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Author: R. Manoj Kannan Publisher: OAE Publishing Inc. ISBN: Category : Social Science Languages : en Pages : 15
Book Description
Although seismic design concepts integrated the idea of shallow rocking foundations as an effective way to dissipate the induced seismic energy, a practical design solution is yet to be established. To attain this objective, it is necessary to identify the key parameters that govern the rocking efficacy of foundation and eventually overall seismic performance of the entire structure. The primary focus of this study is to assess the key parameters such as soil type and embedment depth of footing in conjunction with varying rocking foundation efficacy on the seismic force and displacement demands of the Reinforced Concrete (RC) buildings. A simplified generic high rise RC building along with its foundation is considered for the analytical study which is designed and detailed as per relevant Indian Standards. To highlight the beneficial effects of rocking foundation, seismic responses of the RC buildings with varying foundation rocking efficacy are compared with the conventional foundation design philosophies by conducting nonlinear dynamic time history analyses. From the seismic responses, it is determined that the moment from column to foundation and base shear, owing to seismic action, decreases with an increasing settlement at the base of the foundation for rocking footing. It is also observed from the seismic responses that rocking foundations effectively de-amplifies the peak roof acceleration by utilizing the nonlinear soil responses during earthquakes. Hence, it can be depicted that the foundation rocking improves the overall stability of the buildings by decreasing the seismic force demands with a slight increase in seismic displacement demands. The investigation also indicates that the efficacy of rocking foundation is not sensitive to embedment depth of footing.
Author: R. Manoj Kannan Publisher: OAE Publishing Inc. ISBN: Category : Social Science Languages : en Pages : 15
Book Description
Although seismic design concepts integrated the idea of shallow rocking foundations as an effective way to dissipate the induced seismic energy, a practical design solution is yet to be established. To attain this objective, it is necessary to identify the key parameters that govern the rocking efficacy of foundation and eventually overall seismic performance of the entire structure. The primary focus of this study is to assess the key parameters such as soil type and embedment depth of footing in conjunction with varying rocking foundation efficacy on the seismic force and displacement demands of the Reinforced Concrete (RC) buildings. A simplified generic high rise RC building along with its foundation is considered for the analytical study which is designed and detailed as per relevant Indian Standards. To highlight the beneficial effects of rocking foundation, seismic responses of the RC buildings with varying foundation rocking efficacy are compared with the conventional foundation design philosophies by conducting nonlinear dynamic time history analyses. From the seismic responses, it is determined that the moment from column to foundation and base shear, owing to seismic action, decreases with an increasing settlement at the base of the foundation for rocking footing. It is also observed from the seismic responses that rocking foundations effectively de-amplifies the peak roof acceleration by utilizing the nonlinear soil responses during earthquakes. Hence, it can be depicted that the foundation rocking improves the overall stability of the buildings by decreasing the seismic force demands with a slight increase in seismic displacement demands. The investigation also indicates that the efficacy of rocking foundation is not sensitive to embedment depth of footing.
Author: Publisher: OAE Publishing Inc. ISBN: Category : Social Science Languages : en Pages : 15
Book Description
Although seismic design concepts integrated the idea of shallow rocking foundations as an effective way to dissipate the induced seismic energy, a practical design solution is yet to be established. To attain this objective, it is necessary to identify the key parameters that govern the rocking efficacy of foundation and eventually overall seismic performance of the entire structure. The primary focus of this study is to assess the key parameters such as soil type and embedment depth of footing in conjunction with varying rocking foundation efficacy on the seismic force and displacement demands of the Reinforced Concrete (RC) buildings. A simplified generic high rise RC building along with its foundation is considered for the analytical study which is designed and detailed as per relevant Indian Standards. To highlight the beneficial effects of rocking foundation, seismic responses of the RC buildings with varying foundation rocking efficacy are compared with the conventional foundation design philosophies by conducting nonlinear dynamic time history analyses. From the seismic responses, it is determined that the moment from column to foundation and base shear, owing to seismic action, decreases with an increasing settlement at the base of the foundation for rocking footing. It is also observed from the seismic responses that rocking foundations effectively de-amplifies the peak roof acceleration by utilizing the nonlinear soil responses during earthquakes. Hence, it can be depicted that the foundation rocking improves the overall stability of the buildings by decreasing the seismic force demands with a slight increase in seismic displacement demands. The investigation also indicates that the efficacy of rocking foundation is not sensitive to embedment depth of footing.
