Standards Development

Scope

This International Standard specifies a method for determining the compressive properties in the pultruded FRP (Fibre Reinforced Polymer) using full-section compressive tests. This test is convenient and able to evaluate the mechanical properties of whole section. The test provides a more reasonable compressive parameter for design.

Purpose

Fibre reinforced polymer (FRP) pultruded profiles are manufactured by a continuous modelling process using fibre reinforcement in polyester or other thermosetting resin matrices. The unshaped composite is cured in a heated die and form their geometric shape. This production process brings great flexibility in design and manufacture of FRP pultruded profiles. Thanks to the use of both longitudinal and transversal fibre reinforcement and the shaped cross section, FRP pultruded profiles have necessary strength and stiffness to carry longitudinal and transversal loads. Besides, it is easy to process FRP pultruded profiles into structural members with advantages common to FRP products by simply cutting or opening holes. Therefore, FRP pultruded profiles have been successfully used as structural members in several applications that require fast-deployment, light-weight of structure, resistant of corrosion or mitigating effects of seismic loading.

Several design guides for FRP pultruded members are presented by manufacturers and institutions, which can be divided into two classes, the direct one and the indirect one. A direct design guide contains design tables that every FRP pultruded profiles provided by the manufacturer are listed in. In indirect design methods, the design load-carrying capacity of FRP pultruded profile is function of material and geometric parameters, by which members under coupling loads can be designed. An indirect design method has a much wider scope than a direct one, but it also has some drawbacks. To complete an indirect design function, multiple material parameters are required, usually including elastic module, Poisson’s ratio and strength, in both longitudinal and transversal direction, of each element, because FRP is anisotropic and inhomogeneous . However, in many cases, material tests can’t be carried out on specimens cut from original pultruded profiles because of the limit of size or curvature of the element. For example, according to the design standard from ASCE and the standard test method from ASTM D6641, a typical specimen for determining transversal compression strength and module of the material is a 140mm long squared rod, which exceeds the transversal dimension of many elements, therefore equivalent specimen has to be used in the test instead. It makes the test result doubtable, even though the equivalent specimen has same reinforcement layout and matrix as the original element, because the property of FRP pultruded profiles depends on not only the raw materials but also the whole production process. Besides, rupture at the connection between elements is observed in full-section test. Unlike welding joint rupture in steel members, it can’t be predicted by material test or design equation because of the variation in material and production process. Material tests that indirect design standard requires may be costly but still not enough to estimate the full-section capacity of FRP pultruded profiles.

Full-section test can be a viable solution for this problem. Standard EN 13706 gives an example of fullsection test that three-point bending test is used to estimate equivalent elastic module under moment load. Full-section tests aim to estimate equivalent properties of the whole section in which both elements and connections are included, to estimate the profile’s full-section performance, instead of determining allowable load of a particular structural member under determined loading condition or achieving material properties of individual points at the element. This paper concentrates on estimating equivalent longitudinal compression strength of pultruded profiles by full-section compression test on short column specimens. On the basis of test results, failure modes of specimen and influence of specimen configuration on test result were studied. Researches on using full-section test to determined critical stress of global and local buckling will be carried out in future.