Design of Composite Slabs for Vertical Shear

by Mark Patrick, BHP Research-Melbourne Lab, Victoria,
Russell Q. Bridge, BHP Research-Melbourne Lab, Victoria,

Document Type: Proceeding Paper

Part of: Composite Construction in Steel and Concrete II


Three major modes of failure should be considered in the design of the positive moment regions of composite slabs incorporating profiled steel sheeting, viz.: flexure, longitudinal slip (or longitudinal shear) and vertical shear. The results of the first tests known to produce vertical shear failures in simply-supported composite slabs are presented. The slabs were loaded to failure with concentrated line loads, after being designed using new partial shear connection strength theory so as not to fail by longitudinal slip. This required the shear connection performance of the profile concerned to be known from Slip Block tests, with which it was possible to determine the distance that the ends of the sheets had to extend past the supports in order to develop adequate anchorage. Proprietary high-strength anchors were also fitted to the ends of the sheets to allow for the possibility of strut action, and to restrict the amount of longitudinal slip that could occur at ultimate load. Although light-gauge slabs tested with shear span-to-effective depth ratios Ls/d of between 1.6 and 2.5 failed in flexure rather than vertical shear, heavy-gauge slabs with Ls/d ratios of between 1.9 and 2.0 exhibited classic diagonal splitting failures. The test results are compared with the empirical Zsutty equations used for the vertical shear design of reinforced-concrete slabs, and the results are also shown on `shear-bond' graphs to illustrate the correct occurrence of the cross-over from flexural to vertical shear failures as the shear span reduces.

Subject Headings: Shear failures | Shear tests | Shear strength | Slabs | Failure analysis | Structural failures | Reinforced concrete

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