Load and resistance factor design versus reliability-based design of shallow foundations

Pengpeng He, Gordon A. Fenton, D. V. Griffiths

Research output: Contribution to journalArticlepeer-review

Abstract

The load and resistance factor design (LRFD) approach employed in geotechnical design codes is often calibrated using the reliability-based design (RBD) method. However, the LRFD may not achieve the target safety level exactly. This paper makes comparisons between the LRFD and RBD by considering the ultimate and serviceability limit state design of strip foundations. The RBD is carried out via the Random Finite Element Method. It is found that the failure probability and the resulting foundation width for ULS obtained using the RBD increase with the soil spatial correlation length, gradually reaching a plateau. The comparison between the LRFD and RBD results for ULS suggests that the LRFD is conservative for low to medium soil variability, particularly at smaller correlation lengths. The reliability-based SLS design is less dependent on the soil correlation length, particularly for lower coefficients of variation of the soil elastic modulus. However, a resistance factor of 1.0 for SLS is unconservative, and resistance factors of 0.65, 0.7 and 0.8 are better aligned with the RBD when the target failure probabilities are 1×10−3, 1×10−2 and 1×10−1. The current study can be used to guide the design of shallow foundations and the calibration of the LRFD approach.

Original languageEnglish
Number of pages10
JournalGeorisk: Assessment and Management of Risk for Engineered Systems and Geohazards
Early online date2 Jun 2022
DOIs
Publication statusE-pub ahead of print - 2 Jun 2022

Keywords

  • Load and resistance factor design
  • reliability-based design
  • serviceability limit state
  • shallow foundations
  • ultimate limit state

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