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Structural health monitoring of Attridge Drive overpassSiddique, Abu Bakkar 05 September 2008
Vibration-based damage detection (VBDD) comprises a family of non-destructive testing methods in which changes to dynamic characteristics are used to track the condition of a structure. Although VBDD methods have been successfully applied to various mechanical systems and to simple beam-like structures, significant challenges remain in extending this technology to complex, spatially distributed structures such as bridges. <p> In the present study, numerical simulations using a calibrated finite element model were used to investigate the use of VBDD methods to detect small-scale damage on a two-span, integral abutment overpass structure located in Saskatoon, Saskatchewan. The small scale damage was defined in this study as the removal of a concrete element from the top surface of the bridge deck, resembling the spalled clear cover of concrete deck of the overpass. Five different VBDD techniques were evaluated, including the Change in Mode Shape, Change in Flexibility, Change in Mode Shape Curvature, Change in Uniform Flexibility Curvature and Damage index methods. In addition, the influence of the size of damage, the orientation of damage geometry, sensor spacing (3 m, 5 m and 7.5 m), the approach used for mode shape normalization, and uncertainty in the measured mode shapes was investigated. <p> It was found that localized damage could be reliably detected and located if the sensors were located within 3 m of the damage (the distance between adjacent girders) and if uncertainty in the mode shapes was attenuated through the use of a sufficient number of repeated trials. Furthermore, studies using a limited sensor installation that could be achieved without interrupting the flow of traffic indicated that small scale damage could be detected and potentially located using sensors that are placed well away from the damaged area, provided uncertainty in mode shape was attenuated.
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Structural health monitoring of Attridge Drive overpassSiddique, Abu Bakkar 05 September 2008 (has links)
Vibration-based damage detection (VBDD) comprises a family of non-destructive testing methods in which changes to dynamic characteristics are used to track the condition of a structure. Although VBDD methods have been successfully applied to various mechanical systems and to simple beam-like structures, significant challenges remain in extending this technology to complex, spatially distributed structures such as bridges. <p> In the present study, numerical simulations using a calibrated finite element model were used to investigate the use of VBDD methods to detect small-scale damage on a two-span, integral abutment overpass structure located in Saskatoon, Saskatchewan. The small scale damage was defined in this study as the removal of a concrete element from the top surface of the bridge deck, resembling the spalled clear cover of concrete deck of the overpass. Five different VBDD techniques were evaluated, including the Change in Mode Shape, Change in Flexibility, Change in Mode Shape Curvature, Change in Uniform Flexibility Curvature and Damage index methods. In addition, the influence of the size of damage, the orientation of damage geometry, sensor spacing (3 m, 5 m and 7.5 m), the approach used for mode shape normalization, and uncertainty in the measured mode shapes was investigated. <p> It was found that localized damage could be reliably detected and located if the sensors were located within 3 m of the damage (the distance between adjacent girders) and if uncertainty in the mode shapes was attenuated through the use of a sufficient number of repeated trials. Furthermore, studies using a limited sensor installation that could be achieved without interrupting the flow of traffic indicated that small scale damage could be detected and potentially located using sensors that are placed well away from the damaged area, provided uncertainty in mode shape was attenuated.
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Concurrent Online Testing for Many Core Systems-on-ChipsLee, Jason Daniel 2010 December 1900 (has links)
Shrinking transistor sizes have introduced new challenges and opportunities for system-on-chip (SoC) design and reliability. Smaller transistors are more susceptible to early lifetime failure and electronic wear-out, greatly reducing their reliable lifetimes. However, smaller transistors will also allow SoC to contain hundreds of processing cores and other infrastructure components with the potential for increased reliability through massive structural redundancy. Concurrent online testing (COLT) can provide sufficient reliability and availability to systems with this redundancy. COLT manages the process of testing a subset of processing cores while the rest of the system remains operational. This can be considered a temporary, graceful degradation of system performance that increases reliability while maintaining availability.
