FINITE ELEMENT FOR CONCRETE FRAME

A FINITE, BEAM-COLUMN ELEMENT WHICH CAN BE USED TO MODEL THE BEHAVIOR OF REINFORCED CONCRETE MEMBERS NEAR FAILURE IS DEVELOPED. THE DERIVATION OF THE MATERIAL PROPERTIES AND A STIFFNESS MATRIX FOR THE ELEMENT ARE PRESENTED. INELASTIC MATERIAL PROPERTIES ARE CHARACTERIZED BY THE RIGIDITY OF A CROSS SECTION WHOSE STEEL COULD STRAIN HARDEN, AND BE UNSYMMETRICALLY PLACED. THE ELEMENT STIFFNESS MATRIX INCLUDES NONLINEAR SOFTENING DUE TO INITIAL FORCES AND NONLINEAR CHANGES IN GEOMETRY DUE TO ROTATION OF THE ELE- MENT. INCLUSION OF EACH OF THESE PARAMETERS IS NECESSARY IN ORDER FOR THE ELEMENT TO BE USED TO ADEQUATELY STUDY THE INELASTIC INTERACTION OF ENTIRE FRAMES NEAR LIMIT LOADS.