Bonded connections of pultruded sections for floor system studied using digital image correlation

Abstract

An experimental investigation of bonded connections of Fiber Reinforced Polymer (FRP) pultruded sections for a new floor design is presented. Flat plates with T-up ribs are bonded to the lower flanges of I-beams and used as a structural form for the concrete floor. Adhesively bonded connections with or without mechanical fasteners of different types and configurations were examined through 48 bond specimens tested in tension. Digital Image Correlation (DIC) was used to capture strain and slip profiles along the connection interface, from which shear and peeling stress distributions were established. The study showed that connections reached 80–100% of the full capacity of the member, governed by the transverse strength of the I-beam. Most samples experienced mixed failure modes. The two highest occurrences were fiber-tear of the ribbed plate, where longitudinal fibers appeared on both surfaces, and adhesive failure, where epoxy appeared on one surface only in certain parts. Using fasteners with the adhesive increased the ultimate capacity by up to 19%. Embedment of fasteners inside the concrete had little effect on ultimate strength. A method was developed to convert DIC measured strains into peeling and shear stresses. The combined test data was used to establish the shear-peeling stress failure envelope, which agreed very well with the theoretical interaction expression. A bond-slip relationship was also deduced from the DIC test results.