Academic literature on the topic 'Limiting bending moment'
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Journal articles on the topic "Limiting bending moment"
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Fang, Shu Tian, Ying Zhang, and Wen Zhao Zhong. "Nonlinear Finite Element Analysis on Statically Indeterminate Prestressed Concrete Beam." Advanced Materials Research 482-484 (February 2012): 647–50. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.647.
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Embarked from the ductility theory, the bending moment amplitude modulation limiting value ductility expression which satisfies the bearing capacity requirements have been deduced，on the value of the bending moment amplitude modulation coefficient, the influence of the using stage crack width limiting value has been considered, and the suggesting formula of the bending moment amplitude modulation coefficient has been proposed. With the aid of APDL language in the ANSYS, the entire process force analysis to statically indeterminate prestressed concrete beam has been carried on, the finite element computed result and the experiment result has been confirmed, through the example drew correlation curve, confirmed with the experiment, the beam's ultimate bearing capacity has been discussed, and the plastic hinge's formation and the influence of moment redistribution to the ultimate bearing capacity has been analyzed.
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GUPTA, RAJ K., SHAM S. MALIK, J. S. BATRA, PETER O. HESS, and WERNER SCHEID. "PHENOMENOLOGY OF NUCLEI AT VERY HIGH ANGULAR MOMENTA USING PARAMETRIZED TWO-CENTER NUCLEAR SHAPES." International Journal of Modern Physics E 04, no. 04 (December 1995): 789–800. http://dx.doi.org/10.1142/s0218301395000262.
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The nuclear shapes and variation of moment of inertia with angular momentum, as well as the limiting angular momentum carried by a nucleus at its fissioning stage, are derived from the observed data of the ground-state yrast band and quadrupole deformations of these states. The necking-in of the nuclear shapes are shown to start already at J*~14+−18+. The empirical variation of moment of inertia with angular momentum is found to include the back-bending and forward-bending effects and supports the nuclear softness model of the nucleus. The fission of nuclei is shown to occur at very high angular momenta, which is different for different nuclei. The role of deformation energy is analyzed and the possibility of predicting the quadrupole deformations, or B(E2) transitions, for very high spin states is discussed. The calculations are presented for 156Dy, 158Er, and 164Hf.
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Yee, Albert G., and C. Daniel Mote. "Forces and Moments at the Knee and Boot Top: Models for an Alpine Skiing Population." Journal of Applied Biomechanics 13, no. 3 (August 1997): 373–84. http://dx.doi.org/10.1123/jab.13.3.373.
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The purpose of this study was to identify regression models to predict moments at the boot top and knee from the force components at the bindings for a sample of skiers. Six subjects skied a slalom course, first with their boots set to the least stiff setting and then with their boots set to the most stiff setting. Six load component dynamometers measured force and moment components at the toe and heel bindings. An electrogoniometer measured ankle flexion. Regression models were developed for the subject sample that predicted quasi-static moment components at the boot top and knee from measurements of ankle flexion and the quasi-static force components at the bindings. Large anterior bending moment was not necessarily accompanied by large ankle flexion, which emphasized that binding designs and standards for injury prevention must account for forces and moments at the sites of potential injury, rather than limiting consideration to boot stiffness or forces at the bindings.
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Petranović, Tamara, Antonio Mikulić, Marko Katalinić, Maro Ćorak, and Joško Parunov. "Method for Prediction of Extreme Wave Loads Based on Ship Operability Analysis Using Hindcast Wave Database." Journal of Marine Science and Engineering 9, no. 9 (September 14, 2021): 1002. http://dx.doi.org/10.3390/jmse9091002.
