Effect of correlation structure model on geotechnical reliability-based serviceability limit state simulations Huffman, Jonathan C.; Stuedlein, Armin W.
Reliability-based serviceability limit state (SLS) models for foundation elements commonly employ a two-parameter load-displacement model to relate imposed displacements to a particular load or vice versa. Numerous studies have shown that the load-displacement model parameters tend to be correlated; subsequently, considerable effort is required to appropriately model the correlation structure for Monte Carlo-based reliability simulations. This paper uses copula theory, a database of high quality full-scale loading tests of spread footings on aggregate pier (i.e., stone column) reinforced clay, and a recently developed ultimate limit state (ULS) model to investigate the effect of various correlation structures on the probability of exceeding the SLS. “Lumped” load and resistance factors, which conveniently relate the portion of mobilized resistance to a given footing displacement, accounting for uncertainty in the applied load, ULS resistance of the clay subgrade, allowable displacement, and footing size, generated using various assumed correlation structure models are compared. Additionally, the penalty in reliability associated with ignoring the bivariate correlation is explored for comparison. This study demonstrates that selection of the appropriate copula represents a critical task in the development of calibrated reliability-based geotechnical SLS design approaches.
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