FIELD INVESTIGATION OF PRESTRESSED CONCRETE I-BEAM BRIDGES

RESEARCH WAS UNDERTAKEN TO MEASURE AND EVALUATE THE LONG-TERM BEHAVIOR, UNDER FIELD SERVICE CONDITIONS, OF TYPICAL PRESTRESSED CONCRETE BRIDGES. THE INFORMATION PRESENTED IN THIS INTERIM REPORT RELATED TO A BRIDGE THAT CARRIES TWO LANES OF ILLINOIS 57 ACROSS A SMALL STREAM. THE I-BEAM BRIDGE IS MADE WITH PRECAST, PRETENSIONED GIRDERS, AND THE CAST-IN-PLACE DECK IS REINFORCED TO PROVIDE STRUCTURAL CONTINUITY FOR LIVE-LOAD EFFECTS. ADDITIONAL INFORMATION IS PRESENTED ON A TEST STRUCTURE THAT CROSSES I-57 AT A LOCATION 70 MILES EAST OF ST. LOUIS. THE ONLY UNUSUAL FEATURE OF THE BRIDGE WAS PROVISION FOR STRAIN MEASUREMENTS. IT WAS FOUND FROM STRAIN--TIME CURVES THAT LARGE STRAIN INCREASES OCCURRED DURING THE FIRST SIX MONTHS OF SERVICE, FOLLOWED BY RATHER DECREASES BETWEEN 300 AND 400 DAYS; THE LATTER TOOK PLACE IN THE WINTER, AND PROBABLY REPRESENTS RECOVERY OF SHRINKAGE DURING THE WET TIME OF YEAR. LOSSES IN PRESTRESS, WHILE LARGE, ARE SMALLER THAN THE FINAL VALUE OF THE DESIGN ASSUMPTIONS. FROM ANALYSIS OF CONCRETE SPECIMENS AN UNUSUAL FINDING EMERGED. STRESS-INDUCED, TIME-DEPENDENT DEFORMATIONS WERE NEARLY THE SAME FOR LABORATORY AND FIELD CONCRETE LOADED AT THE TIME OF PRESTRESSING RELEASE. THIS SUGGESTS THAT THE ENTIRE DIFFERENCE BETWEEN THE TOTAL DEFORMATIONS OF THE TWO SETS OF SPECIMENS IS DUE TO THE DIFFERENCES IN SHRINKAGE, AND NOT TO SUBSTANTIAL DIFFERENCES IN THE CREEP STRAINS. CONDITIONS IN THE FIELD ARE NOT CONSTANT, AND ALTHOUGH THE AVERAGE RELATIVE HUMIDITY IS HIGH, THE NEARLY CONTINUOUS MOVEMENT OF MOISTURE INTO AND OUT OF THE TEST SPECIMENS APPARENTLY LED TO CREEP STRAINS APPRECIABLY HIGHER THAN THE AVERAGE RELATIVE HUMIDITY VALUE WOULD LEAD ONE TO EXPECT.

• Supplemental Notes:
  • pp 129-159, 23 FIG, PHOTS
• Authors:
  • Gamble, W L
• Conference:
  • Colo State Univ, Bridge Eng Conf
• Publication Date: 1970

Subject/Index Terms

• TRT Terms: Concrete; Concrete bridges; Creep; Field tests; Humidity; I beams; Laboratory tests; Prestressed concrete; Shrinkage; Strain measurement
• Old TRIS Terms: Concrete creep; Concrete shrinkage
• Subject Areas: Bridges and other structures; Highways;

Filing Info

• Accession Number: 00209519
• Record Type: Publication
• Files: TRIS
• Created Date: Dec 20 1971 12:00AM