Academic literature on the topic 'MODELED PILE'

Defects of concrete piles can occur at any point during the construction of piles. Most common types of pile integrity issues are; presence of voids, inconsistency in concrete mix, entrapped groundwater or slurry, and geometric dislocation. These defects can be categorized based on the place in the construction sequence at which the defect occurs. This research introduces several numerical models of defected piles with various scenarios in order to identify, locate, and quantify the necking occurring in these piles. The finite element software (ADINA) is used to simulate the studied models. The soil domain is modeled as an axisymmetric space around the concrete pile. Five diameters of piles (40, 60, 80, 100 and 120 cm) are studied. Necking is modeled at three different locations along the pile namely; upper, middle, and bottom third. Four ratios between the necking diameter and pile diameter are also studied. The dynamic force used in this research is that simulating the pile integrity test (PIT) case, with 2.5 N impact load applied at the pile head, half wave of sinusoidal pattern, and 0.5 kilo hertz frequency. The time domain of the dynamic force analysis is equal to 0.0175 sec, and applied in 450 steps.

Available case histories on observations on full-scale piled rafts show that the settlement response to applied load can be modeled as that for an Equivalent Pier due to compression of the piles and the soil matrix plus that of an Equivalent Raft for compression of soil layers below the pile toe level. Interior piles engage the soil from the pile toe level upward in contrast to a single pile, which engages it from the ground downward. Piles and soil, combined as a pier, have strain compatibility, which determines the distribution of load between the piles, the contact stress, and the load-transfer movement of the piles. The responses between the interior and perimeter piles differ. Particularly so in non-subsiding and subsiding environment, because perimeter piles can be subjected to downdrag and drag forces, while neither downdrag nor drag force will affect the interior piles. In non-subsiding environment, it is advantageous to make perimeter piles shorter, while in subsiding environment perimeter piles best be longer. The load distribution across the raft is also governed by the degree of rigidity of the raft and by the difference in dishing at the pile toe level and in the dishing of the actual raft.

This paper describes model tests of different types of tapered piles in cohesionless soils. Chromium plated three steel piles, one straight and two taper-shaped piles of same length and pile tip diameters have been executed for pile loading test in a downward frictional mode. Two different types of model grounds have been prepared for the test. Relative densities of 80 % and 60 % have been modeled to penetrate piles in two different types of sands to observe the effectiveness of skin frictions of different types of piles. The response of tapered piles has shown that the skin friction has increased with increasing the tapering angle at normalized settlement ratio of 0.4. High density ground yields higher skin friction when the maximum tapered pile was penetrated. Slightly increased tapering angle of the pile affects remarkably on the skin friction with compared to conventional straight cylindrical pile even at small 0.1 settlement ratios.

Piles or columns have been used successfully in combination with geosynthetics to support embankments over soft soil. The inclusion of geosynthetic reinforcement over piles enhances load transfer from soil to piles, reduces total and differential settlements, and increases slope stability. It creates a more economical alternative than that without the geosynthetic. An existing geosynthetic-reinforced pile-supported embankment in Berlin was selected for numerical modeling and analysis. This embankment was constructed to support railways over deep deposits of peat and soft organic soils. Precast piles and caps were installed with a load transfer platform formed by three layers of geogrid and granular materials installed between the piles and the embankment fill. Instrumentation was installed to monitor the settlements of the embankment and the strains in the geogrid layers over time. A finite difference method, incorporated in the fast Lagrangian analysis of continua three-dimensional software, was used to model this embankment. In the numerical analysis, piles were modeled with pile elements, and caps were modeled as an elastic material. Geogrid elements built in the software were used to represent the geogrid reinforcement. Embankment fill, soft soil, firm soil, and platform fill material were modeled as linearly elastic perfectly plastic materials with Mohr–Coulomb failure criteria. The embankment was built by a number of lifts to simulate its construction. Numerical results and comparisons with field measurements on the vertical and lateral displacements, the tension along the reinforcement, and the axial forces and moments on piles are presented.

Negative skin friction developed on the pile surface causes many problems when piles are built in fully saturated clay. In this work, a study of NSF on a square cross-section pile corresponding to the circular pile circumference was developed. The pile was modeled as a concrete element, embedded and fully contacted with fully saturated soft clay. The clay layer is supported on a sand layer as a sub-base using ABAQUS software, and the NSF was developed on piles due to the consolidation of the clay over a 5-year period. A square pile has been found to provide lower NSF values than a round pile. Then, for the first investigation, both piles were loaded with lateral loads at the top to investigate the effect of the horizontal load on the NSF values, as there is no literature or study done on this point. The results emphasized that lateral loads reduce the NSF developed on piles. A parametric study was performed to investigate the parameters affecting the NSF values induced on piles, such as soil permeability, ballast, and lateral load values. It was concluded that square piles provide better NSF values than round piles for both single piles and pile groups. Doi: 10.28991/CEJ-2022-08-10-08 Full Text: PDF

The behavior of experimental pile groups is simulated by 3-D finite element modeling in this paper. The modeled results are compared to small-scale tests in a row of three closely spaced piles in the London clay. The tests aimed at investigating soil-pile-cap interaction and pile-group effect. It is shown that 3-D FE modeling can be regarded as an appropriate tool to predict settlements and load-transfer mechanisms in pile groups under working conditions, with a satisfactory match between simulated and measured results.

This paper is concerned with the free vibration analysis of Timoshenko piles partially embedded in elastic soil, semi-rigidly connected at the upper end, and subjected to an axial force. The pile is divided into three regions: the pile portion above the soil constitutes the first region, while the second and third regions are the pile portion that is embedded in two different layers of the soil type. The pile material is assumed to be linearly elastic and the axial force is constant along the pile length. The soil is idealized by the Winkler model and the semi-rigid connection of the pile is modeled by a rotational spring. The natural frequencies of the piles are calculated from the transfer matrix for different axial forces, rotational spring constants, subgrade reaction moduli and embedded lengths of the pile. The results indicate that the natural frequency of the pile decreases as the axial force increases. Further, the increase in the stiffness of the rotational spring at the upper end of the pile causes only a small increase in the natural frequency. Finally, both the pile length and the subgrade reaction of the soil influence significantly the natural frequency of the pile.

Combined with the respective advantages in S-R(Sway-Rocking) impedance concept and finite-element method, a simplified 3D structural dynamic FEM considering composite pile-group-soil effects is presented. The structural members including piles are modeled by spacial beam or shell elements, and raft-base is divided into thick-shell elements with its spring-dashpot boundary coefficient obtained by impedance backcalculated. The mass-spring elements for soil between piles are set to simulate vertical, horizontal pile-group effects by strata-equivalent approach. The soil beside composite body is separated into near-field and far-field parts. The former is modeled by nonlinear spring-dashpot elements based on Winkler’s hypothesis, while the latter is modeled by a series of linear mass-spring-dashpots. With the effects of boundary track forces and energy radiation, the presented model enables researchers to conduct the time-domain nonlinear analysis in a relatively simple manner which avoids sophisticated boundary method and solid-element mesh bringing with tremendous computational cost. The seismic effect on dynamic interaction of pile-soil-complicated structures would be efficiently annotated from two structural engineering and geotechnical engineering aspects and the numerical calculation effort would be drastically decreased too. The complete procedure is mainly performed using the parametric design language assembled in the Finite Element Code Ansys. With the dynamic analysis of foundation and superstructure for a pile-supported 15-storey building, the influence of the participant effect on structural dynamic response will be depicted by various dynamic parameters of pile-soil-raft foundation in detail. Not only do the results have an agreement with some conclusions drawn by the general interaction theory, but also certain of phenomena which would be disagree with that by general analysis is involved. Even with the finite-element meshes for 68 piles, the time-history analysis procedure for PGSS (Pile-Group-Soil-Superstructure) system and the qualitative evaluation with various SSI parameters can be also fulfilled efficiently and rapidly by presented means. These results may be of help to the designers to quickly assess the significance of interaction effect for the high-rise buildings resting on any type or layout of pile-group foundation.

This paper presents an application of a method that will be implemented in the embedded data collector (EDC) system in the near future, to estimate the capacity of driven piles with a combined solid and voided cross section. Data from accelerometers and strain gauges located in the solid sections at both the top and the bottom of a pile are used to independently estimate the pile’s skin friction and tip resistance. Wave propagation along the pile is modeled as a one-dimensional wave equation, with a nonuniform cross section and with nonlinear static skin friction and viscous-damping soil resistances acting along multiple segments of the pile. The static skin friction is extracted by least-squares fitting of computed particle velocities with measured data at both the top and the bottom of the pile. The pile tip is modeled as a nonlinear single degree of freedom with viscous damping. Static tip resistance (nonlinear stiffness–displacement relationship) is extracted by least-squares fitting of the predicted total force and energy with the measured tip data. The new EDC method was applied to four combined solid–voided cross section driven piles with capacities varying from 2800 to 6700 kN. The results of the data evaluated with the new EDC method are consistent with those from the static load tests to within 15%.

Piled-raft foundation is a combination of pile foundation and raft foundation. Bearing capacity of piled-raft foundation yielded from contribution of both pile capacity and raft capacity. Most of the time, design of pile foundation is assumed that all load is solely carried by pile and the capacity of raft is ignored. In this study, three-dimensional finite element analysis was applied to analyze the load percentage that can be carried by raft. A case study, which is located in Central Jakarta, Indonesia, was modeled to investigate this issue. This project was instrumented with two pressure cells where the data were used to verified the model and the load distribution. The analysis results showed good agreement with the measurement data, where the load carried by the raft is around 33-42%.

