  This research investigates the analysis of reinforced concrete beams
subjected to combined axial load, bending moment and shear force.
Cross-sections of general shape are divided, along the height, into plane
elements. The biaxial behavior is represented according to the smeared rotating
crack approach. Using traditionally accepted hypotheses for beams, the shear
flow is determined by applying the Jouravski formula to an "equivalent
section", which takes into account the nonlinear material behavior. The
"Equivalent Section Method", originally proposed by Diaz (1980) and Diaz and
Schulz (1981), is improved and simplified. The formulation is implemented
applying the bidimensional constitutive model A, proposed by Vecchio and
Collins (1993). The tension-stiffening effect is considered as adopted by Polak
and Vecchio (1993). Shear slip at crack surfaces, Poisson's ratio and other
secondary effects are not considered. Validation is undertaken by comparison
with experimental results obtained by other researchers. The examples include
reinforced and prestressed concrete beams, for normal and high strength
concrete. The formulation satisfactorily predicts the ultimate capacity under
different load combinations. The whole set of equilibrium, compatibility and
constitutive equations are satisfied, the stiffness derivatives are explicitly
calculated and the algorithms show good convergence.
