ANALYSIS OF REINFORCED CONCRETE COLUMN CAPACITIES

This paper illustrates the variation of the column capacities for circular and rectangular sections as a function of the column capacity axis using the analytical method. The analysis is based on the known stress/strain properties of the concrete and steel materials and the application of the column capacity axis in the development of the ultimate capacities of the column section. The capacities generated by the concrete section are determined separately from that of the steel reinforcement. Basic mathematics and the application of the fundamental equilibrium conditions, ΣF = 0 and ΣM = 0 were employed in the analysis. The variables considered are the column dimensions, ultimate concrete compressive stress, compressive depth encompassing cracked and uncracked section, steel yield stress of reinforcing steel bars, concrete cover to center of rebars, number and spacing of rebars, and the position of the column capacity axis, θ. This axis defines the sets of column capacities plotted in a capacity curve, which can be developed in a column section. The equations for the ultimate strength of circular and rectangular columns were already published in a book by the author. This paper includes the examples showing the variations of the moment capacity, M and the resultant internal moment capacity, M_R for circular and rectangular sections as a function of the position of the capacity axis. These examples will provide the proof that there are several sets of column capacities for circular and rectangular sections.

• INTRODUCTION

• BASIC CONCEPTS

• COLUMN CAPACITY AXIS

• COLUMN CAPACITY CURVES

• EXAMPLE VARIATIONS OF COLUMN CAPACITIES

• CONCLUSIONS

• NOTATIONS

• REFERENCE