Experimental and Numerical Study on the Behavior of Energy Piles Subjected to Thermal Cycles

A laboratory-scale model test is conducted to improve the understanding of the effects of thermal cycles on the mechanical behavior of energy piles. The model pile is composed of cement mortar and dry sand with a relative density of 30% is used for the model ground. After applying the working load to the pile head, the pile is subjected to three thermal cycles with a magnitude of 15°C. The measured temperature response and mechanical behavior are analyzed and used to validate the proposed numerical approach. In the numerical analysis, the temperature variation due to thermal cycles is calculated using uncoupled heat transfer analysis. Then, the computed temperature field is used as the boundary condition in the sequence stress analysis. A series of numerical sensitivity analyses are carried out using the sequentially coupled method to investigate the long-term performance of energy piles under different soil and pile head restraint conditions. The numerical results suggest that the restraint condition at the pile head plays an important role in the mechanical response of energy piles. The ultimate pile resistance after thermal cycles does not decrease significantly. The accumulation of settlement of the free head pile and the reduction in the axial force of the restrained head pile should be considered in the design.

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Dependence of Mechanical Behavior of the Murine Tail Disc on Regional Material Properties: A Parametric Finite Element Study

Journal of Biomechanical Engineering ◽

10.1115/1.2073467 ◽

2005 ◽

Vol 127 (7) ◽

pp. 1158-1167 ◽

Cited By ~ 26

Author(s):

Adam H. Hsieh ◽

Diane R. Wagner ◽

Louis Y. Cheng ◽

Jeffrey C. Lotz

Keyword(s):

Finite Element ◽

Mechanical Behavior ◽

Nucleus Pulposus ◽

Material Properties ◽

Mechanical Response ◽

Swelling Pressure ◽

Transient Behavior ◽

Sensitivity Analyses ◽

Intact Mouse

In vivo rodent tail models are becoming more widely used for exploring the role of mechanical loading on the initiation and progression of intervertebral disc degeneration. Historically, finite element models (FEMs) have been useful for predicting disc mechanics in humans. However, differences in geometry and tissue properties may limit the predictive utility of these models for rodent discs. Clearly, models that are specific for rodent tail discs and accurately simulate the disc’s transient mechanical behavior would serve as important tools for clarifying disc mechanics in these animal models. An FEM was developed based on the structure, geometry, and scale of the mouse tail disc. Importantly, two sources of time-dependent mechanical behavior were incorporated: viscoelasticity of the matrix, and fluid permeation. In addition, a novel strain-dependent swelling pressure was implemented through the introduction of a dilatational stress in nuclear elements. The model was then validated against data from quasi-static tension-compression and compressive creep experiments performed previously using mouse tail discs. Finally, sensitivity analyses were performed in which material parameters of each disc subregion were individually varied. During disc compression, matrix consolidation was observed to occur preferentially at the periphery of the nucleus pulposus. Sensitivity analyses revealed that disc mechanics was greatly influenced by changes in nucleus pulposus material properties, but rather insensitive to variations in any of the endplate properties. Moreover, three key features of the model—nuclear swelling pressure, lamellar collagen viscoelasticity, and interstitial fluid permeation—were found to be critical for accurate simulation of disc mechanics. In particular, collagen viscoelasticity dominated the transient behavior of the disc during the initial 2200s of creep loading, while fluid permeation governed disc deformation thereafter. The FEM developed in this study exhibited excellent agreement with transient creep behavior of intact mouse tail motion segments. Notably, the model was able to produce spatial variations in nucleus pulposus matrix consolidation that are consistent with previous observations in nuclear cell morphology made in mouse discs using confocal microscopy. Results of this study emphasize the need for including nucleus swelling pressure, collagen viscoelasticity, and fluid permeation when simulating transient changes in matrix and fluid stress/strain. Sensitivity analyses suggest that further characterization of nucleus pulposus material properties should be pursued, due to its significance in steady-state and transient disc mechanical response.

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Numerical Study on the Suitability of Centrifuge Testing for Capturing the Thermal-Induced Mechanical Behavior of Energy Piles

Journal of Geotechnical and Geoenvironmental Engineering ◽

10.1061/(asce)gt.1943-5606.0001318 ◽

2015 ◽

Vol 141 (10) ◽

pp. 04015042 ◽

Cited By ~ 12

Author(s):

Alessandro F. Rotta Loria ◽

Alice Di Donna ◽

Lyesse Laloui

Keyword(s):

Mechanical Behavior ◽

Numerical Study ◽

Centrifuge Testing ◽

Energy Piles

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Thermo-mechanical behavior of a full-scale energy pile equipped with a spiral pipe configuration

Canadian Geotechnical Journal ◽

10.1139/cgj-2020-0162 ◽

2021 ◽

Author(s):

Di Wu ◽

Hanlong Liu ◽

Gangqiang Kong ◽

Alessandro F. Rotta Loria

Keyword(s):

