Author: Thomas Brian Algie Publisher: ISBN: Category : Foundations Languages : en Pages : 348
Book Description
The most recent version of the New Zealand design and loadings standard eliminated a clause for the design of rocking foundations. This thesis addresses that clause by presenting a strong argument for rocking shallow foundations in earthquake resistant design. The goals of the research were to perform large scale field experiments on rocking foundations, develop numerical models validated from those experiments, and produce a design guide for rocking shallow foundations on cohesive soil. Ultimately, this thesis investigates the nonlinear rotational behaviour of shallow foundations on cohesive soil. Field experiments were performed on an Auckland residual soil, predominantly clay. The experiment structure - a large scale steel frame - was excited first by an eccentric mass shaker and second by a quick release (snap-back) method. The results show that rocking foundations produce highly nonlinear moment-rotation behaviour and a well defined moment capacity. A hyperbolic equation is proposed in Chapter 4 utilising the initial stiffness and moment capacity to predict nonlinear pushover response. The results show that the initial stiffness should be based on an 'operational soil modulus' rather than a small strain soil modulus. Therefore, the reduction factor from the small strain modulus was around 0.6 for the experiment testing. Additionally, the experiments showed that rocking foundations demonstrate significant damping; snap-back experiments revealed an average damping ratio of around 30%. Experiment data validated two numerical models developed for this study: one, a finite element model in Abaqus and the other, a spring bed model in OpenSEES. The models showed that both forms of nonlinearity in rotating shallow foundations - geometric nonlinearity and material nonlinearity - should be considered in shallow foundation analysis. These models also confirmed the need for an 'operational soil modulus' on shallow foundation rocking, and analysis of varying vertical loads suggested that this reduction factor is dependent on the vertical factor of safety of the foundation. Lastly, two design methods are presented, a displacement-based method and a forcebased method, and two examples of rocking shear walls are given. The displacementbased method is the recommended option, and it is shown that design displacements and rotations compare well to time history analyses performed using the validated OpenSEES model.
Author: Ravindranath Salimath Publisher: ISBN: Category : Clay soils Languages : en Pages : 234
Book Description
This thesis presents a better understanding of nonlinear moment-rotation behavior of shallow foundations resting on stiff clay based on the results of 3D finite element analysis and large scale field experiments. In past decades several researchers have carried out both numerical modelling and experimental studies to understand the rocking behavior and earthquake response of shallow foundations. Algie (2011) performed a series of snap-back tests to study the moment-rotation response of shallow foundations on stiff residual clay. The results showed that snap-back testing is an effective tool for obtaining insight into the nonlinear behavior and earthquake response of shallow foundations. Tests also gave a good assessment of magnitude of damping of rocking shallow foundations resting on stiff clay. Another advantage was that the static moment-rotation curves are obtained during the initial pull-back phase of the test and it turns out that the static response provides considerable insight into the dynamic behavior of the foundation. This first half of the thesis comprises of development of a 3D finite element model in , its validation with available experimental data and the analysis results. The moment-rotation behavior predicted from PLAXIS 3D converged with the experimental data and showed considerable nonlinearity once the footing uplift and partial loss of contact occurs. The contact pressure distribution under the footing showed that the footing uplift and nonlinearity is initiated when the applied moment exceeds around 0.45Mult. The analysis results also showed that direction of the applied moment is important as footing exhibited considerably different rotational stiffness about short and long axis. The analyses also showed that effect of footing L/B ratio, static initial factor of safety and the undrained shear strength of the soil considerably affect the non-linear moment-rotation behavior. The evaluation of actual footing contact area during rocking is critical for assessment of seismic performance of the rocking shallow foundations and it depends on the ultimate moment capacity of the footing. Based on numerical modelling results, a new modified hyperbolic equation was proposed to evaluate nonlinear moment-rotation response of footings on stiff clay incorporating the effects of L/B ratio, direction of the applied moment and undrained shear strength. The remaining half of the thesis deals with field experiments on