B-spline sectional model for general 3D effects in reinforced concrete elements

In this paper, an efficient sectional model for the nonlinear analysis of reinforced concrete elements sensible to 3D stress-components effects is presented. The classic plane-sections kinematic hypothesis is enhanced with a warping-distortion displacement field, which enables the model to reproduce the interaction between normal and tangential forces. The complementary field is obtained explicitly considering the inter-fiber equilibrium. This is solved using b-splines interpolation on the cross-section domain. The proposed method significantly reduces the number of unknowns compared with a finite element solution. The model is able to reproduce the interaction of longitudinal and transverse reinforcement with the concrete matrix. The validation shows that the presented model reproduces accurately complex failure modes as pure shear and coupling between bending and torsion. Further, as the transverse reinforcement is considered explicitly, confinement can be simulated in an objective manner. The presented model is an efficient tool for nonlinear analysis of reinforced concrete sections under general loading.