Mechanical Behavior ◽

Mechanical Response ◽

Full Scale ◽

Vertical Stress ◽

Thermally Induced ◽

Energy Pile ◽

Practical Applications ◽

Total Length ◽

Energy Piles ◽

In Series

This study investigates the thermo-mechanical behavior of energy piles equipped with a spiral pipe configuration. The analysis is based on the results of a full-scale energy pile as well as 3-D thermo-mechanical finite element analyses. The thermo-mechanical behavior of two energy piles with five U-shaped pipes connected in series and parallel, characterized by the same total length of the piping network, is also analyzed numerically for comparison purposes. The results of this work highlight that energy piles equipped with a spiral pipe configuration are characterized by the lowest trends of average temperature variation and thermally induced vertical stress within their volume, as compared to energy piles equipped with five U-shaped pipe configurations connected in series or parallel. Considerable variations in temperature and thermally induced vertical stress arise in the vicinity of the piping network embedded in all of the considered energy piles. Nevertheless, energy piles equipped with a spiral pipe configuration appear the best solution for practical applications in comparison with U-shaped pipe configurations of the same total length, because they maximize the heat exchange that is achieved with the ground and minimize the associated thermally induced variations of their mechanical response.

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Experimental and theoretical studies of laterally loaded finned piles in sand

Canadian Geotechnical Journal ◽

10.1139/cgj-2013-0012 ◽

2014 ◽

Vol 51 (4) ◽

pp. 381-393 ◽

Cited By ~ 21

Author(s):

Ahmed M.A. Nasr

Keyword(s):

Pile Foundation ◽

Numerical Study ◽

Scale Model ◽

Laboratory Model ◽

Small Scale ◽

Lateral Loads ◽

Pile Head ◽

Element Analysis ◽

Fin Efficiency ◽

Lateral Resistance

Large lateral loads may act on pile foundation supporting structures, such as bridge abutments, retaining walls, and structures subjected to wind–earthquake loads. A pile with fins is a newly developed type of pile foundation that is capable of supporting large lateral loads. In the present study an attempt is made to evaluate the improvement in lateral capacity of a pile with fins mounted close to the pile head. Small-scale model tests and a numerical study using finite element analysis were performed on regular piles without (fins) and piles with fins. These piles were installed in sand of different relative densities (Dr = 35% and 78%). The investigations were carried out by varying the length, width, and shape of the fins, and type of pile. Results reveal that there is a significant increase in lateral resistance of the piles after mounting the fins close to the pile head. The increase in lateral resistance gained by placing fins on a pile varies with geometries of the pile and fins. The lateral resistance increases with the increase in length of the fins until the fin’s length is equal to 0.4 of the pile length. Based on the results of the laboratory model and numerical analysis, critical values of fin parameters for maximum improvement are suggested. The agreement between observed and computed results is found to be reasonably good in terms of ultimate lateral load and fin efficiency. A comparison between the model results and the prototype-scale results is also studied.

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Micro-Meso Scale Model of Electrospun Poly (Ester Urethane) Urea Scaffolds

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-205531 ◽

2009 ◽

Cited By ~ 1

Author(s):

Antonio D’Amore ◽

John A. Stella ◽

David E. Schmidt ◽

William R. Wagner ◽

Michael S. Sacks

Keyword(s):

Tissue Engineering ◽

Mechanical Behavior ◽

Fiber Orientation ◽

Structural Changes ◽

Mechanical Response ◽

Multiple Scales ◽

Metabolic Response ◽

Scale Model ◽

Micro Scale ◽

Mechanical Models

Soft tissue engineering applications require accurate descriptions of native and engineered tissue microstructure and their contributions to global mechanical behavior [1–6]. Moreover, micro scale based mechanical models can be used to: (1) guide tissue engineering scaffold design, (2) provide a better understanding of cellular mechanical and metabolic response to local micro-structural deformations, and (3) investigate structural changes as a function of deformation across multiple scales. We present a novel approach to automatically collect micro-architectural data (fibers overlaps, fiber connectivity, and fiber orientation) from SEM images of electrospun poly (ester urethane) urea (PEUU) to recreate statistically equivalent scaffold mechanical models. More importantly, an appropriate representative volume element (RVE) size was selected to fully capture both critical micro-scale architectural information, as well as reproducing the larger-scale directional long fiber mechanical behavior. This approach produced material models by specifying fiber overlap density, fiber orientation, and connectivity allowing the bulk mechanical response to be determined at the meso and micro scale via FEM simulations.