surface shallow foundations resting on stiff residual clay. The experiments were performed on a site located in Silverdale, Auckland. The field experiments included slow-cyclic and snap-back tests on two different sets of footing configurations to simulate static non-linear moment-rotation response and footing rocking. For this study snap-backs were carried out in alternating directions, thus simulating the back and forth motion experienced during an earthquake. The test rig had two parallel foundation strips; in one case the longitudinal axis of the footings was in the plane of the rocking, in the other the footings were oriented perpendicular to the plane of the rocking and placed at the outer edges of the rig. This means that results are obtained for rocking in which there is a gradual uplifting of the foundation strip (foundation longitudinal axis in the plane of rocking), and when the entire footing lifts clear of the underlying soil (foundation strips at the outer edges of the rig). The purpose here was to investigate the validity of the damping mechanism proposed by Housner in his paper on inverted pendulum structures gave the best representation of the foundation damping; so the tests duplicate the partial uplifting of foundations and also foundations that lift completely clear of the underlying soil. The moment-rotation curves from the tests showed that the small strain stiffness is only around 25% of the theoretical stiffness. Also, it was observed the for the case of snap-back tests at higher vertical loads, the damping ratio was generally higher around 20% due to large footing rotation and partial detachment with underlying soil at the time of snap. The direction of rocking and footing L/B ratio also affect the magnitude of damping. Lastly the conclusions from both the finite element analysis and experimental studies are presented in detail. The need of further research and future scope of work is outlined.
Author: Susumu Iai Publisher: Springer ISBN: 331962069X Category : Nature Languages : en Pages : 412
Book Description
This book provides a timely review and summary of the recent advances in state-of-the-art earthquake geotechnics. The earthquake disasters in Japan and New Zealand in 2011 prompted the urgent need for the state-of-the-art earthquake geotechnics to be put into practice for disaster mitigation. By reviewing the developments in earthquake geotechnics over more than half a century, this unique book enables readers to obtain solid grasp of this discipline. It is based on contributions from 18 leading international experts, who met in Kyoto in June 2016 to discuss a range of issues related to the developments of earthquake geotechnics. It comprehensively discusses various areas of earthquake geotechnics, including performance-based seismic design; the evolution of geotechnical seismic response analysis from 1964-2015; countermeasures against liquefaction; solutions for nuclear power plant disasters; the tsunami-caused inundation of the Tokyo metropolitan area; and a series of state-of-the-art effective stress analyses of case histories from the 2011 East Japan Earthquake. The book is of interest to advanced level researchers and practicing engineers in the field of earthquake geotechnics.
Author: Taraka Ravi Shankar Mullapudi Publisher: ISBN: Category : Nonlinear mechanics Languages : en Pages : 92
Book Description
"The response of shallow and raft foundations is having a significant importance due to its complex behavior because of the semi-infinite soil media. Winkler's model is the simplest model to deal with the structure and soil. The Winkler model represents the foundation reaction as proportional to the soil displacement at a particular point, which results in the elasticity of the soil being the only parameter in consideration. But in reality the soil cohesiveness is having a significant contribution in soil structure interaction, and therefore the consideration of coupling effects of Winkler springs need to be accounted. Most of the existing elements either consider certain parameters of the foundation or assume an elastic beam and foundation response. In this research a new finite element formulation was developed in which these limitations were eliminated. This improved model can be viewed as a soil with a combination of cohesive behavior which transmits the rotation due to bending in addition to the Winkler effect. The non linear response of structures resting on this improved foundation model can be analyzed by assuming that the foundation resists compression and tension. In reality soil is very weak in tension and its tension capacity needs to be neglected, which leads to lift-off regions at different locations. This phenomenon becomes much more complicated by considering the inelastic soil structure behavior, which leads to a highly nonlinear problem. In order to estimate the necessary nonlinear soil parameters, an analytical procedure based on the Vlasov model is proposed. The presented solutions and applications show the superiority of the proposed nonlinear foundation model"--Abstract, leaf v.
