No description available.

Suction piles are used for anchoring the mooring lines at the seafloor. One of the challenges of their installing is the occurrence of the heave resonance of the pile-cable system and possibly the heave induced pitch resonance during the lowering process. When the heave and/or pitch frequency of the vessel which operates the lowering of the pile matches the heave natural frequency of the pile-cable system, the heave resonance may occur, resulting in large heave oscillations of the pile and thus significantly increasing loads on the lowering cable and lowering devices. Furthermore, the large heave may resonantly induce the pitch of a pile. To predict and possibly mitigate the heave/pitch resonance of the pile-cable system during the lowering process, it is crucial to under the mechanism of heave induced pitch resonance and estimate the added-mass and damping coefficients of the pile-cable system accurately. The model tests of the forced heave excitation of pile models were first conducted to investigate the added-mass coefficient for a pile model with different opening area ratios at its top cap at the Haynes Coastal Engineering Laboratory of Texas AandM University. In the model tests, it was observed that the resonant heave may occur if the heave excitation frequency matches the related heave natural frequency and the pitch resonance may be induced by the heave resonance. The results of the following theoretical analysis and numerical simulation of the heave excitation of the pile-cable system are found to be consistent with the related measurements, which is helpful to further understand the physics of lowering a pile-cable system. The results of this study may be used to determine the magnitudes of total heave added-mass and damping coefficient of a pile and the heave natural frequency of the pile-cable system based upon its main characteristics. The heave induced resonant pitch is found to occur when 1) the pitch natural frequency is roughly equal to one half of the heave natural frequency and 2) the heave excitation frequency is approximately equal to the heave natural frequency. If only one of the two conditions is satisfied, no significant pitch resonance will occur. These results may have important implications to the operation of lowering offshore equipment to the seafloor in deep water.

In this study, the load bearing behavior of piled raft foundations is investigated performing laboratory and field tests. Piled raft foundation of a multi storey building was also instrumented and monitored in order to study the load sharing mechanism of piled raft foundations. A small reinforced concrete piled raft of 2.3 m square supported by four mini piles at the corners was loaded and contribution of the raft support up to 41 % of the total load was observed. The soil was stiff fissured Ankara clay with no ground water. A building founded on a piled raft foundation was instrumented and monitored using earth pressure cells beneath the raft during its construction period. The foundation soil was a deep graywacke highly weathered at the upper 10 m with no ground water. The proportion of load that was carried by the raft was 21 to 24 % of the total load near the edge and 44 to 56 % under the core. In the laboratory tests, model aluminum piles with outerinner diameters of 2218 mm and a length of 200 mm were used. The raft was made of steel plate with plan dimensions of 176 mm x 176 mm and a thickness of 10 mm. The model piles were instrumented with strain gages to monitor pile loads. Model piled raft configurations with different number of piles were tested. The behavior of a single pile and the plain raft were also investigated. The soil in the model tests was half and half sand &ndash / kaolinite mixture. It has been observed that when a piled raft is loaded gradually, piles take more load initially and after they reach their full capacity additional loads are carried by raft. The proportion of load that was carried by the raft decreases with the increasing number of piles and the load per pile is decreased. Center, edge and corner piles are not loaded equally under rafts. It has been found that rafts share foundation loads at such levels that should not be ignored.

In this thesis, a new modeling technique is proposed for minimizing regression testing effort in software product lines. The &ldquo / Product Flow Model&rdquo / is used for the common representation of products in application engineering and the &ldquo / Domain Service and Object Model&rdquo / represents the variant based relations between products and core assets. This new approach provides a solution for avoiding unnecessary work load of regression testing using the principles of sub-service decomposition and variant based product/sub-service traceability matrices. The proposed model is adapted to a sample product line targeting the banking domain, called Loyalty and Campaign Management System, where loyalty campaigns for credit cards are the products derived from core assets. Reduced regression test scope after the realization of new requirements is demonstrated through a case study. Finally, efficiency improvement in terms of time and effort in the test process with the adaptation of the proposed model is discussed.

Vertical and inclined soil nails under footings as settlement &ndash / reducing elements is investigated using a physical 1g model in the laboratory. Nails are not connected to footing, they are not so long and vertical settlement of nails is very large compared to usual limits encountered for piles or micropiles. Following the settlement of footing, they share the load together with the footing. The skin friction is mostly mobilized and end-bearing failure occurs continuously during the settlement. The system of footing- soil nail is studied by model square footings of 30 mm x 30 mm and 50 mm x 50 mm breadth dimensions and remoulded kaolin clay consolidated under constant controlled stress of 50 kPa in 200 mm cube boxes. In the first section of the testing series 4, 5, 9 and 12 nails were inserted into soil in 3B, 2.4B, 1.33B and B lengths, respectively. In the second section, 4 and 6 nails in 1.5B and 2B lengths were tested for vertical and 15 degrees and 30 degrees inclined cases. Settlements of footings were measured under constant footing pressure for all groups. Several tests were repeated in each group of testing series. It is concluded that keeping the total nail length constant, decreasing the nail number thus using longer individual nails is more effective in decreasing the footing settlements. 15 degrees inclined nails decrease total settlements more.

