Abstract: Offshore wind turbines are considered as an essential part to develop sustainable, alternative energy sources. The structures themselves are both slender and highly flexible, with a subsea foundation typically consisting of a single large diameter monopile. They are subject to intense wind and wave loadings, with the result that significant movement of both the exposed structure and the upper part of the monopile can occur. Although the structures are intended for design life of 25 to 30 years, very little is known about the long term behaviour of these structures. This paper characterizes the dynamic behaviour of these structures. A simplified approach has been proposed for the free vibration analysis of wind turbines taking the effect of foundation into account. The method is based on an Euler-Bernoulli beam-column with elastic end supports. The elastic end-supports are considered to model the flexible nature of the interaction of these systems with the foundation. A closed-form expression of the characteristic equation governing all the natural frequencies of the system has been derived. Theoretical developments are explained by practical numerical examples. Analytical as well as a new experimental approach has been proposed to determine the parameters for the foundation. Some design issues of wind turbine towers are discussed from the point of view of the foundation parameters.

Abstract: In good soil conditions, spread footings for bridges are less expensive than deep foundations. Furthermore, rocking shallow foundations have some performance advantages over conventional fixed-base foundations; they can absorb some of the ductility demand that would typically be absorbed by the columns, and they have better recentering characteristics than conventional reinforced-concrete (RC) columns. Foundations designed for elastic behavior do not have these benefits of nonlinear soil-structure interaction. One potential disad- vantage of rocking systems is that they can produce significant settlement in poor soil conditions. Centrifuge model tests were performed to account for the interaction between soil, footing, column, deck and abutments systems. Bridge systems with rocking foundations on good soil conditions are shown to perform well and settlements are small. An improved method for quantification of settlements is presented. The model tests are described in some detail. One of the important factors limiting the use of rocking foundations is the perception that they might tip over; experiments show that tipping instability is unlikely if the foundations are properly sized. In one experiment, a column for a system with large fixed-base foundation collapsed while the systems with smaller rocking foundations did not collapse. DOI: 10.1061/(ASCE)GT .1943-5606.0000605. © 2012 American Society of Civil Engineers. CE Database subject headings: Earthquakes; Shallow foundations; Bridges; Centrifuge models. Author keywords: Earthquake; Shallow foundation; Rocking; Bridge; Centrifuge modeling.

Abstract: Recent studies have highlighted the beneficial role of foundation uplifting and the potential effectiveness of guiding the plastic hinge into the foundation soil by allowing full mobilization of bearing capacity during strong seismic shaking. With the inertia loading transmitted onto the superstructure being limited by the capacity of the foundation, this concept may provide an alternative method of in-ground seismic isolation: the so-called rocking isolation. Attempting to unravel the effectiveness of this alternative design method, this paper experimentally investigates the nonlinear response of a surface foundation on sand and its effect on the seismic performance of an idealized slender single-degree-of-freedom structure. Using a bridge pier as an illustrative prototype, three foundation design alternatives are considered, representing three levels of design conservatism. Their performance is investigated through static (monotonic and slow-cyclic pushover) loading, and reduced-scale shaking ta...

Abstract: National Natural Science Foundation of China [21074103]; Natural Science Foundation of Fujian Province [2010J05033]; Fundamental Research Funds for the Central Universities [2010121018]

Abstract: In July 2009, the leaders of the European Union and the G8 announced an objective to reduce greenhouse gas emissions by at least 80% below 1990 levels by 2050. In October 2009 the European Council set the appropriate abatement objective for Europe and other developed economies at 80-95% below 1990 levels by 2050. In support of this objective, the European Climate Foundation (ECF) initiated a study to establish a fact base behind this goal and derive the implications for European industry, particularly in the electricity sector. The result is Roadmap 2050: a practical guide to a prosperous, low-carbon Europe, a discussion of the feasibility and challenges of realizing an 80% GHG reduction objective for Europe, including urgent policy imperatives over the coming five years. The scientific basis and the political process behind the setting of that objective are not discussed. This is the first of three volumes. It is a technical and economic assessment of a set of decarbonization pathways. Volume 2 will address the policy and regulatory implications arising from the analysis, and Volume 3 will address the broader implications for society. ECF strongly recommends that further work be carried out that will help stakeholders understand the required change in more detail, including the different ways in which various regions would experience the transformation. Roadmap 2050 breaks new ground by outlining plausible ways to achieve an 80% reduction target from a broad European perspective, based on the best available facts elicited from industry players and academia, and developed by a team of recognized experts rigorously applying established industry standards. This study is funded by ECF, which itself is funded solely by private philanthropic organizations 1. ECF does not have financial ties to EU political bodies, nor to business. Representatives of the European Commission and its services have provided strong encouragement for the development of this undertaking and have given welcome guidance regarding the objectives and the approach. Along with representatives of other EU institutions, notably the European Parliament and Council of Ministers, the European Commission has been consulted periodically throughout the course of the project. In addition, a wide range of companies, consultancy firms, research centers and NGOs have counseled ECF in the preparation of this report. These organizations can be found in the acknowledgements section.