Piles are used in civil construction work from the prehistoric times. They are used for supporting structures having large height, for example chimneys, transmission towers, high potential electrical poles and many more. All the above stated structures faces very high tensile uplift force and other forces which may cause extraction of the structure from the soil, hence pile or group of piles are designed to counter these force and to stabilize the structure, moreover pile/group of piles become indispensable support member when the soil is unstable and exceptionally large loads are involved. Resistance to high tensile uplift is given by the friction between the surrounding soil and the pile along with pile weight. Such piles (which counter uplift) are termed as uplift piles, anchor piles or tension piles, their computed uplift resistance is equivalent to that of friction piles. Uplift resistance is been developed by the uplift piles, from the skin friction generated along with the length of embedment. Uplift piles are driven in such a way that an inflated area is there at the base which expands to bulb like structure. Pile weight is included in this procedure of uplift capacity excluding the point bearing. In this study, theoretical as well as practical evaluation has been done in order to determine the pile’s ultimate uplift capacity when the same were embedded in sand. Different parameters were taken into consideration the soil properties and pile parameters like diameter, length, surface characteristics. In order to work out the uplifting capacity or pull out strength of piles embedded in sand, various charts has been generated. Description of analysis results of modeled pile laid into soil is presented in the study. In order to know the influence of various parameters like size of pile (diameter), embedment depth, comparison tests were done. Pile uplift capacity or pull out strength is not only the function of (depends on) denseness but ` vi it varies with method of laying of pile into the soil i.e. method of installation, depth up to which pile is embedded into the soil, material and size of pile, roughness etc. It is already known that uplift capacity/pull out strength of pile is only summation of frictional resistance and pile weight, on the other hand frictional resistance reaches a constant value after attaining critical depth.

Descrizione dei vantaggi della tecnologia delle fondazioni da pozzo per le pile da ponte. Analisi dei carichi di un viadotto esistente a struttura mista e studio agli stati limite delle più svantaggiose condizioni di carico. Analisi sismica della pila. Progetto e verifica della pila, del plinto e del pozzo nelle diverse fasi di realizzazione e per le combinazioni di carico considerate. Verifiche del terreno, con riferimento ai criteri di dimensionamento del Prof. Jamiolkowski. Analisi tenso-deformativa del terreno con software Plaxis2D e Midas-GTS (3D). Confronti fra il metodo analitico adottato nelle verifiche ed i risultati numerici. Norme di riferimento: NTC2008, Istruzione N°I/SC/PS-OM/2298, Ordinanza 3274 come modificato dall'OPCM 3431

Experimente mit neuartigen Messverfahren lieferten Daten über die Struktur von transienten Flüssig-keits-Gas-Strömungen für die Entwicklung und Validierung von mikroskopischen, d.h. geometrieunabhängigen Konstitutivbeziehungen zur Beschreibung des Impulsaustauschs zwischen Flüssig-phase und Gasblasen sowie zur Quantifizierung der Häufigkeit von Blasenkoaleszenz und -zerfall. Hierzu wurde eine vertikale Testsektion der Zweiphasentestschleife MTLoop in Rossendorf genutzt, wobei erstmals Gittersensoren mit einer Auflösung von 2-3 mm bei einer Messfrequenz von bis zu 10 kHz angewandt wurden. Dabei wurde die Evolution von Gasgehalts-, Geschwindigkeits- und Bla-sengrößenverteilungen entlang des Strömungsweges und bei schnellen Übergangsprozessen aufge-nommen und so die für die Modellbildung erforderlichen Daten bereitgestellt. Für den Test der Mo-dellbeziehungen wurde ein vereinfachtes Verfahren zur Lösung der Strömungsgleichungen entlang des Strömungswegs erstellt. Es basiert auf der Betrachtung einer größeren Anzahl von Blasengrö-ßenklassen. Die erhaltenen numerische Lösungen haben erstmals gezeigt, dass der bei Erhöhung der Gasvolumenstromdichte stattfindende Übergang von einer Blasenströmung mit Randmaximum zu einem Profil mit Zentrumsmaximum und anschließend zu einer Pfropfenströmung ausgehend von einem einheitlichen Satz physikalisch begründeter und geometrieunabhängiger Konstitutivgleichun-gen modelliert werden kann. Die Modellbeziehungen haben sich in einem abgegrenzten Gebiet der Volumenstromdichten als generalisierungsfähig erwiesen und sind für den Einbau in CFD-Modelle geeignet. Weiterhin wurden Arbeiten zur Kondensation durchgeführt, die direkten Bezug zu den Kon-densationsmodellen haben, die in Thermohydraulik-Codes enthalten sind. Die Untersuchung liefert darüber hinaus experimentelle Daten für die Modellvalidierung hinsichtlich des Verhaltens und des Einflusses nichtkondensierbarer Gase. Hierfür wurden spezielle Sonden für die Bestimmung der Konzentration und für die Lokalisierung von Pfropfen nichtkondensierbarer Gase entwickelt und bei transienten Kondensationsversuchen in einem leicht geneigten Wärmeübertragerrohr eingesetzt.

Experimente mit neuartigen Messverfahren lieferten Daten über die Struktur von transienten Flüssig-keits-Gas-Strömungen für die Entwicklung und Validierung von mikroskopischen, d.h. geometrieunabhängigen Konstitutivbeziehungen zur Beschreibung des Impulsaustauschs zwischen Flüssig-phase und Gasblasen sowie zur Quantifizierung der Häufigkeit von Blasenkoaleszenz und -zerfall. Hierzu wurde eine vertikale Testsektion der Zweiphasentestschleife MTLoop in Rossendorf genutzt, wobei erstmals Gittersensoren mit einer Auflösung von 2-3 mm bei einer Messfrequenz von bis zu 10 kHz angewandt wurden. Dabei wurde die Evolution von Gasgehalts-, Geschwindigkeits- und Bla-sengrößenverteilungen entlang des Strömungsweges und bei schnellen Übergangsprozessen aufge-nommen und so die für die Modellbildung erforderlichen Daten bereitgestellt. Für den Test der Mo-dellbeziehungen wurde ein vereinfachtes Verfahren zur Lösung der Strömungsgleichungen entlang des Strömungswegs erstellt. Es basiert auf der Betrachtung einer größeren Anzahl von Blasengrö-ßenklassen. Die erhaltenen numerische Lösungen haben erstmals gezeigt, dass der bei Erhöhung der Gasvolumenstromdichte stattfindende Übergang von einer Blasenströmung mit Randmaximum zu einem Profil mit Zentrumsmaximum und anschließend zu einer Pfropfenströmung ausgehend von einem einheitlichen Satz physikalisch begründeter und geometrieunabhängiger Konstitutivgleichun-gen modelliert werden kann. Die Modellbeziehungen haben sich in einem abgegrenzten Gebiet der Volumenstromdichten als generalisierungsfähig erwiesen und sind für den Einbau in CFD-Modelle geeignet. Weiterhin wurden Arbeiten zur Kondensation durchgeführt, die direkten Bezug zu den Kon-densationsmodellen haben, die in Thermohydraulik-Codes enthalten sind. Die Untersuchung liefert darüber hinaus experimentelle Daten für die Modellvalidierung hinsichtlich des Verhaltens und des Einflusses nichtkondensierbarer Gase. Hierfür wurden spezielle Sonden für die Bestimmung der Konzentration und für die Lokalisierung von Pfropfen nichtkondensierbarer Gase entwickelt und bei transienten Kondensationsversuchen in einem leicht geneigten Wärmeübertragerrohr eingesetzt.

In questo lavoro di tesi viene presentato un modello per lo studio di fondazioni con pali inclinati. La formulazione analitica è sviluppata nel dominio delle frequenze, assumendo che i pali ed il terreno abbiano un comportamento lineare; in particolare si ipotizza che il terreno sia costituito da layer orizzontali viscoelastici, ed i pali da travi di Eulero-Bernoulli. Si ipotizza la compatibilità degli spostamenti dei pali e del terreno nell'ipotesi che non vi siano gaps durante il moto. L'interazione palo-terreno-palo e lo smorzamento per radiazione sono inclusi attraverso l'uso di funzioni elastodinamiche di Green. Le equazioni di equilibrio sono derivate in forma debole attraverso il principio di Lagrange D’Alembert, e la soluzione è stata ottenuta numericamente attraverso l'uso di una formulazione agli elementi finiti. La presenza della zattera rigida in testa ai pali è stata introdotta attraverso un vincolo cinematico. La formulazione è stata semplificata introducendo l'ipotesi di Baranov schematizzando il terreno come un mezzo costituito da layer orizzontali indipendenti tra loro e utilizzando espressioni disponibili in letteratura (funzioni di Green) per descrivere il comportamento dinamico di ogni layer. Il modello permette di valutare la risposta cinematica di una palificata costituita da un numero generico di pali, con geometria ed inclinazione anch'essi generici. In particolare il modello fornisce il moto di fondazione (foundation input motion) e le sollecitazioni nei pali, per il passaggio delle onde sismiche nel terreno; queste ultime possono essere calcolate attraverso una analisi di risposta locale monodimensionale o spaziale (2D e 3D) che tenga conto della reale stratigrafia del deposito. Inoltre la condensazione dei gradi di libertà nel vincolo rigido della zattera permette di ottenere direttamente le funzioni di impedenza dinamica del sitema terrenofondazione; queste possono essere utilizzate insieme al moto di fondazione per eseguire analisi di interazione terreno-struttura mediante un approccio per sottostrutture. Il comportamento non lineare del terreno può essere incluso attraverso un approccio lineare equivalente, calibrando rigidezza e smorzamento del terreno coerentemente con il livello di deformazione raggiunto durante il moto. La validazione del modello è stata eseguita attraverso analisi accurate, confrontando i risultati del modello, in termini di impedenze dinamiche, parametri di risposta cinematica e sollecitazioni nei pali, con quelli ottenuti da modellazione 3D agli elementi finiti o da modelli numerici più rigorosi disponibili in letteratura. Il modello si è rilevato capace di cogliere la risposta orizzontale, verticale, rotazionale e rototraslazionale di fondazioni con pali inclinati. Inoltre la risposta cinematica del sistema terreno-fondazione e le sollecitazioni cinematiche nei pali, dovute alle propagazione delle onde sismiche, sono colte con accurata precisione. In ultimo, al fine di dimostrare la versatilità del modello per affrontare analisi di interazione terreno struttura, è presentato un caso studio di una pila da ponte supportata da una fondazione su 4 pali inclinati.
In this thesis, a 3D analytical model for the dynamic analysis of inclined pile groups is presented. The analytical formulation is derived in the frequency domain assuming that both piles and soil behave linearly; in particular, soil is modelled as a viscoelastic horizontally layered half-space and piles as Euler-Bernoulli beams. Under the assumptions that no gap arises during the motion the compatibility condition between the pile and soil is assumed. The pile-soil-pile interaction and the radiation damping is taken into account by means of elastodynamic Green’s functions. The equilibrium equations are derived in weak from by means of the Lagrange D’Alembert principle and the solution is achieved numerically with a displacement based finite element approach modelling pile with beam finite elements. The presence of a rigid cap is accounted for by constraining the displacements of the pile heads. The formulation is simplified introducing the Baranov’s assumption, namely by schematizing the soil as infinite independent horizontal layers and using expressions available in the literature (Green’s functions) to describe the dynamics of each layer. The model allows evaluating the kinematic response of pile groups with generic number of piles, generic layout and piles inclination. In particular, the motion of the pile cap (foundation input motion) and the stress resultants in piles due to the passage of harmonic shear or seismic waves in the soil may be computed; in the latter case, the incoming free field may be derived from local one dimensional or spatial (2D or 3D) analysis depending on the complexity of the soil deposit. Furthermore, the condensation of the problem on the rigid cap dofs allows obtaining impedances of the pile group; these may be used, in conjunction with the foundation input motion, to perform consistent soilstructure interaction analyses according to the substructure approach. The nonlinear soil behaviour may be captured by considering linear equivalent approaches, calibrating stiffness and damping consistently with soil strain levels. The model validation is carried out performing accuracy analyses and comparing results, in terms of dynamic impedances, kinematic response parameters and pile stress resultants, with those furnished by 3D finite element models or available in the literature from more rigorous approaches. The model revealed able to capture the horizontal, vertical, rotational and coupled roto-translational response of pile foundations with inclined piles, obtained from refined and highly computational demanding 3D finite element models. Furthermore, the kinematic response of the soil-foundation system as well the kinematic stress resultants along the piles due to propagating (seismic) shear waves have been predicted with satisfactory accuracy. Finally, in order to demonstrate the model versatility in performing soil structure interaction analyses of structures, a case study constituted by a single bridge pier supported by a group of 4 inclined piles is presented.

