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Finite Element Modeling of RC Beams with Shear Dominated Behavior

Commercial FE codes are becoming more widely used in engineering practice. However analysis results can be uncertain due to modeling assumptions and solution schemes, particularly for highly nonlinear and non-ductile behaviors. The finite element code ANSYS (2003), version 7.1, was employed in this study to predict behavior of two series of reinforced concrete beams having different sizes and span-to-depth (a/d) ratios. The modeling included concrete confinement to account for developed arching action in RC beams with small a/d ratio, and incorporated a quasi-displacement control loading technique to accelerate the nonlinear solution without loss of accuracy.

Conclusion

Use of finite element analysis has become routine for structural engineers. Nonlinear finite element analyses were performed to predict behavior of two groups of experimental reinforced concrete specimens. Two different a/d ratios were included: 2.0 and 3.0. The specimens are shear dominated and exhibited significant nonlinearity and non-ductile response at failure. The material modeling incorporated effects of concrete confinement for the analyses. A quasi-displacement control technique was employed to reduce solution times. The FE predicted results were compared with the experimental data including ultimate load, deflection at the peak load, steel strain, and crack pattern. Based on FE analysis results, the following conclusions are made:

  • The quasi-displacement control technique can be used for reinforced concrete beam modeling. This technique significantly reduced solution times without loss of result precision and helped convergence of solution for nonlinear FE analysis of reinforced concrete beams with shear-critical behavior.
  • Using proper material models for modeling of reinforced concrete beams resulted in good correlation between FE prediction and test results. Finite element analyses including confining effects well predicted response of reinforced concrete beams with short shear span.
  • The FE prediction predicted the failure behavior of the laboratory specimens reasonably well.

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