Journal of the South African Institution of Civil Engineering
On-line version ISSN 2309-8775
DITHINDE, M and RETIEF, J V. Resistance model uncertainty factors for ultimate limit state design of pile foundations. J. S. Afr. Inst. Civ. Eng. [online]. 2014, vol.56, n.2, pp. 37-45. ISSN 2309-8775.
ABSTRACT The current limit state design procedure for pile foundations presented in geotechnical codes (e.g. SANS 10160-5, EN 1997-1) stipulates that, when the pile capacity is determined using an analytical approach, such as the static analysis using engineering properties of the soil as determined from laboratory or in-situ field testing, the prescribed partial resistance factors (γr) need to be corrected by a partial factor for the uncertainty in the resistance model (γR, d) or the resistance model uncertainty factor. The international position is to derive model uncertainty factors for both actions and resistances from available experimental data. Accordingly this paper makes use of a local pile load test database to derive the appropriate γR, d values for ultimate limit state design of pile foundations. The analysis indicates that γR, d values of 1.3 and 1.5 for piles in cohesive and non-cohesive materials respectively are appropriate. Alternatively, a single value of γR, d = 1.4 for all piles in all soils can be adopted with different γr values for the two distinctive pile classes of piles in cohesive and non-cohesive soils.
Keywords : ultimate limit state; pile foundation design; pile load tests; model factor; static formula.