The concept of Hydrogen Economy, coined in the second half of the twentieth century, has gained strength as a solution to the problems derived from the consumption of fossil fuels. The main idea of the Hydrogen Economy is the use of hydrogen as an energy vector. Fuel cells play a leading role in this economy, since today, fuel cells are the most attractive hydrogen final conversion technology. This technology, invented more than 150 years ago, is well established nowadays. However, there is still research to be done in the fuel cell field, in order to make them economically profitable in comparison to the competing technologies. One of the research lines that have attracted a great attention in recent years, is the development of diagnosis and control tools for fuel cells. This Thesis is framed in this research line. This work's main goal is to obtain a semiempirical model of an individual cell of a commercial 300W PEM fuel cell stack. The developed model is meant to be used in diagnosis and control systems. In order to fulfill this goal, a steady state model and a dynamic model were developed. On the one hand, the developed steady state model consists in a semiempirical steady state model coupled with an open circuit loss model, obtained from the open circuit loss experimental characterization. On the other hand, the proposed dynamic model consists in an electric equivalent circuit with a mechanistic meaning, coupled with an empirical model to represent the evolution of the equivalent circuit parameters with the operation current. Since the dynamic model was built using electrochemical impedance spectroscopy (EIS) spectra, two experimental EIS spectra validation methods were developed in this work. Moreover, the EIS measurement was optimized in order to minimize the experimental error related to EIS measurements. Both, the measurement parameters and the perturbation amplitude, were optimized in this work. Finally, a statistical study was performed in order to determine the effect of the operation conditions (operation temperature and humidity of the inlet gases) on each one of the parameters of the stationary and dynamic models.
El concepto de Economía del Hidrógeno, acuñado en la segunda mitad del siglo XX, ha ido cobrando fuerza como solución a los problemas derivados del consumo de combustibles fósiles. La idea central de la Economía del Hidrógeno es el empleo del hidrógeno como vector energético. Las pilas de combustible tienen un papel protagonista en dicha Economía, siendo la tecnología de conversión final de hidrógeno más atractiva en la actualidad. Esta tecnología, inventada hace más de 150 años, está bien establecida actualmente. Sin embargo, aún quedan líneas de investigación abiertas en el campo de las pilas de combustible, para conseguir que sean rentables frente a las tecnologías competidoras. Una de dichas líneas de investigación es la problemática de su diagnóstico y control. Y es precisamente en esta línea de investigación donde se enmarca la presente Tesis. El objetivo central es la elaboración de un modelo semiempírico de una monocelda individual de un stack comercial de tipo PEM de 300 W. La finalidad del modelo desarrollado es su empleo en sistemas de diagnóstico y control. Para conseguir dicho objetivo se elaboró tanto un modelo estacionario del sistema, como uno dinámico. Por una parte, el modelo estacionario corresponde con un modelo semiempírico estacionario acoplado con un modelo de pérdidas de circuito abierto, este último desarrollado a partir de la caracterización experimental de dichas pérdidas. Por otra parte, el modelo dinámico propuesto corresponde con un circuito eléctrico equivalente con sentido mecanístico, dotado de un modelo empírico para representar la evolución de los parámetros del circuito equivalente con la corriente de operación. Puesto que dicho modelo se construyó empleando la técnica de espectroscopia de impedancias electroquímicas, se decidió desarrollar métodos de validación de espectros de impedancias electroquímicas obtenidos experimentalmente; y se optimizó el método de medida de los espectros, tanto los parámetros de medida como la amplitud de la perturbación. Finalmente, se realizó un estudio estadístico para determinar el efecto de las condiciones de operación (temperatura de operación y humedad de los gases de entrada) sobre cada uno de los parámetros de los modelos estacionario y dinámico acoplados.
El concepte d'Economia de l'Hidrogen, encunyat en la segona mitat del segle XX, ha anat cobrant força com a solució als problemes derivats del consum de combustibles fòssils. La idea central de l'Economia de l'Hidrogen és la utilització de l'hidrogen com a vector energètic. Les piles de combustible tenen un paper protagonista en dita Economia, sent la tecnologia de conversió final d'hidrogen més atractiva en l'actualitat. Esta tecnologia, inventada fa més de 150 anys, està ben establida actualment. No obstant això, encara queden línies d'investigació obertes en el camp de les piles de combustible, per a aconseguir que sigan rendibles enfront de les tecnologies competidores. Una de dites línies d'investigació és la problemàtica del seu diagnòstic i control. I és precisament en esta línia d'investigació on s'emmarca la present Tesi. L'objectiu central és l'elaboració d'un model semiempíric d'una monocel·la individual d'un stack comercial de tipus PEM de 300 W. La finalitat d'aquest model és la seua utilització en sistemes de diagnòstic i control. Per a aconseguir dit objectiu es va elaborar tant un model estacionari del sistema, com un dinàmic. D'una banda, el model estacionari desenrotllat correspon amb un model semiempíric estacionari acoplat amb un model de pèrdues de circuit obert, desenrotllat a partir de la caracterització experimental de dites pèrdues. D'altra banda, el model dinàmic proposat correspon amb un circuit elèctric equivalent amb sentit mecanístic, dotat d'un model empíric per a representar l'evolució dels paràmetres del circuit equivalent amb el corrent d'operació. Ja que dit model es va construir emprant la tècnica d'espectroscòpia d'impedàncies electroquímiques, es va decidir desenrotllar mètodes de validació que permeten validar els espectres d'impedàncies electroquímiques obtinguts experimentalment; i es va optimitzar el mètode de mesura dels espectres, tant els paràmetres de mesura com l'amplitud de la pertorbació. Finalment, es va realitzar un estudi estadístic per a determinar l'efecte de les condicions d'operació (temperatura d'operació i humitat dels gasos d'entrada) sobre cada un dels paràmetres dels models estacionari i dinàmic acoplats.
Giner Sanz, JJ. (2017). Modelado semiempírico de una monocelda de una pila de combustible comercial de tipo PEM de 300 W [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90421
TESIS

Les piles a combustible a membrane echangeuse de protons (pemfc) sont depuis quelques annees a l'origine de nombreuses realisations de vehicules de demonstration. Pour eviter la multiplication des prototypes, la simulation est de plus en plus utilisee pour evaluer les performances de diverses solutions techniques envisageables. Un modele dynamique de pile a combustible a ete realise a l'aide du logiciel matlab/simulink. Il s'integre a un modele de groupe electrogene complet (pile + auxiliaires). La pile modelisee est concue et fabriquee par l'entreprise italienne nuvera fuel cells europe. Sa particularite est l'utilisation d'un poreux pour l'alimentation en gaz des electrodes au lieu des canaux utilises classiquement. Le refroidissement et l'humidification sont assures simultanement par injection d'eau liquide directement en entree de cellule electrochimique. Le modele traite les bilans de masse et d'energie mecanique, thermique et electrique dans les fluides et la structure en regime transitoire. Il permet une discretisation de la cellule elementaire le long de l'ecoulement des gaz. Dans chaque troncon le calcul permet de suivre au cours du temps l'evolution des concentrations, des temperatures, des fractions d'eau liquide, des densites de courant pour rendre ce modele le plus predictif possible, des lois physiques decrivant les phenomenes sont preferees a des relations purement mathematiques. Des essais ont ete effectues sur une pile de 5kw grace a un banc d'essais specifique. Ils ont permis de valider le modele de pile, par calage de chacun des modeles elementaires correspondant aux phenomenes modelises (hydraulique, thermique). Ces travaux ont montre les problemes causes par le concept de cette pile a humidification

