Title:
Design Procedure for Reinforced Concrete Beams
with Large Web Openings
Author(s):
K.H. Tan and M. A. Mansur
Publication:
Structural Journal
Volume:
93
Issue:
4
Appears on pages(s):
404-411
Keywords:
beams (supports); cracking (fracturing); deflection; openings;
reinforced concrete; serviceability; shear tests; stiffness; strength; struc-tural
design.
DOI:
10.14359/9699
Date:
7/1/1996
Abstract:
Based on test evidence, guidelines for the placement of large web openings in reinforced concrete beams are given, following which a simple design procedure is suggested. Generally, openings should be positioned so that chords have sufficient concrete area to develop the ultimate compression block in flexure and adequate depth to provide effective shear reinforcement. They should not be deeper than one-half the beam depth and should be located not closer than one-half the beam depth from supports or con-centrated loads. For analyses for elastic bending moments and shear forces by conventional methods, the recommended procedure uses an equivalent shear stiffness incorporating an effective length for the opening and considers the applied shear to be carried in proportion to the flexural stiffness of the chords. The design of chords for strength follows ACI code provisions. Cracking at the opening is controlled by proper detailing, while deflections are calculated using the same analysis procedure but considering cracked moment of inertia and checking against code requirements.