This thesis is a contribution to the existing knowledge of the nature of the scour hole around bridge piers. The analysis is based on the fictitious, long contraction concept developed by Dr. Emmett M. Laursen. This concept and its equation has been used herein to determine the size of rip-rap particles which will reduce the local scour at bridge piers. Evaluation of the parameters involved in it is required for sizing the rocks in a prototype. Values such as approach velocity, water depth, average diameter of the rip-rap particles in the scour, and geometry of the pier are among the values to be known. Both a graphic and an analytical procedure are proposed as a means to find the size of particles to be used as protection. The discussion and conclusions derived from this investigation will be of great help to civil engineers working in the field of river engineering.

No description available.

Αντικείμενο της παρούσας διατριβής αποτελεί η ανάλυση της συμπεριφοράς αξονικά φορτιζόμενου πασσάλου, η οποία μπορεί να οδηγήσει σε απώλεια φέρουσας ικανότητας. Συγκεκριμένα εξετάζεται η στατική δυσκαμψία του πασσάλου για τις περιπτώσεις ομοιογενούς και ανομοιογενούς εδάφους. Για την επίλυση του προβλήματος αναπτύχθηκε απλή αναλυτική ενεργειακή μέθοδος, η οποία βασίζεται στη θεωρία Winkler και στη χρήση συνάρτησης σχήματος, η οποία περιγράφει αξιόπιστα τις μετατοπίσεις κατά μήκος του πασσάλου. Το έδαφος γύρω από τον πάσσαλο προσομοιώνεται με κατακόρυφα γραμμικά ή μη ελατήρια τύπου Winkler, τα οποία εφαρμόζονται στην παρειά του πασσάλου αλλά και στη βάση του. Με επιλογή κατάλληλης συνάρτησης σχήματος και καμπυλών «τ-w» και «Pb-wb» και μετά από επαναληπτική διαδικασία εφαρμογής της μεθόδου, επιτυγχάνεται με ικανοποιητική ακρίβεια η τιμή της δυσκαμψίας για κατακόρυφη μετακίνηση στην κεφαλή του πασσάλου. / The present thesis deals with the analysis of the axial static response of a single pile, which may lead to bearing capacity loss. Specifically, the static stiffness of the pile located both in homogeneous and in inhomogeneous soil, is studied. For the analysis a simple energy method is employed, based on Winkler theory and on use of a shape function which represents reliably the deflected shape of the pile. The soil around the pile is simulated with vertical linear or nonlinear Winkler springs, applied to the sidewall of the pile and its base. Realistic predictions can be achieved for the value of stiffness of axially loaded piles, after iterative application of the method, by using the appropriate shape functions, “ τ-w “ and “Pb-wb” curves.

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No description available.

As of September 2007, there were over 67,000 U.S. bridges in the National Bridge Inventory classified as having unknown foundations. The bridges spanning rivers are of critical importance due to the risks of potential scour. In fact, over half of all bridge collapses are due to scour. Not only are these failures costly, they can be deadly for the traveling public. On April 5, 1987, ten people were killed in New York when a pier collapsed on the Schoharie Creek Bridge causing two spans of the deck to fall into the creek. Several other fatal collapses have occurred since the Schoharie Creek Bridge failure. Detecting scour is only part of the assessment that must take place to determine risk of failure and knowing the foundation depth is a critical component of the assessment. While this issue is not new, current techniques are typically invasive or costly. This research explores the feasibility and effectiveness of induced polarization (IP) and electrical resistivity imaging (ERI), near surface geophysical methods, for determining the depth of unknown foundations. In this work, forward models are created to ascertain the effects of the bridge layout on data quality such as varying depths and the impact of adjacent foundations on the foundation in question. Next, an experimental study is conducted at a National Geotechnical Experimentation Site (NGES) to further identify key parameters for the testing design and setup in order to obtain optimal surveys of bridge foundations. The conclusions of the forward modeling and NGES investigations are used to plan the field surveys on four bridges with known foundations. The outcomes of the four bridges show that IP and ERI can be used in concert with one another to estimate the type and depth of bridge foundations. The results of the field surveys are used to create a probability of non-exceedance curve for future predictions of unknown bridge foundations using the methods described in this research.

