ACI SP-232-2005
Punching Shear in Reinforced Concrete Slabs (Out of Print)

Standard No.

ACI SP-232-2005

Release Date

2005

Published By

ACI - American Concrete Institute

Scope

INTRODUCTION Flat plates and slabs are an economical structural system for medium height residential and office buildings. However flat plates and flat slabs have to be treated with caution as they can be susceptible to failure by punching shear. Punching shear usually occurs around the support columns of flat slabs which are regions of large moment and where flexural cracks are observed around the periphery of the support. Punching shear is an undesirable mode of failure that occurs without warning and can lead to progressive collapse of large areas of slab or even complete structures. Punching shear can also occur due to large concentrated loads anywhere on the slab area. While most punching shear failures occur during construction when there is insufficient early-age punching shear capacity under the relatively high construction loads Field (1968)@ ACI-ASCE 423 (1989)@ failure can also occur with mature structures. The 1995 Sampoong Department Store (Seoul) collapse by punching shear that killed 500 people is a severe example of a failure in service. Most design codes calculate a nominal shear stress on a control perimeter some fraction??multiple of the slab depth away from the column. Reviews of codes and tests are given in the summarizing reports in-fib Bulletin 12 (2001) and earlier by Regan and Braestrup (1985) and in several papers at the Punching Shear Colloquium in Stockholm@ Silfwerbrand and Hassanzadeh (2000). Most experimental tests have been done on relatively thin slabs and as unit strength decreases with increasing size@ code equations should incorporate a size effect term. Bazant and Cao (1987) established a theoretical basis for the necessity of size effect terms in the punching shear prediction equations for concrete members. The punching shear provisions of AC1 3 18-05@ first adopted in AC1 3 18-63@ are unusual in that there is no consideration of the effect of flexural steel or size effect. The British Code BS 81 10-97@ the CEB-FIP 1990 Model Code@ DIN 1045-1 and EuroCode 2 (2003) have reinforcement ratio and size effect terms in their punching shear equations. This paper summarises and evaluates the punching shear provisions of several major codes@ ACI 318-05@ csa a23.04@ bs 8110-97@ ceb-fip mc 90@ din 1045-1 (2001) and EuroCode 2 (2003) for interior columns without moment transfer and interior column connections@ edge column connections and comer column connections with moment transfer. All codes require the reduced strength@ in terms of load or stress@ to be greater than the factored applied specified loads or stresses respectively. Specified loads * load factor lt; resistance partial safety factor * predicted resistance The resistance partial safety factor should be less than unity in the numerator@ AC1 and CSA@