Influence of Slab Thickness on Punching Shear Strength

Current ACI design code does not account for size effects in the equations for punching shear strength. Tests to study the influence of slab thickness on the punching shear strength of flat slabs show the significant effect of size on the shear stress resistance, particularly for tests without shear reinforcement. This paper presents tests in which the slab thickness varied between 160 and 300 mm (6.3 and 11.8 in.). One test series was designed to fail inside the shear reinforced zone while a second test series was designed to fail outside the shear reinforced zone. These tests and tests by others with slabs up to 500 mm (19.7 in.) thick indicate that slabs without shear reinforcement thicker than approximately 260 mm (10.2 in.) may not have a high factor of safety if designed according to ACI 318-05. Shear stress resistance provided by concrete is also reduced, but to a lesser degree, for thick slabs with shear reinforcement. An equation is proposed for the nominal shear stress resistance of concrete in slabs without shear reinforcement.

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  • English

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Filing Info

  • Accession Number: 01100283
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 23 2008 10:20AM