AASHTO-LRFD Live Load Distribution for Beam-and-Slab Bridges: Limitations and Applicability
Publication: Journal of Bridge Engineering
Volume 12, Issue 6
Abstract
This paper presents a comparison between the live load distribution factors of simple span slab-on-girders concrete bridges based on the current AASHTO-LRFD and finite-element analysis. In this comparison, the range of applicability limits specified by the current AASHTO-LRFD is fully covered and investigated in terms of span length, slab thickness, girder spacing and longitudinal stiffness. All the AASHTO-PCI concrete girders (Types I–VI) are considered to cover the complete range of longitudinal stiffness specified in the AASHTO-LRFD. Several finite-elements linear elastic models were investigated to obtain the most accurate method to represent the bridge superstructure. The bridge deck was modeled as four-node quadrilateral shell elements, whereas the girders were modeled using two-node space frame elements. The live load used in the analysis is the vehicular load plus the standard lane load as specified by AASHTO-LRFD. The live load is positioned at the longitudinal location that produced the extreme effect, and then it is moved transversely across the bridge width in order to investigate all possibilities of one-lane, two-lane and three-lane design loads. A total of 886 bridge superstructure models were built and analyzed using the computer program SAP2000 to perform this comparison. The results of this study are presented in terms of figures to be practically useful to bridge engineers. This study showed that the AASHTO-LRFD may significantly overestimate the live load distribution factors compared to the finite-element analysis.
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Acknowledgments
This research was supported by Bradley University and the International Road Federation. This financial support is highly appreciated.
References
Amer, A., et al. (1999). “Load distribution of existing solid slab bridges based on field tests.” J. Bridge Eng., 4(3), 189–193.
American Association of State Highway and Transportation Officials, (AASHTO). (1994). LRFD bridge design specifications, 1st Ed., Washington, D.C.
American Association of State Highway and Transportation Officials (AASHTO). (2002). Standard specifications for highway bridges, 17th Ed., Washington, D.C.
American Association of State Highway and Transportation Officials (AASHTO). (2004). LRFD bridge design specifications, 3rd Ed., Washington, D.C.
Barr, P. J., Eberhard, M. O., and Stanton, F. (2001). “Live-load distribution factors in prestressed concrete girder bridges.” J. Bridge Eng., 6(5), 298–306.
Brockenbrough, R. L. (1986). “Distribution factors for curved I-girder bridges.” J. Struct. Eng., 112(10).
Cai, C. S. (2005). “Discussion of ‘AASHTO LRFD load distribution factors for slab-on-girder bridges.’” Pract. Period. Struct. Des. Constr., 10(3), 171–176.
Chen, Y. (1999). “Distribution of vehicular loads on bridge girders by the FEA using ADINA: Modeling, simulation, and comparison.” Comput. Struct., 72(1999), 127–139.
Chen, Y., and Aswad, A. (1996). “Stretching span capability of prestressed concrete bridges under AASHTO LRFD.” J. Bridge Eng., 1(3), 112–120.
Computer and Structures, Inc. (2004). SAP2000, version 9.04, analysis reference manual, Berkeley, Calif.
Eby, C. C., Kulicki, J. M., and Kostem, C. N. (1973). “The evaluation of St. Venant torsional constant for prestressed concrete I-beam.” Fritz Engineering Laboratory Rep. No. 400.12, Lehigh Univ., Bethlehem, Pa.
Eom, J., and Nowak, M. E. (2001). “Live load distribution for steel girder bridges.” J. Bridge Eng., 6(6), 489–497.
Hays, C. O., Consolazio, G. R., Hoit, M. I., Garcelon, J. H., and Moy, W. (1995). “Meteric/SI and PC conversion of BRUFEM and SALOAD system.” Structural Research Rep. No. 95-1, Dept. of Civil Engineering, Univ. of Florida, Gainesville, Fla.
Hays, C. O., Sessions, L. M., and Berry, A. J. (1986). “Further studies on lateral load distribution using FEA.” Transportation Research Record. 1072, Transportation Research Board, Washington, D.C.
Huo, X. S., Wasserman, E. P., and Zhu, P. (2004). “Simplified method of lateral distribution of live load moment.” J. Bridge Eng., 9(4), 382–390.
Imbsen, R. A., and Nutt, R. V. (1978). “Load distribution study on highway bridges using STRUDL FEA capabilities.” Proc., Conf. on Computing in Civil Engineering, ASCE, New York.
Mabsout, M. E., Tarhini, K. M., Federick, G. R., and Tayar, C. (1997). “Finite-element analysis of steel girder highway bridges.” J. Bridge Eng., 2(3), 83–87.
Tabsh, S. W., and Sahajwani, K. (1997). “Approximate analysis of irregular slab-on-girder bridges.” J. Bridge Eng., 2(1), 11–17.
Tarhini, K. M., and Frederick, G. R. (1992). “Wheel load distribution in I girder highway bridges.” J. Struct. Eng., 118(5), 1285–1294.
Yousif, Z. (2005). “Live load distribution for highway bridges based on AASHTO LRFD and finite element analysis.” Master’s thesis, Dept. of Civil Engineering and Construction, Bradley Univ., Peoria, Ill.
Zokaie, T., Osterkamp, T. A., and Imbsen, R. A. (1991). “Distribution of wheel loads on highway bridges.” NCHRP 12-26 Final Rep., National Cooperative Highway Research Program, Washington, D.C.
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© 2007 ASCE.
History
Received: Dec 28, 2005
Accepted: Oct 4, 2006
Published online: Nov 1, 2007
Published in print: Nov 2007
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