Journal articles on the topic 'Load and structure nonlinearities'
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1
Kim, A. Yu, S. V. Polnikov, and M. F. Amoyan. "Features of Accounting for Geometric and Physical Nonlinearities in Long-Span Pneumatic Membrane Systems." Herald of Dagestan State Technical University. Technical Sciences 49, no. 4 (February 9, 2023): 152–61. http://dx.doi.org/10.21822/2073-6185-2022-49-4-152-161.
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Objective. The purpose of the study is to substantiate the need to take into account the geometric and physical nonlinearities in large-span membrane-pneumatic systems.Method. The study is based on the application of the parameter variation method; method of successive loadings; the iterative method of parameter increments using the third Euler-Cauchy numerical procedure or the Runge-Kutta method of a higher order of accuracy.Result. It has been established that the geometric non-linearity can be from 5 to 10% if the structure has a small or medium span, and the load on the structure is not very large, especially when it comes to section load. If the span of the structure is 120150 meters, and the load and deflections are large enough, then the geometric nonlinearity can be 20% or more. It was revealed that the physical nonlinearity, which we took into account by the standard Euler-Cauchy procedure of the third order of accuracy, with a large span of the structure and a large load is approximately 13-21%, and the part of the physical nonlinearity of the air pumped between the hermetic membranes of the structure is determined using an improved formula Euler-Cauchy with the number of iterations 20-25, i.e. "aftereffect", according to the results of the study, ranges from 2-7%.Conclusion. A structure consisting of light metal structures can be erected within a few months on a finished pile or strip foundation. Such structures can easily withstand many types of dynamic loads, namely wind, seismic, vibration, and are one-third cheaper than buildings made from traditional materials.
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Neville, Robin M., Rainer M. J. Groh, Alberto Pirrera, and Mark Schenk. "Beyond the fold: experimentally traversing limit points in nonlinear structures." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2233 (January 2020): 20190576. http://dx.doi.org/10.1098/rspa.2019.0576.
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Recent years have seen a paradigm shift regarding the role of nonlinearities and elastic instabilities in engineering science and applied physics. Traditionally viewed as unwanted aberrations, when controlled to be reversible and well behaved, nonlinearity can enable novel functionalities, such as shape adaptation and energy harvesting. The analysis and design of novel structures that exploit nonlinearities and instabilities have, in part, been facilitated by advances in numerical continuation techniques. An experimental analogue of numerical continuation, on the other hand, has remained elusive. Traditional quasi-static experimental methods control the displacement or force at one or more load-introduction points over the test specimen. This approach fails at limit points in the control parameter, as the immediate equilibrium beyond limit points is statically unstable, causing the structure to snap to a different equilibrium. Here, we propose a quasi-static experimental path-following method that can continue along stable and unstable equilibria, and traverse limit points. In addition to controlling the displacement at the main load-introduction point, the technique relies on overall shape control of the structure using additional actuators and sensors. The proposed experimental method enables extended testing of the emerging class of structures that exploit nonlinearities and instabilities for novel functionality.
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Klockiewicz, Zbyszko, Mikołaj Spadło, and Grzegorz Ślaski. "The influence of suspension nonlinearities on fatigue assessment of vehicle structure." IOP Conference Series: Materials Science and Engineering 1199, no. 1 (November 1, 2021): 012074. http://dx.doi.org/10.1088/1757-899x/1199/1/012074.
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Abstract Load spectrums for the fatigue analysis were created using suspension responses generated in a simulation of vehicle and suspension vertical dynamics nonlinear model for different conditions of vehicle use. The next stage presented was the use of finite element method and analysis of obtained stresses with its transformation to a set of cycles that are used in the determination of fatigue characteristics. The qualitative and quantitative analysis of the stresses field in the vehicle structure and suspension elements was done and later the influence of suspension responses on the fatigue assessment for most loaded parts of suspension and vehicle structure. Lastly conclusions were drawn from the results describing qualitative and quantitative influence of different road class and load conditions on fatigue assessment of vehicle structure and suspension components. Conclusion on the proposed and used methodology also was drawn.
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Ramazani, Mohammad Reza, Philip Sewell, Siamak Noroozi, Mehran Koohgilani, and Bob Cripps. "Sensor Optimisation for in-Service Load Measurement of a Large Composite Panel under Small Displacement." Applied Mechanics and Materials 248 (December 2012): 153–61. http://dx.doi.org/10.4028/www.scientific.net/amm.248.153.
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Current methods to estimate the behaviour of composite structures are based on trial and error or oversimplification. Normally the nonlinearities in these structures are neglected and in order to cover this inadequacy in design of composite structures, an overestimate safety factor is used. These methods are often conservative and leading to the heavier structures. A novel technique employs Artificial Neural Network (ANN) as an inverse problem approach to estimate the pressure loads experienced by marine structures applied on a composite marine panel from the strain measurements. This can be used in real-time to provide an accurate load history for a marine structure without requiring knowledge of the material properties or component geometry. It is proposed that the ANN methodology, with further research and development, could be utilised for the quantification of in-service, transient loads in real-time acting on the craft from the craft’s structural response (strain response to load). However, to fully evaluate this methodology for load monitoring of marine structures further research and development is required such as sensor optimisation. The number of sensors should be minimised to reduce the time to train the system, cost and weight. This study investigates the number of sensors required for accurate load estimation by optimising the method.
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Pieńko, Michał. "The analysis of the deformation of single node in a modular scaffolding system." Budownictwo i Architektura 13, no. 2 (June 11, 2014): 349–56. http://dx.doi.org/10.35784/bud-arch.1914.
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The increasingly complex engineering structures of scaffoldings require optimal designing in terms of safety, economy and erection. This approach requires detailed knowledge of the static-strength properties of elements, as well as knowledge of their interconnections. The paper deals with the laboratory tests of deformations in modular scaffolding nodes for the following loads: torque of the ledger, shearing and bending in the horizontal plane. The original grip was used in the study, which allows to load the node with aforementioned loads. The result of research is a description of the deformation of the nodes and the load-displacement graphs. The studies presented in the paper indicate that graphs are repeatable, which is not obvious in the case of nodes assembled manually. This means that it can be used as a basis for the verification of non-linear numerical analysis, which will have to take into account such issues as the material nonlinearities, geometric nonlinearities, contact and friction.
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Mo, O., and T. Moan. "Environmental Load Effect Analysis of Guyed Towers." Journal of Energy Resources Technology 107, no. 1 (March 1, 1985): 24–33. http://dx.doi.org/10.1115/1.3231158.
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A general method for dynamic load effect analysis of slender offshore structures subjected to short crested random waves, current and wind, is given. The structure is represented by a three-dimensional space frame model utilizing dash-pots and linear or nonlinear spring elements to represent guy lines and coupling between structure and foundation. The component mode synthesis formulation is adopted for reduction of the number of degrees of freedom. The hydrodynamic forces are computed by Morison’s equation, accounting for finite wave elevation, directionality, and relative fluid-structure motion. Various kinematic models for the fluid field in the splashing zone are compared. To get a reasonable representation of nonlinearities in the loading and the structural model, a Monte Carlo approach is adopted. Starting with simulated samples of the random fluid field and wind forces, time series of structural responses are found by numerical time integration utilizing the Newmark β-family of time integration operators. Numerical results for a guyed tower at 450-m water depth are presented. The statistical uncertainties associated with the stochastic time domain simulations are discussed. A significant discrepancy is found between linearized frequency domain solutions and the present nonlinear time domain formulation. The importance of an adequate representation of superharmonic responses is particularly discussed. The differences in results due to various solution methods are found to vary significantly with sea-state conditions.
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Mukhlas, Nurul 'Azizah, Noor Irza Mohd Zaki, Mohd Khairi Abu Husain, and Gholamhossein Najafian. "Comparison of Extreme Surface Elevation for Linear and Nonlinear Random Wave Theory for Offshore Structures." MATEC Web of Conferences 203 (2018): 01021. http://dx.doi.org/10.1051/matecconf/201820301021.
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For offshore structural design, the load due to wind-generated random waves is usually the most important source of loading. While these structures can be designed by exposing them to extreme regular waves (100-year design wave), it is much more satisfactory to use a probabilistic approach to account for the inherent randomness of the wave loading. This method allows the statistical properties of the loads and structural responses to be determined, which is essential for the risk-based assessment of these structures. It has been recognized that the simplest wave generation is by using linear random wave theory. However, there is some limitation on its application as some of the nonlinearities cannot be explained when higher order terms are excluded and lead to underestimating of 100-year wave height. In this paper, the contribution of nonlinearities based on the second order wave theory was considered and being tested at a variety of sea state condition from low, moderate to high. Hence, it was proven that the contribution of nonlinearities gives significant impact the prediction of 100-year wave's design as it provides a higher prediction compared to linear wave theory.
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Padovan, J., R. Moscarello, J. Stafford, and F. Tabaddor. "Pantographing Self-Adaptive Gap Elements." Tire Science and Technology 13, no. 3 (July 1, 1985): 154–82. http://dx.doi.org/10.2346/1.2150993.
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Abstract A pantographing self-adaptive gap element type contact strategy is presented. Due to the manner of its formulation, it can handle large deformations in the contact zone, contact initiation in a structure that has either positive or indefinite stiffness characteristics, kinematic and material nonlinearities, as well as self-adaptive load (time) stepping. Contact in pre- and post-buckling structures can be treated in this context. Several illustrative benchmark problems are given. These include coming into contact with a fiat surface, and involve large deformation kinematics and inelastic behavior as well as pre- and post-buckling stiffness characteristics.
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Zhang, Xiaotian, Ruiqing Wang, Xiaogang Li, Chengyang Lu, Zhengkang Wang, and Wenlong Wang. "Dynamics Modeling and Characterization of Sunk Screw Connection Structure in Small Rockets." Aerospace 9, no. 11 (October 25, 2022): 648. http://dx.doi.org/10.3390/aerospace9110648.
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Bolted flange joints are widely used in engineering structures. Sunk screw connection structures commonly used in small rockets and missiles exhibit significant nonlinear characteristics when subjected to forces. In this article, a study of the dynamic characteristics of sunk screw connection is conducted. A 3-dof trilinear dynamic model is proposed, based on the study of the stiffness characteristics of the connection structure and considering contact nonlinearities. The connection surface is simplified as two axial trilinear springs and a lateral linear spring. The motion of the system can be divided into nine regions by the turning point of the trilinear springs. So that the motion of the system in each region can be completely resolved, the dynamic characteristics of the 3-dof trilinear system under impulse load and simple harmonic load are studied by means of semi-numerical analytical method. It is found that the response frequency of the system remains unchanged under a small impulse load, and the response can be obtained by approximate analytical expressions. When the impulse load is large, the response frequency is fluctuant, which reflects the sensitivity of the nonlinear system to the magnitude of impulse load. Under the simple harmonic excitation of bending moment, the response frequency curve of the system presents good single peak characteristics when the excitation amplitude is small. When the amplitude is large, the peak frequency of the system shifts, and the phenomenon of multi-peak resonance is shown in a certain range.
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An, Chao, Chao Yang, Changchuan Xie, and Yang Meng. "Gust Load Alleviation including Geometric Nonlinearities Based on Dynamic Linearization of Structural ROM." International Journal of Aerospace Engineering 2019 (May 12, 2019): 1–20. http://dx.doi.org/10.1155/2019/3207912.