In this dissertation, techniques to assist COLT are proposed and analyzed. The techniques described in this dissertation focus on two major aspects of COLT feasibility: recovery time and test delivery costs. To reduce the time between failure and recovery, and thereby increase system availability, an anomaly-based test triggering unit (ATTU) is proposed to initiate COLT when anomalous network behavior is detected. Previous COLT techniques have relied on initiating tests periodically. However, determining the testing period is based on a device's mean time between failures (MTBF), and calculating MTBF is exceedingly difficult and imprecise.
To address the test delivery costs associated with COLT, a distributed test vector storage (DTVS) technique is proposed to eliminate the dependency of test delivery costs on core location. Previous COLT techniques have relied on a single location to store test vectors, and it has been demonstrated that centralized storage of tests scales poorly as the number of cores per SoC grows. Assuming that the SoC organizes its processing cores with a regular topology, DTVS uses an interleaving technique to optimally distribute the test vectors across the entire chip. DTVS is analyzed both empirically and analytically, and a testing protocol using DTVS is described.
COLT is only feasible if the applications running concurrently are largely unaffected. The effect of COLT on application execution time is also measured in this dissertation, and an application-aware COLT protocol is proposed and analyzed. Application interference is greatly reduced through this technique.
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Techniques and Tools for Mining Pre-Deployment Testing DataChan, BRIAN 17 September 2009 (has links)
Pre-deployment field testing in is the process of testing software to uncover unforeseen problems before it is released in the market. It is commonly conducted by recruiting users to experiment with the software in as natural setting as possible. Information regarding the software is then sent to the developers as logs. Log data helps developers fix bugs and better understand the user behaviors so they can refine functionality to user needs. More importantly, logs contain specific problems as well as call traces that can be used by developers to trace its origins. However, developers focus their analysis on post-deployment data such as bug reports and CVS data to resolve problems, which has the disadvantage of releasing software before it can be optimized. Therefore, more techniques are needed to harness field testing data to reduce post deployment problems.
We propose techniques to process log data generated by users in order to resolve problems in the application before its deployment. We introduce a metric system to predict the user perceived quality in software if it were to be released into market in its current state. We also provide visualization techniques which can identify the state of problems and patterns of problem interaction with users that provide insight into solving the problems. The visualization techniques can also be extended to determine the point of origin of a problem, to resolve it more efficiently. Additionally, we devise a method to determine the priority of reported problems.
The results generated from the case studies on mobile software applications. The metric results showed a strong ability predict the number of reported bugs in the software after its release. The visualization techniques uncovered problem patterns that provided insight to developers to the relationship between problems and users themselves. Our analysis on the characteristics of problems determined the highest priority problems and their distribution among users. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2009-09-16 17:50:31.094
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Development of a Novel Method for Lithium-Ion Battery Testing on Heavy-Duty VehiclesSvens, Pontus January 2011 (has links)
Increasing demands for lower environmental impact from vehicles, including heavy-duty vehicles, have driven several vehicle manufacturers to consider adding hybrid electrical vehicles (HEV’s) to the product portfolio. Present research on batteries for HEV’s is mainly focused on lithium-ion battery chemistries, since lithium-ion batteries has the most promising technical potential compared to other types of batteries. However, the uncertainty regarding battery lifetime combined with a high battery cost can have a negative impact on large scale commercialisation of heavy-duty hybrid vehicles in the near future. A large part of present lithium-ion battery research is focused on new materials, but there is also research focusing on ageing of already established lithium-ion battery chemistries. Cycle ageing of batteries often includes complete charging and discharging of batteries or the use of standardized test cycles. Battery cycling in real HEV applications is however quite different compared to this kind of laboratory testing, and real life testing on vehicles is a way of verifying the soundness of laboratory ageing. The aim of this study was to develop a test method suitable for real life testing of lithium-ion batteries for heavy-duty