The lack of methods for rigorous dynamic analysis of foundations and structures for vibrating machines has resulted in below optimum performance and in some cases reduction of life of machines, structures and foundations. The costs and complexities of these machines make it necessary to conduct proper geotechnical site investigations. and dynamic analyses to obtain the response of the soil, foundation and structure as a system to excitation. In order to highlight the use of dynamic analyses, the response of the foundations and structures were compared to the "rule of thumb" which is based on mass ratio. Furthermore sensitivity analyses were carried out comprising the following variables: • Shear modulus of soil, G • Poisson's ratio of soil,Y • Type of structure (ie raft, table top and multi-storey) • Stiffness of structure • Stiffness of foundation The fundamentals of structural dynamics have not been dealt with in this dissertation. The dynamic analyses were carried out using a finite element analysis program called Strand 7. The results were typical of a finite element analysis, giving stresses, strains, deflections, amplitudes, frequencies and velocities of vibration. The traditional "elastic halfspace model" is deficient as it does not account for soil comprising various layers. The theory has been based on an isolated circular footing. Most foundations are located in soils with layered mediums, are rectangular and in some cases are affected by the interaction of foundations in close proximity. Furthermore there is a need to account for the non-linear effects and properties of soil. It is therefore becoming more attractive to adopt mathematical models of soils using finite elements, where the visco-elastoplastic properties of soils can be realized and modeled. Furthermore the finite element method overcomes limitations such as layering and shapes or foot-prints of foundations. The "rule of thumb" or mass ratio method of design procedure is as follows:- • firstly the requirements of stresses and serviceability must be satisfied. This is usual in a statically loaded system. the ratio of the machine mass to that of the foundation together with the structure should be greater than 3 in the case of a revolving machine and 5 in the case of a reciprocating machine. • in order to obtain uniform settlement of the foundation the distance of the combined centre of gravity of the machine and foundation from the centre of area in contact with the soil is limited to 5% of the corresponding dimension of the foundation. It is evident that the mass ratio lacks accuracy in that there are several parameters that are required to describe the satisfactory performance of a system such as amplitude, frequency and velocity of vibration. The finite element method allows for calibration of the model to account for the real behaviour of the system. Calibration is generally conducted using sensitive transducers called accelerometers. The accelerometers produce power spectral density (PSD) graphs from which deflections and stresses can be back calculated. The deflections and stresses are compared with calculated deflections and stresses. Descriptions of the methods of analysis followed by presentation of results, discussions and interpretations have been included. To motivate the use of dynamic analyses case histories have been presented and discussed. Finally the dissertation concludes with findings of the study together with recommendations for the way forward in terms of research. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

This dissertation analyzes competition for foundation grants in the nonprofit sector. First, I examine how inter-organization competition and foundation activity in local grants markets affect organization behavior through institutional pressure on (1) firm fundraising expenses, (2) program expense ratios, and (3) revenue diversification. Second, I explore the impacts of nonprofit program expense ratios and fundraising expenses on foundation grantmaking. This analysis focuses on the relative "prices" of donations to competing nonprofit organizations, represented by these expense ratios, and the impact prices have on foundation grant decisions relative to the impact that nonprofit marketing has. Finally, I examine whether greater competition in grants markets increases the importance of program expense ratios and firm marketing behavior for grant selection. Overall, this dissertation contributes to our understanding of organization behavior and foundation influence in grant-seeking markets and competition's role in the distribution of charitable grants.

&Ccedil / ayirhan soil is a collapsible soil. Collapsible soils are generally unsaturated, low-density soils with high voids between grains where the binding agents are sensitive to saturation. When exposed to water, binding agents break, soften or dissolve such that the soil grains shear against each other and reorient in denser configurations. This reconfiguration causes a net decrease in the soil mass, resulting in large and often unexpected settlements, which can totally destroy roads, underground utilities, and structures and alter surface drainage. Uses of collapsible soils as a natural construction material in fills or embankments also may cause serious stability problems. In this study, an extensive research program was carried out to investigate some geotechnical properties such as compaction, triaxial strength, bearing ratio and permeability of collapsible soil, found in &Ccedil / ayirhan Thermal Power Plant area, by treating with Class C fly ash and desulphogypsum (thermal power plant by-products that are to be handled for environmental reasons) in various proportions. The study has revealed that 20% and 25% fly ash or 5% desulphogypsum treatments (by dry weight of the mixture) improve the strength and bearing characteristics of &Ccedil / ayirhan soil.

Footings are often founded on multi-layered soil profiles. Real soil profiles are often multi-layered with material constantly varying with depth, which affects the footing response significantly. Furthermore, the properties of the soil are known to vary with location. The spatial variability of soil can be described by random field theory and geostatistics. The research presented in this thesis focuses on quantifying the effect of soil variability on the bearing capacity of rough strip footings on single and two layered, purely-cohesive, spatially variable soil profiles. This has been achieved by using Monte Carlo analysis, where the rough strip footings are founded on simulated soil profiles are analysed using finite element limit analysis. The simulations of virtual soil profiles are carried out using Local Average Subdivision (LAS), a numerical model based on the random field theory. An extensive parametric study has been carried out and the results of the analyses are presented as normalized means and coefficients of variation of bearing capacity factor, and comparisons between different cases are presented. The results indicate that, in general, the mean of the bearing capacity reduces as soil variability increases and the worst case scenario occurs when the correlation length is in the range of 0.5 to 1.0 times the footing width. The problem of estimating the bearing capacity of shallow strip footings founded on multi-layered soil profiles is very complex, due to the incomplete knowledge of interactions and relationships between parameters. Much research has been carried out on single- and two-layered homogeneous soil profiles. At present, the inaccurate weighted average method is the only technique available for estimating the bearing capacity of footing on soils with three or more layers. In this research, artificial neural networks (ANNs) are used to develop meta-models for bearing capacity estimation. ANNs are numerical modelling techniques that imitate the human brain capability to learn from experience. This research is limited to shallow strip footing founded on soil mass consisting of ten layers, which are weightless, purely cohesive and cohesive-frictional. A large number of data has been obtained by using finite element limit analysis. These data are used to train and verify the ANN models. The shear strength (cohesion and friction angle), soil thickness, and footing width are used as model inputs, as they are influencing factors of bearing capacity of footings. The model outputs are the bearing capacities of the footings. The developed ANN-based models are then compared with the weighted average method. Hand-calculation design formulae for estimation of bearing capacity of footings on ten-layered soil profiles, based on the ANN models, are presented. It is shown that the ANN-based models have the ability to predict the bearing capacity of footings on ten-layered soil profiles with a high degree of accuracy, and outperform traditional methods. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1368281 / Thesis (Ph.D.) - University of Adelaide, School of Civil, Environmental and Mining Engineering, 2009