Ziele Die Forsteinrichtung in Litauen war in den vergangenen Jahrzehnten vom Leitgedanken geprägt, die Optimierung der Bestandsdichte und die Maximierung der Produktivität in jeder Phase der Bestandsentwicklung als gleichrangige Ziele zu betrachten. Deshalb wurden große Anstrengungen in die Herleitung von Bestandswuchsmodellen für gleichaltrige Kiefern- oder Fichtenreinbestände gelegt. Bei der Anwendung dieser Modelle auf gemischte oder in der Umwandlung befindliche Wälder sind allerdings nur ungenaue Resultate zu erzielen. Um den Erfordernissen einer zeitgemäßen Forstwirtschaft gerecht zu werden, sind geeignete Instrumente zur Prognose von Wachstum und Ertrag strukturreicher Wälder vonnöten. Das Hauptziel dieser Arbeit bestand deshalb in der Neuparametrisierung des Einzelbaumwachstumssimulators BWINPro-S (entwickelt für sächsische Wuchsverhältnisse) für Kiefernwälder auf mineralischen Standorten in Litauen. Zur Zielerreichung dienten folgende Schritte: • Schaffung und Evaluierung einer Datengrundlage für die Modellierung. • Abschätzung der Effekte von Konkurrenz um Wuchsraum auf den Durchmesser-, Grundflächen- und Höhenzuwachs von Einzelbäumen. • Entwicklung eines Durchmesser-Zuwachsmodells sowie Neuparametrisierung der Grundflächen- und Höhenwachstumsmodelle. • Bestimmung der Einzelbaummortalität durch Konkurrenz um Wuchsraum. • Entwicklung eines ersten Ansatzes für einen Einzelbaumwachstumssimulator für Kiefer in Litauen. Hypothesen: 1. Die Standorteigenschaften sind der prägende Faktor für Wachstum und Ertrag von Waldbeständen. 2. Distanzabhängige Konkurrenzindizes zeigen höhere partielle Korrelationen zu Grundflächen- und Höhenzuwachs der Einzelbäume als distanzunabhängige Konkurrenzindizes. 3. Im Vergleich zum Ursprungsmodell BWINPro-S kann durch die Neuparametrisierung eine bessere Anpassung an die Wachstumswirklichkeit in Litauen erzielt werden (in Bezug auf Durchmesser-, Grundflächen- und Höhenzuwachs sowie Mortalitätsschätzung). 4. Ein Einzelbaumwachstumssimulator unterstützt die Entscheidungsträger und Forstplaner in Litauen bei der Optimierung der Waldbewirtschaftung ganz wesentlich. Material und Methoden Der Forschungsansatz gliederte sich wie folgt: 1) Vervollständigung der Datengrundlage. 2) Analyse der Konkurrenzverhältnisse. 3) Modellierung des Einzelbaumwachstums. 4) Validierung der neuentwickelten bzw. neuparametrisierten Modelle. Die Datengrundlage bestand aus Messwerten von 18 Dauerversuchsflächen (PEP) und zwei Validierungsflächen (VP), von denen letztere nur zur Modellüberprüfung herangezogen wurden. Auf allen Flächen stocken vorwiegend aus Naturverjüngung hervorgegangene, einschichtige Kiefernbestände auf kieferntypischen Standorteinheiten. Die Vervollständigung der Datengrundlage erforderte (a) die Erzeugung der Ausgangsdatenbasis, (b) Berechnung fehlender Werte, und (c) Evaluierung der vervollständigten Datengrundlage. Dabei lag das Hauptaugenmerk auf: • Stichprobenumfang und Schätzung der Populationsmittelwerte. • Schätzung des potentiellen Standort-Leistungsvermögens. • Analyse der Beziehung zwischen dem potentiellen Standort-Leistungsvermögen und dem tatsächlichen Waldertrag. Zur Abschätzung der Effekte von Konkurrenz um Wuchsraum auf den Durchmesser-, Grundflächen- und Höhenzuwachs von Einzelbäumen diente folgendes Vorgehen: Zur Konkurrentenidentifikation wurde ein inverser Lichtkegel mit einem Öffnungswinkel von 60 und 80 Grad konstruiert, dessen nach unten gerichtete Spitze (a) an der Kronenansatzhöhe, (b) an der Höhe der größten Kronenbreite, und (c) am Stammfuß des Zentralbaumes ansetzte. Zur Quantifizierung des Konkurrenzdrucks wurden mit Hilfe der partiellen Korrelationsanalyse 20 Konkurrenzindizes geprüft, von denen letztendlich sechs distanzabhängige und zwei distanzunabhängige Indizes in der weiteren Auswertung Berücksichtigung fanden. Die Modellierung des Einzelbaumwachstums erfolgte in drei Schritten: (a) Entwicklung eines originären Einzelbaum-Durchmesserzuwachsmodells, (b) Neuparametrisierung des Grundflächen- und Höhenzuwachsmodells, und (c) Entwicklung und Neuparametrisierung von Mortalitätsmodellen. Zur Bewertung einfacher linearer Regressionsmodelle wurden die statistische Signifikanz und das Bestimmtheitsmaß herangezogen. Bei multiplen linearen Regressionsmodellen wurde die Signifikanz jeder unabhängigen Variablen gesondert geprüft (hinsichtlich Normalverteilung, Varianzhomogenität der Residuen und Multikollinearität). Zur Bewertung einfacher nichtlinearer Regressionsmodelle diente in erster Linie das korrigierte Bestimmtheitsmaß, bei multiplen nichtlinearen Regressionsmodellen fanden darüber hinaus Q-Q-Plots (Quantil-Quantil-Diagramme) und die Prüfung auf Varianzhomogenität der Residuen Verwendung. Die Evaluierung multipler logistischer Regressionsmodelle erfolgte mit Pearsons Chi-Quadrat-Test, die Signifikanz jedes Modellparameters wurde mit der Wald-Statistik geprüft. Die Anpassungsgüte wurde mit Hilfe der Log-Likelihood-Funktion, Cox & Snell- bzw. Nagelkerke-Bestimmtheitsmaßen, Klassifikationstabellen und ROC-Kurven bewertet. Zur Prüfung der neuparametrisierten Grundflächen- und Höhenzuwachsmodelle wurden die modellierten Werte gegen die Messwerte und darüber hinaus die Residuen gegen die Modellwerte geplottet. Außerdem wurden zur Beurteilung die Verzerrung, die Präzision und die Treffgenauigkeit (sowohl als Absolut- als auch als Relativwerte) herangezogen. Ergebnisse und Schlussfolgerungen Die Wachstumsmodelle des Simulators BWINPro-S konnten erfolgreich an die Bedingungen in Litauen angepasst werden. Daraus lassen sich folgende Schlussfolgerungen ableiten: 1. Der stehende Vorrat und die Gesamtwuchsleistung von Kiefernbeständen werden nur z. T. vom standörtlichen Leistungsvermögen determiniert. Die Standorteigenschaften bestimmen das theoretische Leistungsvermögen von Beständen. Ob dieses Potential auch tatsächlich ausgeschöpft werden kann, hängt weitgehend von der Bewirtschaftungsart ab, die geprägt ist durch Beginn, Häufigkeit und Stärke der Durchforstungseingriffe. 2. In Kiefernreinbeständen eignen sich distanzabhängige Konkurrenzindizes besser zur Prognose des mittleren Grundflächenzuwachses als distanzunabhängige Indizes. Zur Beschreibung des Einzelbaum-Durchmesserzuwachses hat sich der Index nach BIGING & DOBBERTIN (1992, in dieser Arbeit als Index CI4 bezeichnet) in Kombination mit der Konkurrentenidentifikationsmethode „Suchkegelansatz in Kronenansatzhöhe, Öffnungswinkel 80 Grad“ als der bestgeeignetste Ansatz erweisen. 3. Der distanzunabhängige Konkurrenzindex nach HEGYI (1974) erreichte die höchsten partiellen Korrelationskoeffizienten mit den mittleren Einzelbaum-Höhenzuwächsen und ergab etwas bessere Resultate bei der Wachstumsprognose als distanzabhängige Indizes. Allerdings waren die Beziehungen zwischen den Konkurrenzindizes und den Einzelbaum-Höhenzuwächsen nur schwach ausgeprägt. 4. Konkurrenz wirkt sich dämpfend auf den Einzelbaum-Durchmesserzuwachs aus, bei zunehmender Konkurrenz sinkt der Zuwachs kontinuierlich ab. Im Gegensatz dazu beschleunigt leichte Konkurrenz das Einzelbaum-Höhenwachstum, bei starker Konkurrenz jedoch wird auch der Höhenzuwachs negativ beeinflusst. 5. Das im Rahmen dieser Arbeit hergeleitete nichtlineare Durchmesserzuwachsmodell ist zur Prognose des Kiefernwachstums bestens geeignet, das Bestimmtheitsmaß beträgt 0,483, die Residuen waren normalverteilt. 6. Die Neuparametrisierung des Grundflächen- und Höhenzuwachsmodells verbesserte die Anpassung an die Wuchsbedingungen in Litauen bedeutend. Eine erste Validierung, durchgeführt für eine Wachstumsprognose über einen 30-jährigen Zeitraum, ergab zufriedenstellende Ergebnisse. 7. Die zwei im Rahmen dieser Arbeit hergeleiteten Mortalitätsschätzer sind zur Vorhersage der natürlichen Absterbeprozesse in den Kiefernbeständen gut geeignet. Beide Ansätze klassifizierten lebende und tote Bäume mit einer Treffgenauigkeit von über 83%, während der in BWINPro-S enthaltene Schätzer nur 77% der Bäume korrekt zuordnete. 8. Der für litauische Verhältnisse neuparametrisierte Wachstumssimulator BWINPro-S ist ein wichtiges Instrument zur Entscheidungsunterstützung für Forstplaner in Litauen
Objectives In Lithuania, during the most recent decades, the leading theory in forest management and planning combined optimization of forest stand density and maximal productivity at every time point of stand development. Thus, great effort was spent in creating stand level models that are highly effective in managing even-aged monocultures of pine or spruce forests. But these models produce significant errors in mixed or converted forests. In order to meet the requirements of contemporary forestry, appropriate forest management tools are required that would be capable to predict the growth and yield of more structured forests. Thus, the overall objective for this study was to re-parameterise the single tree level simulator BWINPro-S (developed for forests in Saxony/Germany) for Lithuanian pine forests that grow on mineral sites. To reach this goal, the following tasks were set: • To create, and to evaluate, a database for modelling. • To estimate the impact of competition for growing space on diameter, basal area and height growth of trees. • To develop a tree diameter model, and re-parameterise basal area and height growth models. • To assess natural tree mortality induced by competition between trees for growing space. • To develop the first approach of STLS for pine in Lithuania. Hypotheses 1. Site quality is the most important factor that affects forest growth and yield. 2. Distance dependent Competition Indices had higher partial correlation with tree basal area and height increment than distance independent Competition Indices. 3. The re-parameterised model based on Lithuanian data fits better under Lithuanian conditions (regarding diameter, basal area, height increment and mortality) than the original model BWINPro-S. 4. A single tree level simulator provides valuable support for decision makers and forest managers to improve forest management in Lithuania. Materials and methods To reach the main goals of this study, the research was structured to four sections: 1) Database completion, 2) Analysis of competition, 3) Modelling tree growth, 4) Validation of developed models. The database consisted of analytical data from 18 permanent experimental plots (PEPs) and 2 Validation Plots (VP) that were used only for the validation of the models. All plots (PEPs and VP) represent mainly naturally regenerated, single layer pine stands that grow on very typical pine sites. Database completion involved (a) establishment of the initial database, (b) modelling of missing data values and (c) evaluation of the complete database, which focused on: • Sample size and estimation of the population’s mean • Estimation of potential site productivity • Estimation of relationship between potential site productivity and forest yield In order to estimate the impact of competition for growing space on diameter, basal area and height growth of trees the following methods were used. To select the competitors, this study focuses on three separate positions for setting the inverse cone: a) at the height of the crown base, b) at the height of widest crown width, and c) at the stem base. The opening angle of the search cone was either 60 or 80 degrees. To estimate the competition, the study by partial correlation analysis evaluated a total of 20 competition indices, of which six distance dependent and two distance independent CIs were applied in the research programme. Modelling of tree growth was divided into three parts: a) development of an original tree diameter increment model, b) re-parameterisation of basal area and height increment models, and c) development of new natural mortality models and re-parameterisation of natural mortality models. Simple linear regression models were evaluated by estimating each model’s statistical significance and coefficient of determination. Statistical analysis of multiple linear regression models was enlarged by conducting further tests: statistical significance was checked for each independent variable: regression assumptions (concerning normal distribution and homogeneity of variance of the models’s residuals, and multicollinearity of the independent variables) were checked. Simple nonlinear regression models were evaluated mainly by adjusted coefficient of determination. For multiple nonlinear regression models, regression assumptions were also checked by producing normal Q-Q plots and by checking homogeneity of variance of model’s residuals. Multiple logistic regression models were evaluated by estimating each model’s statistical significance with Pearson’s chi square statistics and the statistical significance of each model’s parameters with Wald statistics. Goodness of fit was estimated by using log likelihood function values, Cox-Snell and Nagelkerkle’s coefficients of determination, classification tables and ROC curves. The re-parameterised basal area and height increment models were validated by plotting each model’s predicted values against observed values. Also each model’s residuals were plotted against predicted values. Bias, relative bias, precision, relative precision, accuracy and relative accuracy when comparing predicted and observed values were estimated as well. Results and Conclusions The growth models used in the BWINPro-S simulator were successfully re-parameterised for Lithuanian growth conditions. Thus the study may state these conclusions: 1. The accumulated standing volumes and overall productivity of pine stands only partially depends on the productivity potential of sites. Site quality defines the growth potential that could be reached in a stand. The realization of growth potential largely depends on the growing regime in the stand that is defined by the beginning, frequency and intensity of thinning. 2. In pure pine stands, distance dependent competition indices show greater capabilities to predict mean annual basal area increment than distance independent indices. Competition index (coded as CI4 in this study) proposed by BIGING & DOBBERTIN (1992) combined with the selection method height to crown base with opening angle of 80 degrees is recommended as the most efficient for describing the individual diameter growth of trees. 3. HEGYI\\\'S (1974) distance independent competition index scored the highest partial correlation coefficients and produced slightly better results than distance dependent competition indices in predicting mean annual height increment for individual trees. Yet, the generally poor performance of competition indices to predict height increment of individual pine trees was also recorded. 4. Competition has a purely negative impact on tree diameter growth. Increasing competition leads to steady decreases in diameter increment. Nevertheless, although a small amount of competition does stimulate tree height growth, stronger competition has a lasting negative impact on tree height growth. 5. The nonlinear diameter increment model, developed by this study, has high capabilities to predict growth of pine trees. The model’s coefficient of determination value was equal to 0.483. The distribution of the model’s residuals fulfilled the requirements of regression assumptions. 6. The re-parameterisation of the BWINPro-S basal area and height increment models for use in Lithuanian permanent experimental plots, increased their performance. During the first validation procedure, based on 30 years growth simulation, the re-parameterised models produced reliable results. 7. Two individual mortality models, developed by this study, showed very high capabilities to predict the natural mortality of pine trees. The distance dependent natural mortality model scored slightly better results. Both models managed to correctly classify dead and living trees, slightly more than 83% of the time. The re-parameterisation of the BWINPro-S natural mortality model increased its ability to predict the natural mortality of pine trees in Lithuania. Correctly classifying growing and dead trees increased by 6%, from 77 to 83%. 8. BWINPro-S simulator with re-parameterised growth models for Lithuanian conditions is a valuable support tool for decision makers and forest managers in Lithuania
Darbo tikslai Lietuvoje ilgą laiką ūkininkavimas miškuose buvo grindžiamas medynų tankumo optimizavimu ir maksimalaus medynų produktyvumo siekimu visose medynų vystymosi stadijose. Mokslininkai dėjo daug pastangų kurdami medyno lygmens našumo modelius. Šie modeliai buvo patikimi ūkininkaujant vienaamžiuose medynuose. Tačiau jie yra sunkiai pritaikomi mišriuose medynuose. Siekiant patenkinti šiuolaikinio miškininkavimo poreikius, kai vis didesnis dėmesys skiriamas mišrių medynų su keliais ardais auginimui, reikalingi nauji modeliai, kurie sėkmingai prognozuotų mišrių medynų augimą, jų našumą bei reakcijas į įvairias ūkines priemones. Todėl pagrindinis šio darbo tikslas yra parametrizuoti iš naujo BWINPro-S medžio lygio stimuliatorių sukurtą Vokietijos rytinėje žemėje Saksonijoje taip pritaikant jį Lietuvos sąlygoms. Šiam tikslui pasiekti, buvo suformuluoti sekantys uždaviniai: • Paruošti ir įvertinti duomenų bazę reikalingą modeliavimui. • Įvertinti medžių tarpusavio konkurencijos įtaką medžių skersmens, skerspločių sumos ir aukščio prieaugiui. • Sukurti naują medžio skersmens prieaugio modelį ir parametrizuoti iš naujo skerspločių sumos bei aukščio modelius. • Įvertinti pušynų savaiminio retinimosi dėsningumus atsižvelgiant į medžių tarpusavio konkurenciją dėl augimo erdvės. Tikrintinos hipotezės: 1. Medyno augavietė yra svarbiausias veiksnys, lemiantis medynų našumą ir produktyvumą. 2. Konkurencijos indeksai, įvertinantys atstumą tarp medžių, turi didesnes dalinės koreliacijos reikšmes su medžių skerspločių sumos, skersmens ir aukščio prieaugiais lyginant su konkurencijos indeksais, neįvertinančiais atstumo tarp medžių. 3. Parametrizuoti naujai, panaudojant Lietuvoje augančių pušynų duomenis, modeliai geriau tinka Lietuvos sąlygoms (pagal skersmens, skerspločių sumos ir aukščio prieaugį bei savaiminį retinimąsi) lyginant su modeliais, sukurtais Vokietijos sąlygoms. 4. Medžio lygmens augimo simuliatorius yra naudinga priemonė miškų valdytojams siekiant pagerinti ūkininkavimo kokybę Lietuvoje. Darbo metodai Šis darbas buvo suskirstytas į keturias pagrindines dalis: 1) duomenų bazės suformavimas, 2) konkurencijos indeksų analizė, 3) medžių augimo modeliavimas, 4) augimo modelių patikrinimas. Duomenų bazę sudarė 20 pastovių tyrimo barelių, iš kurių 18 buvo skirti modelių kūrimui ir 2 modelių patikrinimui. Tyrimo bareliai buvo įsteigti natūraliai atsikūrusiuose vienaardžiuose pušynuose, augančiuose tipingose pušiai augavietėse. Duomenų bazės įvertinimas buvo atliekamas tokiais etapais: (a) pirminės duomenų bazės suformavimas, (b) trūkstamų matavimų modeliavimas ir (c) duomenų bazės įvertinimas yra grindžiamas: • Imties dydžiu ir populiacijos vidurkio nustatymo tikslumu. • Potencialaus medynų našumo įvertinimu. • Ryšių tarp potencialaus medynų našumo ir medynų našumo bei produktyvumo įvertinimu. Vertinant konkurencijos įtaką medžių skersmens, skerspločių sumos ir aukščio prieaugiui, buvo naudoti konkurentų parinkimo ir konkurencijos įvertinimo metodai. Konkuruojantys medžiai buvo atrenkami pagal apversto kūgio viršūnę, sutapatintą su tiriamojo medžio a) lajos pradžia, b) plačiausia lajos vieta, ir c) medžio šaknies kakleliu. Kūgio kampas buvo keičiamas nuo 60 iki 80 laipsnių. Iš viso buvo tiriama dvidešimt konkurencijos indeksų (du konkurencijos indeksai, nepriklausantys nuo atstumo tarp medžių ir aštuoniolika konkurencijos indeksų, priklausančių nuo atstumo tarp medžių). Konkurencijos indeksai vertinti taikant dalinės koreliacijos metodus. Medžių augimo modeliavimas buvo atliekamas trim etapais: a) originalaus medžių skersmens prieaugio modelio sukūrimas, b) medžių skerspločių sumos ir medžių aukščio prieaugio modelių parametrizavimas naujai, c) sukūrimas originalių ir parametrizavimas naujai jau esamų natūralaus retinimosi modelių. Paprastieji tiesinės regresijos modeliai buvo vertinami naudojant jų statistinį reikšmingumą ir skaičiuojant determinacijos koeficientą. Daugialypių tiesinės regresijos modelių statistinė analizė buvo išplėsta papildomais testais: statistinis reikšmingumas tiriamas kiekvienam nepriklausomam kintamajam, taip pat vertinama ar modelis tenkina pagrindines regresijos sąlygas (nepriklausomi kintamieji nėra tarpusavyje susieti, modelio liekanos turi normalųjį skirstinį, yra tolygiai išsidėstę). Paprastieji netiesinės regresijos modeliai buvo vertinami skaičiuojant koreguotąjį determinacijos koeficientą. Atliekant daugialypių netiesinės regresijos modelių analizę taip pat buvo tikrinama ar tenkinamos regresijos sąlygos. Logistiniai savaiminio retinimosi modeliai buvo vertinami naudojant šiuos statistinius parametrus: modelio X2 suderinamumo kriterijų, Voldo kriterijų, didžiausio tikėtinumo funkcijos vertę, Kokso-Snelo ir Nagelkerkės pseudodeterminacijos koeficientus, klasifikavimo lenteles ir klasifikatoriaus jautrumo ir specifiškumo (ROC) kreives. Parametrizuoti naujai medžių skerspločių sumos ir medžių aukščio prieaugių modeliai buvo tikrinami lyginant modeliuotas medžių skersmens ir aukščio reikšmes su realiai išmatuotomis reikšmėmis analizuojamo periodo pabaigoje. Taip pat buvo tiriamas modelių liekanų išsidėstymas modeliuojamų verčių atžvilgiu. Galiausiai, poslinkio, santykinio poslinkio, tikslumo, santykinio tikslumo, tikslumo be poslinkio ir santykinio tikslumo be poslinkio buvo naudojami vertinant modelių prognozes. Rezultatai ir išvados Augimo modeliai, naudojami BWINPro-S medžio lygio simuliatoriuje, buvo sėkmingai parametrizuoti naujai ir pritaikyti Lietuvos sąlygoms. Remiantis šio darbo rezultatais, buvo gautos sekančios išvados: 1. Sukauptas tūris ir bendras medynų našumas pušynuose tik dalinai priklauso nuo potencialaus augaviečių derlingumo. Augavietės sąlygos lemia tik potencialų medynų našumą kuris gali būti pasiektas medyne. Ar potencialus augavietės našumas bus realizuotas priklauso nuo medžių auginimo rėžimo, kuris apibūdinamas ugdomųjų kirtimų pradžia, kartojimų dažnumu ir jų intensyvumu. 2. Grynuose pušynuose, konkurencijos indeksai, įvertinantys atstumą tarp medžių turi didesnes galimybes prognozuoti skerspločių sumos prieaugį negu konkurencijos indeksai, neįvertinantys atstumo tarp medžių. Konkurencijos indeksas CI4, pasiūlytas BIGING & DOBBERTIN (1992), grindžiamas konkurentų parinkimu pagal apverstą 80 laipsnių kūgį, kurio viršūnė yra sutapatinama su medžių lajos pradžia yra rekomenduojamas kaip pats efektyviausias modeliuojant medžių skersmens prieaugį. 3. HEGYI (1974) konkurencijos indeksas, neįvertinantis atstumo tarp medžių tiriant konkurencijos indeksų įtaką medžių aukščio prieaugiui, parodė kiek geresnius dalinės koreliacijos rezultatus negu kad konkurencijos indeksai, įvertinantys atstumą tarp medžių. Tyrimų rezultatai parodė gana silpną konkurencijos indeksų galimybę prognozuoti medžių aukščio prieaugį. 4. Konkurencija turi išskirtinai neigiamą įtaką medžių skersmens prieaugiui. Didėjanti konkurencija lemia mažėjantį skersmens prieaugį. Nedidelė konkurencija padidina medžių aukščio prieaugį. Tačiau stipresnė konkurencija taip pat turi neigiamą įtaką medžių aukščio prieaugiui. 5. Originalus skersmens prieaugio modelis turi geras galimybes prognozuoti pušies medžių augimą. Šio modelio determinacijos koeficientas buvo lygus 0.483. Modelio liekanos turėjo normalųjį skirstinį ir buvo tolygiai pasiskirsčiusios modeliuojamų verčių atžvilgiu. 6. Parametrizuoti naujai BWINPro-S medžių skerspločių sumos ir medžių aukščio prieaugio modeliai, panaudojant Lietuvos pušynų pastovių tyrimo barelių duomenis, padidino jų prognozavimo galimybes. Pirmieji modelių tikrinimo rezultatai pagrįsti trisdešimties metų augimo prognozėmis, parodė, kad šie modeliai yra patikimi. 7. Du originaliai sukurti pušynų savaiminio retinimosi modeliai pasižymi geromis galimybėmis prognozuoti pušynų savaiminį išsiretinimą. Savaiminio retinimosi modelis, atsižvelgiantis į atstumą tarp medžių pasižymi geresnėmis galimybėmis prognozuoti pušynų savaiminį retinimąsi negu savaiminio retinimosi modelis, neatsižvelgiantis į atstumą tarp medžių. Abu modeliai teisingai klasifikavo daugiau negu 83% augančių ir savaime išsiretinančių medžių. BWINPro-S savaiminio retinimosi modelio parametrizavimas naujai padidino jo teisingai prognozuojamų augančių ir savaime išsiretinančių medžių dalį šešiais procentais, nuo 77 iki 83%. 8. Medžio lygio augimo simuliatorius BWINPro-S su parametrizuotais naujai augimo modeliais yra naudingas įrankis Lietuvos miškų augintojams

