Proceedings of the 9 th ICCAE-9 Conference, 29-31 May, 2012 GE 1 1 Experimental Study on the Behavior of Pile Group under Cyclic Lateral Loading Mahmoud FawzyAwad-Allah*, Noriyuki Yasufuku**, and Kiyoshi Omine*** Abstract Pile foundations supporting bridge piers, offshore platforms, and towers are required to resist not only static loading but also cyclic or dynamic lateral loading resulted from winds, sea waves, or earthquake actions. Therefore, it is necessary to examine the effects of slow cyclic loads on the pile foundation behavior. This paper presents an experimental study on pile models of different arrangements founded in both dense and loose sands of relative densities equal to D r =75% and 35%, respectively. In this work, series of two-way lateral cyclic loading tests were performed on three pile arrangements (single, 3 ×1, and 3 ×3 groups) having length to diameter ratio (L/d) of 10 and 20 with spacing to diameter ratio (S/d) of 3. The experimental setup was explained in details and the results were presented in the form of cyclic load–deflection curves and normalizedbending moment charts against the number of cycles. Moreover, cyclic group efficiency, and cyclic p-multipliers were evaluated. Keywords: Cyclic loading, experimental work, lateral deflection, sand, pile group, foundation. 1. INTRODUCTION Pile foundations are widely used to support various structures such as offshore platforms, jetties, wharfs, docks, dolphin structures, and bridges. These structures are subjected to cyclic lateral loading due to wave and wind actions. In practice, however, after a foundation is constructed, it is quasi-statically loaded axially due to gravity loads of the superstructure. All cyclic loading sequences are characterized by four parameters, including: the maximum applied lateral load H max , the number of cycles N, the frequency (rate of loading) f, and maximum lateral displacement y max . Two-way cyclic loading can be considered as a simplified representation of dynamic loading without inertia nor damping. However, although alternating loading is symmetrical, the direction of the first loading remains in the pile memory (Rosquoet, 2007). * Research Associate, National Research Center, Egypt, Tel: 0202-01006201192, Email: mahmoudfawzy1980@yahoo.com ** Prof. of Geotechnical Engineering, Faculty of Engineering, Kyushu Univ., Japan, E-mail: Yasufuku@civil.kyushu-u.ac.jp ** Asso. Prof. of Geotechnical Engineering, Faculty of Engineering, Kyushu Univ., Japan, Email:oomine@civil.kyushu-u.ac.jp Military Technical College Kobry El-Kobbah, Cairo, Egypt 9 th International Conference on Civil and Architecture Engineering ICCAE-9-2012