Moment/Rotation Effects on Laterally Loaded Drilled Shaft Group Response
Publication: International Journal of Geomechanics
Volume 5, Issue 4
Abstract
Drilled shaft groups are often designed to resist lateral loads for transportation structures. The shaft group capacity usually corresponds to a load being applied at the shaft cap level. However, in abutment wall applications, the lateral load is, in fact, applied well above the cap elevation. Thus, the load is transferred to the cap with an additional moment, causing the cap to deflect and rotate more than if this added moment were absent. As a result, the lateral capacity for a given allowable deflection of the group should be reduced because of this effect. Design engineers usually select or approve the allowable deflection at the top of the abutment wall. However, deflection at the cap level is needed to design the group capacity. The main objective of this paper is to report the results from a series of finite-element analyses on abutment wall cap configurations to study the effect of moment on the capacity of the shaft group under lateral load. A scaling factor is defined as the ratio between the group capacity for load applied at a given height above the cap and the group capacity for load applied at the bottom of the cap, and it was found to be dependent on the wall height, the spacing between shafts, and the cap deflection level, and more or less independent of the soil type, the cap thickness, and the shaft diameter. The ratio between the deflection at the top of the abutment wall and the deflection at the cap was found to be dependent on the wall stiffness (wall thickness to wall height ratio).
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The work described here was conducted as part of a cooperative research program sponsored by the Arizona Department of Transportation (ADOT) under Project No. SPR 483, Optimization of Drilled Shaft Group Spacing. The writers are grateful to Mr. Frank McCullagh of the Arizona Transportation Research Center and the members of the Technical Advisory Committee. Helpful discussions and suggestions were provided by the Steering Committee, consisting of Ken Ricker, Randy Marwing, Rob Turton, Keith Dahlen, and the late Dwaine Sergent. The opinions expressed in this paper are those of the writers and not necessarily of ADOT.
References
American Association of State Highway and Transportation Officials (AASHTO). (1996). AASHTO specifications for highway bridges, 17th Ed., Washington, D.C.
ABAQUS user’s manual: version 5.8. (1998). Hibbit, Karlsson, and Sorensen, Pawtucket, R.I.
Brown, D. A., Morrison, C., and Reese, L. C. (1988). “Lateral load behavior of pile group in sand.” J. Geotech. Eng., 114(11), 1261–1276.
Chen, W. F., and Baladi, G. Y. (1985). Soil plasticity: theory and implementation, Elsevier, New York.
Davisson, M. T. (1970). “Lateral load capacity of piles.” Highway Research Record. 333, Transportation Research Board, Washington, D.C. 104–112.
Department of the Navy, Naval Facilities Engineering Command. (1986). “Foundations and earth structures—design manual 7.2.” Rep. NAVFAC DM-7.2, Washington, D.C.
Frechette, D. N., Walsh, K. D., and Houston, W. N. (2002). “Review of design methods and parameters for laterally loaded groups of drilled shafts.” Proc., Foundation Engineering Congress, ASCE, Reston, Va., 1261–1274.
Hoit, M., Hays, C., and McVay, M. C. (1997). “The Florida Pier Analysis Program methods and models for pier analysis design.” Transportation Research Record. 1569, Transportation Research Board, Washington, D.C., 1–7.
McVay, M. C., Hays, C., and Hoit, M. (1995). User manual for FLORIDA-PIER Program, version 5.0, Univ. of Florida, Gainesville, Fla.
McVay, M. C., Hays, C., and Hoit, M. (1996). “Development of a coupled bridge superstructure—foundation finite element code.” Final Rep. B-8415, Dept. of Civil Engineering, University of Florida, Gainesville, Fla.
McVay, M. C., Zhang, L., Han, S., and Lai, P. (2000). “Experimental and numerical study of laterally loaded pile groups with pile caps at variable elevations.” Highway Research Record. 1736, Transportation Research Board, Washington, D.C., 12–18.
Mokwa, R. L., and Duncan, J. M. (2003). “Rotational restraint of pile caps during lateral loading.” J. Geotech. Geoenviron. Eng., 129(9), 829–837.
Muqtadir, A., and Desai, C. S. (1986). “Three-dimensional analysis of a pile-group foundation.” Int. J. Numer. Analyt. Meth. Geomech., 10, 41–58.
Patra, N. R., and Pise, P. J. (2001). “Ultimate lateral resistance of pile group in sand.” J. Geotech. Geoenviron. Eng., 127(6), 481–487.
Reese, L. C., and Matlock, H. (1956). “Non-dimensional solutions for laterally loaded piles with soil modulus assumed proportional to depth.” Proc., 8th Texas Conf. on Soil Mechanics and Foundation Engineering, Bureau of Engineering Research, The Univ. of Texas, Austin, Tex.
Reese, L. C., Wang, S. T., Isnhower, W. M., Arréllaga, J. A., and Hendrix, J. (2000). A program for the analysis of piles and drilled shafts under lateral loads, Ensoft, Inc., Austin, Tex.
Walsh, K. D.,Frechette, D. N., Houston, W. N., and Houston, S. L. (2000). “The state of the practice for the design of groups of laterally loaded drilled shafts.” Highway Research Record. 1736, Transportation Research Board, Washington, D.C., 33–40.
Walsh, K. D., Houston, W. N., Houston, S. L., Fréchette, D. N., and Douthitt, B. (1999). “Optimization of drilled shaft group spacing.” Interim Rep. for Project No. T99-13-00060, Ariz.
Walsh, K. D., Houston, W. N., Houston, S. L., Harraz, A. M., Perry, C. R., and Fréchette, D. N. (2002). “Optimization of drilled shaft group spacing.” Final Rep. for Project No. T99-13-00060, Ariz.
Zhang, L., McVay, M. C., and Lai, P. (1999). “Numerical analysis of laterally loaded to pile groups in sands.” J. Geotech. Geoenviron. Eng., 125(11), 936–946.
Information & Authors
Information
Published In
International Journal of Geomechanics
Volume 5 • Issue 4 • December 2005
Pages: 304 - 310
Copyright
© 2005 ASCE.
History
Received: Sep 30, 2003
Accepted: Jul 19, 2004
Published online: Dec 1, 2005
Published in print: Dec 2005
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.