Tesis para optar al grado de Magíster en Ciencias de la Ingeniería, Mención Matemáticas Aplicadas
Memoria para optar al título de Ingeniero Civil Matemático
En este trabajo se presenta y estudia un modelo para el campo de temperaturas en la cara superior de una pila de lixiviación en presencia de evaporación e irrigada de forma puntual.El modelo consiste en un sistema de ecuaciones en derivadas parciales deducido del balance de los flujos de calor y masa en la cara superior de la pila. En estas ecuaciones las incógnitas son el flujo de masa en la superficie de la cara superior de la pila y la temperatura de la pila.Se muestran distintos resultados acerca de la existencia de soluciones para estas ecuaciones evaluando tres casos: Modelo radial: La cara superior es un circulo. Modelo geometría general sin evaporación: La cara superior es una superficie plana con borde suave y evaporación nula. Modelo geometría general con evaporación: La cara superior es una superficie plana con borde suave, tomando en cuenta evaporación no nula. En cada uno de los modelos se estudian las condiciones bajo las cuales los sistemas de ecuaciones en derivadas parciales tienen solución y además que propiedades cumplen estas soluciones. En el modelo radial se demuestra la existencia y unicidad del campo bajo ciertas condi-ciones. También obtiene la existencia y unicidad de soluciones en el modelo con geometría general sin evaporación asumiendo que el riego no es puntual, en caso contrario solo se puede asegurar la existencia. En el modelo con geometría general y evaporación no nula, solo se logra demostrar la existencia de soluciones en un sentido débil. En todos los modelos se obtienen cotas que permiten entender el comportamiento del campo de temperaturas en función de las variables del problema.
CMM - Conicyt PIA AFB170001