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This paper describes a framework for an active control technique applied to gust load alleviation (GLA) of a flexible wing, including geometric nonlinearities. Nonlinear structure reduced order model (ROM) and nonplanar double-lattice method (DLM) are used for structural and aerodynamic modeling. The structural modeling method presented herein describes stiffness nonlinearities in polynomial formulation. Nonlinear stiffness can be derived by stepwise regression. Inertia terms are constant with linear approximation. Boundary conditions and kernel functions in the nonplanar DLM are determined by structural deformation to reflect a nonlinear effect. However, the governing equation is still linear. A state-space equation is established in a dynamic linearized system around the prescribed static equilibrium state after nonlinear static aeroelastic analysis. Gust response analysis can be conducted subsequently. For GLA analysis, a classic proportional-integral-derivative (PID) controller treats a servo as an actuator and acceleration as the feedback signal. Moreover, a wind tunnel test has been completed and the effectiveness of the control technology is validated. A remote-controlled (RC) model servo is chosen in the wind tunnel test. Numerical simulation results of gust response analysis reach agreement with test results. Furthermore, the control system gives GLA efficacy of vertical acceleration and root bending moment with the reduction rate being over 20%. The method described in this paper is suitable for gust response analysis and control strategy design for large flexible wings.
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Carpinteri, Alberto, Giuseppe Lacidogna, and Domenico Scaramozzino. "Geometrically nonlinear behavior of lattice domes coupled with local Eulerian instability." Curved and Layered Structures 7, no. 1 (December 31, 2020): 247–60. http://dx.doi.org/10.1515/cls-2020-0020.
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AbstractStructural analysis is an intricate subject when nonlinearities occur. They make the structural behavior complex and may have important consequences in the design choice as well. Especially for lattice domes, as snap-through phenomena and local Eulerian instabilities generally affect the structural response, linear analysis is not enough. In this paper, a semi-analytical formulation is used in order to study the geometrically nonlinear behavior of lattice domes subject to vertical loads. The formulation is derived from the equilibrium equations written in the deformed configuration, considering large displacements and taking also into account local buckling conditions. The resulted system of equations, being strongly nonlinear, has been solved by means of a numerical procedure, based on a mixed load-displacement control scheme, leading to the evaluation of the complete equilibrium path. The influence of geometrical parameters on the critical load multiplier and shape of the load-displacement curve is also discussed. In particular, a complex equilibrium path for a sixteen-member five-node lattice structure is analyzed, which is characterized by several branches which can generate ‘snapping’ conditions.
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Carpinteri, Alberto, Giuseppe Lacidogna, and Domenico Scaramozzino. "Geometrically nonlinear behavior of lattice domes coupled with local Eulerian instability." Curved and Layered Structures 7, no. 1 (December 31, 2020): 247–60. http://dx.doi.org/10.1515/cls-2020-0020.
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AbstractStructural analysis is an intricate subject when nonlinearities occur. They make the structural behavior complex and may have important consequences in the design choice as well. Especially for lattice domes, as snap-through phenomena and local Eulerian instabilities generally affect the structural response, linear analysis is not enough. In this paper, a semi-analytical formulation is used in order to study the geometrically nonlinear behavior of lattice domes subject to vertical loads. The formulation is derived from the equilibrium equations written in the deformed configuration, considering large displacements and taking also into account local buckling conditions. The resulted system of equations, being strongly nonlinear, has been solved by means of a numerical procedure, based on a mixed load-displacement control scheme, leading to the evaluation of the complete equilibrium path. The influence of geometrical parameters on the critical load multiplier and shape of the load-displacement curve is also discussed. In particular, a complex equilibrium path for a sixteen-member five-node lattice structure is analyzed, which is characterized by several branches which can generate ‘snapping’ conditions.
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Rossini, Mayara Bortolotti, and Maurício Vicente Donadon. "Numerical and Experimental Analysis of Adhesively Bonded Stiffened Panels Subjected to In-Plane Compression Loading." Advanced Materials Research 1135 (January 2016): 140–52. http://dx.doi.org/10.4028/www.scientific.net/amr.1135.140.
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This paper presents a numerical and experimental study on the pre and post-buckling behavior of adhesively bonded stiffened panels subjected to in-plane compression loading. An experimental programme was carried out to characterize the buckling load, buckling modes and collapse loads. The mechanical tests were performed in the Aerospace Structures Laboratory at ITA. The structural performance of the bonded stiffened panels in terms of buckling and collapse loads was compared to conventional riveted stiffened panels. Finite element models accounting for material, geometrical nonlinearities as well as progressive failure in the bonded interface were developed and validated experimentally. A good agreement between numerical and experimental results was found for buckling and collapse loads through number of semi-waves and measured strains. The experimental and numerical results indicate a superior performance in buckling load and failure load of the bonded stiffened panels over the riveted panels. Both numerical and experimental results showed that the bonded stiffened panels had over 19% higher failure load in comparison with the riveted panels.
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Hu, Da Lin, Kai Jiang, Qi Xin Sun, and Lin Han. "Ultimate Bearing Capacity Analysis of Long-Span Continuous Stone Arch Bridge." Applied Mechanics and Materials 71-78 (July 2011): 3800–3805. http://dx.doi.org/10.4028/www.scientific.net/amm.71-78.3800.
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In the past 50 years, many long-span continuous stone arch bridges have been built in China. Analysis of mechanical performances and load capacities of long-span continuous stone arch bridges has important significances for the safety assessment of the similar bridges. 3D elastoplastic finite element method is employed to analyze ultimate bearing capacity of a three-span arch bridge with sandstone masonry in this paper. The characteristics of structural geometric and material nonlinearities and cracking and crushing of the masonry are taken into account. Compared with single-span arch bridge, both the coaction of spandrel structure and main arch and the influence of loading arrangements on ultimate bearing capacity is analyzed. The failure characteristics of the structure under the ultimate load are also introduced. The analysis results and conclusions can be referenced for the safety assessment of similar bridges.
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Jiao, Jialong, Yong Jiang, Hao Zhang, Chengjun Li, and Chaohe Chen. "Predictions of Ship Extreme Hydroelastic Load Responses in Harsh Irregular Waves and Hull Girder Ultimate Strength Assessment." Applied Sciences 9, no. 2 (January 10, 2019): 240. http://dx.doi.org/10.3390/app9020240.
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In this paper, the hydroelastic motion and load responses of a large flexible ship sailing in irregular seaways are predicted and the hull girder ultimate strength is subsequently evaluated. A three-dimensional time-domain nonlinear hydroelasticity theory is developed where the included nonlinearities are those arising from incident wave force, hydrostatic restoring force and slamming loads. The hull girder structure is simplified as a slender Timoshenko beam and fully coupled with the hydrodynamic model in a time domain. Segmented model towing-tank tests are then conducted to validate the proposed hydroelasticity theory. In addition, short-term and long-term predictions of ship responses in irregular seaways are conducted with the help of the developed hydroelastic code in order to determine the extreme design loads. Finally, a simplified strength-check equation is proposed, which will provide significant reference and convenience for ship design and evaluation. The hull girder ultimate strength is assessed by both the improved Rule approach and direct calculation.
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Sayed-Ahmed, Ezzeldin Y., and Nigel G. Shrive. "Design of face-shell bedded hollow masonry subject to concentrated loads." Canadian Journal of Civil Engineering 23, no. 1 (February 1, 1996): 98–106. http://dx.doi.org/10.1139/l96-010.
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Many parameters affect the behaviour and failure of face-shell bedded hollow masonry subject to concentrated load. Detailed study of these parameters is needed to develop realistic design rules for this situation. The effects of loaded length and wall dimensions on capacity of the face-shell bedded hollow masonry subject to concentrated load are studied; the effect of mortar joint strength is also evaluated. The current design detail of filling some of the blocks under the concentrated load with grout is reviewed. The study was performed with a nonlinear elastoplastic finite element model that takes into account geometric and material nonlinearities as well as damage due to progressive cracking. The methodology, when combined with substructuring, allows analysis of substantially larger walls than would more typical three-dimensional analyses. The results indicate that the length of the loading plate is the significant parameter for load capacity. A possible design equation for plain hollow masonry subject to concentrated loads, concentric across the width of the wall, is provided. Adjustments could be made given the precise loading detail specified. Improvement details are explained. Key words: masonry, hollow concrete masonry, finite element modelling, cracking, failure, strength-enhancement factor, concentrated loads.
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Deniziak, Patryk, and Karol Winkelmann. "Influence of nonlinearities on the efficiency and accuracy of FEM calculations on the example of a steel build-up thin-walled column." MATEC Web of Conferences 219 (2018): 02010. http://dx.doi.org/10.1051/matecconf/201821902010.
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Due to the increase of computing capabilities of standard processing units, it is possible to perform complex analyses, considering a number of nonlinearities, such as geometric, material and boundary (contact) even on personal computers. In the paper, the authors have analysed the efficiency and accuracy of standard PC’s FEM calculations performed in Abaqus CAE 2017 software on the example of a critical load assessment of a thin-walled steel column element with selected nonlinearities. A cross-section shape of a built-up column used by an international steel structures manufacturer was adopted. The analysis serves to check the behavior of their product. Several types of FEM analysis, strictly based on the EN standard regulations were performed. In turn, the relation of computational time to the adopted analysis type was obtained. Moreover, the produced load values in different types of independent calculation were compared and analysed. A possible future development in the field, based mainly on full-scale experimental tests, was also highlighted.
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Suzuki, Toshiro, Toshiyuki Ogawa, and Kikuo Ikarashi. "Elasto-Plastic Buckling Analysis of Rigidly Jointed Single Layer Reticulated Domes." International Journal of Space Structures 7, no. 4 (December 1992): 363–68. http://dx.doi.org/10.1177/026635119200700412.
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The purpose of this paper is to examine the elasto-plastic buckling behaviours of a rigidly jointed single layer reticulated dome to a static load applied at its centre. The numerical formulation is based on the incremental finite element method incorporating geometric and material nonlinearities. The buckling behaviour is investigated in regard to the shell geometry, the member property and the material property. The nonlinear buckling load and the deformation of the dome are discussed based on parametric study.
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Vecchio, F. J., and S. Balopoulou. "On the nonlinear behaviour of reinforced concrete frames." Canadian Journal of Civil Engineering 17, no. 5 (October 1, 1990): 698–704. http://dx.doi.org/10.1139/l90-083.
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An experimental investigation is described in which a large-scale reinforced concrete plane frame is tested to study factors contributing to its nonlinear behaviour under short-term loading conditions. The test results indicate that frame behaviour can be significantly affected by second-order influences such as material nonlinearities, geometric nonlinearities, concrete shrinkage, tension stiffening effects, shear deformations, and membrane action. A nonlinear frame analysis procedure, previously developed taking these mechanisms into account, is shown to accurately predict most aspects of behaviour, including deflection response, ultimate load capacity, and failure mechansim. Aspects of the theoretical modelling which are in need of further improvement are also identified. Key words: analysis, behaviour, deformation, frame, large scale, nonlinear, reinforced concrete, strength, test.
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Shuai, Cheng, and Song Jian. "Extended state observer based control scheme for the A-EHPS with load pressure estimation." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 231, no. 13 (February 12, 2017): 1858–73. http://dx.doi.org/10.1177/0954407016686495.
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The accumulative electro-hydraulic power steering system (A-EHPS) is essentially an electro-hydraulic servo system with high parametric uncertainties and nonlinearities that are caused by the characteristics of the hydraulic system. The throttle structure in the steering gear and the on-way resistance increase the control difficulty of the plant. This paper reports the construction of a mathematical model that contains the throttle structure and the on-way resistance for the A-EHPS system. Furthermore, an extended state observer and a sliding mode controller are synthesized to estimate uncertain nonlinear components and improve the quality of control in the A-EHPS. The uncertain nonlinear parts contain important information on the high-pressure chamber’s load pressure, which cannot be directly measured. That is, the proposed control scheme can be used to estimate steering resistance, which is essential for the top-layer control strategy. Simulations are performed to validate the control performance and the parameter design principle of the proposed extended state observer scheme. The scheme is then implemented in an actual system, and its robustness advantages over traditional controllers are verified.
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Zabojszcza, Paweł, Urszula Radoń, and Paulina Obara. "Impact of single-layer dome modelling on the critical load capacity." MATEC Web of Conferences 219 (2018): 02017. http://dx.doi.org/10.1051/matecconf/201821902017.
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In the study an attempt was made to evaluate the effect produced by the modelling of the single-layer lattice dome on its critical load capacity. The modelling concerned the means of connecting bars in a node, bars of the lattice dome, and the effect of geometric imperfections. Taking steel covers, two basic means of modelling of how bars are connected in the node can be distinguished, namely pin and rigid joints. In the study, the pin joint was SBP-1 type connector, whereas the rigid joint - WABI-1 connector. In the description of bars, truss and frame elements were employed. Each element accounted for geometric nonlinearities in the Lagrange description. Regarding a frame element, the physical relationships represented the elastic behaviour of the structure with the use of the Hooke’s law. With respect to the compression truss elements, a nonlinear relationship resulting from experimental investigations was additionally employed. Stability analysis of the structure was performed by means of the Finite Element Method using Abaqus and Robot Structural Analysis software. In order to obtain the load-displacement relations, the Riks arc length method was used. The analysis was focused on global modes of stability loss due to snap-through and bifurcation.
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Savino, Pierclaudio, Marco Gherlone, Francesco Tondolo, and Rita Greco. "Shape-Sensing of Beam Elements Undergoing Material Nonlinearities." Sensors 21, no. 2 (January 13, 2021): 528. http://dx.doi.org/10.3390/s21020528.
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The use of in situ strain measurements to reconstruct the deformed shape of structures is a key technology for real-time monitoring. A particularly promising, versatile and computationally efficient method is the inverse finite element method (iFEM), which can be used to reconstruct the displacement field of beam elements, plate and shell structures from some discrete strain measurements. The iFEM does not require the knowledge of the material properties. Nevertheless, it has always been applied to structures with linear material constitutive behavior. In the present work, advances are proposed to use the method also for concrete structures in civil engineering field such as bridges normally characterized by material nonlinearities due to the behavior of both steel and concrete. The effectiveness of iFEM, for simply supported reinforced concrete beam and continuous beams with load conditions that determine the yielding of reinforcing steel, is studied. In order to assess the influence on displacements and strains reconstructions, different measurement stations and mesh configurations are considered. Hybrid procedures employing iFEM analysis supported by bending moment-curvature relationship are proposed in case of lack of input data in plastic zones. The reliability of the results obtained is tested and commented on to highlight the effectiveness of the approach.
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Gioncu, Victor, and Nicolae Balut. "Instability Behaviour of Single Layer Reticulated Shells." International Journal of Space Structures 7, no. 4 (December 1992): 243–52. http://dx.doi.org/10.1177/026635119200700402.
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The aim of the present paper is to draw the attention of the designers (often fascinated by the beauty of static analysis) to the essential factors influencing the behaviour of single-layer reticulated shells. These can be classified into geometrical factors (shell geometry and mesh density) and behaviour factors (geometrical and material nonlinearities, forms of instability, imperfections, stiffness of joints, load distribution). The analysis and design conceptions (equilibrium bifurcation or limitation, continuum or discrete structure) are discussed in the final part of the paper. It was tried to present all aspects in the simplest possible form, emphasizing the essence of the investigated phenomena.
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Liu, Yi, and J. L. Dawe. "Analytical modeling of masonry load-bearing walls." Canadian Journal of Civil Engineering 30, no. 5 (October 1, 2003): 795–806. http://dx.doi.org/10.1139/l03-036.
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An analytical technique was developed and encoded for computer application to study the behaviour of concrete masonry load-bearing walls under various loading conditions. Both geometrical and material nonlinearities to account for the moment magnification effect and the degradation of material stiffness are included in the development. Effects of vertical reinforcing steel, masonry tensile cracking, and compressive crushing are included directly in the momentcurvature relationship, which is used in the determination of element stiffnesses at successive load increments. A parametric study was conducted following verification of the analytical model by comparing results with experimental test data. Effective flexural rigidity (EIeff) values at failure were obtained analytically and compared with values suggested in the Canadian masonry code CSA-S304.1-M94. It was concluded that CSA-S304.1-M94 tends to underestimate EIeff values for reinforced walls and thus leads to a conservative design over a range of parameters. Based on approximately 500 computer model tests, a lower bound bilinear limit for the effective rigidity of reinforced masonry walls was established. This limit is believed to provide an accurate and realistic estimate of EIeff.Key words: walls, load bearing, masonry, analytical, nonlinear, rigidity, stressstrain, momentcurvature.
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Li, Jiehao, Junzheng Wang, Shoukun Wang, Hui Peng, Bomeng Wang, Wen Qi, Longbin Zhang, and Hang Su. "Parallel structure of six wheel-legged robot trajectory tracking control with heavy payload under uncertain physical interaction." Assembly Automation 40, no. 5 (July 6, 2020): 675–87. http://dx.doi.org/10.1108/aa-08-2019-0148.
