ABSTRACT: Previous studies have shown that footing uplift can activate a rigid body rotation, and thus reduce the plastic hinge development in structures. Development of a plastic hinge will limit the inertial force which may lead to uplift. Therefore, determination of the bending moment when a plastic hinge develops and the structure uplifts is a challenge. Because of this intrinsic difficulty the inter-relationship between plastic hinge development and structural uplift is seldom investigated. In this paper results of shake table tests on a single-degree-of-freedom model with concurrent plastic hinge development and footing uplift will be presented and discussed. An artificial plastic hinge with rotational slippage is introduced to simulate the plastic deformation of the structure. The model, founded on a rigid base, is subjected to a simulated ground motion based on NZS 1170.5 design spectra. Different ratios of the moment to initiate uplift to that to initiate slippage moment are adjusted. The results show that the moment to initiate plastic hinge development will be similar to that to initiate uplift if the two effects occur concurrently. After discussion on the effect of plastic hinge development and uplift on footing response, structural damage and induced vibrations, recommendations on design with consideration of the slippage-uplift interaction is also provided. KEY WORDS: Uplift; Plastic hinge development; Shake table tests; Slippage-uplift interaction; Load-displacement characteristic; Induced vibration. 1 INTRODUCTION During a strong earthquake separation of the foundation mat and the supporting ground interface may occasionally occur. Several examples of towers and oil tanks uplifting were observed during the 1952 Arvin Tehachapi, 1964 Alaska, and 1979 Imperial Valley earthquakes [1]. Previous research shows that smaller seismic force will be transmitted to the structure when foundation uplift occurs. However, uplift is not recommended in conventional design. The beneficial effect of structural uplift was probably first recognized by Housner [2], who reported on the positive performance of several elevated water tanks in the 1960 Chile earthquake. He also initiated the study of structural uplift using a rectangular rigid free standing block. The studies of a rigid rocking block were enhanced by several researchers using different numerical models [3, 4]. These investigations suggested that rocking behavior is related to the geometry of the structure. The flexibility of the rocking structure was included by Psycharis [5]. He performed a parametric analysis of a single-degree-of-freedom (SDOF) model subjected to harmonic base motions. This analytical model was improved by Oliveto et al. [6] who focused on the simulation of the transition conditions between uplift and re-contact and vice versa. The authors also developed a set of formulas to simulate large rotations. The results revealed that as expected more flexible structures on a rigid base are more prone to uplift and overturn than rigid structures. Before the 21 st century physical studies on a structure with uplift were hindered due to the limitations of experimental technique. Huckelbridge and Clough [7] were among the pioneers who tested a nine-storey steel frame model with uplift using a shake table. They found that significant uplift will occur when the structure is subjected to strong earthquakes. It also confirmed that a structure with a designed uplift capability is likely to have a higher probability of surviving a strong earthquake. At approximately the same time Priestly et al. [8] carried out shake table tests on a SDOF model. Based on these results they suggested the first design approach for a rocking structure. This design approach has been adopted by the FEMA 356 Guidelines [9]. In the design approach suggested by FEMA 356, the effective damping and rocking period of a rigid rocking block are determined based on its geometry. The maximum displacement of the rocking block can be estimated from the elastic spectrum. However, Makris and Konstantinidis [10] revised the research of Priestley et al. [8] and pointed out that the FEMA 356 design approach was oversimplified and experimental verification was limited to a single earthquake record. To overcome this issue, they proposed an improved formula for the effective damping of a rigid rocking block. Based on the FEMA 356 guidelines and New Zealand loadings code NZS1170.5 [11], a design procedure to estimate the maximum displacement of rocking shear walls was developed by Kelly [12]. In this approach the soil flexibility is considered using a Winkler Spring Model and the structural period is based on a rigid wall assumption. Kodama and Chouw [13] investigated structural uplift in near-source earthquakes including soil-structure interaction. However, the studies on structures with uplift discussed above have not taken the effect of concurrent plastic hinge development into account. Hung et al. [14] performed a set of pseudo-dynamic and cyclic load tests on bridge piers with and without a plastic hinge. In this study rocking of the spread footing of the pier did not always occur. Qin et al. [15] also Experimental investigation on interaction between plastic hinge development and foundation uplift Yuanzhi Chen 1 , Pierrick Matheaud 2 , Tam Larkin 1 , Nawawi Chouw 1 1 Department of Civil and Environmental Engineering, Faculty of Engineering, the University of Auckland, 20 Symonds Street, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand 2 School of Engineering, Ecole des mines d’Albi-Carmaux, Allée des sciences, 81000 Albi, France Email: yche521@aucklanduni.ac.nz, pierrick.matheaud@mines-albi.fr, t.larkin@auckland.ac.nz, n.chouw@auckland.ac.nz Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014 Porto, Portugal, 30 June - 2 July 2014 A. Cunha, E. Caetano, P. Ribeiro, G. Müller (eds.) ISSN: 2311-9020; ISBN: 978-972-752-165-4 3791