ABSTRACT

Abstract For the design, structural detailing and the execution of concrete members prestressed and or reinforced with FRP tensile elements the mechanical properties of the latter must be known to the engineer. In contrast to prestressing and reinforcing steel, standards of testing the mechanical properties of FRP bars, strands, etc. for structural concrete application do not yet exist. Existing standards mostly pertain to laminated FRP. Because the methods to assess a particular property may in many instances significantly and adversely affect such property, the development of suitable test methods by which the true material behaviour is tested becomes important. The necessary comparability of the test results of different producers and research laboratories had to be ascertained. This leads to the development of common rules for testing, measurements and data evaluation of the axial short-term strength, stress-rupture strength, fatigue strength, relaxation etc. thereby also including the effects of hostile environments and the strength of tendon-anchorage assemblies. The test methods developed for the above-mentioned properties permit the quantification of the relevant properties free from detrimental testing influences. Keywords: Laboratory testing, tensile strength, stress-rupture, fatigue

1 Introduction

With the development of FRP tensile elements, based on glass, aramid or carbon fibers embedded in epoxy or polyester resin an alternative to high strength prestressing steel units has emerged due to the excellent corrosion resistance in combination with high tensile strength. The FRP elements used for structural concrete applications are unidirectional fiber composites in the shape of round bars and strands. They will in practical

Laboratory testing of FRP 111

use be axially stressed in tension, i.e. in parallelity to the fibers. Hence, the axial tensile strength under short-term and also under long-term force is one of the most important properties. The determination of these mechanical properties of FRP elements requires suitable experimental techniques and subsequent test regulations. The existing standards dealing with the testing of FRP mostly pertain to laminated FRP. They are in many respects not suitable for the testing of FRP tensile elements to be used for structural engineering applications. This report submits proposals for the necessary test work for FRP in short-and long-term tensile and fatigue testing, in order to exploit the highest level of structural utilization.