A hypoplastic model for the analysis of requested colums tubular mixing cross-section retangular to the oblique composed flexão.

Abstract

This paper presents a numerical model for analysis of concrete-filled steel tubular columns. The columns are constituted by rectangular cross-section steel tubes filled by normal and high strength concrete and are subjected to combined axial load and bending about two axes. The model is based on the finite alement method, using a total Lagrangean kinematics formulation and nonlinear constitutive relations for the materials, allowing the description of the behavior of the columns in pre and post critical stages. The model adopts the following basic assumptions: a) Sections which are plane before bending remain plane after bending; b) There is perfect bond between the tube and the concrete core; c) The steel is a perfectly elastoplastic material; d) compressed concrete has a hypoplastic orthotropic behavior. The formulation takes into account the tensile strrength of the concrete. In the analysis, the cross sections of the columns are divided into rectangular elements with sides , respectively, parallel to the edges of the tube. Results of several columns with distinct mechanics and geometric characteristics are presented. Such results are given as critical losd – lateral displacement diagrams. To validate the model, the results are compared with experimental values.