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Purpose This paper aims on the trajectory tracking of the developed six wheel-legged robot with heavy load conditions under uncertain physical interaction. The accuracy of trajectory tracking and stable operation with heavy load are the main challenges of parallel mechanism for wheel-legged robots, especially in complex road conditions. To guarantee the tracking performance in an uncertain environment, the disturbances, including the internal friction, external environment interaction, should be considered in the practical robot system. Design/methodology/approach In this paper, a fuzzy approximation-based model predictive tracking scheme (FMPC) for reliable tracking control is developed to the six wheel-legged robot, in which the fuzzy logic approximation is applied to estimate the uncertain physical interaction and external dynamics of the robot system. Meanwhile, the advanced parallel mechanism of the electric six wheel-legged robot (BIT-NAZA) is presented. Findings Co-simulation and comparative experimental results using the BIT-NAZA robot derived from the developed hybrid control scheme indicate that the methodology can achieve satisfactory tracking performance in terms of accuracy and stability. Originality/value This research can provide theoretical and engineering guidance for lateral stability of intelligent robots under unknown disturbances and uncertain nonlinearities and facilitate the control performance of the mobile robots in a practical system.
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Fărăgău, Andrei B., Chris Keijdener, João M. de Oliveira Barbosa, Andrei V. Metrikine, and Karel N. van Dalen. "Transition radiation in a nonlinear and infinite one-dimensional structure: a comparison of solution methods." Nonlinear Dynamics 103, no. 2 (January 2021): 1365–91. http://dx.doi.org/10.1007/s11071-020-06117-0.
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AbstractTransition zones in railway tracks are locations with a significant variation of track properties (i.e. foundation stiffness) encountered near structures such as bridges and tunnels. Due to strong amplification of the track’s response, transition zones are prone to rapid degradation. To investigate the degradation mechanisms in transition zones, researchers have developed a multitude of models, some of them being very complex. This study compares three solution methods, namely an integral-transform method, a time-domain method, and a hybrid method, with the goal of solving these systems efficiently. The methods are compared in terms of accuracy, computational efficiency, and feasibility of application to more complex systems. The model employed in this paper consists of an infinite, inhomogeneous, and piecewise-linear 1-D structure subjected to a moving constant load. Although the 1-D model is not particularly demanding computationally, it is used to make qualitative observations as to which method is most suitable for the 2-D and 3-D models, which could lead to significant gains. Results show that all three methods can reach similar accuracy levels, and in doing so, the time-domain method is most computationally efficient. The integral-transform method appears to be efficient in dealing with frequency-dependent parameters, while the time-domain and hybrid methods are efficient in dealing with a smooth nonlinearity. For multi-dimensional models, if nonlinearities and inhomogeneities are considered throughout the depth, the time-domain method is likely to be most efficient; however, if nonlinearities and inhomogeneities are limited to the surface layers, the integral-transform and hybrid methods have the potential to be more efficient than the time-domain one. Finally, although the 1-D model presented in this study is mainly used to assess the three methods, it can also be used for preliminary designs of transition zones in railway tracks.
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Kato, Shiro, and Yutaka Niho. "Evaluation of Load Factor to Be Applied in Buckling Design of Cylindrical Lattice Shells Under Asymmetric Snow Load." Journal of the International Association for Shell and Spatial Structures 61, no. 3 (September 1, 2020): 211–26. http://dx.doi.org/10.20898/j.iass.2020.005.
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The load factor is one of the keys in anti-buckling design for safety together for construction cost, and studies have been becoming demanded in a recent situation that super large and super light spatial structures have been constructed. This paper investigates the relationship between reliability index β and snow load factor γs for anti-buckling design of a simply supported cylindrical lattice shell roof under simultaneous action of both dead load and asymmetric snow load. The cylindrical lattice shell analyzed is composed of an equilateral triangle grid of which members are of steel circular hollow sections. Members are connected rigidly to nodes at their both ends. The snow distribution as a main target is assumed in a way that the snow depth on the half of the arch-like roof is half of the amount on the other half roof. The snow fall depth is here assumed 50cm evaluated as 100-year return period, and its probability is assumed as Gumbel distribution with 100-year reference period. The probability distribution of buckling strength Pcr including geometrical and material nonlinearities is approximately evaluated based on a first-order perturbation. The reliability is calculated based on AFOSM, and the relationship in a form of β to γs is finally expressed for design use.
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Meleka, N. N., M. A. Safan, A. A. Bashandy, and A. S. Abd-Elrazek. "Repairing and Strengthening of Elliptical Paraboloid Reinforced Concrete Shells with Openings." Archives of Civil Engineering 59, no. 3 (September 1, 2013): 401–20. http://dx.doi.org/10.2478/ace-2013-0022.
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Abstract This investigation is carried out to evaluate the repair and strengthening the techniques of elliptical paraboloid reinforced concrete shells with openings. An experimental program of several different techniques in repair and strengthening is executed. The materials, which are considered for strengthening, are; Glass fiber reinforced polymers GFRP at different position of the shell bottom surface, steel strip and external tie. They loaded by four concentrated loads affected on the corners of the opening. The initial and failure loads as well as the crack propagation for the tested shells at different loading stages, deflections and failure load for repaired and shells are recorded. A non-linear computer program based on finite element techniques is used to study the behavior of these types of shells. Geometric and materials nonlinearities are considered in the analysis. The efficiency and accuracy of computer program are verified by comparing the program results with those obtained experimentally for the control shell with opening and strengthened shells.
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Cai, Wen, and Ryan L. Harne. "Electrical power management and optimization with nonlinear energy harvesting structures." Journal of Intelligent Material Systems and Structures 30, no. 2 (November 2, 2018): 213–27. http://dx.doi.org/10.1177/1045389x18808390.
