Undrained bearing capacity of tripod skirted foundations under eccentric loading

The undrained bearing capacity of a group of three rigidly connected skirted foundations (tripod) under vertical, moment or combined vertical-moment loading is investigated. Three-dimensional displacement finite element analyses of a single footing are first presented in order to validate the numerical modelling procedure. Various loading paths are considered and comparisons with known solutions are made. Subsequently, a series of analyses of undrained loading on a three-footing group is presented. Different footing spacings and loading directions are considered. The predominant failure mechanisms for characteristic load combinations are determined and the calculated failure loads are presented in dimensionless and normalized form. Based on the numerical results, a unique normalized failure load surface is proposed which applies to all loading directions and footing spacings for a given skirt length to footing diameter ratio. Undranierte Grenztragfahigkeit von Tripod-Grundungen mit Schurze unter ausermittiger Belastung. Die undranierte Grenztragfahigkeit einer Gruppe von drei starr miteinander verbundenen Grundungselementen (Tripods) unter Vertikallast, Momentenbelastung oder unter einer kombinierten Vertikal- und Momentenbelastung wird untersucht. Zunachst werden dreidimensionale Finite-Elemente-Berechnungen von einem einzelnen Grundungskorper prasentiert, um die numerische Modellierung zu validieren. Unterschiedliche Belastungspfade werden untersucht und mit bekannten Losungen verglichen. Anschliesend wird eine Reihe von undranierten Analysen mit allen drei Grundungskorpern eines Tripods vorgestellt. Variiert werden die Fundamentabstande und die Lastrichtung. Die vorherrschenden Versagensmechanismen werden fur charakteristische Lastkombinationen bestimmt und die berechneten Grenztraglasten in dimensionsloser und normierter Form dargestellt. Basierend auf den numerischen Ergebnissen wird eine einzige normierte Grenzzustandskurve vorgeschlagen, welche auf alle Lastrichtungen und Fundamentabstande fur ein gegebenes Verhaltnis von Schurzenlange zu Durchmesser der Grundungskorper anwendbar ist.

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