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The method for the prediction of extreme vertical wave bending moments on a passenger ship based on the hindcast database along the shipping route is presented. Operability analysis is performed to identify sea states when the ship is not able to normally operate and which are likely to be avoided. Closed-form expressions are used for the calculation of transfer functions of ship motions and loads. Multiple operability criteria are used and compared to the corresponding limiting values. The most probable extreme wave bending moments for the short-term sea states at discrete locations along the shipping route are calculated, and annual maximum extreme values are determined. Gumbel probability distribution is then fitted to the annual extreme values, and wave bending moments corresponding to a return period of 20 years are determined for discrete locations. The system reliability approach is used to calculate combined extreme vertical wave bending moment along the shipping route. The method is employed on the example of a passenger ship sailing across the Adriatic Sea (Split, Croatia, to Ancona, Italy). The contribution of the study is the method for the extreme values of wave loads using the hindcast wave database and accounting for ship operational restrictions.
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Becht, C. "Behavior of Pressure-Induced Discontinuity Stresses at Elevated Temperature." Journal of Pressure Vessel Technology 111, no. 3 (August 1, 1989): 322–25. http://dx.doi.org/10.1115/1.3265682.
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Conventional wisdom has been that discontinuity bending stresses at temperatures within the creep regime are self-limiting, and therefore secondary. A series of creep relaxation analyses were performed on typical discontinuities (junctions). The analyses show that, in general, discontinuity bending moment and stress due to pressure do not relax, but remain more or less constant with time. These stresses should therefore be evaluated as primary. A creep follow-up mechanism was identified that sustains the discontinuity stresses. The implications for design are discussed.
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Wiśniewski, Jan, Krzysztof Rogowski, Konrad Gumowski, and Jacek Szumbarski. "Wind tunnel comparison of four VAWT configurations to test load-limiting concept and CFD validation." Wind Energy Science 6, no. 1 (February 24, 2021): 287–94. http://dx.doi.org/10.5194/wes-6-287-2021.
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Abstract. The article describes results of experimental wind tunnel testing of four different straight-bladed vertical axis wind turbine model configurations. The experiment tested a novel concept of vertically dividing and azimuthally shifting a turbine rotor into two parts with a specific uneven height division in order to limit cycle amplitudes and average cycle values of bending moments at the bottom of the turbine shaft to increase product lifetime, especially for industrial-scale turbines. Testing reduction effects of simultaneously including a vertical gap between turbine rotor levels, increasing shaft length but also reducing aerodynamic interaction between rotor levels, has also been performed. Experiment results have shown very significant decreases of bending moment cycle amplitudes and average cycle values, for a wide range of measured wind speeds, for dual-level turbine configurations as compared to a single-level turbine configuration. The vertical spacing between levels equal to a blade's single chord length has proven to be sufficient, on laboratory scale, to limit interaction between turbine levels in order to achieve optimal reductions of tested parameters through an operating cycle shift between two position-locked rotor levels during a turbine's expected lifetime. CFD validation of maintaining the effect on industrial scale has been conducted, confirming the initial conclusions.
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Vales, Jan, Zdenek Kala, and Jindrich Melcher. "Application of Fuzzy Set Theory to the Serviceability Limit State of a Steel Beam under Bending." Applied Mechanics and Materials 769 (June 2015): 91–96. http://dx.doi.org/10.4028/www.scientific.net/amm.769.91.
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Deformations of an I-section steel beam under equal end moments are studied in this article. Initial geometric imperfection of the beam axis was introduced according to the Eurocode standard. Numerical studies have shown that the lateral deflection of slender beams under major axis bending can be relatively high. The acceptability of high values of lateral deflections within the framework of the serviceability limit state is discussed. In the next part of the paper, the limit value of maximum deflection was introduced as a fuzzy number. Fuzzy analysis of the maximum moment, which causes maximum deflection, was performed. The slenderness values of beams for which the serviceability limit state is the limiting condition for design were identified.
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REN, Zhigui, Junli WANG, Zhihong ZOU, Yanyan WANG, and Haojie ZHU. "Modeling of the limiting digging force of hydraulic excavator based on resistance characteristics." Mechanics 25, no. 5 (October 22, 2019): 357–62. http://dx.doi.org/10.5755/j01.mech.25.5.22805.
