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Collaborating Authors
Research on the Method to Detect Vertical Bearing Capacity for High-Piled Wharf Piles Based on Prototype Test
Sun, Xi-ping (Tianjin Research Institute of Water Transport Engineering, Key Laboratory of Harbor & Marine Structure Safety Ministry of Communications) | Zhang, Hua-qing (Tianjin Research Institute of Water Transport Engineering, Key Laboratory of Harbor & Marine Structure Safety Ministry of Communications)
Abstract There are many mature methods to detect the bearing capacity of single pile. But for high-piled wharf piles, as they are parts of high-piled wharf, and complex structures are built on them, for these non-free end piles, there are no effective and feasible bearing capacity detection methods at this stage. In this paper, regional heap load method to detect high-piled wharf piles capacity was proposed, and this method did not destroy the original structure. The high-piled wharf piles capacity prototype testing was carried out, and the deformation displacement of while high-piled wharf, the displacement of piles, and the strain of structural elements were tested under grading loads. Also the numerical model was established to analysis the bearing capacity of high-piled wharf piles, and the numerical model was corrected by the experimental results. Then the whole prototype test process was simulated using the modified mathematical model, finally the vertical bearing capacity of high-piled wharf piles was determined by compared numerical and experimental results. Introduction Now there are a number of time-honored wharfs in domestic port engineering field, so it becomes urgent to evaluate their safety performance and give full play to their potential through upgrading and reforming. As for the high-piled wharf, the determination of foundation pile's bearing capacity is an important premise for the later evaluation, upgrading and reforming. After being used for many decades, the highpiled wharf changes in the concrete material properties, foundation soil parameters, and structural boundary conditions when compared with designed values. It is, thus, really difficult to figure out the bearing capacity of in-service foundation piles at the high-piled wharf completely in light of related theories, and we'd rather combine the onsite test with numerical analysis to determine the bearing capacity of the foundation piles. Many relatively mature methods have been developed for the test of single-pile bearing capacity, such as static load test, high strain power test, static-and-dynamic pile test. They have been included in the JTJ254–98 Code for Pile Foundations in Port Engineering, JTJ255–2002 Code for Static Load Test of Foundation Piles in Port Engineering, and JTJ249–2001 Code for Dynamic Test of Pile Foundations in Port Engineering. In recent years self-balanced test has become a focus in this field, which has been widely promoted in America, Japan and Canada (Jori, 1989). and is studied in depth in China from the end of last century (Ma YG, 2010; Wang DY, 2006). As a part of the whole high-piled wharf system, the foundation piles have complicated top structure that is not a free end at all, so the test approaches for single pile's bearing capacity do not apply here.
ABSTRACT In this paper, linear and nonlinear soil- pile interaction behavior is taken into consideration in the seismic safety analysis of marine piled structures. Comparisons between the results of linear and nonlinear soil condition with the results from analysis without taking into consideration of the soil-pile interaction are made. INTRODUCTION Based on a series of tests made in the late 70s, the present Seismic Design Code for Port Structures in China recommends that the piled pier structures may be analyzed as a single mass system using standard design response spectrum for earthquakes in evaluating seismic force acting on the pier. However, the soil- pile interaction behavior is not required to be taken into consideration in evaluating the internal forces in piles which might set the piles into a state of unsafe design. In this paper, the safety of piles of marine piled pier structures against earthquakes is investigated with the consideration of linear as well as nonlinear soil pile interaction behavior. MODELLING OF SEISMIC SOIL-PILE INTERACTION Under seismic condition, the earthquakes set the soil medium in which the piles are embedded into motion and yield deformation of soil medium that in turn motivating the deformation of the piles of the piled structure. The relative lateral dynamic deformation between the soil medium and the pile at any point can be represented as (equation 1 shown in paper) where ū=u+ub denotes the absolute dynamic deformation of the soil adjacent to the pile and equals the sum of the rock base movement ub. and the relative dynamic deformation u of the soil adjacent to the pile at any point; y = y + ub. denotes the absolute dynamic deformation which is the sum of the rock base movement u. and the relative deformation u of the pile at that point.
