Compressive Behavior of Pultruded GFRP Boxes with Concentric Openings Strengthened by Different Composite Wrappings

Web openings often need to be created in structural elements for the passage of utility ducts and/or pipes. Such web openings reduce the cross-sectional area of the structural element in the affected region, leading to a decrease in its load-carrying capacity and stiffness. This paper experimentally studies the effect of web openings on the response of pultruded fiber-reinforced polymer (PFRP) composite profiles under compressive loads. A number of specimens have been processed to examine the behavior of PFRP profiles strengthened with one or more web openings. The effects of the size of the web opening and the FRP-strengthening scheme on the structural performance of PFRP profiles with FRP-strengthened web openings have been thoroughly analyzed and discussed. The decrease in load-carrying capacity of un-strengthened specimens varies between 7.9% and 66.4%, depending on the diameter of the web holes. It is observed that the diameter of the hole and the type of CFRP- or GFRP-strengthening method applied are very important parameters. All CFRP- and GFRP-strengthening alternatives were successful in the PFRP profiles, with diameter-to-width (D/W) ratios between 0.29 and 0.68. In addition, the load-carrying capacity after reinforcements made with CFRP and GFRP increased by 3.1-30.2% and 1.7-19.7%, respectively. Therefore, the pultruded profiles with openings are able to compensate for the reduction in load-carrying capacity due to holes, up to a D/W ratio of 0.32. The capacity significantly drops after a D/W ratio of 0.32. Moreover, the pultruded profile with CFRP wrapping is more likely to improve the load-carrying capacity compared to other wrappings. As a result, CFRP are recommended as preferred composite materials for strengthening alternatives.