HEV-usage, with the purpose of investigating the correlation of battery ageing and usage in real life applications. This concept study includes both cell level battery cycling and performance testing on board vehicles. The performance tests consist of discharge capacity measurements and hybrid pulse power characterization (HPPC) tests. The main feature of this test equipment is that it is designed to be used on conventional vehicles, emulating an HEV environment for the tested battery. The functionality of the equipment was verified on a heavy-duty HEV with satisfying results. Results from real life testing of 8 batteries using the developed test equipment on four conventional heavy-duty trucks shows that the concept of comparing battery ageing with battery usage has a most promising potential to be used as a tool when optimizing battery usage vs. lifetime. Initial results from this real life study shows significant differences in state of charge (SOC) and power distributions between cycled batteries, but so far only small differences in ageing. Lithium-ion batteries of the type lithium manganese spinel/lithium titanate (LMO/LTO) were used in this study. / Ökande krav på minskad miljöpåverkan från fordon, inklusive tunga fordon, har drivit flera fordonstillverkare till att addera hybridiserade fordon till produktportföljen. Forskning på hybridfordonsbatterier är idag huvudsakligen inriktad på litiumjonbatterikemier, vilken har den mest lovande tekniska potentialen jämfört med andra typer av batterikemier. Det finns idag en risk att osäkerheten kring litiumjonbatteriers livslängd i kombination med en hög batterikostnad kan ha en negativ inverkan på en storskalig kommersialisering av tunga hybridfordon inom den närmsta framtiden. En stor del av batteriforskningen är inriktad på nya material, men det finns även forskning som fokuserar på åldring av redan etablerade litiumjonbatterikemier. Vid åldringsprov används ofta standardiserade testcykler eller cykler där batterierna blir fullständigt laddade och urladdade. Cykling av batterier i verkliga förhållanden skiljer sig dock från den typen av laboratorietester och provning på fordon är därför ett sätt att kontrollera att laboratorieprovning ger relevanta resultat gällande åldring. Syftet med denna studie var att utveckla en testmetodik lämplig för provning av litiumjonbatterier för tunga hybridfordon i verklig drift, med syfte att undersöka kopplingen mellan batteriers åldrande och hur det används. Detta koncept inkluderar battericykling på cellnivå och möjligheten att utföra batteriprestandatester på fordon, där prestandatesterna består av kapacitetsprov och pulsprov. Den viktigaste egenskapen hos den utvecklade testmetodiken är att provning sker på konventionella fordon genom att emulera en hybridmiljö för det testade batteriet. Funktionaliteten hos den utvecklade testutrustningen verifierades på en tung hybridlastbil med goda resultat. Resultaten från en fältstudie av 8 batterier på 4 lastbilar där den utvecklade testutrustningen användes påvisar att testmetodiken har en lovande potential att kunna användas som ett verktyg vid optimering av utnyttjandegrad och livslängd för HEV-batterier. De initiala resultaten från denna fältstudie påvisar skillnader i laddningsgradsfördelning och batterieffektfördelning mellan cyklade batterier, men ännu bara små skillnader i åldring. Litiumjonbatterier av typen litiummanganspinel/litiumtitanat (LMO/LTO) användes i denna studie. / QC 20111205
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Dynamic Testing for a Steel Truss Bridge for the Long Term Bridge Performance ProgramSantos, Cody Joshua 01 May 2011 (has links)
Under the direction of the Federal Highway Administration the Long Term Bridge Performance Program (LTBP) selected Minnesota Bridge number 5718 as a pilot bridge for evaluation. This program focuses on the monitoring of bridges for a 20-year period to understand the structural behavior over time due to the various loads and weathering. In monitoring this bridge a better understanding can be acquired for the maintenance issues related to the nation's deteriorating bridge infrastructure.
Bridge Number 5718, which is located just outside of Sandstone Minnesota, is a steel truss bridge that spans the Kettle River. Constant monitoring of the bridge along with periodic testing of the bridge will allow for the collection of data over a 20-year period. The focus of this work is to establish a baseline for the bridges characteristics through nondestructive dynamic testing. Later tests will be compared to these results and changes can then be tracked.
In order to perform the required testing, two electromagnetic shakers were used to produce the excitation. The bridge was also outfitted with an array of velocity transducers to allow for the response to be recorded. The data was then used to extract the resonant frequencies, mode shapes, and damping ratios. A modal assurance criterion was also performed to solidify the findings. These parameters define the structural identity of the bridge. Through performing these tests the database that is being collected under the Long Term Bridge Performance Program will be used to better the overall health and safety of the nation's bridges.
