n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Horizontal shear strength in rib and block slab systems : technical paper

Volume 43, Issue 1
  • ISSN : 1021-2019



A recent amendment to the horizontal shear clause of SABS 0100 requires that the average horizontal shear stress is distributed according to the shape of the shear diagram. This change effectively doubled the design shear stress in simply supported members subjected to a uniformly distributed load and therefore threatened the economy of rib and block slabs. In response, a study into the specifications of international codes of practice was undertaken and compared with the South African code. An extensive experimental program was also conducted to determine the shear capacity along the contact interface of the in-situ concrete and precast ribs. It was found that the South African specification (as amended) is consistent with other international codes. It was also found that the surface roughness has a profound influence on the horizontal shear capacity and is a better indicator of shear strength than the strength of the in-situ concrete.

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