Ductile reinforced concrete frames

Abstract

The 1971 building code of the American Concrete Institute contains an appendix with special provisions for the seismic design of reinforced concrete structures. The provisions are based on the code of the Structural Engineers' Association of California and on research evidence and studies of damage to buildings. This paper comments on a number of the provisions for reinforced concrete frames and where necessary indicates where improvements appear to be required. The comments on flexural members and columns cover curvature ductility factors resulting from the flexural steel provisions, the transverse steel required for shear strength, concrete confinement, and restraint against buckling of compression bars, and the affect of cyclic loading. The comments on columns also cover the avoidance of plastic hinges in columns by taking into account the probable distribution of bending moments during dynamic excitation and biaxial bending. The comments on beam-column connections touch on the design of shear reinforcement for joint cores. Some observations on capacity design, and suggestions for capacity design procedures, are also made.