The comparative body model in material and geometric nonlinear analysis of space RC frames

• Published in: Engineering computations Vol. 25; no. 2; pp. 155 - 171
• Main Authors: Trogrlic, Boris, Mihanovic, Ante
• Format: Journal Article
• Language: English
• Published: Emerald Group Publishing Limited 07-03-2008
• Subjects: Concretes; Framed structures; Numerical analysis
• ISSN: 0264-4401
• DOI: 10.1108/02644400810855968

Purpose This paper aims to present a new numerical model for the stability and loadbearing capacity computation of space reinforcedconcrete RC frame structures. Both material and geometric nonlinearities are taken into account. The RC crosssections are assumed to undergo limited distortion under torsional action. Designmethodologyapproach A simple, global discretization using beamcolumn finite elements is preferred to a full, global discretization using 3D elements. This is more acceptable from a practical point of view. The composite crosssection is discretized using 2D elements to apply the fiber decomposition procedure to solve the material and geometrical nonlinear behavior of the crosssection under biaxial moments and axial forces. A local discretization of each beam element based on the comparative body model i.e. a prismatic body discretized using brick elements, element by element, during the incrementaliterative procedure allows determining the torsional constant of the crosssection under limited warping. The classical global iterativeincremental procedure is then used to solve the resulting material and geometric nonlinear problem. Findings It has been noticed that, in case of a limited distortion of the crosssection, the torsional constant of homogeneous linear elastic materials is greater than the one obtained from the SaintVenant theory. However, due to lowtensile strength of concrete materials, the torsional constant decreases significantly after an early loading phase, primarily due to the lack of reinforcing flanges. Research limitationsimplications The current study does not cover the torsion analysis of RC crosssection with stirrups. Besides, the bondslip effect between concrete and steel reinforcement is not taken into account, nor is the local buckling of the beam flanges and rebar. Practical implications This new numerical model has been implemented in a computer program for effectively computing the nonlinear stability and load bearing capacity of space RC frames. Originalityvalue The authors believe that the comparative body model should bring a new approach to the solution of torsion problems with limited distortion of crosssections in material and geometric nonlinear analysis of space RC frames.