No description available.

Die vorliegende Arbeit beschäftigt sich mit der Prozessführung der Fallgewichtsverdichtung. Konkret wird der Einfluss der eingetragenen kinetischen Energie und des Impulses auf die Kinematik des Fallgewichts und die Reaktion des Bodens untersucht. Die aktuell etablierte Dimensionierung der Fallgewichtsverdichtung erfolgt einzig auf Basis der potentiellen Energie des Fallgewichts. Mindestens eine weitere unabhängige Steuergröße fehlt, um den Prozess zu optimieren. Die Arbeit analysiert hierzu den Einfluss des Impulses mit 1-g-Modellversuchen. Die Beschleunigung des Fallgewichts zeigt zwei charakteristische Bereiche: (1) eine starke Überhöhung, kurz nach dem Einschlag und (2) ein Plateau, welches länger anhält und dann abrupt endet. Die Überhöhung der Beschleunigung ist direkt proportional zur quadratischen Einschlaggeschwindigkeit und ergibt sich aus der Impulsfortpflanzung im Boden. Dies mobilisiert eine zusätzliche Masse im Boden, die gemeinsam mit dem Fallgewicht mit gleicher Geschwindigkeit in den Boden eindringt. Diese Phase wird dominiert durch den Unelastischen Stoß zwischen Fallgewicht und Boden. In der zweiten Phase erfolgt ein reibungsbehafteter Lastabtrag, der mit der Änderung der Kratertiefe korreliert. Mit dem Wissen um diese Mechanismen wird ein Optimierungsparameter vorgeschlagen, Mit dem gezeigt wird, dass durch Reduktion der Einschlaggeschwindigkeit bei gleichbleibendem Impuls die Fallgewichtsverdichtung effizienter ausgeführt werden kann. Ferner wird demonstriert, dass die Kratertiefenentwicklung mit fortschreitender Ausführung progressiv oder degressiv verlaufen kann. Zusammenfassend zeigt die Arbeit, dass der Einsatz schwerer Fallmassen, die aus geringer Höhe fallen effizienter ist, als der Einsatz leichter Fallmassen, welche aus großer Höhe fallen. Der Grund dafür liegt in der nachteiligen Mobilisierung der zusätzlichen Bodenmasse, welche proportional zur quadratischen Einschlaggeschwindigkeit zunimmt und das Eindringen des Fallgewichts durch seine zusätzliche axiale Trägheit hemmt.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The design of the Berg River Dam bottom outlet structure with multitude draw offs was based on various hydraulic model tests on a 1:40 model that was used for original design and a 1 in 20 physical model which was used to produce the final design. These tests indicated no foreseeable malfunction and showed that the 1.8 m² air vent would provide sufficient air flow to minimize the negative pressures that would develop behind the emergency gate during its closure or opening. However, during the first trial commissioning of the dam outlet structure, air was unexpectedly expelled through the air vent at a velocity so high that the recta-grids covering the shaft were blown to a height of over 3m while the gate was closing at a rate of approximately 0.0035 m/s. The air flow velocity up the air vent was approximately 45m/s and occurred when the gate was approximately 78% closed. A brief report on the test indicated that the source of air may have been a vortex formation in the vertical intake tower upstream of the emergency gate entraining air which was drawn through the gate and released up the air vent. The purpose of this research was to utilize 3-dimensional numerical modelling employing Computational Fluid Dynamics (CFD) to carry out numerical simulations to investigate the above mentioned malfunction and thereby establishing whether the given hypotheses for the malfunction were valid. For purposes of validating the CFD modelling, a 1:14.066 physical model was constructed at the University of Stellenbosch hydraulics laboratory. The 3-dimensional CFD model was used to investigate the said incident, using steady state simulations that were run for various openings of the emergency gate. The intenetion was to establish whether there was an emergency gate opening which would reproduce the air release phenomenon. The results obtained from the numerical model showed a similar trend to those of the physical model although there were differences in values. Neither model, showed a sudden release of air through the vent. It was concluded that the unsteady air-water flow out of the air vent may have been caused by the variation of the discharge with time causing unbalanced negative pressures in the outlet structure. Therefore, it was recommended that further CFD transient simulations should be undertaken incorporating a moving emergency gate. / AFRIKAANSE OPSOMMING: Die ontwerp van die bodemuitlaat van die Bergrivierdam met multivlakuitlate is gebaseer op verskeie hidrouliese modeltoetse op a 1:40 fisiese model wat vir die oorspronklike ontwerp gebruik is, asook „n 1 tot 20 fisisiese model wat gebruik is om die finale ontwerp te lewer in 2003. Hierdie toetse het geen beduidende afwykings aangedui nie en het bewys dat die 1.8mª lugskag voldoende lugvloei sal toevoer om die negatiewe drukking wat stroomaf van die noodsluis ontstaan gedurende die sluitingsproses, sal minimaliseer. Gedurende die inlywingtoets in die veld in 2008 van die noodsluis, is lug onverwags teen 'n hoë snelheid deur die lugskag opwaarts uitgelaat, wat die rooster wat die skag beskerm teen 'n hoogte van oor 3m geblaas het terwyl die sluis teen 'n tempo van ongeveer 0.0035 m/s toegemaak het. Die lugvloeisnelheid in die lugskag was ongeveer 45m/s en het plaasgevind toe die sluis ongeveer 78% toe was. 'n Kort verslag oor die veldtoets dui aan dat die bron van die lug dalk werwelvorming in die vertikale inlaattoring stroomop van die noodsluis was, met lug wat deur die sluis getrek was en opwaarts in die lugskag vrygelaat is. Die doel van die navorsing was om drie-dimensionele numeriese modellering met rekenaar vloeidinamika (RVD) te benut om numeriese similasies uit te voer om die bogenoemde abnormale werking van die lugskag te ondersoek en daarmee vas te stel of die gegewe aannames van krag is. Vir die doel om die RVD modellering te verifieer is 'n 1:14.066 fisiese model gebou by die Universiteit van Stellenbosch se waterlaboratorium. Die 3-dimensionele RVD model is gebruik om die genoemde probleem te ondersoek, deur stasionêre simulasies wat vir verskillende openinge van die noodsluis geloop is te gebruik. Die doel was om vas te stel of daar 'n spesifieke noodsluisopening is wat die vrylating van die lug veroorsaak het. Die uitslag verkry deur die numeriese model het dieselfde windrigting soos die van die fisiese model gewys, alhoewel daar verskille in die waardes was. Nie een van die modelle het .n skielike vrystelling van lug deur die lugskag gewys nie. 'n Afleiding is gemaak dat die nie stasionêre lug-water vloei uit die lugskag moontlik veroorsaak was deur die verandering van die vloei met tyd veroorsaak deur ongebalanseerde negatiewe druk in die uitlaatstruktuur. Daarom is daar voorgestel dat verdere RVD nie stasionêre simulasies gedoen word met 'n bewegende noodsluis.