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Based on the resistance characteristics, a model of theoretical digging force was proposed in this paper, taking the tangential force, the normal force, and the bending moment into account simultaneously. Utilizing the relation among the normal resistance, the resistance moment, and the tangential resistance in practical digging process, three independent unknown quantities are transformed into only one variable. Afterwards, according to different digging patterns and complete machine limiting conditions, this research derived the constraint inequalities of the limiting digging force (LDF) and established the calculation models for LDF. Then, based on the value distribution laws of the digging resistance coefficient and the resistance moment coefficient, the calculation process and corresponding method of LDF under a given digging posture were obtained. Taking the digging resistance obtained by testing for 35 t hydraulic excavator with backhoe attachment as the reference, this paper compared the calculation results of the theoretical digging force for complete machine with those of the LDF model proposed in this research. The comparative results indicate that the LDF is consistent with the fact that the theoretical digging force is larger than or at least equal to the actual digging resistance. So, the LDF can exactly show the real limiting digging ability of the excavator more accurately. In this way, it can provide basis for mechanism optimization, structural strength design, trajectory planning, and control automation of the excavator.
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Pasini, D., D. J. Smith, and S. C. Burgess. "Structural efficiency maps for beams subjected to bending." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 217, no. 3 (July 1, 2003): 207–20. http://dx.doi.org/10.1177/146442070321700303.
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The structural efficiency of different cross-sections subjected to bending is considered in this paper. An envelope efficiency parameter, λ, is defined in terms of two shape transformers, A and 1. These transformers describe the relative ratio of the area and the second moment of area of the cross-sectional shape with respect to a rectangular envelope surrounding the shape. It is shown in a structural efficiency map that the mass efficiency of all cross-sectional shapes subjected to bending is bounded by two limiting curves. One limit curve represents cross-sections with material as far as possible from the neutral axis, the other limit curve is for cross-sections with material close to the neutral axis. The application of the map to two practical cases is also considered, together with scaling of the rectangular envelope.
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Elliott, Kim S. "Comparison of the design of prestressed concrete hollow-core floor units with Eurocode 2 and ACI 318." PCI Journal 66, no. 2 (2021): 21–57. http://dx.doi.org/10.15554/pcij66.2-01.
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A typical 1200 mm (48 in.) wide × 200 mm (8 in.) deep prestressed concrete hollow-core unit is analyzed and designed in order to make a comparison between Eurocode 2 and ACI 318-08. This includes calculations for serviceability limit state of stress and moment of resistance, ultimate moment of resistance, ultimate shear capacities, flexural stiffness (that is, for deflection), and cover to pretensioning tendons for conditions of environmental exposure and fire resistance. Concrete cylinder strength is 40 MPa (5.8 ksi), and concrete cube strength is 50 MPa (7.3 ksi). The hollow-core unit is pretensioned using seven-wire helical strands. Worked examples are presented in parallel formation according to Eurocode 2 and ACI 318. For uniformly distributed loads, the design criterion between the service moment to service moment of resistance (Ms/Msr for EC2 and Ms/Msn for ACI 318) and the ultimate design bending moment to ultimate moment of resistance (MEd/MRd for EC2 and Mu/φMn for ACI 318) is well balanced for this example. Usually the service moment is critical unless the amount of prestress is small. For EC2-1-1, flexurally uncracked shear capacity VRd,c is only limiting when the span-to-depth ratio in this example is less than about 35. For ACI 318, flexurally cracked shear capacity φVci is limiting when span-to-depth ratio is 42, showing that shear cracked in flexure will often be the governing criterion.
Dissertations / Theses on the topic "Limiting bending moment"
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Лазарєв, Іван Вікторович, Иван Викторович Лазарев, and Ivan V. Lazariev. "Розробка та вдосконалення методів розрахунку міцності елементів конструкції силових трансформаторів." Thesis, Запорізький національний технічний університет, 2016. http://eir.zntu.edu.ua/handle/123456789/887.