Investigation of the Behavior of Piled Raft Foundations In Sand By Numerical Modeling
Oh, E.Y.N. (Griffith School of Engineering, Griffith University Gold Coast Campus, Queensland, Australia) | Bui, Q. M. (Griffith School of Engineering, Griffith University Gold Coast Campus, Queensland, Australia) | Surarak, C. (Griffith School of Engineering, Griffith University Gold Coast Campus, Queensland, Australia) | Balasurbamaniam, A.S. (Griffith School of Engineering, Griffith University Gold Coast Campus, Queensland, Australia)
This paper is on 3-D analysis of piled raft foundations on sand. The numerical analysis was carried out with three typical load intensities of the serviceability load. Further, extensive parametric studies were carried out with the variables pile spacing, number of piles, pile diameter, raft dimension ratio, and raft thickness. The maximum settlement of the piled rafts depends on the pile spacing and the number of piles; while the raft thickness does not have a significant effect. In all cases, the normalized settlement recorded is mostly less than 2% of the raft width and the maximum value was noted for the 8x27m piled raft. The increase in raft thickness reduces the differential settlement in the foundations. The raft-soil stiffness (Krs) is shown to influence the differential settlement and has the largest influence. The performance of piled raft in sandy soil condition is assessed and general conclusions are also made. INTRODUCTION This paper is on a detail 3-D analysis of piled raft foundations using the PLAXIS. A six-layer soil model is adopted which is commonly encountered in Surfers Paradise of Gold Coast. The numerical work is carried out on 3-D PLAXIS analysis. Extensive parametric studies were carried out with the variables pile spacing, number of piles, pile diameter, raft dimension ratio, and raft thickness. Historically, the pile raft analysis has its origin to the pile group analysis. The early work of Skempton (1953) and Meyerhof (1959) were empirical in nature and relates to the settlements of pile groups. The important work of Fraser and Wardle (1975), Poulos and Davis (1980), Randolph (2003), and Poulos (2006) are reviewed in relation to the pile group analysis, load transfer mechanism and other pertinent aspects related to the fundamentals of pile group analysis. The contributions from Tomlinson (1986), Coduto (1996), Poulos (1993) and Van Impe (1991) are also studied in relation to the equivalent raft methods of analysis.
Model Experimental Study on the Load Sharing of Piled Raft on Foundation Underpinning
Wang, ChengCan (Korea University of Science and Technology ) | Han, JinTae (Korea Institute of Civil Engineering and Building Technology) | Kim, SeokJung (Korea Institute of Civil Engineering and Building Technology) | Jang, YoungEun (Ulsan National Institute of Science and Technology) | Park, HeonJoon (Ulsan National Institute of Science and Technology)
ABSTRACT Existing pile foundations underpinning is needed when the bearing capacity is not enough to resist the superstructures. In this study, a series of experiments were carried out on the 2x2 model piled raft foundation considering underpinning by a micropile in sand soil. The experiments aimed at investigating the effect of the raft on load sharing characteristics and settlement reduction behavior subjected to additional loads after underpinning with the micropile. The experimental results showed the raft had higher capacity on reducing the settlement and transferring loads from piles to the raft under vertically loading than the free-standing pile group which is not in contact with soil. The results also showed that consideration of the raft effect is an efficient way to save construction cost and reduce the number of underpinning piles in the practical underpinning design. INTRODUCTION Due to the rapid population growth and limited land in urban cities, reuse of existing buildings in terms of remodeling with vertical extension is one of the effective ways to solve the problem of old existing buildings and the accompanying problems. In South Korea, to enhance the utilization of existing buildings, the government stated that old high-rise buildings more than 15 years could be remodeled and vertically extended to 2–3 floors (MOLIT, 2013). During vertical extension of existing buildings, allowable bearing capacity of the existing foundations could not be able to support the structural loads from the additional stories. In this case, foundation underpinning is required to secure the safety and stability of the structure from the additional load by vertical extension. For the existing