The monograph presents the results of experimental and theoretical studies conducted using models of driven piles and tape dies. The influence of the cross-section size, length, shape of the trunk and the lower end of the piles on their submergability, energy intensity of driving and load-bearing capacity was evaluated. The design and technological features of new types of piles are considered. A method for determining the load-bearing capacity of a pile model based on the results of dynamic tests has been developed. Similarity conditions and formulas are presented that provide modeling of the pile driving process in the laboratory. The influence of the shape of the tape dies on their submersibility, energy consumption of the driving and the bearing capacity of the foundations arranged in the vyshtampovannyh pits was evaluated. The method of determining the load-bearing capacity of a belt Foundation model based on the results of pit vyshtampovyvaniya is described. Recommendations on the choice of optimal parameters of piles and foundations, arranged in vystupovani pits. Recommended for researchers, specialists of design and construction organizations, doctoral students, postgraduates, undergraduates and students of construction and water management specialties.

AbstractAt present, based on the transfer coefficient method, most of the anti-slide pile design thrusts are calculated by the overload method and the strength reserve method respectively. Many algorithms only consider the remaining sliding force behind the pile and the safety factor that meets the requirements of the design conditions. Generally, the safety factor is the safety factor of the sliding slope behind the pile after the anti slide pile is reinforced. For the entire landslide, there are two safety factors before and after the pile, which is not the design safety factor target value, and there is a big difference between the safety factor and the treatment goal required by the specification. Through the study of the pile-soil interaction of anti-slide piles, it is believed that in addition to the active residual sliding force transmitted by the blocks behind the pile, the anti-slide piles are simultaneously subjected to the passive residual anti-sliding force transmitted upwards by the blocks in front of the pile. The stress analysis shows that: Firstly, according to the different active and passive properties of anti-sliding force transmission and sliding force transmission, the mechanical model of anti-sliding force transmission is studied, and the calculation formula of anti-sliding force transmission coefficient is derived; Secondly, It is believed that the anti-slide pile provides horizontal thrust to the landslide, and two components of the sliding surface direction and the vertical sliding surface direction are generated. The balance equation is established and the overload method and the strength reserve method of anti-slide pile thrust calculation formula are derived; Thirdly, according to the principle of setting piles in the anti-slip section, the optimal location of anti-slide piles are proposed; Fourthly, after verification of cases, the safety factors before and after the piles calculated by the overload method are basically equal, and consistent with the design safety factors. Calculation result shows that the strength reserve method to calculate the safety factor before the pile is accurate and reliable, and the result of the safety factor behind the pile is relatively small.

