Experiments on Pultruded FRP Beam-to-Column Joints: Failure Mode Analysis and Stiffness Determination

Abstract

The design of pultruded fiber-reinforced polymer (PFRP) structures can be governed by the beam-to-column joints because they exhibit brittle behavior. The objectives of this study were to understand the load path in PFRP structural joints, improve the failure mode, and delay the brittle mode of failure by modifying the joint configuration. The components in the PFRP beam-to-column joints were made from E-glass pultruded structural shapes. Ten beam-to-column joint tests were carried out, including parameters such as three different end distances (e1), cleat thicknesses (ta), and additional T–stiffeners. The conventional beam-to-column joints failed in a brittle mode, with cracks initiated at flange cleats followed by progressive stiffness reduction leading to ultimate failure. The analysis using strain data confirmed that there is a need for an additional load transfer component in the top flange to delay the first brittle failure. The use of T-stiffeners significantly increased the initial stiffness of the beam-to-column joint and delayed the first failure. The overall rotational stiffness of the PFRP beam-to-column joint was determined using the joint component method in the Eurocode. It is shown that the Eurocode method is conservative for connection components with higher end distances. The appropriateness of the stiffness prediction method in the Eurocode was demonstrated with a design example. Since the introduction of PFRP in construction, it has gained traction among industries and researchers to further enhance it for various applications. However, there is an inconsistency in the design standards of PFRP structures. This paper demonstrates a simple method to develop a connection stiffener to accommodate the complicated load transfer and improve the beam–column joint structural performance by (1) increasing the initial stiffness, and (2) delaying the first failure. It also demonstrates how to use the traditional joint component method of Eurocode to calculate the initial stiffness of the PFRP beam–column joint. Several research directions are possible from this paper, and the conclusions drawn can be added to the prestandards.