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In recent years, great advances in understanding the opportunities for nonlinear vibration energy harvesting systems have been achieved giving attention to either the structural or electrical subsystems. Yet, a notable disconnect appears in the knowledge on optimal means to integrate nonlinear energy harvesting structures with effective nonlinear rectifying and power management circuits for practical applications. Motivated to fill this knowledge gap, this research employs impedance principles to investigate power optimization strategies for a nonlinear vibration energy harvester interfaced with a bridge rectifier and a buck-boost converter. The frequency and amplitude dependence of the internal impedance of the harvester structure challenges the conventional impedance matching concepts. Instead, a system-level optimization strategy is established and validated through simulations and experiments. Through careful studies, the means to optimize the electrical power with partial information of the electrical load is revealed and verified in comparison to the full analysis. These results suggest that future study and implementation of optimal nonlinear energy harvesting systems may find effective guidance through power flow concepts built on linear theories despite the presence of nonlinearities in structures and circuits.
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Andonov, Anton, Kiril Apostolov, Dimitar Stefanov, and Marin Kostov. "Parametric Study on the Floor Response Spectra and the Damage Potential of Aircraft Impact Induced Vibratory Loading." Journal of Disaster Research 5, no. 4 (August 1, 2010): 417–25. http://dx.doi.org/10.20965/jdr.2010.p0417.
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Assessment of the effects of a large aircraft impact on a NPP reactor building are the basic topics of the present work. The focus is on the dynamic response of the internal sub-structures, by means of floor response spectra. Factors influencing the floor response spectra, as the nonlinearities of the impact area, load time function shape and the impact velocity are pointed out and subsequent conclusions are made. Alternative motion parameters for assessment of the damage potential and procedure for indirect assessment of the equipment capacity are also discussed.
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Alam, Md Shafiul, Majed A. Alotaibi, Md Ahsanul Alam, Md Alamgir Hossain, Md Shafiullah, Fahad Saleh Al-Ismail, Md Mamun Ur Rashid, and Mohammad A. Abido. "High-Level Renewable Energy Integrated System Frequency Control with SMES-Based Optimized Fractional Order Controller." Electronics 10, no. 4 (February 22, 2021): 511. http://dx.doi.org/10.3390/electronics10040511.
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The high-level penetration of renewable energy sources (RESs) is the main reason for shifting the conventional centralized power system control paradigm into distributed power system control. This massive integration of RESs faces two main problems: complex controller structure and reduced inertia. Since the system frequency stability is directly linked to the system’s total inertia, the renewable integrated system frequency control is badly affected. Thus, a fractional order controller (FOC)-based superconducting magnetic energy storage (SMES) is proposed in this work. The detailed modeling of SMES, FOC, wind, and solar systems, along with the power network, is introduced to facilitate analysis. The FOC-based SMES virtually augments the inertia to stabilize the system frequency in generation and load mismatches. Since the tuning of FOC and SMES controller parameters is challenging due to nonlinearities, the whale optimization algorithm (WOA) is used to optimize the parameters. The optimized FOC-based SMES is tested under fluctuating wind and solar powers. The extensive simulations are carried out using MATLAB Simulink environment considering different scenarios, such as light and high load profile variations, multiple load profile variations, and reduced system inertia. It is observed that the proposed FOC-based SMES improves several performance indices, such as settling time, overshoot, undershoot compared to the conventional technique.
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Yi, Junyi, and Nigel G. Shrive. "Behaviour of hollow concrete masonry walls with one-course bond beams subjected to concentric and eccentric concentrated loading." Canadian Journal of Civil Engineering 30, no. 1 (February 1, 2003): 181–90. http://dx.doi.org/10.1139/l02-102.
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Three-dimensional finite element models of unreinforced hollow concrete masonry walls with one-course bond beams subjected to concentrated loading have been analyzed. The walls were modelled with different loading plate sizes, different loading locations along the wall (at the midpoint of the wall, at the end of the wall, and between these points), and different out-of-plane eccentricities (e = 0, t/6, and t/3). The hollow block units, mortar, grout, and bond beam blocks in the walls were modelled separately. Both smeared and discrete cracking methods have been utilized for predicting cracking under load. Geometric and material nonlinearities and damage due to progressive cracking were taken into account in the analyses. The predicted failure modes and ultimate capacities of the walls with the concentric concentrated load applied at the midpoint or at the end of the wall compared very well with the experimental results. When the load was between the midpoint and the end of the wall, the predicted ultimate capacity was between those for the load at the midpoint and at the end. The strength of the walls decreases with increasing out-of-plane eccentricities.Key words: finite element models, hollow masonry, smeared and discrete cracking models, concentrated load, loading locations, out-of-plane eccentricities.
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Shayeghi, Hossein, Alireza Rahnama, Reza Mohajery, Nicu Bizon, Alin Gheorghita Mazare, and Laurentiu Mihai Ionescu. "Multi-Area Microgrid Load-Frequency Control Using Combined Fractional and Integer Order Master–Slave Controller Considering Electric Vehicle Aggregator Effects." Electronics 11, no. 21 (October 24, 2022): 3440. http://dx.doi.org/10.3390/electronics11213440.
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Because of the lack of upstream grid support and low inertia, independent microgrids are very susceptible to load variations and uncertainty in the generation of renewable energy sources. Disruption of microgrid frequency stability causes severe damage to various system equipment and frequency-sensitive loads. By taking into account the effects of electric vehicles (EVs), this paper introduces an innovative control strategy with a master-slave configuration for frequency control of interconnected microgrids. In the proposed configuration, an integer-order controller serves as the master, while a merely fractional-order integrator acts as the slave controller. The master and slave controllers are concurrently optimized by the JAYA intelligent algorithm to achieve robust effectiveness. Additionally, nonlinearities in the system are implemented, such as diesel generator operating limits, signal controllers, and sending/receiving time delays. To assess the effectiveness of the proposed control strategy in a two-area microgrid, six basic scenarios are investigated: sudden load changes, perturbations at the inputs of renewable energy-based units, parametric uncertainties, time-delay effects as a nonlinear factor, complicated working conditions, and EVs impacts. Moreover, the controller’s performance on a simple closed-loop system has been carried out in order to confirm the viability of its practical implementation, and a comparison of experimental and simulation findings has also been provided. Studies demonstrate the proposed controller’s robustness as well as its fast-response capability. Besides, this controller features a simple structure that allows extra design flexibility.
