LRFD calibration of simple limit state functions in geotechnical soil-structure design - Risk and Reliability in Geotechnical Engineering - page 346

The results of LRFD calibration are sensitive to the database of measured values used
to perform the calibration. Hence, calibrated LRFD limit state design equations should be
restricted to project-specific designs that fall within the database envelope that was used to
perform calibration. For the example used in this chapter, this means projects that fall within
the same range of problem geometry, reinforcement type, and soil properties. As more data
become available, it may be necessary to periodically recalibrate load and resistance factors.
8.7 ConCluSIonS
The focus of this chapter has been on a methodology to carry out LRFD calibration of
simple linear limit state design functions for which quality load and resistance bias data are
available and the underlying deterministic models to compute load and resistance values are
reasonably accurate. In order to demonstrate concepts and to facilitate plotting, the calcula-
tions have been described with implementation within Excel spreadsheets in mind. Once the
reader is comfortable with the calibration methodology, the calculation steps can be easily
implemented within simple numerical codes (e.g., Visual Basic, MATLAB ® ).
While the example used in this chapter to illustrate fundamental steps is for the pullout
limit state in an MSE wall structure, the general approach is valid for other types of soil
structures for which databases of physical load and resistance measurements are available.
Examples can be found in publications by Allen (2005), Bathurst et al. (2011a, b, c, 2012,
2013) and Huang et al. (2012).
reFerenCeS
AASHTO 2012. AASHTO LRFD Bridge Design Specifications. . American Association of State Highway
and Transportation Officials, 6th Edition, Washington, DC, USA.
Allen, T., Christopher, B., Elias, V. and DeMaggio, J. 2001. Development of the Simplified Method
for Internal Stability . Report WA-RD 513.1 July 2001, Washington State Department of
Transportation, Olympia, WA, USA.
Allen, T.M. 2005. Development of Geotechnical Resistance Factors and Downdrag Load Factors for
LRFD Foundation Strength Limit State Design . Publication No. FHWA-NHI-05-052, Federal
Highway Administration, Washington, DC, USA.
Allen, T.M., Bathurst, R.J., Holtz, R.D., Lee, W.F. and Walters, D.L. 2004. A new working stress
method for prediction of loads in steel reinforced soil walls. ASCE Journal of Geotechnical and
Geoenvironmental Engineering 130(11): 1109-1120.
Allen, T.M., Nowak, A.S. and Bathurst, R.J. 2005. Calibration to Determine Load and Resistance
Factors for Geotechnical and Structural Design. Transportation Research Board Circular E-C079,
Washington, DC, USA.
Barker, R.M., Duncan, J.M., Rojiani, K.B., Ooi, P.S.K., Tan, C.K. and Kim. S.G. 1991. Manuals for the
Design of Bridge Foundations . NCHRP Report 343, National Cooperative Highway Research
Program, Transportation Research Board, Washington, DC, USA.
Bathurst, R.J., Allen, T.M., Miyata, Y. and Huang, B. 2013. LRFD calibration of metallic reinforced soil
walls. ASCE Geotechnical Special Publication No. 229, “Foundation Engineering in the Face of
Uncertainty” Honoring Fred H. Kulhawy , 585-601.
Bathurst, R.J., Allen, T.M. and Nowak, A.S. 2008a. Calibration concepts for load and resistance factor
design (LRFD) of reinforced soil walls. Canadian Geotechnical Journal 45(10): 1377-1392.
Bathurst, R.J., Huang, B. and Allen, T.M. 2011a. Load and resistance factor design (LRFD) calibration
for steel grid reinforced soil walls. Georisk 5(3-4): 218-228.
Bathurst, R.J., Huang, B. and Allen, T.M. 2011b. Analysis of installation damage tests for LRFD cali-
bration of reinforced soil structures. Geotextiles and Geomembranes 29(3): 323-334.