Effect of Openings on Deflections and Strength of Reinforced Concrete Slabs


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Title: Effect of Openings on Deflections and Strength of Reinforced Concrete Slabs

Author(s): M. A. Bhatti, B. Lin, and J. P. Idelin Molinas Vega

Publication: Special Publication

Volume: 161


Appears on pages(s): 149-164

Keywords: Cracking (fracturing); deflection; finite element analysis; loads (forces); nonlinear analysis; openings; reinforced concrete; slabs; strength

Date: 4/1/1996

The usual design practice for analysis of reinforced concrete slabs with openings is to neglect holes if their area is less than 10- 12% of the total slab area. This practice is based in part on studies conducted in early sixties regarding the effects of holes on the elastic behavior of plates. A literature survey revealed no specific studies regarding the effects of holes on deflection and strength of reinforced concrete slabs with openings. This paper presents a numerical study of the effects of openings of different sizes on the behavior of reinforced concrete slabs. A nonlinear finite element model for reinforced concrete slabs is developed using three dimensional brick elements taking into account cracking and crushing of concrete, and plasticity of both reinforcement and concrete. Distributed and concentrated loads are applied to slabs until collapse. Results show that when slabs are subjected to uniformly distributed loads, the openings do not have much effect on their strength and serviceability. The openings should be considered, however, when designing slabs subjected to concentrated loading where the opening ratios are larger than 2.5% .