This study is aimed at investigating the sensitivity of the Drucker-Prager modeling parameters and the use of it in plasticity theory for shear design. The Drucker-Prager yield criterion is evaluated using finite element simulation with optimum mesh size for reinforced concrete (RC) beams with different geometrical and material properties. Providing an optimum mesh size configuration for the nonlinear analysis, the whole load-deflection behavior of the beams has been analyzed and the main results of the numerical analyses have been compared with the experimental results of RC beams to demonstrate how accurately the Drucker-Prager yield criterion for concrete predicts the load carrying capacity. The considered variables are compressive strength of concrete (f(c)), tensile reinforcement ratio (rho), shear span-to-depth ratio (a/d) and size effect (d/d(a),). The nonlinear analyses of the beams, employing the Drucker-Prager yield criterion for concrete, have been performed and reasonable concrete cohesion has been investigated. (c) 2006 Elsevier Ltd. All rights reserved.