Kinematic response analysis of piled foundations under seismic excitation Rosa Maria Stefania Maiorano, Luca de Sanctis, Stefano Aversa, and Alessandro Mandolini Abstract: This paper presents the results of an extensive parametric study on single piles and pile groups embedded in a two-layer subsoil profile, and is aimed to evaluate kinematic bending moments developing during earthquakes. A quasi three-dimensional finite element program has been used to perform dynamic analyses in the time domain. Piles have been considered as elastic beams, while the soil has been modelled using a linear elastic constitutive model. The aims of the pa- per are: (i) to evaluate kinematic bending moments in single piles and pile groups with dynamic analyses in the time do- main, in different subsoil conditions; (ii) to review some existing design methods; (iii) to propose a simplified analysis procedure to evaluate maximum kinematic bending moments between two subsequent soil layers. The results of the dy- namic analyses have shown that some of the simplified approaches provided in published literature tend to be conservative and can predict bending moments at the soil-layer interface with adequate accuracy only within certain depths of the soil layer interface. On the basis of the obtained results, a modified criterion to evaluate the transient peak bending moments at interfaces between layers is proposed. Key words: kinematic interaction, single pile, pile groups, finite elements, seismic response. Re ´sume ´: Cet article pre ´sente les re ´sultats d’une e ´tude parame ´trique extensive sur des pieux simples et groupe ´s inse ´re ´s dans un sol de surface compose ´ de deux couches. Cette e ´tude avait comme objectif d’e ´valuer les moments de torsion cine ´- matiques qui se de ´veloppement pendant un se ´isme. Un programme d’e ´le ´ments finis quasi tridimensionels a e ´te ´ utilise ´ pour effectuer des analyses dynamiques dans le domaine temps. Les pieux ont e ´te ´ conside ´re ´s comme des poutres e ´lastiques, tan- dis que le sol a e ´te ´ mode ´lise ´a ` l’aide d’un mode `le e ´lastique constitutif line ´aire. Les objectifs de cet article sont : (i) d’e ´valuer les moments de torsion cine ´matiques pour des pieux simples et groupe ´s avec des analyses dynamiques dans le domaine temps, et ce pour diffe ´rentes conditions de sol; (ii) de re ´viser quelques me ´thodes de conception existantes; (iii) de proposer une proce ´dure simplifie ´e pour e ´valuer les moments de torsion cine ´matiques maximum entre deux couches subse ´quentes de sol. Les re ´sultats des analyses dynamiques ont de ´montre ´ que certaines approches simplifie ´es de la litte ´ra- ture ont tendance a `e ˆtre conservatrices et peuvent pre ´dire les moments de torsion a ` l’interface entre les couches de sol de fac ¸on pre ´cise seulement pour quelques profondeurs de l’interface de la couche de sol. Selon les re ´sultats obtenus, un cri- te `re modifie ´ est propose ´ qui permet d’e ´valuer le moment de torsion maximum en re ´gime transitoire a ` l’interface entre des couches de sol. Mots-cle ´s : interaction cine ´matique, pieu simple, pieux groupe ´s, e ´le ´ments finis, comportement sismique. [Traduit par la Re ´daction] Introduction Dynamic soil pile interaction is a very complex problem in- volving a number of factors, such as soil profile, soil proper- ties, nonlinear soil behaviour, seismically induced pore-water pressure, inertial effects, and kinematic interaction between soil and pile. Despite these complexities, engineering practice is still based on pseudostatic approaches and neglects the ef- fects of kinematic interaction. In contrast, there is extensive research on kinematic interaction, including field measure- ments (Gazetas et al. 1993; Nikolaou et al. 2001); in addition, pile damage confirming the role of kinematic bending mo- ments has been observed after the earthquake events of Mex- ico City (Mexico) in 1985, Kobe (Japan) in 1995, and Chi Chi (Taiwan) in 1999. The importance of kinematic bending mo- ments has been recently recognized by regulations such as Eurocode 8 (CEN/TC 250 2003b). Studies on the kinematic response of pile foundations have been based on both simplified models (Dobry and O’Rourke 1983; Mylonakis 2001; Nikolaou et al. 2001; Sica et al. 2007) and more complex analyses in which the subsoil was assumed to be linear–elastic (Wu and Finn 1997a; Bentley and El Naggar 2000; Maiorano and Aversa 2006) or nonlin- ear (Wu and Finn 1997b; Maheshwari et al. 2005; Maiorano et al. 2007). Analyses based on simplified approaches have been essentially performed to define approximate analytical solutions capable of reproducing kinematic bending mo- ments at the interface between two layers characterized by Received 4 March 2008. Accepted 31 December 2008. Published on the NRC Research Press Web site at cgj.nrc.ca on 7 May 2009. R.M.S. Maiorano, L. de Sanctis, and S. Aversa. 1 Department of Technology, University of Napoli Parthenope, Centro Direzionale - Isola C4, 80143 Napoli, Italy. A. Mandolini. Department Civil Engineering, Second University of Napoli, Via Roma 29, 81031 Aversa (CE), Italy. 1 Corresponding author (e-mail: stefano.aversa@uniparthenope.it). 571 Can. Geotech. J. 46: 571–584 (2009) doi:10.1139/T09-004 Published by NRC Research Press