Flexural Strength and Ductility of Extended Pile-Shafts. I: Analytical Model

• Published in: Journal of structural engineering (New York, N.Y.) N.Y.), 2002-05, Vol.128 (5), p.586-594
• Main Author: Chai, Y. H
• Format: Article
• Language: English
• Subjects: TECHNICAL PAPERS
• ISSN: 0733-9445; 1943-541X
• DOI: 10.1061/(ASCE)0733-9445(2002)128:5(586)

An analytical model, based on the commonly used equivalent cantilever concept, is developed for assessing the local ductility demand of a yielding pile-shaft when subjected to lateral loading. For elastic response of the pile-shaft, an equivalent depth-to-fixity is assumed, which can be derived by equating the lateral stiffness of the cantilever to that of the elastic soil-pile system. In adapting the equivalent cantilever model to yielding pile-shafts, however, the depth-to-maximum-moment is assumed to occur at a depth above the depth-to-fixity. The lateral strength, which depends on the depth-to-maximum-moment, is determined using the flexural strength of the pile and the ultimate pressure distribution of the soil. By assuming a concentrated plastic hinge rotation at the depth-of-maximum-moment, a kinematic model relating the local curvature ductility demand to global displacement ductility demand is developed. The kinematic relation is shown to depend on the aboveground height, depth-to-maximum-moment, depth-to-fixity, and equivalent plastic hinge length. The model is illustrated using a pile-shaft embedded in cohesive and cohesionless soils.