Full textAbstract:
Лазарєв, І.В. Розробка та вдосконалення методів розрахунку міцності елементів конструкції силових трансформаторів [Текст]: дис. … канд. техн. наук: 01.02.04 /Лазарєв Іван Вікторович. – Запоріжжя, 2016. – 243 с.UK: Створено узагальнені методи визначення критичних напружень радіальної стійкості та розрахунку на міцність при дії радіальних і осьових сил гнучкого кругового кільця круглого та прямокутного з заокругленнями кутів перерізу, яке моделює провідники обмоток трансформаторів. Визначено осьові зусилля в деформівних елементах механічної системи, утвореної двома простими осциляторами з розташованими на одній осі безінерційними пружинами і твердими тілами, звязаними паралельними стержнями, на які діють відмінні у часі зосереджені аперіодичні осьові сили, що виникають при коротких замиканнях в обмотках різних фаз трансформатора, розміщених на одному стрижні магнітної системи. Розроблено методи визначення осьових зусиль в деформівних компонентах складної механічної системи, яку утворіють обмотки та конструкція їх пресування, при дії сил, що виникають у процесі виготовлення, транспортування, та експлуатації трансформаторів. EN: Transformer winding conductors were simulated by a flexible circular ring with round and rectangular (filleted and non-filleted) cross-section. For such a ring there were created generalised methods for determining critical stresses of radial stability and for strength analysis under the action of radial an axial forces. There were determined axial internal forces in deformable elements of the mechanical system comprising two simple oscillators with inertialess springs and rigid bodies located on the same axis and connected by parallel rods with the latter being loaded by concentrated aperiodic axial forces that change in time by distinct time functions and originate in windings of different transformer phases installed on the same magnetic system leg. There were developed methods for determining axial internal forces in deformable components of a complex mechanical system comprising windings and their clamping structure under the action of forces occurring in the process of transformer manufacture, shipment and in service. RU: Разработаны обобщенные методы определения критических напряжений радиальной устойчивости и расчета прочности при действии радиальных и осевых сил гибкого кругового кольца круглого и прямоугольного с закруглениями углов сечения, которое моделирует проводники обмоток трансформаторов. Определены осевые усилия в деформируемых элементах механической системы, образованной двумя простыми осцилляторами с расположенными на одной оси безынерционными пружинами и твердыми телами, связанными параллельными стержнями, на которые действуют сосредоточенные апериодические осевые силы, которые изменяются во времени по различающимся функциям, и возникают в обмотках разных фаз трансформатора, расположенных на одном стержне магнитной системы. Разработаны методы определения осевых усилий в деформируемых компонентах сложной механической системы, которую образуют обмотки и конструкция для их прессовки, при действии сил, которые возникают в процессе изготовления, транспортирования и эксплуатации трансформаторов.
Book chapters on the topic "Limiting bending moment"
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"Combinations of Limiting Axial Force and Bending Moment for a Reinforced Concrete Section." In Principles of Reinforced Concrete Design, 204–11. CRC Press, 2014. http://dx.doi.org/10.1201/b17165-27.
Full textConference papers on the topic "Limiting bending moment"
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Liu, Shulong, Alastair Walker, and Philip Cooper. "Bending Capacity of Pipe Bends in Deepwater Conditions." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20394.
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Offshore pipeline systems commonly incorporate induction-heating formed bends along flowlines and in pipeline end termination assemblies and spools. In deepwater locations, the pipeline and bends are subjected to various combinations of external pressure, internal pressure, bending moment and temperature changes, during installation, and operation. Although there is a history of research into the limiting loads and failure modes of such bends and pipelines systems there is, as yet, no comprehensive guidance to enable the calculation of the maximum capacity under combined bending and external pressure loading. Conservative guidance is presented in DNV OS-F101 (2007) [1] that proposes increasing the pipe wall thickness to reduce the effect of external pressure collapse effects thus enabling bending formulations relevant to straight pipe to be used. This proposed approach leads to unfeasibly large wall thickness requirements in very deepwater applications. There is therefore a requirement for a method to design deepwater bends for installation and operation conditions with levels of safety comparable with those used in the design of straight sections of pipelines that does not depend on the requirement to increase the wall thickness to the extent proposed in the current DNV guidance. In this study, a nonlinear FE method using ABAQUS is proposed to evaluate the ultimate capacities of induction-heating formed bends. The method takes into account the combined effects of non-linear material properties, initial ovality, wall thinning/thickening, external or internal pressure, internal CRA cladding and temperature change on the ultimate moment capacity of the bend. The numerical model is validated by comparison with available published results. The method developed here is based on the limit state design formulations in the current DNV OS-F101 guidance.
