LOAD FACTOR DESIGN FOR STEEL HIGHWAY BRIDGES

TO ENSURE SAFE AND SERVICEABLE PERFORMANCE WHILE PROVIDING A CONSISTENT LIVE LOAD CARRYING CAPACITY FOR ALL HIGHWAY BRIDGES, THE LOAD FACTOR DESIGN (LFD) WAS DEVELOPED. THE LFD CONSISTS OF: SERVICE LOADS, OVERLOADS, AND MAXIMUM DESIGN LOADS. LFD AND WORKING STRESS DESIGN (WSD) ARE DISCUSSED IN TERMS OF THE TENTATIVE CRITERIA FOR LFD OF STEEL HIGHWAY BRIDGES WHICH WERE ADOPTED BY THE AASHO COMMITTEE ON BRIDGES AND STRUCTURES IN 1970 AS AN ALTERNATE DESIGN METHOD AND PUBLISHED IN THE 1971 AASHO INTERIM DESIGN SPECIFICATIONS. A COMPARATIVE STUDY INVOLVING 15 BRIDGES OF THE BEAM AND GIRDER TYPE, SPECIFICALLY BOTH SIMPLE AND CONTINUOUS DESIGNS WITH SPANS LENGTHS VARYING FROM 40 TO 360 FT., IS INCLUDED.'''''THE BRIDGES WERE DESIGNED FOR H15 OR H520 LOADINGS USING A36, A441, AND A514 STEELS. BOTH ROLLED BEAM AND WELDED PLATE GIRDER DESIGN WERE INCLUDED. SOME OF THE CONCLUSIONS ARE (1) THE LEVEL OF SAFETY FOR LFD BRIDGES IS CONSISTENT WITH THE MINIMUM SAFETY INHERENT IN CURRENT HIGHWAY BRIDGE DESIGN. (2) THE LFD/WSD STEEL WEIGHT RATIO DECREASES WITH INCREASING SPAN AND DEAD TO LIVE LOAD RATIO. (3) THE LFD APPROACH GIVES DESIGNS THAT UTILIZE MORE OF THE INHERENT STRENGTH OF COMPOSITE CONSTRUCTION THAN IS PERMITTED BY CURRENT WSD PROCEDURES. (4) FATIGUE REQUIREMENTS UNDER SERVICE LOADS CONTROLLED THE DESIGN OF SHEAR CONNECTORS AND THE LOCATION OF COVER PLATE CUTOFFS AND SOME SPLICES. (5) ALL WELDED GIRDER BRIDGES WERE NONCOMPACT; THEIR DESIGN WAS BASED ON THE MAXIMUM STRENGTH AT FIRST YIELD. (6) THE LFD OFFERS THE POTENTIAL OF REDUCING THE WEIGHT OF STEEL BEAMS AND GIRDERS BY UP TO 15 PERCENT, WITH NO INCREASE IN FABRICATION LABOR AND NO DECREASE IN THE LOAD-CARRYING CAPABILITIES OF THE TOTAL HIGHWAY SYSTEM. /EJ/

• Supplemental Notes:
  • Vol 8, No 4, PP 113-123, 6 FIG, 8 TAB, 8 REF
• Authors:
  • Hansell, W C
  • Viest, I M
• Publication Date: 1971-10

Media Info

• Serial:
  • Engineering J, Am Inst Steel Constr

Subject/Index Terms

• TRT Terms: Beams; Bridge design; Bridges; Design load; Fatigue (Physiological condition); Girders; Highway bridges; Live loads; Load factor; Metal bridges; Oversize loads; Plate girders; Specifications; Static loads; Steel bridges; Structural design
• Uncontrolled Terms: Overloads
• Subject Areas: Bridges and other structures; Highways;

Filing Info

• Accession Number: 00209574
• Record Type: Publication
• Files: TRIS
• Created Date: Feb 15 1972 12:00AM