Concrete Floor with GFRP-Embedded I-Beams and Stay-in-Place Structural Forms

This paper introduces a new concrete floor concept comprising embedded glass fiber-reinforced polymer (GFRP) I-beams and GFRP stay-in-place (SIP) structural forms spanning between the lower flanges of the I-beams. The forms are flat plates with T-up ribs. The flexural behavior in the direction transverse to the I-beams, which is more critical because of the bonded connection between SIP forms and I-beam, is investigated using 2,575 × 610 × 225 mm slab segments. Both connection tests and member tests were conducted. Different SIP forms, concrete thicknesses, and surface treatments were explored. Both adhesive bonding and mechanical fasteners were explored for the connection. Also, behavior in the negative moment regions of the floor was simulated by testing the specimen inverted. The connection with adhesive and mechanical fasteners failed at a 48% higher bending than that with adhesive only. Increasing GFRP form size (reinforcement ratio) increased stiffness but not strength, neither for the connection nor for the member, due to debonding failure modes. A case study of a floor design was presented and showed that adhesively bonded connections met the strength requirement. A design-oriented analytical model was developed to predict connection strength based on bond failure. It accounts for the nonuniform shear and peeling stresses and includes corrections for the imbalance between the SIP form and the I-beam flange, as well as the additional peeling due to bending in the SIP form.