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Clauss, Günther F., Marco Klein, Carlos Guedes Soares, and Nuno Fonseca. "Response Based Identification of Critical Wave Scenarios." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83861.
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In the last years the identification and investigation of critical wave sequences regarding offshore structure responses became one of the main topics in the ocean engineering community. Thereby the area of interest covers the entire field of application spectra at sea — from efficient and economic offshore operations in moderate sea states to reliability as well as survival in extreme wave conditions. For most cases, the focus lies on limiting criteria for the design, such as maximum global loads, maximum relative motions between two or more vessels or maximum accelerations, at which the floating structure has to operate or to survive. These criteria are typically combined with a limiting characteristic sea state (Hs, Tp) or a rogue wave. For the investigation of offshore structures as well as the identification of critical wave sequences, different approaches are available — most of them are based on linear transfer functions as it is an efficient procedure for the fast holistic evaluation. But, for some cases the linear method approach implies uncertainties due to nonlinear response behavior, in particular in extreme wave conditions. This paper presents an approach to these challenges, a response based optimization tool for critical wave sequence detection. This tool, which has been successfully introduced for the evaluation of the applicability of a multi-body system based on the linear method approach, is adjusted to a nonlinear task — the vertical bending moment of a chemical tanker in extreme wave conditions. Therefore a nonlinear strip theory solver is introduced into the optimization routine to capture the nonlinear effects on the vertical bending moment due to steep waves acting on large bow flares. The goal of the procedure is to find a worst case wave sequence for a certain critical sea state. This includes intensive numerical investigation as well as model test validation.
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Clauss, Gu¨nther F., Matthias Dudek, and Marco Klein. "Influence of Wave Group Characteristics on Loads in Severe Seas." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49940.
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The precise knowledge of loads and motions in extreme sea states is indispensable to ensure reliability and survival of ships and floating offshore structures. In the last decades, several accidents in severe weather with disastrous consequences have shown the need for further investigations. Besides the sea state behavior and the local structural loads, one key parameter for safe ship design is the vertical bending moment. Previous investigations revealed that different ship design criteria, such as bow geometry and wave board height, affect the global loads significantly. Investigations in regular waves as well as in single high waves of vessels with different bow flares and freeboard heights show that the vertical bending moment increases significantly with increasing bow flare and freeboard height. Furthermore it became apparent that critical loads and motions do not have to come along with the highest wave which results in the main question of this paper: What is the worst case scenario — the highest rogue wave or a wave group with certain frequency characteristics? Which sea states have to be taken into account for the experimental evaluation of limiting criteria? This paper presents investigations in different critical wave sequences, i.e. two real-sea registrations accompanied by results in regular waves to evaluate the influence of the encountering wave characteristics on the vertical bending moment. For the model tests in the seakeeping basin of the Technical University Berlin a segmented RoRo vessel with large bow flare has been built at a scale of 1:70 and equipped with force transducers. The paper proves that critical loads and motions depend most notably on combinations of wave height, wave group sequences, crest steepness, encountering speed and the ships target position: Even small wave heights with unfavorable wave lengths can cause a critical situation.
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Pothana, S., G. Wilkowski, S. Kalyanam, Y. Hioe, G. Hattery, and J. Martin. "Development of Secondary Stress Weighting Factor and Plastic Reduction Factor From Moment-Rotation Curves of Surface Cracked Pipe Tests." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-66033.