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Upgrading concrete bridges : post-tensioning for higher loadsNilimaa, Jonny January 2013 (has links)
There are a great number of old structures around the world, some of which were designed for completely different purposes than in their current application. Swedish railway bridges were for example only designed for maximum axle loads of 200 kN in the beginning of the 20th century, while the highest axle loads of today are twice as high. The traffic intensities have also increased dramatically and the velocities are now higher than ever before. Reinforced concrete trough bridges were typically designed and built in the mid-20th century and it is still one of the most frequent railway bridge types in Sweden. The trough bridges were normally designed for traffic loads which were smaller than the loads today and in order to maintain an old structure as the loads increases, structural upgrading of the load bearing capacity might be necessary. Upgrading the load carrying capacity can be performed in two ways, namely administrative upgrading or strengthening. Administrative upgrading refers to refined design calculations, using real material data, geometry and loads, which provides a higher capacity than the original design and the bridge can thereby be upgrading with minor physical impact. Upgrading by strengthening on the other hand, refers to, often, larger physical alteration of the structure in order to enhance the original load carrying capacity.Upgrading methods for increased flexural resistance of concrete trough bridges has been developed and tested previously, but strengthening methods for increased shear resistance in the bridge deck are still absent. The objective of this thesis is therefore to find an existing- or develop a new strengthening method which can be applied in order to enhance the shear resistance of concrete trough bridge decks. The difficulties associated to strengthening of existing railway bridges include traffic during the strengthening work and concrete surfaces concealed by the ballast.The State-of-the-Art indicated that none of the existing strengthening techniques were sufficient for this application and internal unbonded post-tensioning in the transverse direction was nominated as the most promising method. The research was thereafter focused on testing the possibilities and strengthening effects of post-tensioning. Two laboratory investigations were performed during the research project and the method was finally tested in a field test on a 50 years old trough bridge in Haparanda, Sweden. The strengthening procedure of internal unbonded post-tensioning consists of four consecutive steps:1.Transverse drilling of the horizontal holes through the bottom slab.2.Installation of the prestressing system.3.Post-tensioning of the system.4.Sealing of the prestressing system.The laboratory and field tests were successful and the results proved that the internal steel reinforcement within the concrete was compressed when the trough bridge was post-tensioned. Due to the compression, a higher load could be carried by the bridge deck before the tensile reinforcement yields and the bridge fails. In other words, the flexural capacity of the bridge deck was increased. The field test actually showed that eight steel bars, post-tensioned with 430 kN per bar on the Haparanda Bridge, completely counteracted the tensile stresses caused by a train with 215 kN axle loads. The effect on the shear resistance was however not as easy to measure, but the laboratory test recorded a significant strain reduction in the tensile reinforcement which was bent up at the transition zone between the bridge deck and the main girders. The reduced strain might be interpreted as lower shear stresses and post-tensioning can thereby be considered to have a positive effect on the shear resistance of the bridge deck. Shear design according to the protocol of Eurocode 2 or BBK was however found to be restrictive in predicting the post-tensionings effect on the shear capacity and further research is proposed in chapter 8. / Det finns ett stort antal gamla konstruktioner runtom i världen och många byggdes för helt andra användningsområden än vad de numera används till. Som ett exempel kan nämnas att svenska järnvägsbroar i början av 1900-talet byggdes för att klara av att bära axellaster på maximalt 200 kN, medan några av våra nybyggda broar är konstruerade för dubbelt så stora axellaster. Även traffikmängden har mångdubblats och tåghastigheterna är nu högre än någonsin. Trågbroar i armerad betong är en typisk bro som byggdes i Sverige framförallt på 50-talet och den är fortfarande en av de vanligaste brotyperna i Sverige. Trågbroarna konstruerades normalt för att bära lägre laster än vad vi har idag och för att kunna ha kvar dessa broar när lasterna ökar kan det krävas någon form av uppgradering av bärförmågan. Det finns två sätt att förbättra bärförmågan på en gammal bro, nämligen administrativ uppgradering eller förstärkning. Administrativ uppgradering innebär att nya förbättrade beräkningsmetoder används tillsammans med verkliga materialhållfastheter, geometrier och laster för att mer noggrant räkna ut brons bärförmåga. Normalt visar det sig att bärförmågan är högre än vad de ursprungliga beräkningarna antydde. På så vis höjs kapaciteten med minimal fysisk åverkan på bron. Uppgradering genom förstärkning innebär däremot att