Author: Braja M. Das Publisher: CRC Press ISBN: 9781420049565 Category : Technology & Engineering Languages : en Pages : 394
Book Description
The First Comprehensive Guide to Shallow Foundations Over the last few decades, the bearing capacity of shallow foundations has been studied more thoroughly than any other subject in geotechnical engineering. Until now, however, most references on foundation engineering devoted only a single chapter to the subject. Shallow Foundations: Bearing Capacity and Settlement provides what many engineers have been waiting for-a concise, comprehensive reference containing all the relevant material on shallow foundation behavior under static and dynamic loads related to their ultimate bearing capacity, allowable bearing capacity, and settlement. Estimation Techniques, Earthquake Loading, and Experimental Results The author-a renowned expert-presents the various theories developed during the past fifty years for estimating the ultimate bearing capacity of shallow foundations under various types of loading and subsoil conditions. He discusses the principles of estimating foundation settlement and for estimating the stress increase in a soil mass supporting a foundation. Earthquake loading and its effects on ultimate bearing capacity have received considerable attention in recent years, and the author provides an overview of these developments. He also offers details regarding permanent foundation settlement caused by cyclic and transient loading-details derived from laboratory and field experimental observations. Progress in Soil Reinforcement Researchers have made steady progress in evaluating the potential of soil reinforcement to reduce settlement and increase ultimate and allowable bearing capacities of shallow foundations. This book provides an entire chapter on the subject, including discussions of the materials used: galvanized steel strips, geotextile, and geogrid. The presentation of Shallow Foundations is clear, concise, and filled with examples and exercises that illustrate the theory. This book stands alone as an in-depth, authoritative guide to shallow foundation bearing capacities and the effects of different soil types, slopes, settlement, reinforcement, and seismic activity. Researchers, students, and practicing engineers will all welcome its addition to their reference shelves.
Author: Jacquelyn Denise Allmond Publisher: ISBN: 9781321361995 Category : Languages : en Pages :
Book Description
Current research has shown the capabilities and improved seismic performance of shallow rocking foundations for bridges, and much work has been done for implementation of such a mechanism in industry. By properly reducing the size of the footing in design, rocking behavior due to seismic loading can occur about the footing base. Allowing the foundation to rock causes a natural recentering of the foundation, ultimately preserving the structural integrity of the column and reducing residual rotations of the structure if soil conditions are favorable. It has been shown experimentally that rocking foundations on competent soils can reduce seismic ductility demand on bridge columns and improve bridge performance through significant energy dissipation at the foundation level, rather than from a hinging column in conventional design. This beneficial energy dissipation potential is attractive for design, but has not been validated for rocking foundations in difficult soils. The overall goals of this research are to (1) evaluate the performance of rocking foundations in liquefiable and saturated soils and (2) explore the viability of rocking foundations in poor soil conditions if the foundations are supported on unattached piles. Two centrifuge tests were performed with similar model structures representing a deck mass-column-footing system on fully saturated sand with a liquefiable layer and surface water. The tests explored the structure, soil, and fluid responses due to suction, erosion, and liquefaction induced settlements under the footings. It was found that the rocking footing embedded in fine soil experienced high residual rotations throughout testing. This is due to a "no breakaway" condition, a mechanism which emerges from a relatively large drop in pore water pressure directly under the footing as it uplifts in lower permeable soil, ultimately pulling in material under the footing and increasing residual rotations with each event. Deep soil foundation improvement by use of unattached piles was also tested in both experiments to explore applicability, effectiveness, and practicality of settlement reduction while still allowing rocking. The results were used to evaluate effects of pile capacity, number of piles, and arrangement of piles on the residual settlement and base shear coefficient to initiate rocking. Finally, a new centrifuge test database was created, whereby the performance of isolated mat and rocking foundations, and adjacent mat foundations from 9 different centrifuge experiments on liquefiable sand are compared. Results from this research will help define the appropriate applicability range of rocking foundations in seismic design.
Author: Steven J. Greenfield Publisher: ISBN: Category : Technology & Engineering Languages : en Pages : 264
Book Description
Describes the different foundation systems in use, and how a system is selected to meet particular objectives, on a regional and a site-specific basis. The importance of long term costs and benefits of each is discussed, and common construction and design oversights are presented.
Author: Masaki Kitazume Publisher: CRC Press ISBN: 0203589637 Category : Technology & Engineering Languages : en Pages : 436
Book Description
The Deep Mixing Method (DMM), a deep in-situ soil stabilization technique using cement and/or lime as a stabilizing agent, was developed in Japan and in the Nordic countries independently in the 1970s. Numerous research efforts have been made in these areas investigating properties of treated soil, behavior of DMM improved ground under static and d
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: Harry G. Poulos Publisher: CRC Press ISBN: 1351652141 Category : Technology & Engineering Languages : en Pages : 761
Book Description
This book provides a comprehensive guide to the design of foundations for tall buildings. After a general review of the characteristics of tall buildings, various foundation options are discussed followed by the general principles of foundation design as applied to tall buildings. Considerable attention is paid to the methods of assessment of the geotechnical design parameters, as this is a critical component of the design process. A detailed treatment is then given to foundation design for various conditions, including ultimate stability, serviceability, ground movements, dynamic loadings and seismic loadings. Basement wall design is also addressed. The last part of the book deals with pile load testing and foundation performance measurement, and finally, the description of a number of case histories. A feature of the book is the emphasis it places on the various stages of foundation design: preliminary, detailed and final, and the presentation of a number of relevant methods of design associated with each stage.
Author: R. Manoj Kannan
Author: R. Manoj Kannan
Author: 
Author: Braja M. Das
Author: Jacquelyn Denise Allmond
Author: Steven J. Greenfield
Author: Masaki Kitazume
Author: Manmohan Dass Goel
Author: Thomas Brian Algie
Author: United States. Army. Corps of Engineers
Author: Harry G. Poulos