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In flaw evaluation criteria, the secondary stresses (displacement controlled) may have different design limits than primary stresses (load-controlled stress components). The design limits are based on elastic stress analysis. Traditionally the elastic design stresses are used in the flaw evaluation procedures. But realistically a flaw in the piping system can cause non-linear behavior due to the plasticity at the crack plane as well as in the adjacent uncracked-piping material. A Secondary Stress Weighting Factor (SSWF) was established which is the ratio of elastic-plastic moment to the elastic moment calculated through an elastic stress analysis. As long as the remote uncracked pipe stresses are below yield, the SSWF is 1.0, and if the uncracked pipe plastic stresses are above the yield stress, the SSWF reaches a limit which is called the Plastic Reduction Factor (PRF). Four-point-bend tests were conducted on pipes with varying circumferential surface-crack lengths and depths. The moment-rotation plots obtained from various pipe tests were used in the determination of PRF. A lower-bound limiting PRF can be calculated from a tensile test, but pipe systems are not uniformly loaded like a tensile specimen. The actual PRF value for a cracked pipe was shown to have a lower bound, which occurs when the test section of interest is at a uniform stress (such as the center region in a four-point pipe bend tests). When multiple plastic hinges develop in a pipe system (a “balanced system” by ASME Section III NB-3650 design rules), this gives a greater reduction to the elastically calculated stresses since there is more plasticity. It was found that the plastic reduction is less when most parts of the pipe system remains elastic, or if the crack is located in the high strength/ lower toughness pipe or welds, or if the pipe size is large enough that elastic-plastic conditions occur even for a higher toughness material. Interestingly, it was shown that the same system with different loading directions could exhibit different actual PRF values if the change in the loading direction changes how much of the pipe system experiences plastic stresses. For smaller cracks, where the bending moments are high, the actual PRF is controlled by plasticity of the uncracked pipe, which is much larger than the plasticity that occurs locally at the crack. However, for large cracks where the bending moments are lower (closer to design conditions), the plasticity at the crack is equally important to the smaller amount of plasticity in the uncracked pipe for the actual PRF. Hence the plasticity of both the uncracked pipe and at the cracked sections is important to include in the determination of actual PRF values.
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Wille, Sjoerd F., Guido L. Kuiper, and Andrei V. Metrikine. "On the Dynamic Interaction Between Drifting Level Ice and Moored Downward Conical Structures: A Critical Assessment of the Applicability of a Beam Model for the Ice." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-50120.
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Downward conical structures are believed to be an interesting concept of a floating host for oil and gas developments in deeper Arctic waters. The conical structure forces the ice to fail in bending, thereby limiting the ice loads on the structure. During the last two years, several conical structures were investigated at the Hamburg Ship Model Basin (HSVA) as part of a Joint Industry Project. This paper presents a numerical model for drifting level ice interacting with a moored downward conical structure. The goal of this development was to get insight in the key processes that are important for the interaction process between moving ice and a floating structure. The level ice is modelled as a moving Euler-Bernoulli beam, whereas the moored offshore structure is modelled as a damped mass-spring system. The ice-structure interaction process is divided into two phases. During the first phase, the ice sheet bends down due to interaction with the structure until a critical bending moment is reached at a cross-section of the beam. At this moment, the beam is assumed to fail at the critical cross-section in a perfectly brittle manner. During the second phase, a broken off block of ice is pushed further down the slope of the structure. These phases were built into one, piece-wise in time continuous model. A key result found by means of the numerical analysis of the model is that the motions of the moored floating structure do not significantly influence the bending failure process of level ice. Also the influence of the in-plane deformation and the heterogeneity of ice on the bending failure process is negligible. As a consequence, the dynamic response of the structure is for the biggest part determined by the ice failure process. Although the response of the structure can be dynamically amplified due to resonance for some particular ice velocities, no frequency locking of the ice failure onto one of the natural frequencies of the structure was observed. The model output showed qualitative agreement with the HSVA test results. It was however concluded that one-dimensional beamlike models of level ice sheets cannot accurately predict loading frequencies on downward conical moored floating structures because the ice blocks that break off are too long. Modelling level ice in two dimensions using plate theory is expected to give better results, since it takes into account the curvature of a structure and both radial and circumferential ice failure.
