basis of experiments in several stages and the theoretical studies - an engineering model for the prediction of the stress rupture strength of stressed AFRP in concrete or grout. This model was verified by tests. Provided the stress rupture strength of AFRP in dry air or in alkaline solutions etc. was experimentally established afore-hand, the deliberations are however necessary to transfer the model into the real environment of concrete or grout around the FRP element. Suitable procedures are presented.