INDUCED BRIDGE LOADS AND MOMENTS DURING A TEN YEAR PERIOD: STUDY OF EFFECT OF NEW VEHICLE WEIGHT LAW ON STRUCTURES

STUDY WAS CONDUCTED TO DETERMINE THE PRESENT AND FUTURE EFFECTS OF THE INCREASE IN THE LEGAL VEHICLE WEIGHT LIMITS ON THE EXISTING BRIDGE STRUCTURES THROUGHOUT THE STATE OF MARYLAND. STATISTICAL STUDY INVOLVED THE DETERMINATION OF THE YEARLY TRAFFIC PICTURE AND THE MAXIMUM MOMENTS INDUCED ON BRIDGES OF VARIOUS SPAN LENGTHS BY THIS TRAFFIC. FROM THE MOMENTS AND TRAFFIC VOLUMES, THE STRESS HISTORIES AND CONSEQUENTLY THE FATIGUE DAMAGE TO THESE BRIDGES CAN BE OBTAINED. A METHOD IS PRESENTED FOR ESTIMATING THE CUMULATIVE FATIGUE DAMAGE ON HIGHWAY STRUCTURES DUE TO THE RANDOM LOADING OF HEAVY TRUCK TRAFFIC. THIS METHOD IS SUBDIVIDED INTO THREE SEPARATE OPERATIONS: (1) EXPANSION OF THE 24-HOUR TRUCK LOADOMETER DATA TO YEARLY VALUES, (2) DETERMINATION OF THE MAGNITUDE AND FREQUENCY OF OCCURRENCE OF THE MAXIMUM BENDING MOMENTS INDUCED BY THE YEARLY HEAVY TRUCK TRAFFIC, AND (3) TRANSFORMATION OF THE RANGE OF MOMENTS INTO A RANGE OF STRESSES BY UTILIZING THE CONVENTIONAL FLEXURAL STRESS-MOMENT RELATIONSHIP AND THE SECTION PROPERTIES OF A TYPICAL SECTION OF THE STRUCTURE UNDER INVESTIGATION. THE FIRST OPERATION CAN BE ACCOMPLISHED BY TWO DIFFERENT PROCEDURES: (1) UTILIZING EXPANSION FACTORS DEVELOPED AT A STATE-WIDE LEVEL, (2) DEVELOPING FACTORS WHICH ACCOUNT FOR VARIATIONS IN TRAFFIC CONDITIONS THROUGHOUT THE STATE. THE PROCEDURE TO BE USED IS DETERMINED BY THE AMOUNT OF DATA TO BE EXPANDED AND THE AVAILABILITY OF FACILITIES TO HANDLE IT. FROM THE DISTRIBUTIONS OBTAINED IN THE SECOND OPERATION THE RANGE OF MOMENTS ARE FOUND INCLUDED WITHIN PLUS AND MINUS TWO STANDARD DEVIATIONS FROM THE MEAN, AND THE NUMBER OF TRUCKS WHICH CAUSE MOMENTS WITHIN THIS RANGE. AFTER OBTAINING THE THIRD OPERATION DATA, THE FATIGUE LEFT OF THE STRUCTURE UNDER THIS RANGE OF STRESSES IS THEN DETERMINED FROM MODIFIED GOODMAN DIAGRAMS FOR THE CRITICAL FATIGUE CONDITION WHICH IS PRESENT IN THE STRUCTURE. THE CUMULATIVE FATIGUE DAMAGE OF THE STRUCTURE IS OBTAINED BY CALCULATING THE CYCLE RATIOS AND APPLYING MINER'S CUMULATIVE DAMAGE HYPOTHESIS. THIS METHOD OF ESTIMATING CUMULATIVE FATIGUE DAMAGE WAS APPLIED TO EIGHT HIGHWAY BRIDGES OF VARIOUS TYPES AND IN VARIOUS LOCATIONS IN MARYLAND. RESULTS OF THE ANALYSIS INDICATED THAT THE CUMULATIVE FATIGUE DAMAGE CAUSED BY HEAVY TRUCK TRAFFIC DURING THE TEN YEAR PERIOD WAS OF SUCH A SMALL PERCENTAGE OF THE ESTIMATED FATIGUE LIFE THAT THERE IS NO FEAR OF FATIGUE FAILURE FOR A SUSTAINED PERIOD OF TIME. IT APPEARS THAT THE WEIGHT LAW SHOWS NO VISIBLE INFLUENCE ON THESE SPECIFIC STRUCTURES.

• Supplemental Notes:
  • Progr Rept, 319 PP, 51 FIG, 54 TAB, 22 REF, 4 APP
• Corporate Authors:

  University of Maryland, College Park

  Department of Civil and Environmental Engineering
  College Park, MD  United States  20742
• Authors:
  • Werner, J D
  • Heins, C P
  • Looney, C T
• Publication Date: 1968-6

Subject/Index Terms

• TRT Terms: Average daily traffic; Axle load force; Bending moments; Bridge superstructures; Bridges; Fatigue (Mechanics); Fatigue (Physiological condition); Highway bridges; Loadometers; Loads; Mathematical analysis; Regulation; Size and weight regulations; Statistical analysis; Stresses; Traffic volume; Trucks; Vehicle weight; Vehicles
• Uncontrolled Terms: Bridge spans; Fatigue life; Loading
• Old TRIS Terms: Truck effects (Bridges)
• Subject Areas: Bridges and other structures; Data and Information Technology; Highways; Law; Motor Carriers; Vehicles and Equipment;

Filing Info

• Accession Number: 00209006
• Record Type: Publication
• Files: TRIS
• Created Date: Jul 28 1994 12:00AM