Fractile-based method for selecting characteristic values for geotechnical design with LRFD

• Published in: Soils and foundations Vol. 60; no. 1; pp. 115 - 128
• Main Authors: Zhang, Yongjie, Shen, Mengfen, Hsein Juang, C., Tan, Xiaohui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2020
• Subjects: Characteristic value; Fractile; LRFD; Partial factors; Robustness; Robustness; Fractile; Partial factors; LRFD; Characteristic value
• ISSN: 0038-0806
• DOI: 10.1016/j.sandf.2020.01.010

Load and resistance factor design (LRFD), also known as partial factor design, is becoming a design method of choice in geotechnical practice. The partial factors (i.e., resistance factor and load factor) to ensure safety are specified in the adopted code; however, engineers still need to select values for the uncertain soil parameters in a design. The selection of these parameter values, often called characteristic values, is quite challenging given soil variability and limited test data. This paper presents a fractile-based method for the selection of the characteristic values for the uncertain soil parameters in a design with LRFD. A framework that considers safety, cost, and robustness is established to determine an appropriate fractile for selecting the characteristic values. This framework is demonstrated with two examples, a drilled shaft in sand and a shallow spread foundation. The results show that robust designs can be achieved using LRFD with the characteristic values obtained through the proposed fractile-based method.