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Clauss, Günther F., Marco Klein, Matthias Dudek, and Miguel Onorato. "Application of Breather Solutions for the Investigation of Wave/Structure Interaction in High Steep Waves." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83244.
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During the design process of floating structures, different specifications have to be aligned such as the range of application, the warranty of economical efficiency as well as the reliability and are an inevitable integral part of the evaluation process during the design stage. The validation of the performance by means of model tests in terms of sea state behavior and the associated local and global structural loads are an important milestone within this process. Therefore it is necessary to determine an adequate test procedure which covers all essential areas of interest. Thereby one field of interest are limiting criteria of the design such as maximum local and global loads as well as maximum accelerations due to the impact of extraordinarily high waves, at which the floating structure has to survive. Different alternatives are available to conduct model tests in high, steep waves — transient wave packages, regular waves, irregular waves with random phases or more sophisticated deterministic tailored irregular wave sequences such as reproductions from numerical simulations and real-world measurements. This paper introduces a new approach for the systematic investigation of wave/structure interaction in high, steep waves. Exact solutions of the nonlinear Schrodinger equation — the so called breather solutions — are implemented for the generation of extraordinarily high waves. Three types of breather solutions are investigated in the seakeeping basin and to cover the full range of interest, each solution has been used to generate freak waves at certain frequencies. To evaluate the applicability of breather solutions for model tests two types of ships — a LNG Carrier and a Chemical Tanker — are investigated in the seakeeping basin. The ships are segmented and connected with strain gauges to detect the vertical wave bending moment. Furthermore, green water probes are installed on deck to evaluate the local impact on the bow of the freak waves. The obtained results are compared to investigations in regular waves with certain frequency and steepness as well as in real-world freak wave reproductions.
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Liu, M. "Subsea Pipeline Lateral Buckling Design: Strain Concentration or Strain Reduction Factors." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61200.
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Strain based design is normally applied for HPHT pipelines when the conventional stress based method becomes impractical. In addition to a design safety factor, a strain concentration factor is typically incorporated in the lateral buckling assessment to account for non-uniform stiffness or plastic bending moment due to geometry and material strength mismatch between adjacent pipe joints. Increased strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the strain concentration factor is examined. The local buckling behaviour is evaluated in relation to strain concentration. Global strain reduction and evolution against buckling is analysed with respect to varying joint mismatch level derived according to a structural reliability analysis. The concept of a strain reduction factor due to mismatch is developed and proposed based on the global strain capacity reduction with reference to the uniform configuration. It is demonstrated that the strain reduction factor is a unique characteristic parameter. As opposed to strain concentrations it is an invariant insensitive to evaluation methods and the design strain demand level, hence more representative as a limiting design metric to maintain the safety margin. The use of the strain reduction factor is thus put forward in strain based lateral buckling design as an alternative to using the strain concentration factor. The method for obtaining the strain reduction factor and its application is developed. The rationale for its introduction is outlined and some of its benefits are established. The discernible difference and scenarios for application of either factors are discussed, including low and high cycle fatigue, linearity and stress concentration (SNCF from SCF for welds), ECA and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of FE analyses are performed for a pipe-in-pipe configuration in a case study.
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Sollund, Ha˚var, Knut Vedeld, and Olav Aamlid. "Advanced Lateral Stability Analyses for Lightweight Pipelines on Clay: A Case Study." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20990.
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In 2007 DNV issued the new recommended practice DNV-RP-F109 On-Bottom Stability Design of Submarine Pipelines which replaced RP-E305 from 1988 with the same title. The new DNV-RP-F109 describes three different design approaches; full dynamic analysis, absolute static stability, and the generalized method with design curves for virtually stable pipes (allowing up to 0.5 diameters lateral displacement) and for up to 10 pipe diameters displacement in an extreme storm condition. DNV-RP-F109 recommends limiting the sum of the lateral displacement in the temporary condition and during operation to 10 diameters. For larger displacements one should perform a full dynamic analysis and special considerations with respect to bending and fatigue should be made. This paper is concerned with the consequences of exceeding the 10-diameter displacement criterion described in DNV-RP-F109, and how to use different methodologies in accordance with DNV-RP-F109 to ensure limited lateral displacements, acceptable environmental loads/strains and limited/acceptable fatigue damage accumulation. The methodologies covered in this paper include advanced assessments of passive resistance in soil, and account for increased vertical penetration due to laying and lateral fixation of the pipe at regular intervals. For the laterally restricted pipe, studies on reaction forces and reaction moments are made in addition to fatigue estimations at the points of maximum local longitudinal stress. Variations in environmental conditions, soil conditions and levels of effective axial force have also been considered.
