Ali Zaidi

Thermal effect on fiber reinforced polymer reinforced concrete slabs

The difference between the transverse coefficients of thermal expansion of fiber reinforced polymer (FRP) bars and concrete generates radial pressure at the FRP bar - concrete interface, which induces tensile stresses within the con- crete under temperature increase and, eventually, failure of the concrete cover if the confining action of concrete is insuf- ficient. This paper presents the results of an experimental study to investigate the thermal effect on the behaviour of FRP bars and concrete cover, using concrete slab specimens reinforced with glass FRP bars and subjected to thermal loading from -30 to +80 8C. The experimental results show that failure of concrete cover was produced at temperatures varying between +50 and +60 8C for slabs having a ratio of concrete cover thickness to FRP bar diameter (c/db) less than or equal to 1.4. A ratio of c/db greater than or equal to 1.6 seems to be sufficient to avoid splitting failure of concrete cover for concrete slabs subjected to high temperatures up to +80 8C. Also, the first cracks appear in concrete at the FRP bar - concrete interface at temperatures around +40 8C. Comparison between experimental and analytical results in terms of thermal loads and thermal strains is presented.

Finite element modeling of fiber reinforced polymer bars embedded in prismatic concrete beams under high temperatures

Numerous experimental tests and analytical investigation were carried out on thermal effects on fiber reinforced polymer bars reinforced concrete structures. Nevertheless, the finite element modeling of thermal behavior of fiber reinforced polymer bars embedded in concrete was insufficiently analyzed, particularly, for asymmetric problems. This paper presents a nonlinear numerical study using ADINA finite element software to investigate the effect of the ratio of concrete cover thickness to fiber reinforced polymer bar diameter (c/d b ) on the distribution of transverse thermal stresses and deformations in fiber reinforced polymer bars and concrete cover for an asymmetric problem using prismatic concrete beams reinforced with fiber reinforced polymer bars submitted to high temperatures up to + 60℃. Also, to predict the thermal loads (ΔT cr ) that produce the first radial cracks within concrete and the thermal loads (ΔT sp ) which cause the splitting failure of the concrete cover as a function of the ratio of concrete cover thickness to fiber reinforced polymer bar diameter for an asymmetric problem. Nonlinear numerical results in terms of cracking thermal loads, thermal deformations, and thermal stresses are compared to those evaluated from analytical models and experimental tests.

Concrete Strength Variation Effect on Numerical Thermal Deformations of FRP Bars-Reinforced Concrete Beams in Hot Regions

The steel corrosion phenomenon could reduce the durability and the serviceability of concrete structures reinforced with steel bars. Moreover, the repair cost of these structures is very expensive. Consequently, it seems necessary to substitute steel bars by fiber reinforced polymer (FRP) bars, in concrete structures, because of their high properties, particularly, their excellent corrosion resistance and high tensile strength-to-weight ratio. Nevertheless, the use of FRP bars in concrete structures, built in hot regions, may cause splitting cracks within concrete at the interface of FRP bars-concrete, and eventually the failure of the concrete cover. This paper presents a nonlinear finite element investigation using ADINA software to analyze the effect of concrete strength variations on thermal deformation distributions in the concrete cover surrounding glass FRP (GFRP) bars for reinforced concrete beams under high temperatures up to 70 °C. The main results show that the concrete strength variation has no big influence on the transverse thermal deformation of FRP bars-reinforced concrete beams for thermal loads less than the cracking thermal load ΔT cr , producing the first radial cracks in concrete at the FRP bar-concrete interface, varied from 20 to 35 °C depending on the ratio of concrete cover thickness to FRP bar diameter (c/d b ) and the compressive concrete strength \( f_{c}^{{\prime }} \) varied from 1 to 3.2 and 25 to 90 MPa, respectively. However, for thermal loads greater than ΔT cr , the transverse thermal deformations decrease with the increase in the concrete strength. Comparisons between analytical and numerical results in terms of thermal deformations are presented.