Author: T. G. Sitharam Publisher: Springer Nature ISBN: 981165669X Category : Science Languages : en Pages : 547
Book Description
This volume presents select papers presented at the 7th International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. The papers discuss advances in the fields of soil dynamics and geotechnical earthquake engineering. Some of the themes include ground response analysis & local site effect, seismic slope stability & landslides, application of AI in geotechnical earthquake engineering, etc. A strong emphasis is placed on connecting academic research and field practice, with many examples, case studies, best practices, and discussions on performance based design. This volume will be of interest to researchers and practicing engineers alike.
Author: Cesar Ovalles Publisher: CRC Press ISBN: 1138001465 Category : Science Languages : en Pages : 1351
Book Description
Effective measurement of the composition and properties of petroleum is essential for its exploration, production, and refining; however, new technologies and methodologies are not adequately documented in much of the current literature. Analytical Methods in Petroleum Upstream Applications explores advances in the analytical methods and instrumentation that allow more accurate determination of the components, classes of compounds, properties, and features of petroleum and its fractions. Recognized experts explore a host of topics, including: A petroleum molecular composition continuity model as a context for other analytical measurements A modern modular sampling system for use in the lab or the process area to collect and control samples for subsequent analysis The importance of oil-in-water measurements and monitoring The chemical and physical properties of heavy oils, their fractions, and products from their upgrading Analytical measurements using gas chromatography and nuclear magnetic resonance (NMR) applications Asphaltene and heavy ends analysis Chemometrics and modeling approaches for understanding petroleum composition and properties to improve upstream, midstream, and downstream operations Due to the renaissance of gas and oil production in North America, interest has grown in analytical methods for a wide range of applications. The understanding provided in this text is designed to help chemists, geologists, and chemical and petroleum engineers make more accurate estimates of the crude value to specific refinery configurations, providing insight into optimum development and extraction schemes.
Author: Rolando P. Orense Publisher: CRC Press ISBN: 9780415600408 Category : Technology & Engineering Languages : en Pages : 260
Book Description
Soil-Foundation-Structure Interaction contains selected papers presented at the International Workshop on Soil-Foundation-Structure Interaction held in Auckland, New Zealand from 26-27 November 2009. The workshop was the venue for an international exchange of ideas, disseminating information about experiments, numerical models and practical engineering problems relating to soil-foundation-structure interaction. A topic of long standing interest to both structural and geotechnical engineers is what is traditionally known as soil-structure interaction (SSI). For a long period, this has involved linear elastic interaction between the foundation and the underlying soil and the appropriate analysis is well developed for both static and dynamic interaction. In recent years, there has been a growing interest in considering nonlinear soil-foundation interaction in the design of shallow foundations, both for static and earthquake loading. To distinguish these approaches from the classical linear elastic soil-structure interaction, the term soil-foundation-structure-interaction (SFSI) has been coined recently. The development of various approaches is occurring rapidly in many research groups all over the world, with the inclusion of nonlinear structure and nonlinear soil interaction using FEM-based numerical methods, as well as the use of shallow foundation macro-elements as an alternative to using finite elements. The workshop brought together representatives from several of these groups to review the current state of development, discuss the potential for application in foundation design, and consider how work in this area might develop in the next few years. The emphasis in the workshop was on application of these ideas to the foundation design process. The book will be much of interest to post-graduates in Foundation Engineering, Earthquake Geotechnical Engineering, Earthquake Engineering, and Advanced Structural Dynamics.