AbstractModel test is a common method to study the bearing peculiarity of pile foundation. The influence of overlying soil thickness and overburden pressure on the bearing capacity of soft rock-socketed pile should be considered in the physical model test of mini piles in soft rock. In this paper, the influence of coverage on the bearing characteristics of rock-socketed sections is studied by finite element analysis, and the modelling method of equivalent overburden pressure is proposed. This method can be used to study the carrying peculiarity of soft rock-socketed pile and reveal the failure mechanism of pile tip. The development of pile model test technology considering overburden pressure promotes more scientific design methods for pile foundation.

AbstractAlthough the construction of concrete piles has a relevant environmental footprint, they are commonly used to reduce settlements of embankments on soft soil strata. A more sustainable choice to further reduce settlements (and, consequently, the number of piles) is to place geosynthetics below the embankment. However, existing design methods cannot calculate settlements at the embankment top and cannot be used to optimise the number of piles in a displacement-based design. In this note, an innovative model for assessing settlements at the top of Geosynthetic-Reinforced and Pile-Supported embankments induced by the embankment construction process is presented and validated against finite difference numerical analyses. The model is used to optimise the design of both piles and geosynthetic, and applied to a practical example, where the mass of CO2 saved by designing geosynthetics to reduce the pile number. Graphical Abstract

AbstractThe uncertainty of pile and soil and slope effect are two of the major factors affecting the horizontal bearing capacity of piles of transmission tower in sloping ground. In order to analyze the influence of the two factors on the reliability of pile, this paper proposes a reliability analysis method for horizontal bearing of pile foundation in sloping ground based on proxy model. Firstly, the analytical model of horizontal bearing of the pile foundation in sloping ground was derived, and corresponding performance functions were constructed. Secondly, by combining Kriging model method with the performance functions, the reliability analysis method of pile foundations in sloping ground is established. Finally, taking a typical transmission line project in mountainous area as an example, the horizontal bearing reliability of pile foundation was analyzed. The results show that the proposed analysis method can quickly converge to the horizontal bearing limit state of pile. Slope effect has more significant influence on horizontal deformation than that of material yield. Among the uncertainty parameters, the bearing capacity of pile foundation is sensitive to the dispersion degree of horizontal force, pile diameter and the elastic modulus of foundation pile.

AbstractIn order to further reveal the pile-soil interaction mechanism during precast pile driving in saturated soft soil in coastal areas, the compaction effect and excess pore pressure response of a single pile and adjacent pile penetration under hammer driven pile construction are analyzed by using the cavity expansion and model test method. The results show that pile driving in saturated soil layer will cause large soil compaction and accumulation of excess pore water pressure. Under the model test conditions, the variation range of soil pressure and excess pore pressure is about 0.7–3.0 times and 0.5–1.5 times of soil mass weight stress. As the driving of adjacent pile, soil pressure at the constructed pile-soil interface increases gradually and fluctuates at the same time, and multi peak phenomenon appears under the influence of different soil layers. At the initial stage of driving, the pile driving force is mainly borne by the pile side friction, and the pile tip resistance will actions as the increase of penetration depth, and the relationship between them is basically linear. These results have certain guiding and reference value for the construction of precast pile driving in saturated soft soil in coastal areas.

AbstractOne key aspect in analysis of heat pipe microreactors is the efficient modeling of heat pipes and its coupling with the solid reactor core. Various options exist for modeling of heat pipes. Most models require an explicit coupling between the vapor core, which brings in an additional layer of coupling when the heat pipe model is integrated into a system-level safety analysis model. This additional layer of coupling causes both convergence concern and computational burden in practice. This article aims at developing a new heat pipe modeling algorithm, where the heat pipe wall, wick, and vapor core are discretized and coupled in a monolithic fully-implicit manner. The vapor core will be modeled as a one-dimensional compressible flow with the capability of predicting sonic limit inherently; a two-dimensional axisymmetric heat conduction model will be used to model the heat pipe wall and wick region. The heat pipe wick and vapor core are coupled through a conjugate heat transfer interface. Eventually, the coupled system will be solved using the Jacobian-Free Newton-Krylov (JFNK) method. It is demonstrated that the new coupled system works well. Consideration of the vapor compressibility in the two-equation model allows more detailed representation of the vapor core dynamics while remains light-weight in terms of computational complexity. The new model is verified by an approximate analytical solution to the heat pipe vapor core and is validated by a sodium heat pipe experiment.

AbstractHigh-temperature heat pipe is an important element in a mobile heat pipe reactor, and the study of the steady-state heat transfer performance of the heat pipe is of great value to the design and safe application of the heat pipe. Based on COMSOL software, a three-dimensional heat pipe model is established to study the effects of the input power of the evaporative section of the heat pipe and the horizontal acceleration of the heat pipe due to its movement on the heat transfer performance of the potassium heat pipe in steady-state operation. The results show that the overall temperature of the outer wall surface of the heat pipe and the axial temperature variation of the center of the heat pipe are less affected by the horizontal acceleration and more affected by the input thermal power within the study range; the thermal resistance of the heat pipe decreases with the increase of the input power of the evaporation section of the heat pipe, and shows a trend of decreasing and then increasing with the increase of the horizontal acceleration.

In this paper a nonlinear fiber elements is used for modeling of pile soil intraction. In the model, both of steel pile and surronding soil nonlinear behavior is considered using fiber element. In this paper the model is developed using DRAIN-3DX software. The method used in this paper, however, allows pile and surronding soil inelastic behavior to be modeled accurately using a single elements. The model is used to simulate nonlinear behavior of pile -soil system and the results are compared with the other analytical and available experimental results. The lateral capacities of offshore piles can be calculated using methods presented in this paper. The analysis results using method presented in this paper in terms of pile head load deformation, pile lateral capacity and pile internal forces are in a good agreement with the other available analytical or experimental results. The model can be used for the pile soil structure interaction analysis of jacket type offshore structures.

Pile foundations supporting offshore platforms and marine structures are required to resist dynamic lateral loading due to wind and wave forces. The response of a jacket offshore tower is affected by the foundation flexibility and the nonlinear behaviour of the supporting piles. In the present study, the soil resistance to the pile movement is modeled using dynamic p-y curves and t-z curves to account for soil nonlinearity and energy dissipation through radiation damping. The model also allows separation at the pile soil interface. The wave forces on the tower members and the tower response are calculated in the time domain using a finite element package (ASAS). The tower response is calculated with emphasis placed on the effects of dynamic pile-soil interaction on the tower performance and the forces acting on the piles for a range of wave conditions.

In this paper vertical piles have been studied with a view to identifying the range of sea-states suitable for the safe pile driving operation. Pile configuration, including the non-linear foundation and the gap between the pile and the pile sleeve shims have been modeled using the finite elements (FE) analysis facilities within ABAQUS. Dynamic analyses of the system for various sea-states characterized by significant wave heights and mean zero upcrossing periods and modeled as a combination of several wave components, have been performed. Repeating the above procedure can generate a table of safe and unsafe sea-states. If the prediction is repeated N times from which n times proved to be safe, then it can be said that the predicted sea-state is safe with a probability of 100(n/N)%. The significant wave height (Hs) and mean zero upcrossing period (Tz) of a future sea-state of a location in NE Pacific (near 46° N 131° W) were generated using the artificial neural networks (ANNs) already trained for this purpose — the location of US National Oceanographic Data Center (NODC) Buoy 46005 is used in this study. The Hs and Tz of some future sea-states were generated from their corresponding conditional 7-parameter probability density functions (pdf’s) given some information including a number of previously measured Hs’s and Tz’s. The parameters of the pdf’s have been estimated from the outputs of 2 different 7-network sets of trained ANNs. This gives a predicted sea-state for a specific time in future. The methodology explained in this paper can identify all control parameters and offer possible solution strategy. The finding reveals that how slight changes in the design configuration can be beneficially exploited to limit the pile response.

A nonlinear seismic soil-pile-structure interaction (SSPSI) analysis of fixed offshore platforms constructed on pile foundations including both vertical and battered piles is presented. The analysis is carried out in time domain and the effects of soil nonlinearity, discontinuity at pile soil interfaces, energy dissipation through soil radiation damping, formation of soil layers on bed rock, structural material nonlinearity and geometrical nonlinearity are considered. A combination of FEM approach and BNWF approach is used in modeling pile (substructure), platform structure (superstructure) and soil media. Gapping in clay is modeled by a special connector configuration. To find out the ground motion of soil layers caused by earthquake excitations at bed rock, a nonlinear site response analysis is performed. The effects of soil-pile-structure interaction on nonlinear seismic analysis of offshore platforms are discussed. It is generally concluded that considering soil-pile-structure interaction causes higher deflections and lower stresses in the platform elements due to soil flexibility, nonlinearity and radiation damping and leads to a more feasible and realistic platform design. The sequence of generation of plastic zones in the structure and their distribution are also investigated. Sensitivity of results to soil layers configuration and soil material damping ratio are discussed.

A nonlinear seismic soil-pile-structure interaction (SSPSI) analysis of fixed offshore platforms constructed on pile foundations including both vertical and battered piles is presented. The analysis is carried out in time domain and the effects of soil nonlinearity, discontinuity at pile soil interfaces, energy dissipation through soil radiation damping, formation of soil layers on bed rock, structural material nonlinearity and geometrical nonlinearity are considered. A combination of FEM approach and BNWF approach is used in modeling pile (substructure), platform structure (superstructure) and soil media. Gapping in clay is modeled by a special connector configuration. To find out the ground motion of soil layers caused by earthquake excitations at bed rock, a nonlinear site response analysis is performed. The effects of soil-pile-structure interaction on nonlinear seismic analysis of offshore platforms are discussed. A comparison of SSPSI model and pile stub modeling is investigated and it is generally concluded that considering soil-pile-structure interaction causes higher deflections and lower stresses in the platform elements due to soil flexibility, nonlinearity and radiation damping and leads to a more feasible and realistic platform design. The sequence of generation of plastic zones in the structure and their distribution are also investigated. Results show that this nonlinear behavior is started at brace elements and then propagated to leg elements as earthquake last.