Abstract: In the last few decades, a great amount of interest has developed in the evaluation of the influence of bearing capacity of shallow foundations on slopes. When a footing is placed near a slope the bearing capacity may be reduced. In fact, the failure mechanism is influenced by the distance of the foundation from the edge of the sloping ground. In order to investigate the effect of the bearing capacity of shallow foundations on slopes, model footing tests were performed. This paper presents the results of the investigation, to establish both qualitative and quantitative relationships between the ultimate load of the soil–foundation system and the location of the footing with respect to the slope. Values of ultimate loads deduced from experimental tests are compared with values derived by a numerical analysis based on the limit equilibrium method. Modified bearing capacity factors which take into account the effect of the sloping ground are proposed.

Abstract: A nonlinear finite element model for earthquake response analysis of arch dam–water–foundation rock systems is proposed in this paper. The model includes dynamic dam–water and dam–foundation rock interactions, the opening of contraction joints, the radiation damping of semi‐unbounded foundation rock, the compressibility of impounded water, and the upstream energy propagating along the semi‐unbounded reservoir. Meanwhile, a new equivalent force scheme is suggested to achieve free‐field input in the model. The effects of the earthquake input mechanism, joint opening, water compressibility, and radiation damping on the earthquake response of the Ertan arch dam (240 m high) in China are investigated using the proposed model. The results show that these factors significantly affect the earthquake response of the Ertan arch dam. Such factors should therefore be considered in the earthquake response analysis and earthquake safety evaluation of high arch dams. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract: In China, more and more underground structures are being built close to buildings of architectural merit. When installing deep foundations, three ways of controlling seepage are suggested. In Mode III, an installed curtain extends partly into the confined aquifer so that the hydraulic connection between the excavated section and the water in the host material is partly isolated. The combined effects of pumping, curtain efficiency and recharge are discussed. Based on the engineering geological conditions of the deep foundation pit of the Yishan Road Station of Metro Line 9, Shanghai, China, in situ pumping and recharge tests were carried out. The combined effects are similar to the results obtained using a three-dimensional finite difference method (FDM) numerical simulation.

Abstract: : This handbook discusses the application of engineering techniques and scientific knowledge to the investigation of seafloor materials, their characteristics, and their response to foundation and mooring loads. Its primary thrust is with problems engineers will encounter beyond the continental shelf or below 600 foot water depth, but the information is also applicable to shallow water tasks.

Abstract: Many engineers are hesitant to specify rocking foundations for ordinary bridges because of the unsubstantiated notion that rocking bridges are more susceptible to instability than conventional fixe...

Abstract: Near-fault ground motion effects in comparison with far-fault ground motions on seismic performance of a symmetry concrete arch dam are investigated. Various sets of near-fault and far-fault ground motions with approximately identical peak ground acceleration were used for analyses of coupled system. For this purpose the Karaj arch dam was selected as case study and two different options were considered for dam-foundation interaction. In the first case, foundation rock was assumed rigid, and in the second case foundation rock was simulated as a massless medium. The behavior of the dam and foundation was expressed in terms of displacement, and the reservoir was modelled based on fluid elements. The seismic performance evaluation of the arch dam was performed using demand-capacity ratios obtained from linear analyses.

Abstract: The paper deals with the modern nondestructive elastic-wave testing of concrete in foundation slab in a very important office building put under the ground water level. After the construction water has appeared in lower level of the building. The reason for the tests was to find the place where water gets for building, and also check the technical condition of the foundation slab to take a decision about the range of repairs to be done to the foundation slab or about their strengthening. The primary test methods were: ultrasonic Tomography, Impulse Response and Impact-Echo technique. The auxiliary methods were: the electromagnetic method and the ultrasonic method. About 100 m2 of foundation slab were tested at a time. On the basis of an analysis of the results, in particular the tomography images and the distribution of the amplitude-frequency spectra of elastic waves the damage was found. The damage had the form of cracks running along the foundation slab and delamination of the reinforcement concrete. The depths of cracks were measured, the places of delamination were found, the thickness of slab did not conform to the design and zones of concrete containing honeycombing were identified. The results of the nondestructive tests and the analyses were corroborated by exposures.

Abstract: This study describes various types of foundation designs to be considered for structural engineering projects when the subsoil foundation consists of expansive or swelling soils. Among civil and architectural engineers expansive soils are known to be difficult foundation materials and problematic. These type of soils swell when they are subjected to moistures and shrink due to moisture loss. Because of this different behaviour upon wetting and drying, they cause minor to major structural damages to pavements as well as buildings. Every year millions of dollars spent dealing with the consequences of swelling soils. For design of foundations on swelling soil, it is first essential to recognize and evaluate the soil based on its swelling potential, and then determining the most proper foundation design that can be constructed on this problematic soil. In general, this study presents some of the most common techniques to evaluate the swelling potential of expansive soils. Also, it discusses problems associated with swelling soil, classification of structural damages caused to buildings, and various foundation designs to combat the problems based on the degree of detrimental effects of swelling potential to civil engineering projects.