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Investigation of the effects of heat loss through below-grade envelope of buildings in urban areas on thermo-mechanical behaviour of geothermal piles

E3S Web of Conferences ◽

10.1051/e3sconf/202020505010 ◽

2020 ◽

Vol 205 ◽

pp. 05010

Author(s):

Maryam Saaly ◽

Pooneh Maghoul ◽

Hartmut Holländer

Keyword(s):

Heat Loss ◽

Mechanical Behaviour ◽

Urban Areas ◽

Energy Demand ◽

Heat Dissipation ◽

Mechanical Response ◽

Pile Head ◽

Thermal Cycles ◽

Head Displacement ◽

Heat Leakage

Harvesting geothermal energy through the use of thermo-active pile systems is an eco-friendly technique to provide HVAC energy demand of buildings. Mechanical behaviour of thermo-active piles is impacted by thermal cycles. Moreover, in urban areas, the temperature of the ground is higher than non-constructed areas due to the heat loss through the below-grade enclosure of buildings. This heat dissipation increases the thermal capacity of the soil and affects the mechanical response of the geothermal pile foundation subjected to thermo-mechanical loading. To investigate the effect of buildings heat loss on thermo-active piles, a numerical thermo-mechanical (TM) analysis was carried out on a proposed energy foundation system for an institutional building, the Stanley Pauley Engineering Building (SPEB) in the campus of the University of Manitoba, Winnipeg, Canada. The mechanical response of the geothermal piles to the thermal cycles with and without considering heat leakage through the basement of the SPEB is compared. Results showed that the cooling loads induced a maximum vertical pile head displacement of -1.18 mm. After 5 years operation of the system, the maximum vertical pile head displacement decreased to -1.05 mm for the case in which heat loss through the basement in considered in the models. In addition, the maximum axial load effective along the pile axis was 6% higher for the case that considers heat loss through the basement compared to the case without considering heat leakage through the building’s below-grade envelope.

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AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-1993-0009 ◽

1993 ◽

Vol 17 (2) ◽

pp. 145-160

Author(s):

P.H. Oosthuizen ◽

A. Sheriff

Keyword(s):

Heat Transfer ◽

Numerical Study ◽

Local Heat Transfer ◽

Lower Surface ◽

Local Heat ◽

Electrical Heating ◽

Temperature Profiles ◽

Measured Temperature ◽

Transfer Rates ◽

Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

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Numerical Study of the Mean and Filtered Characteristics of Turbulent Jets Impinging on Convex and Flat Surfaces Using LES

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-89211 ◽

2012 ◽

Author(s):

Adra Benhacine ◽

Zoubir Nemouchi ◽

Lyes Khezzar ◽

Nabil Kharoua

Keyword(s):

Convex Surface ◽

Numerical Study ◽

Three Dimensional ◽

Turbulent Jets ◽

Scale Model ◽

Wall Jet ◽

Potential Core ◽

Flat Surfaces ◽

Free Jet ◽

Eddy Simulation

A numerical study of a turbulent plane jet impinging on a convex surface and on a flat surface is presented, using the large eddy simulation approach and the Smagorinski-Lilly sub-grid-scale model. The effects of the wall curvature on the unsteady filtered, and the steady mean, parameters characterizing the dynamics of the wall jet are addressed in particular. In the free jet upstream of the impingement region, significant and fairly ordered velocity fluctuations, that are not turbulent in nature, are observed inside the potential core. Kelvin-Helmholtz instabilities in the shear layer between the jet and the surrounding air are detected in the form of wavy sheets of vorticity. Rolled up vortices are detached from these sheets in a more or less periodic manner, evolving into distorted three dimensional structures. Along the wall jet the Coanda effect causes a marked suction along the convex surface compared with the flat one. As a result, relatively important tangential velocities and a stretching of sporadic streamwise vortices are observed, leading to friction coefficient values on the curved wall higher than those on the flat wall.

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Fully Coupled Large Eddy Simulation of Conjugate Heat Transfer in a Ribbed Channel with a 0.1 Blockage Ratio

Energies ◽

10.3390/en14082096 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2096

Author(s):

Joon Ahn ◽

Jeong Chul Song ◽

Joon Sik Lee

Keyword(s):

Heat Transfer ◽

Gas Turbine ◽

Conjugate Heat Transfer ◽

Heat Transfer Analysis ◽

Scale Model ◽

Computational Domain ◽

Blockage Ratio ◽

Ribbed Channel ◽

Large Eddy ◽

Cooling Passage

Large eddy simulations are performed to analyze the conjugate heat transfer of turbulent flow in a ribbed channel with a heat-conducting solid wall. An immersed boundary method (IBM) is used to determine the effect of heat transfer in the solid region on that in the fluid region in a unitary computational domain. To satisfy the continuity of the heat flux at the solid–fluid interface, effective conductivity is introduced. By applying the IBM, it is possible to fully couple the convection on the fluid side and the conduction inside the solid and use a dynamic subgrid scale model in a Cartesian grid. The blockage ratio (e/H) is set at 0.1, which is typical for gas turbine blades. Through conjugate heat transfer analysis, it is confirmed that the heat transfer peak in front of the rib occurs because of the impinging of the reattached flow and not the influence of the thermal boundary condition. When the rib turbulator acts as a fin, its efficiency and effectiveness are predicted to be 98.9% and 8.32, respectively. When considering conjugate heat transfer, the total heat transfer rate is reduced by 3% compared with that of the isothermal wall. The typical Biot number at the internal cooling passage of a gas turbine is <0.1, and the use of the rib height as the characteristic length better represents the heat transfer of the rib.

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