Static and dynamic interaction mechanism of the retained soil-compressible geofoam buffer and yielding retaining structures requires further investigation. The present study, initiated on this motive, discusses the results of 1-g physical model tests and numerical analyses of cantilever retaining walls with and without deformable geofoam buffers between the wall and cohesionless granular backfill. 0.7m high walls with various wall thicknesses were utilized in the physical modeling. Dynamic tests were carried out by using a laminar container placed on a uni-axial shaking table. Influence of buffer thickness, geofoam type and wall flexibility as well as base excitation characteristics on the lateral earth pressures and flexural wall deflections were under concern. Outcomes of the analyses performed with FLAC-2D (v6.0) finite difference code were validated against the results of the physical model tests. It was observed that the arching effect induced in the retained soil by the lateral compression of the lower half of the geofoam buffer has a positive effect, as this zone is able to absorb a portion of the total unbalanced lateral force exerted by the backfill thus causing a reduction in the static and seismic lateral wall pressures. Relative thickness and stiffness of the geofoam buffer appear to be the most dominant factors affecting the reduction in earth thrust. Lateral earth pressure coefficients determined from physical model tests were compared with those calculated using methods available in the literature. Good agreement was observed between the predictions. Graphs were provided to estimate the static and dynamic lateral earth pressure coefficients for various combinations of wall stiffness and buffer characteristics. Analysis of a 6m high prototype cantilever wall subjected to an excitation recorded in August 17, 1999 Kocaeli earthquake by finite difference method exhibited the contribution of geofoam buffers on seismic performance of cantilever earth retaining walls. It was observed that the presence of an EPS geofoam inclusion provides a reduction of the permanent flexural wall deflections as well as total seismic thrust likely to be experienced by the wall during an earthquake.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24896号 / 工博第5176号 / 新制||工||1988(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)准教授 PIPATPONGSA Thirapong, 教授 肥後 陽介, 教授 岸田 潔, 教授 安原 英明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM