DIFFERENTIAL CAMBER IN PRESTRESSED CONCRETE BEAMS
A study was made to determine the cause or causes of differences in cambers that occur in prestressed concrete beams of identical design for highway bridges. Beams of AASHTO Type IV, and State Department of Highways and Public Transportation of Texas Types C, 54, B, and A were studied. Data from elevations taken at construction sites were reduced to camber information on over 4000 beams. Design information and some information on fabrication were obtained from SDHPT on those beams for purposes of isolating the causes of camber differences. A statistical T test was used to identify those beams with unusual camber. A measure of the extent of unusual camber was developed in determining the amount of wasted concrete in using unusually cambered beams in a span. A regression analysis was made to determine the effect of span on the range of camber computed from elevation measurements. Analytical studies were made to determine the effect of variations in tendon forces and positions, variations in concrete modulus in the overall beam, variations of concrete modulus in layers in the beam and in longitudinal sections of the beam, and of time. Camber measurements were made at release on a few beams, and modulus of elasticity measurements were made in the field in an effort to determine variations in the concretes used in beams of the types reported in field data. Four prestressing plants were visited while they were in the process of producing highway bridge beams of the types studied. Procedures that were followed in producing beams to the SDHPT specifications were carefully observed. /FHWA/
- Research performed in cooperation with Department of Transportation, Federal Highway Administration. Study Title: Camber in Prestressed Concrete Beams.
Arlington, TX United States 76011
- Jones, H L
- Publication Date: 1977-9
- Pagination: 196 p.
- TRT Terms: Beams; Bridge construction; Bridge foundations; Bridges; Construction; Curvature; Highway bridges; Mix design; Prestressed concrete; Prestressing
- Subject Areas: Bridges and other structures; Construction; Highways;
- Accession Number: 00193732
- Record Type: Publication
- Source Agency: Federal Highway Administration
- Report/Paper Numbers: FHWA-TX-77-1931F Final Rpt., FCP 45F3-112
- Contract Numbers: 2-5-75-193
- Files: TRIS, USDOT
- Created Date: Aug 15 1979 12:00AM