Abstract: A concrete tower construction (10) comprising; - a foundation (12), - a plurality of prefabricated concrete tower elements (24) each having an outside (32), an inside (34), a material thickness (36) provided there between, and top (38) and bot- tom (40) surfaces, said tower element (24) having a hollow centre, said tower elements (24) are arranged one tower element (24) on top of another forming a column (22) on top of the foundation (12), - a plurality of tendons (28) arranged in the hollow centre, for applying a tension force to the column (22), wherein the tower construction (10) further comprises an upper force distribution element (26) arranged on top of the column (22) and a lower force distribution element (18) arranged in the foundation (12), wherein each tendon (28) is connected to the upper force distribution element (18) and the lower force distribution element (26) by co-operating attachment means (30, 30'). Furthermore a method of erecting said tower construction (10), a tower element and a foundation element is described.

Abstract: This paper emphasizes on the dynamic interaction of two closely spaced embedded square or rectangular foundations under the action of machine vibration. One of the foundations is excited with a known vibration source placed on the top of it, called the active foundation. The objective is to study the effect of dynamic motion of the active foundation on the nearby passive foundation through a layered soil medium. The analysis is performed numerically by using the explicit finite difference code FLAC 3D . The soil profile is assumed to obey the Mohr–Coulomb yield criteria with non-linear failure envelope. The analysis is performed under sinusoidal dynamic loading with varying amplitude. Under the dynamic excitation, the settlement behavior of the interacting foundations is studied by varying the spacing between the foundations. In addition, the variation of vertical normal and shear stress developed beneath the interacting foundations is also explored. The present theoretical investigation indicates that the settlement and vertical normal stress below the active foundation is generally found to be higher than that obtained for the passive foundation, whereas the shear stress response below the foundations follows the reverse trend.

Abstract: Soil-Structure-Interaction (SSI) for offshore wind turbine supporting structures is essentially the interaction of the foundation/foundations with the supporting soil due to the complex set of loading. This paper reviews the different aspects of SSI for different types of foundations used or proposed to support offshore wind turbines. Due to cyclic and dynamic nature of the loading that acts on the wind turbine structure, the dominant SSI will depend to a large extent on the global modes of vibration of the overall structure. This paper summarises the modes of vibration of offshore wind turbines structures supported on different types of foundations based on observations from scaled model tests and numerical analysis. As these are new structures with limited monitoring data, field records are scarce. Field records available in the public domain are also used to compare with the experimental findings.

Abstract: This study describes some of the most important swelling characters of expansive soils when used as foundation materials to support various types of civil engineering structures Expansive soils are considered among difficult foundation materials and expand upon wetting and shrink upon losing moisture They are considered problematic soils for architectural and civil engineers These types of soils may cause minor to major structural damages to pavements as well as buildings It is therefore essential to detect swelling soils from non-problematic foundation soils before any civil engineering projects are constructed over or adjacent to them The study begins with definition of expansive soils and shows its distributions in the world as well as the basic causes for swelling potential that these type of soils poses It is also shown that, the most probable depth of expansion to check for possible swelling potential for swelling soils is soil's active zone This zone is the most upper depth of expansive soil and it may extend up to 20 ft (6 m) below ground level The moisture content of soil through active zone varies during different seasons while in lower part of expansive soil the moisture content stays constant during hot and cold season Among various methods to check for swelling potential, plastic index and liquid limits are two most crucial factors, as these factors tend to increase, the swelling potential increase as well

Abstract: Many concrete hydropower structures develop faults before they reach the end of their life. Why this happens is of increasing concern to many countries, not least because the cost of restoring the structures is quite high. There are many reasons why concrete hydropower structures suffer defects before the end of their natural life. Imperfections may be induced by thermal effects, cement shrinkage, foundation conditions, carbonation and reinforcement corrosion, freezing and thawing, concrete expansion and contraction, chloride and sulfate attacks on concrete, alkali–aggregate reaction, seepage water scouring, abrasion, cavitation, and so on. The main task facing durability design of concrete hydropower structures is maximizing their life, taking into consideration cost and the environment in which they will be placed and used. This is a task that requires the efforts of not only designers but also constructors and administrators. The most cost-effective way to maximize the life of a concrete hydropower structure is to produce concrete that is fit for purpose during the construction stage. This, and careful consideration of the selection of materials and the design, construction, servicing, and repair of concrete hydropower structures, should ensure that the life of the structures is 80–100 years. Looking ahead, it is predicted that expert systems with a life of 150 years or longer will be able to be designed to meet the requirements of specific construction projects. When this happens, it will be possible to estimate the anticipated life of a structure and thus aid decision-making about the value of repairing a structure.