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TESTS TO DETERMINE THE TORSIONAL STIFFNESS OF FLEXURALLY CRACKED SLAB ELEMENTS

When carrying out a non-linear analysis of a reinforced concrete slab by the global plate stiffness approach, it is usual to adopt the Huber value of D sub xy = 1/2 (1 - nu) square root D sub x D sub y for the torsional stiffness of a flexurally cracked slab. In order to determine whether this value is correct for an orthotropically or anisotropically reinforced concrete slab, a series of 21 tests on flexurally cracked slabs under torsional loading was carried out. The results of these tests are presented in this report. It is concluded that such slabs only behave orthotropically under torsional loading if they are reinforced symmetrically with respect to the axes of maximum twisting moment. If non-symmetrically reinforced, the slabs behave anisotropically and such behaviour is dependent upon the sign of the reinforcement orientation. The torsional stiffness of all slabs, after flexural cracking, was found to decrease with an increase in the severity of that cracking (defined as an increase in crack width and/or number of cracks) but did not necessarily tend to the Huber value. Indeed, the Huber stiffness can grossly underestimate the actual stiffness, particularly for slabs in which the reinforcement is included to the direction of maximum twisting moment. The contributions to torsional stiffness of direct stress in such reinforcement and of dowel action of any reinforcement were found to be small compared with those of the uncracked concrete and of aggregate interlock. The latter component was independent of maximum aggregate size for the range of crack widths examined. /Author/

  • Corporate Authors:

    Cement and Concrete Association

    Wexham Spring
    Slough SL3 6PL, Buckinghamshire,   England 
  • Authors:
    • CLARK, L A
    • White, I G
  • Publication Date: 1978-1

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 22 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00179370
  • Record Type: Publication
  • Report/Paper Numbers: Report No. 42.517
  • Files: TRIS
  • Created Date: Sep 14 1978 12:00AM