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Alnuaimi, Mohammed, Abdulaziz BuAbdulla, Tarcísio Silva, Sumaya Altamimi, Dong-Wook Lee, and Mohamed Al Teneiji. "Active Vibration Control of Piezoelectric Beam Using the PID Controller." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-70960.
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Abstract Vibration control using piezoelectric materials has been widely investigated over the past decades. Particularly, active controllers achieve greater vibration control over wider frequency ranges than other vibration control techniques. Active controllers make use of sensors, actuators, and control laws. While most researchers focus on improving the control law, investigations on the optimal placement of sensors and actuators remain much less explored. This work presents a simple and quick methodology to obtain the optimal placement of piezoelectric sensors and actuators on different electromechanically coupled systems, without using classical beam or plate structures or limiting assumptions (symmetrical bending, linear strain, etc.). Optimal placement of sensors and actuators is performed based upon two criteria: i) varying the number of piezoelectric layers used for sensing and actuation and ii) varying the position over the structure’s thickness. Each criterion (i and ii) is presented and discussed in a different study case. Results show that as the number of piezoelectric layers increases, vibrations are controlled more efficiently. However, stacking several piezoelectric materials is not easily feasible in practice, leading to a tradeoff between reducing vibrations (using more layers) and ease of assembly. As of criterion ii), optimal placement of piezoelectric sensors and actuators is the farthest possible from the neutral line since sensors generate larger signal output (increased sensor gain), and actuators apply larger momentum on the system reducing more vibrations.
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Huo, Xiaotong, Shawn Kenny, Amgad Hussein, and Michael Martens. "Evaluation of Back-Beveled and Counterbore-Tapered Joints in Energy Pipelines." In 2016 11th International Pipeline Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ipc2016-64390.
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Wall thickness transition joints are used to connect energy pipeline segments; such as straight pipe to fittings with different wall thicknesses. The transition joint may be subject to axial forces and bending moments that may result in a stress concentration across the transition weld and may exceed stress based design criteria. Current engineering practices, such as CSA Z662, ASME B31.4, and ASME B31.8, recommend the use of back-bevel transition welded connections. An alternative transition weld configuration is the counterbore-taper design that is intended to reduce the stress concentration across the transition. In this study, the relative mechanical performance of these two transition design options (i.e., back-bevel and counterbore-taper) is examined with respect to the limiting burst pressure and effect of stress concentrations due to applied loads. The assessment is conducted through numerical parameter study using 3D continuum finite element methods. The numerical modelling procedures are developed using Abaqus/Standard. The performance of continuum brick elements (C3D8I, C3D8RH, C3D20R) and shell element (S4R) are evaluated. The continuum brick element (C3D8RI) was the most effective in terms of computational requirements and predictive qualities. The burst pressure limits of the transition weld designs were evaluated through a parameter study examining the significance of pipe diameter to wall thickness ratio (D/t), wall thickness mismatch ratio (t2/t1), material Grade 415 and Grade 483 and end-cap boundary condition effects. The limit load analysis indicated the burst pressure was effectively the same for both transition weld designs. The effect of pipe diameter, D/t, t2/t1, and counterbore length on the stress concentration factor, for each transition weld design, was also assessed. The results demonstrate the improved performance of the counterbore-taper weld transition; relative to the back-bevel design as recommended by current practice, through the relative decrease in the stress concentration factor. The minimum counterbore length was found to be consistent with company recommended practices and related to the pipe diameter and wall thickness mismatch.