METHODS TO REDUCE BUILT-IN RESIDUAL STRESSES IN STEEL BRIDGE DIAPHRAGMS (PHASE I)

This investigation determined the magnitude and origin of residual stresses in plate girders, diaphragms and stiffeners built-in during construction. Residual stresses can contribute to crack formation. Three different steel bridges were studied: (1) a multi-girder bridge anchored at the abutments with no center pier; (2) a 4-span continuous multi-girder bridge with piers; (3) a movable, double-leaf bascule bridge. Bridges were instrumented with strain gages at the fabricator. Changes in reference strains were monitored: (a) after steel erection and bolt-up; (b) after deck placement; and (c) after parapet placement. Built-in stresses varied widely. Mean tensile stress was 35 MPa (5.1 ksi), with a standard deviation (SD) of 40 MPa (5.8 ksi). Mean compressive stress was -51 MPa (-7.4 ksi) with an SD of 39 MPa (5.7 ksi). Highest tensile stress measured was 146 MPa (21 ksi). Methods to attenuate the effects of built-in strain were proposed, including: (1) lower-modulus aluminum and zinc alloys for diaphragm components; (2) synthetic rubber used in shear connectors; (3) new designs which accommodate misalignment, distortion and deflection; and (4) retrofit attachments to X and K-brace diaphragms. The study recommends Phase II testing of proposed modifications which could improve constructibility and durability in actual bridges.

• Corporate Authors:

  Illinois Department of Transportation

  Bureau of Materials and Physical Research
  126 East Ash Street
  Springfield, IL  United States  62704-4766

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • South, J M
  • Hahin, C
• Publication Date: 2000-7

Language

• English

Media Info

• Features: Figures; Photos; References; Tables;
• Pagination: 94 p.

Subject/Index Terms

• TRT Terms: Aluminum alloys; Bridges; Design; Diaphragms (Engineering); Monitoring; Plate girders; Residual stress; Retrofitting; Steel; Stiffeners (Plates); Strain (Mechanics); Strain gages; Stresses; Synthetic rubber; Zinc alloys
• Subject Areas: Bridges and other structures; Construction; Design; Highways; I24: Design of Bridges and Retaining Walls; I53: Construction of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00796931
• Record Type: Publication
• Report/Paper Numbers: FHWA/IL/PRR-109,, Final Report
• Contract Numbers: HR-25-318-97-1
• Files: TRIS, ATRI, USDOT, STATEDOT
• Created Date: Aug 8 2000 12:00AM