Nima Farzadnia

Reinforcement Benefits of Nanomodified Coir Fiber in Lime-Treated Marine Clay

AbstractIn this study, reinforcing effect of nanomodified coir fibers with ferric hydroxide, Fe(OH)3, and aluminum hydroxide, Al(OH)3, on shear strength of limed marine clay soil was investigated. Accordingly, triaxial compression strength (TCS) testing was carried out to determine the shear strength parameters of the reinforced soil. Also, wetting/drying cycle testing was conducted to assess the durability of samples. The results from the experimental investigation show that the lime and nanomodified fibers improved the shear strength and durability through the intended modification on natural coir fiber. Moreover, an increase in the effective stress internal friction angle and the cohesion intercept were observed. To confirm the morphology alteration in fibers, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) tests were performed. Nanomodification of fibers increased their tensile strength and caused a better interaction with the limed matrix by an enhanced interfacial adhesion. The ...

Behavior of high-strength concrete cylinders repaired with CFRP sheets

This study aims to investigate the behavior of damaged high-strength concrete cylinders repaired using carbon fiber reinforced polymer (CFRP) sheet. The experimental work on CFRP-wrapped concrete cylinders with various predamage levels indicated that CFRP can precisely resist the axial aggravated deformation of cylinders caused by damaging under uniaxial loading. The findings also revealed that the energy absorption of the damaged specimens confined with CFRP was restored approximately three times more than that of the undamaged specimens without confinement. Therefore, an empirical relationship exists between the pre-damage levels and the uniaxial compressive strength reduction of the concrete cylinders.

A simple and practical model for FRP-reinforced cracked beam

In this paper, a numerical method is developed to model tensile crack in a three-point bending concrete beam which is reinforced with fibre-reinforced polymer (FRP). In this method, the energy release rate is estimated by considering fracture process zone (FPZ) and more accurate stiffness. To do so, the depth of the beam, the effective crack and the initial notch are considered in the FPZ length. To improve the accuracy of estimation, a spring element is used to model the cohesive zone. The energy dissipation rate is also calculated using virtual crack closure technique in FRP-reinforced concrete beam and then, the crack propagation criterion is presented. The model is easy and accurate, converges fast and is capable to model the crack growth in FRP-reinforced concrete cracked beam. Also, the model presented in this study shows acceptable similarity to the experimental data used.