Philippine E-Journals

The analysis and design of reinforced concrete columns with biaxial bending are difficult because a trial and adjustment procedure is necessary to find the inclination and the depth of the neutral axis that satisfies equilibrium conditions. This study addresses the problem of accurately predicting the behavior of a reinforced concrete column with biaxial bending through fiber method modeling in order to be able to establish its capacity at the ultimate stage. The fiber method has been found to be an effective method in predicting the flexural response of structural members, especially when bending moments and axial loads dominate the behavior. In implementing the fiber method, Bazant's Endochronic theory was used as a constitutive model for concrete while the Ciampi model was used for steel. The effects of different structural parameters were considered in establishing the interaction surfaces. Numerical analyses of square reinforced concrete columns with symmetrical reinforcement were conducted. The strength of concrete considered varied from 21 MPa (3,000 psi) to 62 MPa (9,000 psi). The result of the fiber method modeling agreed well with some available experimental data. The development of interaction diagrams for the biaxial bending of column sections provides structural designers with an alternative way to analyze and design such column sections.