Reliability Based Analysis of Axial Load Capacity of Drilled Shaft in Louisiana Soils

This paper presents the evaluation of axial load resistance of drilled shafts installed in Louisiana soils based on reliability analysis. Twelve drilled shafts that were tested using the Osterberg cell method or the static load test method were analyzed in this investigation. The predictions of axial shaft resistance were conducted using α method (total stress analysis) for cohesive soils and β method (effective stress analysis) for cohesionless soils as proposed by Reese and O’Neill, which are based on soil characteristics obtained from soil borings and laboratory tests. A short-term loadsettlement relationship was also estimated using the FHWA approach. The objective of this study is to calibrate the resistance factors (φ) for drilled shafts based on Louisiana experiences. In this research, the serviceability limit state is considered, because it has higher probability of occurrence than the ultimate limit state in Louisiana soils. Statistical data, validated by the Reese and O'Neill design method, was used to obtain the LRFD resistance factor (φ) for the serviceability limit state of drilled shafts by means of the First Order Second Moment (FOSM) method.

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