In this paper Fiber Element is used for modeling soil–pile interaction during earthquakes. In this model, both pile and surrounding soil are modeled using fiber elements. This model is developed using DRAIN–3DX software. In this method, behavior of soil is assign to fiber elements using p-y curves. In order to consider effects of free field soil on the motion, EERA and NERA software are used. In this paper pile behavior embedded in sandy soil subjected to strong ground motion were analyzed and compared with available experimental results. The model can be used for soil – pile – structure interaction analysis of jacket type offshore structure.

The configuration of braces has a considerable influence in the lateral behavior of pile supported steel jacket type offshore platforms. In this paper nonlinear static push over analyses and hysteresis curves are used to investigate lateral behavior of a jacket type offshore platform considering different configurations for vertical bracings of the jacket. One sample platform, constructed in Persian Gulf, is precisely modeled using the finite element program Opensees. Since the lateral response of offshore platforms is completely dependent on their foundations’ behavior, an accurate model is used for modeling the foundation of this structure. Soil-pile-structure interaction is considered using Beam on Nonlinear Winkler Foundation model (BNWF). Lateral and vertical soil stiffness and end bearing were considered using p-y, t-z and q-z nonlinear models, respectively. Moreover, the buckling behavior of the braces is considered in the simulation of the platform to consider the behavior of the platform after buckling, and redistribution of the shear forces in the structure due to the bracings failures. The structure was modeled using nonlinear beam-column elements which have the ability to consider the spread of plasticity along the elements. The sections used for elements are fiber sections which are suitable for considering composite section of pile-grout-leg. Displacement controlled nonlinear static pushover analysis and cyclic loading analysis are conducted applying lateral load which its pattern is according to the predominant vibration modes. Three different configurations for lateral bracings are assumed and the behavior of the platform using these three bracing forms is investigated. The first configuration considered is the original bracing of the platform which is a combination of X and chevron braces; the second one is a case in that X braces were used in all of the bays of the jacket; and in the third form chevron braces are used for all of the bays. According to the push over and hysteresis curves, it is concluded that in the jacket modeled using X vertical braces, lateral load capacity, ductility, residual strength ratio and the absorbed energy in cyclic loadings are considerably more than the jackets which were modeled using a combination of chevron and X braces or just chevron braces. In comparison with the jacket modeled using only chevron braces, the jacket constructed using a combination of X and chevron bracings presents better lateral behavior and capacity.

Offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. In seismic design of offshore platforms, it is often necessary to perform a dynamic analysis that accounts for nonlinear soil-pile-structures interaction effects. Nonlinear dynamic analysis for offshore structures has been a major challenge in marine structural and earthquake engineering. In this paper, nonlinear dynamic analysis of jacket type offshore platforms considering soil-pile-structure interaction subjected to strong ground motion have been studied. A jacket type offshore platform is included of piles, jacket and topside with different behaviors in seismic loading. Both jacket and pile elements have been modeled using fiber cross-sections. In this paper, free field ground motion analysis with respect to bedrock excitations has been done using nonlinear stress-strain relations for soil. This model has been developed using Open System for Earthquake Engineering Simulation (OpenSEES) software. In this paper, nonlinear seismic response analysis of an existing sample offshore platform in Persian Gulf subjected to strong ground motions in different bedrock depths has been performed and the results in terms of lateral deflections of platform, soil layers displacement-time history and acceleration response spectra of pile head, top of jacket and deck have been presented.

Nonlinear response of piles is the most important source of potentially nonlinear behavior of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviors of the piles. Incremental dynamic analysis is an analysis method that has recently emerged as a promising tool for thoroughly evaluating the seismic performance of structures. It involves subjecting a structural model to a suite of ground motion records, each scaled to several intensities and recording the responses at each level to form IDA curves of response versus intensity. In this paper, jacket and soil-pile system is modeled and the effects of Soil-Pile-Structure Interaction (SPSI) are considered, and the Incremental Dynamic Analysis (IDA) is used to investigate nonlinear behavior of offshore platforms. An attempt is made to introduce a practical BNWF (Beam on Nonlinear Winkler Foundation) model for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. This model was incorporated into a Finite Element program (OpenSees). All the analyses are performed in two directions and the results are compared with each others. A computer program for Nonlinear Earthquake site Response Analyses of layered soil deposits (NERA) is used for analysis nonlinear response of soil layers. Limit state of the jacket is calculated from incremental dynamic analysis of the jacket using fiber elements for the nonlinear modeling of the system.

Abstract The vibratory hammer is one of the tools for the extraction of offshore foundation piles as well as monopiles for the decommissioning of offshore structures. In addition to the standard application, where a pile is driven downward to be installed, a vibratory hammer can also be applied to extract piles. For an efficient and commercially attractive application of vibratory hammers for this purpose, the extraction process needs to be modeled during the planning phase to ensure that the appropriate equipment is used. This paper describes how pile driving simulation software can be used to model the extraction process. This is further illustrated through a case study covering the extraction phase of the 1st (onshore) and 2nd (offshore) part of the Delft Offshore Turbine Project. A monopile with a diameter of 4.0 m was extracted approximate 6 months after installation onshore and then extracted several times offshore shortly after installation in the 2nd phase. The paper will not only present the actual extraction predictions, but also the monitoring data obtained during extraction and the results of the post-analysis.

The objective of the project was to develop a numerical model than may be used to predict the wrinkle formation and post formation behavior of a pipeline considering the effect of soil confinement and define the specifications for the development of a comprehensive wrinkle integrity assessment process. The result of this research is the development of wrinkle assessment techniques that could be used directly or could be used to codify maintenance guidelines. This project focused specifically on the pipe soil interaction modeling wrinkle formation as a result of the relative movement of the pipe and soil. The structural model developed and validated in this program and previous work could be applied to wrinkle bends, however, this issue is not specifically addressed in this report. In addition, the project development efforts focused on the monotonic soil interaction event of idealized (e.g., no secondary degradation like corrosion features) pipe segments. The project completed a critical review of existing structural and soil modelling techniques to identify the most suitable technologies for this application. The soil-pipe interaction under soil movement was found to be best represented using the LS-DYNA Multi-material Eulerian technique which permitted the application of a number of suitable soil constitutive models. This analysis tool permitted the consideration of a range of soil types and large soil displacements. Having defined the most suitable tool set, several pipe soil interaction models were developed. These models were used to illustrate the types of analyses that could be completed and the capabilities of the models to illustrate the sensitivity of the scenario loads, displacements to changes in soil, pipe and other parameters. The modeling results were discussed to demonstrate that their trends and results were in line with intuitive assumptions and engineering judgment. Additional models were developed to simulate large scale pipe-soil interaction laboratory test programs. The results of the simulated test programs were compared with the laboratory results as an initial validation of the modeling techniques and tools. The simulated soil displacement patterns, pipe strains and pipe displacement were shown to agree well with experimental results and as such illustrated the ability of the models to reproduce idealized pipe-soil interaction events. Full-scale soil displacement events were modeled to illustrate the application of the modeling tools to forecast or predict the effects of axial and transverse soil movements on buried pipeline segments. These results were used to illustrate the methods and assumptions inherent in the application of the modeling tools to predict soil loading on pipeline systems.

The purpose of this project was to complete a handbook with practical design procedures for submarine pipeline on-bottom stability. The remaining part of the handbook was primarily a description of the interaction between non-trenched pipelines and the seabed where the pipelines were free to move under environmental loading. The objective of this project was to determine the lateral soil resistance forces on a pipeline moving cyclically during hydro-dynamic loading. To meet the goal, full-scale pipe-soil interaction tests were conducted. The models presented in this report are based on the results and general understanding obtained from 110 experimental tests of pipe-soil interaction on loose and dense sand, and soft clay. Raw data from 29 experimental tests on stiff clay in the PIPESTAB project have been qualitatively considered.

This program contributes to maintaining and improving the integrity and safety of existing pipelines with regard to ground movement hazards, and reducing the capital costs of new pipeline systems. The research program focused on the axial, lateral and complex loading of pipeline due to soil movements. It includes (1) a literature review: it presents significant issues related to modeling pipe-soil interaction with a focus to recent development since ASCE (1984); (2) axial loading: it includes a summary of the methods to estimate the axial soil forces on pipeline and recent field measurements on decommissioned pipe sections in weak to desiccated, cohesive to sandy silts in California; (3) lateral loading of buried pipeline: it covers the effects of cover depth, soil strength, loading rate, trench geometry and backfill strength on pipe-soil interaction; (4) complex loading of buried pipeline: the interaction between the lateral and axial soil forces on pipeline are studied; and (5) quantification of mitigative methods: a physical testing program including a total of 20 laterally loaded pipelines are used to identify and quantify the effects of various mitigative methods on reducing lateral loads transferred to a buried pipeline.

This report presents guidelines based on the study of current practices in the design and manufacture of high-pressure pipe fittings (size tees, reducing tees, elbows, and caps) from 4 to 12 inches. Based on fitting measurements, finite-element models for linear analysis were developed and the results were compared to existing standards. The models were verified with two experimental burst tests. Tensile strength proved to be the most significant factor for burst pressure and fatigue. For fittings of unknown origin, the tensile strength can be estimated with non-destructive material hardness tests. Yield strength showed no effect on burst pressure or fatigue due to cyclical pressure loading.

Covers a project to develop a fluid/structure/fracture interactive, inelastic-dynamic computational model for ductile fracture in gas transmission pipelines developed in cooperation with SNAM in Italy to infer specimen-size independent measures of the propagating fracture toughness from small-scale tests on line pipe materials. Verification by CSM on 56-in. diameter.See PR-15-527 (also L51673)