Moment-rotation relationships of reinforced concrete beams with and without web openings

Abstract

In developing inelastic methods of analyzing indeterminate reinforced concrete frameworks, one of the fundamental relationships that must be determined is that of moment versus rotation. In order for moment redistribution to take place, the cross-section must have adequate rotational capacity so that "hinges" can form.

This thesis reports some recent findings showing that reinforced concrete members do possess considerable ductility and ability to form such hinges. Specifically, results are presented on a series of 4" x 7" x 6” -0" beams loaded at the third points up to and beyond their ultimate capacities. Comparisons are made of ultimate moments and moment-rotation relationships for beams with and without web openings.

The web openings are made in the tension zone of the beams; they vary in size from one-third to two-thirds of the affective area. The range of steel area is from 1% to 3%.