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Numerical Modelling of Undrained Capacity of Hybrid Skirted Foundation Under Combined Loading
Bienen, Britta (The University of Western Australia) | Gaudin, Christophe (The University of Western Australia) | Cassidy, Mark J. (The University of Western Australia) | Rausch, Ludger (University of Applied Sciences) | Purwana, Okky A. (Keppel Offshore & Marine Technology Centre)
This paper establishes the undrained capacity of a circular skirted mat under uniaxial horizontal and moment loading, respectively, and presents the combined vertical, horizontal and moment (VHM) capacity envelopes for a novel concept for foundations that combines a skirted mat with a suction caisson. This foundation concept enables self-installation and preloading of the footing. Specifically, this research explores the effect of the central caisson on the failure mechanisms and the resulting VHM capacity through finite element analysis. The results demonstrate that the central caisson more than doubles the horizontal capacity while moderately increasing the capacity in the vertical and moment loading directions. INTRODUCTION Combinations of vertical load 4V 5, horizontal load 4H5 and moment 4M5 are typically applied to foundations in the offshore environment, due to platform self-weight, wind, waves and current. The industry increasingly embraces the use of VHM interaction surfaces to describe foundation capacity rather than (semi) empirical modifications to the classical bearing capacity theory that assumes predominantly vertical loading characteristics of onshore applications. These failure envelopes are affected by the footing shape, the embedment and the soil shear strength profile. Skirted foundations are often used in shallow waters. The skirt, which may extend up to 0.5 diameters below the mudline, is used predominantly to increase the horizontal capacity of the foundation. Recent research established the combined vertical, horizontal and moment (VHM) capacity of skirted foundations, although the research excluded the combined load capacity of circular skirted mats. Table 1 provides an overview of the available solutions for cohesive soils with uniform or nonuniform strength profiles. These numerical studies are supplemented by experimental results, including those shown in Cassidy et al. (2004) and Kelly et al. (2006). Note that only the most recent study explicitly modelled the skirts on strip footings.
The coastal development on the Persian Gulf has increased recently with the development of Abu Dhabi, the United Arab Emirates. To ensure the stability and serviceability of the coastal structures, the resistance against the horizontal and uplift forces should be considered in the design process of the foundations supporting those structures. Unlike the resistance against compression and lateral forces, however, the pullout resistance of piles has not yet been fully investigated; also, belled piles are known to be very effective against pullout forces, but research on their pullout behavior has been limited. Hence, in this study, pullout load tests of belled tension piles were performed at 4 sites in Abu Dahbi, and subsequently the bearing capacity, characteristics of load-displacement of piles and load distribution considering skin friction were investigated. Based on the numerical simulation analyses, proved to capture the ultimate uplift capacities from the load tests, the shape and size of the bell has influence on the load-displacement behaviors of belled piles rather than the ultimate uplift capacity of the belled piles in the weathered sandstone ground conditions. In addition, the limit pullout bearing capacity calculated by 3D finite element analysis and theoretical methods were compared. The theoretical methods overestimate the ultimate pull out capacity regardless of the bell-shape considerations. INTRODUCTION Drilled shafts (piers or caissons) are the most common type of foundation for tall structures in coastal areas. To ensure the stability and serviceability of the coastal structures, the resistance against horizontal and uplift forces should be considered in the design process of the foundations supporting those structures. It is necessary to characterize the pullout behavior of pile foundations due to the increasing demand on the offshore and onshore construction and the structures resisting the wind and earthquake loadings.
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.24)
- Asia > Middle East > Saudi Arabia > Arabian Gulf (0.24)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.76)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.54)
Evaluation of Dynamic Group-Pile Effect In Dry Sand By Centrifuge Model Tests
Yoo, Min-Taek (Department of Civil & Environmental Engineering, Seoul National University) | Cha, Se-Hwan (Department of Civil & Environmental Engineering, Seoul National University) | Kim, Myoung-Mo (Department of Civil & Environmental Engineering, Seoul National University) | Choi, Jung-In (Department of Civil & Environmental Engineering, University of California) | Han, Jin-Tae (Korea Institute of Construction Technology)
It is well known that the average load for a pile in a closely spaced group is substantially less than that for a single isolated pile at the same deflection. Thus, the p-multiplier has been used to determine p-y curves for groups of piles. The p-multiplier under seismic loading is yet to be determined. In this study, a series of centrifuge shaking-table tests for a 3_3 group pile was performed for various pile spacings, ranging from 3 to 7 times the pile diameter. Test results confirm that the p-multiplier increases with increasing pile spacing. The p-multiplier of the piles in rows 1 and 3 within a group is smaller than that of the center pile in row 2. Thus, under seismic loading conditions, the group pile effect in rows 1 and 3 piles is greater than that in row 2 piles. In addition, the behavior of piles in the same row is different according to the location of each pile within group piles. INTRODUCTION In the seismic design of a pile foundation, pseudo-static analysis is widely used to convert dynamic loads to equivalent static loads. The p-y curve method, which considers the relationship between the relative displacement of a pile against soil and the nonlinear soil resistance, is most frequently used to model the lateral behavior of a pile foundation for pseudo-static analysis. To consider the group pile effect during the design of a laterally loaded group pile, the p-y curve of a pile group is determined by applying the p-multiplier to the p-y curve of a single pile. The p-multiplier recommended by AASHTO (2000), which is identical to that recommended by the Canadian Geotechnical Society (1992), is possibly the most widely used in practice (Rollins et al., 2006).
Ice Force Measurement Technology of Jacket Platform In Bohai Sea
Wang, Yanlin (State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology) | Yue, Qianjin (State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology) | Shiotani, Shigeaki (State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology)
This paper reports the direct ice force measurement technology of jacket structures conducted in the Bohai Sea. Specially designed ice load panels are described in detail, including the measurement principle of the load panel, the specially designed elastic cell and the single panel form. Some factors that ought be considered during the design process are proposed; 2 kinds of ice load panels, for both vertical and conical structures, were designed and installed on some prototype structures in Bohai. Some measured ice force is discussed, and it indicates that the dynamic performance of the panels is good. INTRODUCTION Understanding and prediction of ice forces on structures are needed for the safe and economical design in ice-covered waters. The best way to study this problem is to measure ice force directly on prototype structures. A number of measurement approaches has been developed to meet this need. Starting in the late 1970s, petroleum exploration activities in the Arctic stimulated an effort to measure ice forces on large caisson-type structures (Hardy et al., 1996; Timco and Johnston, 2003, 2004). Lately there have been measurements on smaller structures, such as the jacket structures in China's Bohai Sea (Wessels and Jochmann, 1991; Qu et al., 2006; Yue et al., 2009), the Confederation Bridge in Canada (Brown and Määttänen, 2002; Brown, 1997; Mayne and Brown, 2000); and the Norströmsgrund lighthouse in Sweden (Engelbrekston, 1977, 1983; Nordlund et al., 1988; Määttänen, 1994, 1996; Määttänen et al., 1997.) A wide variety of techniques has been used for measuring ice forces on structures. An earlier sensor, the Esso sensor, used the changing electrical capacitance of the panel as an index of its overall deformation; its nonlinear behavior and susceptibility to drift gave rise first to the Medof panel and later to the EPR sensor.
- Asia > China (0.67)
- North America > Canada (0.49)
- North America > United States (0.46)