Abstract
This paper presents the residual behavior of wide-flange steel beams strengthened with high-modulus carbon fiber-reinforced polymer (CFRP) laminates subjected to thermal loading. Because the coefficients of thermal expansion of the steel and the CFRP are different, temperature-induced distress may take place along their interface. Periodic unbonded zones are considered to represent local interfacial damage. Five test categories are designed depending on the size of the unbonded zones from 10 to 50 mm, and corresponding beams are loaded until failure occurs after exposing to a cyclic temperature range of ΔT = 25 °C (−10 to 15 °C) up to 84 days. The composite action between the CFRP and the steel substrate is preserved until yielding of the beams happens, regardless of the thermal cycling and periodic unbonded zones. The initiation and progression of CFRP debonding become apparent as the beams are further loaded, particularly at geometric discontinuities in the vicinity of the unbonded zones along the interface. A simple analytical model is employed to predict the interfacial stress of the strengthened beams. A threshold temperature difference of ΔT = 30 °C is estimated for the initiation and progression of CFRP debonding. Multiple debonding-progression stages in conjunction with the extent of thermal distress appear to exist. It is recommended that high-modulus CFRP be restrictively used for strengthening steel members potentially exposed to a wide temperature variation range.
Highlights
High-modulus carbon fiber-reinforced polymer (CFRP) laminates may be used for strengthening constructed steel girder bridges
Rabinovitch [7] developed an analytical model for CFRP-strengthened concrete beams at elevated temperatures from10 to 80 ̋C, based on high-order mathematical equations combined with a fracture mechanics approach
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Summary
High-modulus carbon fiber-reinforced polymer (CFRP) laminates may be used for strengthening constructed steel girder bridges. Nguyen et al [6] examined the time-dependent response of a CFRP-steel interface exposed to thermal and mechanical loading. Rabinovitch [7] developed an analytical model for CFRP-strengthened concrete beams at elevated temperatures from to 80 ̋C, based on high-order mathematical equations combined with a fracture mechanics approach. Gao et al [9] expanded the modeling approach with various bond-slip relationships, such as elastic-brittle, trapezoidal, rigid-softening, elastic-perfectly plastic, and exponential cases. These bond-slip models were found to be insensitive to thermal loading, whereas they affected the size of effective bond length
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