Abstract

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 (γ_r) need to be corrected by a partial factor for the uncertainty in the resistance model (γ_{R, 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 γ_{R, d} values for ultimate limit state design of pile foundations. The analysis indicates that γ_{R, d} values of 1.3 and 1.5 for piles in cohesive and non-cohesive materials respectively are appropriate. Alternatively, a single value of γ_{R, d} = 1.4 for all piles in all soils can be adopted with different γ_r 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.

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