An efficient beamcolumn formulation for 3D reinforced concrete frames
This paper presents a new beamcolumn formulation which can be used for the accurate, yet efficient, modelling of 3D reinforced concrete (R/C) frames. The formulation is intended for modelling the nonlinear elastic behaviour of a whole R/C beamcolumn with only one element, which is an essential ingredient of adaptive elasto-plastic analysis. On the longitudinal axis level, quartic shape functions are used to represent the two transverse displacements. A constant axial force criterion is employed instead of shape functions for the axial displacement, which is largely responsible for the accuracy of the proposed formulation. For concrete, the formulation assumes a nonlinear compressive stressstrain relationship and no tensile resistance; whereas for steel, a linear stressstrain relationship is utilised. On the cross-sectional level, the formulation is capable of modelling the interaction between the axial force and the biaxial moments for a general R/C cross-section, with explicit expressions obtained using a novel approach based on integration over triangular subdomains. The paper provides the details of the proposed formulation, and presents several verification examples to demonstrate the accuracy of this formulation and its ability to model the nonlinear elastic response of reinforced concrete beamcolumns with only one element per member.
beamcolumns reinforced concrete nonlinear analysis efficient formulation