konstruktionens bärförmåga höjs genom att förändra bron ur ett rent fysiskt perspektiv. Metoder för att öka böjkapaciteten på trågbroar i betong har utvecklats och testats tidigare, men förstärkningsmetoder för att höja tvärkraftskapaciteten saknas däremot fortfarande. Målet för denna avhandling ligger därför i att utveckla en förstärkningsmetod som kan användas för att förbättra tvärkraftskapaciteten för bottenplattan på trågbroar i betong. Det finns dock några svårigheter sammankopplade med förstärkning av befintliga järnvägsbroar, t.ex. tågtraffik under förstärkningsförfarandet och att viktiga betongytor är skyddade av ballast.Inga befintliga förstärkningsmetoder bedömdes däremot som lämpliga för det avsedda användningsområdet vid ”State-of-the-Art’’ studien. Invändig efterspänning av broplattan i tvärledd bedömdes som den bäst lämpade förstärkningsmetoden och efterföljande forskning fokuserades på att reda ut möjligheter för och förstärkningseffekter av efterspänning. Två olika laboratorieförsök genomfördes under forskningsprojektet och förstärkningsmetoden testades slutligen vid ett fältförsök på en 50 år gammal järnvägsbro i Haparanda.Själva tillvägagångssättet för förstärkningsmetoden består av fyra viktigaoch sammanhängande arbetssteg:1. Borrning av horisontella hål tvärs igenom trågbrons bottenplatta.2. Installation av själva försstärkningssystemet.3. Efterspänning av förstärkningssystemet.4. Förslutning av förstärkningssystemet.Både laboratorie och fältförsöken blev lyckade och resultaten visade att stålarmeringen inuti betongen trycktes ihop när trågbron efterspänndes. Tack vare denna kompression så kan broplattan bära högre laster innan dragarmeringen börjar flyta och bron slutligen går sönder. Med andra ord så höjdes brons böjkapacitet. Fältförsöket visade att de åtta spännstagen, efterspännda med 430 kN per stag, helt och hållet motverkade dragarmeringens påkänningar av ett tåg med axellasten 215 kN. Förstärkningsmetodens effekt på tvärkraftskapaciteten är däremot inte lika lätt att påvisa men laboratorieförsöken visade att töjningen reducerades betydligt i den uppbockade dragarmeringen, i zonen där plattan fäster i huvudbalkarna. De lägre töjningsnivåerna kan tolkas som lägre skjuvpåkänningar och efterspänningen kan därmed ha en positiv effekt på broplattans tvärkraftskapacitet. Laboratorieförsöken visade däremot att både Eurokod 2 och BBK är restriktiva när det gäller att uppskatta efterspänningens effekt på tvärkraftskapaciteten. En ny förstärkningsmetod för trågbroar i betong har därmed föreslagits i och med denna avhandling, men en del frågetecken kvarstår och i kapitel 8 ges därför förslag på fortsatta forskningsområden.
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Evaluation of Precast Portland Cement Concrete Panels for Airfield Pavement RepairsPriddy, Lucy Phillips 23 April 2014 (has links)
Both the identification and validation of expedient portland cement concrete (PCC) repair technologies have been the focus of the pavements research community for decades due to ever decreasing construction timelines. Precast concrete panel technology offers a potential repair alternative to conventional cast-in-place PCC because the panel is fully cured and has gained full strength prior to its use. This repaired surface may be trafficked immediately, thus eliminating the need for long curing durations required for conventional PCC. The literature reveals a number of precast PCC panel investigations in the past 50 years; however precast technology has only recently gained acceptance and increased use in the US for highway pavements. Furthermore, only limited information regarding performance of airfield applications is available. Following a review of the available technologies, an existing panel prototype was redesigned to allow for both single- and multiple-panel repairs. A series of various sized repairs were conducted in a full-scale airfield PCC test section. Results of accelerated testing indicated that precast panels were suitable for airfield repairs, withstanding between 5,000 and 10,000 passes of C-17 aircraft traffic prior to failure. Failure was due to spalling of the transverse doweled joints. The load transfer characteristics of the transverse joint were studied to determine if the joint load test could be used to predict failure. Results showed that the load transfer efficiency calculations from the joint load test data were not useful for predicting failure; however differential deflections could possibly be applied. Additionally, the practice of filling the joints with rapid-setting grout may have resulted in higher measurements of load transfer efficiency. To determine the stresses generated in the doweled joint, three-dimensional finite element analyses were conducted. Results indicated that the dowel diameter should be increased to reduce stresses and to improve repair performance. Finally, the precast repair technology was compared to other expedient repair techniques in terms of repair speed, performance, and cost. Compared to other methods, the precast panel repair alternative provided similar return-to-service timelines and traffic performance at a slightly higher cost. Costs can be minimized through modification to the panel design and by fabricating panels in a precast facility. Modifications to the system design and placement procedures are also recommended to improve the field performance of the panels. / Ph. D.
