Stiffness Degradation of FRP Strengthened RC Beams Subjected to Hygrothermal and Aging Attacks

Abstract

The past decade has witnessed an ever increasing interest in strengthening, repairing, retrofitting, and upgrading of deteriorated concrete structures using fiber reinforced plastics (FRP). Enhanced load carrying capacity by FRP strengthening has been observed by a large number of researchers through experiments at ambient environments. In a harsh environment, however, FRP will degrade. This may result in structural degradation of FRP strengthened concrete members. The possible structural degradation has become a major obstacle for the wide-spread acceptance of this new strengthening technique. In the present study, boiling water and ultraviolet (UV) radiation were used to study the structural degradation of concrete beams strengthened with GFRP and CFRP fabrics. A total of eighteen 170 Â 7.62 Â 15.2 cm steel reinforced concrete (RC) beams were prepared as control specimens, conditioned specimens, and unconditioned specimens. Finite element modeling was used to analyze stiffness degradation of FRP layers. The Downloaded from tested and calculated results showed that environmental attacks had a considerable effect on the structural degradation of FRP strengthened concrete beams. 57-76% of the strengthening efficiency and 43-48% of the stiffness of FRP were lost after conditioning.

Effect of hot temperature on pull-off strength of FRP bonded concrete

“…The presence of moisture (100% humidity) slightly improved cohesive strength compared to the 0% humidity samples while the differences in cohesive strength at each humidity reduced with increasing cycle numbers. When submerged in water, the strengths were the lowest with the largest coefficient of variation, which could be partially attributed to the higher moisture uptake by the resin and, consequently, plasticization [6,37]. The dry air (0% relative humidity) exposure at 100°C showed a slight increase in strength over time, which is consistent with Elarbi's results [16] but is yet to be understood.…”

“…Although the short term performance of FRP sheets has been satisfactory, the long term performance of FRP bonded concrete structures are still uncertain. Environmental factors have been reported to have negative effects on the durability performance of FRP [5,6]. Environmental conditions may involve temperature, humidity, salt water, chemicals, and freeze-thaw cycles [7].…”

Pull-out Strengths of GFRP-Concrete Bond Exposed to Applied Environmental Conditions

“…Various environmental conditions such as freeze-thaw cycles, wet-dry cycles, combined environmental cycles, boiling water and UV radiation, hydrothermal ageing under constant temperature and humidity, and dry heat were applied by Chajes et al (1995), Toutanji and Gó mez (1997), Myers et al (2001), Li et al (2002) and Grace (2004) to investigate the long term performance of FRP strengthened concrete beams in terms of ultimate strength and/or stiffness of beams. Chajes et al (1995) reported wet-dry cycles as slightly more severe than freeze thaw cycles (Calcium Chloride was solution was used in both cases) and graphite reinforced beams as the most durable compared to aramid and E-glass reinforced beams (36 % drop in strength was observed for aramid and E-glass reinforced beams due to wet-dry cycles).…”

Fatigue performance of RC beams strengthened with CFRP under coupling action of temperatures and vehicle random loads

“…[7][8][9] The research results showed that the environmental temperature cannot be ignored as the most common influencing factor. [7][8][9] The research results showed that the environmental temperature cannot be ignored as the most common influencing factor.…”

“…At present, the influence of environments on fatigue performance and durability of the RC structures strengthened with FRP has attracted more and more attention in civil engineering field. [7][8][9] The research results showed that the environmental temperature cannot be ignored as the most common influencing factor. Adimi et al 7 found out the fatigue lives of concrete beams strengthened with carbon fibre-reinforced polymer (CFRP) bars Nomenclature: D, Palmgren-Miner accumulated damage; D c , Palmgren-Miner accumulated critical damage; N, fatigue life; N m , average fatigue life; n i , loading cycles under the ith stress level; ΔP mean , average loading amplitude of the vehicle random loading spectrum; P max , average peak load of the vehicle random loading spectrum; P u , ultimate load-bearing capacity of the strengthened beam; S R , loading level of the vehicle random loading spectrum were obviously decreased as temperature was increased from room temperature to 40°C.…”