foundations, piled foundations are commonly used to support the loads from the superstructures. The conventional design of the piled raft, which based on the assumption that the resistance provided by the piles, would ignore the resistance provided by the pile cap or raft. Therefore, this conventional design method may lead to an overly conservative design approach. Combined pile-raft foundations have been increasing recognition to be an economical and rational foundation system, which can take advantage of the bearing capacity and reduce the settlement for high-rise buildings. Many researchers have conducted numerical analysis and experimental tests to provide a better understanding of piled rafts (Horikoshi and Randolph, 1996; 1999; Poulos, 2001; Horikoshi et al., 2003; Lee and Chung, 2005; Nguyen, 2012). Horikoshi et al. (2003) studied the behavior of piled raft under vertically and horizontally loading and the load sharing ratio of the piles and raft by centrifuge test. Lee and Chung (2005) investigated the effect of pile spacing on raft-soil-pile interaction by model tests. Basuony et al. (2013) conducted a series of 1g model tests to investigate the effect of the number of piles beneath the raft on the behavior of piled raft in loose sand. Alnuiam et al. (2013) investigated the influencing factor on load sharing between the raft and pile such as raft rigidity, pile diameter, raft thickness. Bajad and Sahu (2008) carried out a series of parametric studies by 1g model tests to evaluate the effect of the pile length and number on load sharing between the raft and piles. Recently, piled raft foundations have been applied to building designs, and some researchers have been reported on actual buildings (Katzenbach, 2000; Yamashita, 2011; Poulos, 2011). However, in South Korea, pile-raft foundations are not mostly considered on the design of actual buildings because of the uncertain factors in the pile-soil-raft interaction. Pile foundations are mainly applied to high-rise buildings when bearing capacity of shallow foundations are not enough. In the case of the vertical extension for the high-rise buildings, taking into no account of raft's effect, the load sharing behavior of existing foundation elements and underpinning foundation elements are underestimated. Consequently, to prevent the existing foundations not exceeding their bearing capacities, a large number of underpinning piles would be installed which leads to the increase in the construction cost and the limit of construction areas.
- Construction & Engineering (1.00)
- Materials > Construction Materials (0.34)
Abstract This paper presents the results of a study examining the feasibility of a Conical Piled Monopod (CPM) offshore Northern Alaska in about 41m water depth, fairly competent soil conditions, and Multi Year Ice environment. The study was conducted jointly by ConocoPhillips Company based in Houston, Texas and Granherne Ltd, a KBR Company based in Leatherhead, UK. ConocoPhillips sponsored the study. Two CPM concepts were considered, the Standalone CPM covered in this paper and a Dual Rig Jack Up (Gemini) Assisted CPM. The latter is the subject of another paper to be published later. The CPM was configured for two drilling rigs, assuming topsides weights ranging from 35,000 tonnes to 45,000 tonnes and corresponding operating weights from 60,000 tonnes to 70,000 tonnes respectively. Ice loads were calculated using ISO 19906 formulae where possible, otherwise using references within the ISO 19906 code and specialist ice load advice (Ken Croasdale) where necessary. The CPM has been shown to be feasible in the Alaskan Sea for the two ice conditions considered, 6m thick level ice and a very rare 25m thick ice island event. The ice island event represents a very conservative scenario and further data may allow its severity to be reduced. In addition, there will be many months, if not years, after discovery before an ice island can potentially impact the CPM. The CPM has a large enclosed volume available, which could accommodate a potentially significant amount of oil storage. However, this has not been quantified within this study work. The CPM concept eliminates or greatly minimizes the need for seabed preparation, being a pile supported structure. It also does not require solid ballast for resistance against sliding due to ice loads; these two characteristics of the CPM can have a major positive impact on the cost and schedule of an offshore Arctic project. ConocoPhillips has a Patent Pending on the CPM concept.
- North America > United States > Alaska (0.61)
- North America > United States > Texas > Harris County > Houston (0.55)