Finite-element and simplified models of GFRP connections

Finite-element models of a variety of joints between glass fiber reinforced plastic (GFRP) pultruded members are described that reproduce experimentally measured linear elastic stiffnesses to within 10%. The models were constructed using shell finite elements. The material properties of the pultrusions were measured using a combination of tests and fits to numerical models. This approach produced elastic constants that proved reliable in the subsequent finite-element modeling of the joints. Standard data provided by the manufacturer gave inaccurate predictions of the joint stiffness. Two types of simplified models were also considered: (1) simplified beam models; and (2) a condensed finite element model. The simplified beam models replace the joint with an elastic connection region and a torsional spring. The condensed finite-element models use a detailed shell element model of the joint to extract the equivalent stiffnesses of the joint that can be used with a standard frame analysis package. When compared with experimental data, the simplified beam models performed poorly. However, the condensed finite-element models performed almost as well as the detailed finite models.