Tables for Plastic Design of Beams with Rectangular Holes

Abstract

The requirement for holes in the webs of beams and girders in building structures for the passage of utility ducts has become common, and rational methods for the design of beams with certain types of such holes have become available. In this paper, tables are presented which provide an aid to the design of reinforcement for rectangular holes in the webs of flanged beams. The reinforcement considered consists of horizontal bars placed above and below the holeand located close to its edge. Single holes centered on the mid-depth of symmetrical beams are considered, and the limitations pertaining to proportioning on the basis of plastic design apply to the beams. (See for example, Sect. 2.7 of Ref. 1, or Par. 30.11 of Ref. 2.) Figure 1 shows typical holeand reinforcement details; the reinforcement may be either on both sides or on one side of the web. The tables give, for a wide range of combinations of moment and shear acting at the center line of the hole, the minimum area of reinforcement required for the beam to carry that moment and shear before plastic collapse, expressed as a fraction of the area of the beam flange. The tables also indicate when reinforcement is not necessary, and when horizontal bar reinforcement is not adequate.