Author: Rolando P. Orense Publisher: CRC Press ISBN: 0203838203 Category : Technology & Engineering Languages : en Pages : 258
Book Description
Soil-Foundation-Structure Interaction contains selected papers presented at the International Workshop on Soil-Foundation-Structure Interaction held in Auckland, New Zealand from 26-27 November 2009. The workshop was the venue for an international exchange of ideas, disseminating information about experiments, numerical models and practical en
Author: Andreas Gerasimos Gavras Publisher: ISBN: 9781658413060 Category : Languages : en Pages :
Book Description
The concept of intentional mobilization of controlled soil inelasticity and foundation uplift, as a rational and economical seismic protection strategy, has much matured as a result of extensive research over the last two decades. This dissertation provides further evidence and tools that contribute toward the implementation of rocking foundations in practice with emphasis on bridges applications. In response to the lack of high-quality experimental data on the seismic response of full-scale rocking foundations, a series of large-scale tests, involving reinforced concrete bridge columns with footings embedded into dense sand, was completed. The experimental program investigated the alignment of the footings to the shaking direction and included varying groundwater table elevations and footing backfill conditions. This study yielded results that corroborate the cumulative centrifuge experiments-based understanding of the dynamic behavior of rocking foundations and confirmed that loose and dry cohesionless backfill soil can ravel under the rocking footing at large rotations, resulting in reduced settlement, reduced stiffness degradation, enhanced energy dissipation, but potentially also causing permanent rotations. A modified beam-on-nonlinear-Winkler-foundation (BNWF) modeling scheme, representing a departure from previous attempts to capture both the vertical and rotational nonlinear responses of a shallow footing, was proposed. The considered scheme is cast around the foundation critical contact area ratio and the trilinear moment-rotation backbone of Deng et al. (2014), and is calibrated to four physical model tests. The calibrated scheme captured successfully the experimental response in terms of moment-rotation envelope, hysteretic energy dissipation and recentering across a range of rotation amplitudes and rocking-induced soil inelasticity. Settlement accumulation was captured for rotation amplitudes less than 0.025 rad but was overestimated at larger rotations. Displacement-based assessment (DBA) guidelines for bridges with rocking foundations were developed. Nonlinear response history analyses of idealized footing-column-mass models, using the calibrated BNWF model, were conducted to determine the fraction of the area-based hysteretic damping that is effective in reducing the seismic displacement demand and evaluate the importance of P-[delta] effects, in refinement of the Deng at al. (2014) study for elastic cantilever bridge columns on rocking foundations. The DBA guidelines were subsequently extended to bridge bents that also include plastic hinging at the top of the column. The bent-level equivalent-linear properties are derived, considering independent foundation-rocking and column-hinging subsystems and constant location for the contraflexure point based on their inelastic capacities. Comparison with a detailed nonlinear pushover analysis-based procedure for representative cases showed that the simplified procedure is practical and sufficient for estimating the total displacement demand, but less accurate at the component level. Lastly, provisions for multi-span bridges that follow a system-level approach for the longitudinal direction and an isolated-bent approach with modified mass and stiffness characteristics for the transverse direction were presented. The guidelines were applied to hypothetically redesign two existing bridges with rocking foundations. Numerical analyses of the full bridges demonstrated the accuracy of the procedure, except for the transverse response of bridges with high strength and energy dissipation at the abutments. Finally, a new rocking shallow foundation performance database, containing dynamic experimental results from five centrifuge and three 1g shaking table test series, was created. Its usefulness was illustrated through example correlations between the peak drift ratio demand of the structures and selected ground motion intensity measures. The fundamental value of the database is that it allows easy access to summary information and derived time series data that can be used to obtain empirical correlations, validate numerical models and design guidelines, and identify future experimental priorities.
Author: Thomas Brian Algie
Author: Ravindranath Salimath
Author: Susumu Iai
Author: Sivapalan Gajan
Author: Taraka Ravi Shankar Mullapudi
Author: T. G. Sitharam
Author: Cesar Ovalles
Author: Rolando P. Orense
Author: Rolando P. Orense
Author: Andreas Gerasimos Gavras