STRESS LOSSES IN HIGH STRENGTH STRAND IN A PRESTRESSED PRETENSIONED CONCRETE I GIRDER

STRESS LOSS WAS EVALUATED IN PRETENSIONED HIGH STRENGTH PRESTRESSING STRANDS DURING THE CURING OF THE CONCRETE, AFTER THE STRAND WAS DETENSIONED, AND AFTER STRESS LOSS REACHED AN EQUILIBRIUM CONDITION. THREE I-GIRDERS EACH 99 FEET - 4 INCHES LONG AND 4 FEET DEEP WERE USED. PRESTRESS STEEL IN EACH GIRDER CONSISTED OF 14 STRAIGHT AND 12 HARPED 1/2 INCH 7-WIRE HIGH STRENGTH /270 KSI/ STRANDS. LOAD CELLS, STRAIN GAGES, AND THERMOCOUPLES WERE INSTALLED DURING FABRICATION OF THE GIRDERS. STRAIN AND LOAD WERE RECORDED FROM INITIAL PRESTRESSING UNTIL THE GIRDERS WERE IN PLACE AT THE BRIDGE SITE. TEMPERATURE WAS RECORDED CONTINUOUSLY FROM CONCRETE POUR UNTIL THE GIRDERS COOLED TO THE AMBIENT TEMPERATURE. FOR THE HIGH STRENGTH STRAND, THE CREEP FOR A 90 HOUR PERIOD RESULTED IN A MAXIMUM LOSS OF 14,000 PSI COMPARED TO A RECOMMENDED ALLOWANCE OF 6000 PSI. THE LOSS DUE TO ELASTIC SHORTENING WAS A MAXIMUM OF 11,500 PSI AS COMPARED TO A RECOMMENDED ALLOWANCE OF 12,000 PSI. MAXIMUM FINAL TOTAL LOSS IN STRESS AFTER 53 DAYS WAS 36,000 PSI WHICH COMPARES FAVORABLY WITH A RECOMMENDED ALLOWANCE OF 35,000 PSI. HOWEVER CONSIDERABLE ADDITIONAL LOSS CAN BE REASONABLY EXPECTED BECAUSE PREVIOUS RESEARCH HAS SHOWN THAT ABOUT 50 PERCENT OF THE CREEP OCCURS WITHIN THE FIRST 2 OR 3 MONTHS.

• Supplemental Notes:
  • Hpr-1/2/, PART II, ITEM 59, APR65
• Corporate Authors:

  California Division of Highways

  Bridge Department
  Sacramento, CA  United States  05914
• Authors:
  • Sequeira, A
  • Myhres, F
• Publication Date: 1965-4

Subject/Index Terms

• TRT Terms: Beams; Concrete; Concrete curing; Equilibrium (Mechanics); Evaluation; Girders; High strength steel; I beams; Loads; Losses; Measurement; Prestressed concrete; Prestressing; Pretensioning; Strain (Mechanics); Stresses; Temperature; Wire rope
• Old TRIS Terms: Strains
• Subject Areas: Bridges and other structures; Highways;

Filing Info

• Accession Number: 00207744
• Record Type: Publication
• Files: TRIS
• Created Date: Oct 1 1994 12:00AM