Failure Mode Of Reinforced Concrete Beams Research Articles

Deterioration behavior of reinforced concrete beam under compound effects of acid-salt mist and carbon dioxide

An experimental investigation on the deterioration behavior of reinforced concrete (RC) beams under compound effects of acid-salt mist and carbon dioxide was conducted. The changes of failure mode, neutralization depth, strength loss of concrete, corrosive rate of rebar and the expansive crack width were tested. And then the relationship between the experimental time and service time was achieved with theoretical analysis. Results indicated that neutralization depth of concrete increased with time linearly while corrosion of rebar changed nonlinearly. When the concrete cracked, the corrosion increased rapidly. The bond between the corroded rebar and deteriorated concrete decreased, and then the failure mode of RC beams under flexural load change from crushing of compression concrete to yielding of rebar. The relationship between the service time and investigation time was achieved, according to the neutralization ratio of concrete and corrosion ratio of rebar respectively. It was found between the calculation results and the calculation of corrosion ratio was closer.

Effects of Eccentric Load on Un-Strengthen and CFRP Strengthened RC Beams

CFRP strengthened reinforced concrete (RC) beams are usually tested under either three points or four point concentric loads; the effect of eccentricity is neglected in many studies. In this experimental program eight RC beams tested in two groups, GROUP ‘A’ & ‘B’. In group ‘A’ four RC beam tested, one control beam tested under concentric load and three under the eccentricity of 40, 60 and 80 mm respectively. The remaining four RC beams in group ’B’ strengthened using carbon fibre reinforced polymer (CFRP) strip and tested under the 60mm eccentricity. The experiment has confirmed the behaviour transformation from flexure failure to local failure due to variation in eccentricity. Therefore, the effects of eccentricity cannot be neglected and required special consideration before applying strengthening scheme on RC beam. The RC beams strengthen using CFRP have the ability to enhanced the load carrying capacity of beams tremendously, but the eccentric load effect on ductility, and failure mode of RC beams.

Finite element modeling of the shear capacity of RC beams strengthened with FRP sheets by considering different failure modes

In this study, three-dimensional (3D) finite element (FE) analyses were carried out to study the effects of several variables on the failure modes and ultimate shear capacity of reinforced concrete (RC) beams strengthened with fiber-reinforced polymer (FRP) sheets. Fifty-eight cases were analyzed by FE modeling. The parameters considered to affect the failure modes and the shear capacity included the beam width, the concrete strength, the height and thickness of the FRP sheet, the elastic modulus of the FRP and the strengthening configuration (complete wrapping, U-jacketing, and side bonding). A model for predicting the failure mode and the shear capacity were proposed on the basis of the results of the parametric analysis. Experimental results for 307 beams collected from previously published work were analyzed to verify the accuracy of the proposed model. The results show that the failure modes of RC beams are affected by the parameters considered and can be predicted by the proposed model. The results also indicate that the proposed model can be used to calculate the shear capacity of RC beams strengthened with FRP sheets and to predict the failure mode with greater accuracy than existing models.

Finite element simulation of reinforced concrete beams externally strengthened with short-length CFRP plates

Fiber Reinforced Polymer (FRP) materials have been recently used as novel materials to retrofit aging and deficient structures. Several research programs have succeeded in narrowing down the knowledge gap of the debonding mechanism associated with the failure of externally bonded FRP systems. This study seeks numerical investigation of plate debonding and performance of reinforced concrete (RC) beams externally strengthened with bonded Carbon Fiber Reinforced Polymers (CFRPs) plates running for a length covering 25% of the shear span. The results are compared with plates covering 85% of the shear span in addition to a control unstrengthened specimen. The aim of this paper is to develop 3D finite element (FE) models that can accurately simulate the response and performance of RC beams externally strengthened with short-length CFRP plates. A total of six beams were modeled and the load–midspan deflection results and failure modes were compared with experimentally measured data published in the literature. Two out of the five strengthened beams were bonded to the soffit of the beams without any means of end anchorages. The other three beams were strengthened with CFRP plates and anchored transversely at the plate’s ends with different arrangements of CFRP U-wrap sheets. The developed models incorporate the different material nonlinear constitutive laws including the bond-slip action between steel rebars and surrounding concrete and debonding at the CFRP–concrete interface. The predicted and measured load–midspan deflection response results in addition to the failure modes are compared. It was observed that the predicted FE results are in good agreement with the experimental measured test data. A parametric study was then performed using the validated FE model to investigate the effect of the flexural reinforcement bar diameter as well as arrangements of the CFRP U-wraps. It has been concluded that the developed FE models are capable of accurately predicting and capturing capacity the debonding failure mode of RC beams strengthened with FRP plates.

Applicability of the Impact Response Analysis Method for Reinforced Concrete Beams Mixed with Polyvinyl Alcohol Short Fibers

Abstract The impact-resistant capacity of reinforced concrete (RC) structures can be rationally upgraded by mixing polyvinyl alcohol (PVA) short fibers into concrete. The static and dynamic post peak residual tensile strength of the concrete that occurs because of the bridge effects of PVA short fibers. In this paper, to establish a simple impact response analysis method for RC structures under impact loading, a method that treats PVA short fibers mixed into concrete as shell elements of PVA plates with an equivalent tensile strength to the post peak residual tensile strength of the concrete is proposed. The applicability of the method has been investigated by conducting a three-dimensional elastoplastic finite element analysis using LS-DYNA code and comparing the results with the falling-weight impact test results for RC beams. From this study, it was confirmed that the crack distributions and the failure mode of RC beams mixed with PVA short fibers can be predicted and that the effects of mixing PVA short fibers on improving the impact resistant capacity can be estimated by using the proposed numerical analysis method.

Numerical Simulation for Failure Modes of Reinforced Concrete Beams under Blast Loading

The reinforced concrete (RC) beams have three failure modes using large-scale finite element procedure LS-DYNA to simulate dynamic responses and failure modes of RC beams under blast loading. Holmquist-Johnson-Cook material model was used in concrete, the damage and strain rate effects were considered the kinematic hardening plasticity material model was used in reinforcing bars. With different rebar ratios and charges of weight TNT equivalent and stand-off distance were investigated and discussed. The numerical simulation can predict responses and flexure, flexure-shear and direct shear of the RC beams under different blast loading. The influence of the several factors have been identified and provided a theoretical basis for blast resistant design and retrofitting of the RC beam.