Lightweight Concrete Reduces Weight and Increases Span Length of Pretensioned Concrete Bridge Girders

摘要

style="text-align: left;">The maximum lengths for simple-span pretensioned concrete composite girders using high strength lightweight concrete (HSLWC) were investigated analytically using concrete strengths of 8, 10, and 12  si (55, 69, and 83 MPa) and prestressing strands of 0.6 in. (15.2 mm) diameter. The use of HSLWC produced spans up to 4 percent longer than the same section made with high strength normal weight concrete (HSNWC). Based on the AASHTO I-girder and AASHTO PCI bulb-tee sections examined in this study, the reduced girder weight eliminated the need for special transportation a€?superloada€? permits. Modified AASHTO-PCI bulb-tees with one extra row of strands in the bottom flange extended the girdersa€? maximum span length by at least 10 ft (3.1 m). In all cases, the use of  lightweight concrete caused greater girder deflections, but all of these values were within the AASHTO specified limit of L/800. Overall, the advantages of lightweight concrete with compressive strengths up to 12 ksi (83 MPa) include lower girder weight, relief from special permitting requirements, and longer span lengths.>References style="text-align: left;">1. Kahn, Lawrence F., and Saber, Aziz,target="_blank" title=" a€?Analysis and Structural Benefits of High Performance Concrete for Pretensioned Bridge Girders,a€? " href="http://dx.doi.org/10.15554/pcij.07012000.100.107 "> a€?Analysis and Structural Benefits of High Performance Concrete for Pretensioned Bridge Girders,a€? PCI JOURNAL, V. 45, No. 4, July-August 2000, pp. 100-107.  style="text-align: left;">2. Harmon, Kenneth S., a€?Physical Characteristics of Rotary Kiln Expanded Slate Lightweight Aggregate,a€? Second International Symposium on Structural Lightweight Concrete, Sandefjord, Norway,   June 2000, pp. 574-583. style="text-align: left;">3. Holm, Thomas A., and Bremner, T.W., Chapter 10 of High Peiformance Concretes and Applications, S.P. Shah and S.H. Ahmad (Editors), Edward Arnold, London, 1994, Pp. 341-374. style="text-align: left;">4. Leming, Michael L., a€?Properties of High Strength Concrete - An Investigation of High Strength Concrete Characteristics Using Materials in North Carolina,a€? North Carolina State University Report  for NCDOT and FHWA, No. 23241-86-3,  Raleigh, NC, 1988, 186 pp. style="text-align: left;">5. Shideler, J. J., target="_blank" title="a€?Lightweight-Aggregate Concrete for Structural  Use,a€?" href="http://dx.doi.org/10.14359/11441 ">a€?Lightweight-Aggregate Concrete for Structural  Use,a€?ACI Journal, V. 29, No.4, October 1957, pp. 299-328. style="text-align: left;">6. Meyer, Karl F., and Kahn, Lawrence F., a€?Annotated Bibliography for High Strength Lightweight Prestressed Concrete,a€? Report to the Office of Materials and Research, Georgia Department of   Transportation, Atlanta, GA, January 2001, 12pp. style="text-align: left;">7. AASHTO, Standard Specifications for Highway Bridges, 16th Edition, American Association of State Highway and Transportation Officials, Washington, DC, 1996. style="text-align: left;"> 8. Bilodeau, Alain, Chevrier, Raymond, Malhotra, Mohan, and Hoff, George C., a€?Mechanical Properties, Durability and Fire  Resistance of High Strength Lightweight Concrete,a€? International   Symposium on Structural Lightweight Aggregate Concrete, Sandefjord, Norway, June 1995, pp. 432-443. style="text-align: left;">9. Brown, William R., and Davis, C.R., a€?A Load Response Investigation of Long Term Performance of a Prestressed Lightweight Concrete Bridge at Fanning Springs, Florida,a€? State Project Number  30010-3507, FY 1962, Florida Department of Transportation, 1962, Tallahassee, FL, 66 pp. style="text-align: left;">10. Fdd??ration Internationale de la Prdcontrainte (FTP), Manual of  Lightweight Aggregate Concrete, Second Edition, John Wiley & Sons, New Yo