V Broujerdian - Ph.D. Candidate, Department of Civil Engg., Sharif University of Tech., Tehran
Mohammad T. Kazemi - Associate Professor, Department of Civil Engg., Sharif University of Tech., Tehran,

Introducing a new constitutive model a smeared rotating crack model was developed having the capability of predicting the entire load-deformation response of reinforced concrete elements. The important features of the model are considering the effect of reinforcement ratio on average stress-strain relationships of cracked concrete and considering the gradual reduction of average stiffness of steel bars embedded in concrete. The model applied to predict the response of available test panels and showed a good correlation. Using the simplified version of the model a new expression for shear capacity of reinforced concrete beams without stirrups was derived. The proposed relation captures the dependence of shear strength on size, shear span-to-depth ratio, longitudinal reinforcement ratio, maximum aggregate size, and concrete strengt h. The model agrees well with fracture mechanics concepts. The proposed relation was calibrated by least-square fitting of the existing experimental beam test database and showed a good agreement.

reinforced concrete, shear strength, membrane elements, beams, size effect