PERMANENT DEFLECTIONS AND LOSS OF CAMBER IN STEEL BRIDGE BEAMS

The findings are reported of 2 projects in which the available field data concerning evidence of permanent deformations in existing highway bridges, and the data on residual stresses in rolled beams were surveyed. Existing practices for cambering beams and a categorization of campering methods were also surveyed. The effects of slip in the shear connection, shrinkage of the concrete slab and creep in concrete slab in composite construction was determined. The projects also included the determination of the magnitude and distribution of residual stresses and the variation of yield point in steel beams as rolled and delivered to the fabricator without camber, and the determination of certain cambering methods on residual stresses. The permanent deformation in steel beams, with and without camber, subjected to repeated loads of various levels lower than those causing computed yield point stress was determined; the number of cycles of load applied approximated six months of service load on a bridge. A method of analysis to predict the permanent deformation of steel beams was developed. The study showed that because the apparent yield point of a material is sensitive to the rate of loading, yielding may occur in a beam under slowly applied overloads at stresses substantially less than the nominal yield point, which must be satisfied by a standard mill test. Conclusions are also presented relating to residual stresses in as-received beams, residual stress in flanges during cold cambering, variations in loss of camber, stable beams which suffer no loss of camber, residual stress at the yield point, wedge-heating and spot-heating, flame cambering, shrinkage of deck slab in composite beams, slip in the shear connection in composite beams, and cold cambering and continous heating.

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  • Supplemental Notes:
    • Appeared in NCHRP Summary of Progress Through 1975. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
  • Corporate Authors:

    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Baldwin Jr, J W
    • Guell, D L
  • Publication Date: 1975

Media Info

  • Features: Figures; Tables;
  • Pagination: p. 128-140
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00131407
  • Record Type: Publication
  • Contract Numbers: 12-1 & 12-6
  • Files: TRIS, TRB
  • Created Date: May 14 1976 12:00AM