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Differences in the relationship of heart rate and blood lactate values between running on track versus inclined treadmill : Improving laboratory testing to accurately prescribe exercise intensitiesBramell, Axel January 2016 (has links)
The purpose of the study was to evaluate the generalisability of the heart rate-blood lactate relationship determined in laboratory testing in comparison to running over ground. This plays a crucial role to prescribe exercise intensity from laboratory results. Ten well trained runners performed a maximal oxygen uptake (VO2max) pre-test and an incremental submaximal test performed at a two degrees inclined treadmill and a running track. Statistical analysis included student’s t-test of heart rate at interpolated blood lactate levels and comparison of second order polynomial regression lines. VO2max was 60,4 ± 6 ml/kg/min for men and 56,3 ± 4,3 ml/kg/min for women. There was no significant difference in heart rate at interpolated blood lactate of 3 and 4 mmol/L. There was no significant difference between heart rate values at any running velocity. A significant difference between blood lactate values was observed 14km/h (p=0,04). When considering blood lactate values up to 6mmol/L, heart rate-blood lactate relationships were similar. In conclusion, lactate threshold testing on treadmill through incremental test protocols on a two degrees incline gives similar heart rate- blood lactate relationship as running over ground and may be used to prescribe intensity in training performed over ground.
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Thermo-Mechanical Behavior of Energy Piles: Full-Scale Field Testing and Numerical ModelingSutman, Melis 09 September 2016 (has links)
Energy piles are deep foundation elements designed to utilize near-surface geothermal energy, while at the same time serve as foundations for buildings. The use of energy piles for geothermal heat exchange has been steadily increasing during the last decade, yet there are still pending questions on their thermo-mechanical behavior. The change in temperature along energy piles, resulting from their employment in heat exchange operations, causes axial displacements, thermally induced axial stresses and changes in mobilized shaft resistance which may have possible effects on their behavior. In order to investigate these effects, an extensive field test program, including conventional pile load tests and application of heating-cooling cycles was conducted on three energy piles during a period of six weeks. Temperature changes were applied to the test piles with and without maintained mechanical loads to investigate the effects of structural loads on energy piles. Moreover, the lengths of the test piles were determined to represent different end-restraining conditions at the toe. Various sensors were installed to monitor the strain and temperature changes along the test piles. Axial stress and shaft resistance profiles inferred from the field test data along with the driven conclusions are presented herein for all three test piles. It is inferred from the field test results that changes in temperature results in thermally induced compressive or tensile axial stresses along energy piles, the magnitude of which increases with higher restrictions such as structural load on top or higher toe resistance. Moreover, lower change in shaft resistance is observed with increasing restrictions along the energy piles. In addition to the design, deployment, and execution of the field test, a thermo-mechanical cyclic numerical model was developed as a part of this research. In this numerical model, load-transfer approach was coupled with the Masing's Rule in order to simulate the two-way cyclic axial displacement of energy piles during temperature changes. The numerical model was validated using the field test results for cyclic thermal load and thermo-mechanical load applications. It is concluded that the use of load-transfer approach coupled with the Masing's Rule is capable of simulating the cyclic thermo-mechanical behavior of energy piles. / Ph. D.
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