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Misiūnaitė, Ieva, Algirdas Juozapaitis, and Alfredas Laurinavičius. "COMPREHENSIVE STUDY ON UNDERSLUNG GIRDER BRIDGE UNDER DIFFERENT LOADING CONDITIONS." Baltic Journal of Road and Bridge Engineering 12, no. 1 (March 24, 2017): 21–29. http://dx.doi.org/10.3846/bjrbe.2017.03.
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The comprehensive study on the structural behaviour of underslung girder bridge is examined in this study through both numerical modelling and experimental 3D model tests. The structural design of steel bridges in many cases is governed by their ability to withstand asymmetric loading conditions. Three different symmetric and asymmetric load cases were investigated to capture the deformational and flexural response of the main girder. It was found that under distributed load the structural response of underslung girder bridge was similar to beam-column with intermediate elastic supports. The numerical model was validated against experimental data with good agreement perceived, allowing an extensive parametric study to be performed. The observed influence of initial geometric imperfections and nonlinearities are discussed. It was found that symmetric load governs the ultimate limit state. However, the asymmetric one takes over in the case of serviceability. Finally, the study presented herein summarises experimental investigations, numerical simulations and design proposals obtained through the recent few years research program, carried on to deepen the knowledge on the structural behaviour of underslung girder bridges.
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Gil-oulbé, Mathieu, Aleksey S. Markovich, Prosper Ngandu, and Svetlana V. Anosova. "Geometric nonlinear analysis of thin elastic paraboloid of revolution shaped shells with radial waves." RUDN Journal of Engineering Researches 21, no. 3 (December 15, 2020): 208–14. http://dx.doi.org/10.22363/2312-8143-2020-21-3-208-214.
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From the old ancient types of roof and dome construction, various forms of shells have been discovered which attract special attention. A shell is a structure composed of sheet material so that the curvature plays an important role in the structural behaviour, realizing its spatial form. There are different types of shells, namely thick and thin shells. G. Brankov, S.N. Krivoshapko, V.N. Ivanov, and V.A. Romanova made interesting researches of shells in the form of umbrella and umbrella-type surfaces. The term nonlinear refers to a given structure undergoing a change in stiffness in its loaded state. There are basically three different types of nonlinearities: geometric, physical and contact (boundary condition nonlinearity). For further analysis of the stress-strain state, a paraboloid with an inner radius of 4 m and an outer radius of 20 m and the number of waves equal to 6 was considered. The test shell is made of reinforced concrete. The minimum load parameter at which the shell loses stability indicates a more than three times the margin.
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Chakrabarti, Subrata K. "Numerical Simulation of Multiple Floating Structures With Nonlinear Constraints." Journal of Offshore Mechanics and Arctic Engineering 124, no. 2 (April 11, 2002): 104–9. http://dx.doi.org/10.1115/1.1463735.
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A versatile and efficient numerical analysis is developed to compute the responses of a moored floating system composed of multiple floating structures. Structures such as tankers, semisubmersibles, FPSOs, SPARs, TLPs, and SPMs connected by mooring lines, connectors or fenders may be analyzed individually or collectively including multiple interaction. The analysis is carried out in the time domain assuming rigid body motion for the structures, and the solution is generated by a forward integration scheme. The analysis includes the nonlinearities in the excitation, damping, and restoring terms encountered in a typical mooring system configuration. It also allows for instabilities in the tower oscillation as well as slack mooring lines. Certain simplifications in the analysis have been made, which are discussed. The exciting forces in the analysis are wind, current, and waves (including a steady and an oscillating drift force), which are not necessarily collinear. The waves can be single frequency or composed of multiple frequency components. For regular waves either linear, stretched linear or fifth order theory may be used. The irregular wave may be included as a given spectral model (e.g., PM or JONSWAP). The vessels are free to respond to the exciting forces in six degrees of freedom—surge, sway, heave, roll, pitch, and yaw. The tower, when present, is free to respond in two degrees of freedom—oscillation and precession. The loads in the mooring lines are determined from prescribed tension-strain tables for the lines. Rigid mooring arms can be analyzed by allowing for compression in the load-strain table. Fenders may be input similarly through load compression tables. In order to establish the stability and accuracy of the solution, comparison of the results with linearized frequency domain analysis was made. The analysis is verified by several different model test results for different structure configurations in regular and random seas. Some of the interesting aspects of nonlinear system are shown with a few examples.
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Martin, A., S. F. Stiemer, and P. Osterrieder. "Ultimate load capacity of square shear plates with circular perforations." Canadian Journal of Civil Engineering 15, no. 3 (June 1, 1988): 470–76. http://dx.doi.org/10.1139/l88-063.
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Working platforms and support caissons of offshore steel structures are often designed with plate boxes or plate girders. The important shear walls or shear webs must often be perforated to allow utilities, etc., to pass through. The failure mode of these large perforated shear panels is typically shear buckling, usually in the plastic range. The paperpresents results of a finite element buckling analysis with inelastic material behaviour and gives general guidelines for the ultimate capacity design of perforated shear plates. The parameters affecting the ultimate capacity of square plates with circular perforations under uniform shear stress were investigated using the incremental structural analysis program NISA83. Nonlinearities in material properties and geometry were taken into account in the calculation of ultimate capacities of each perforated shear plate.The parameters investigated in the study were hole size for a concentric hole and hole location for a constant hole size. Only single unreinforced round holes were considered. Three capacities were calculated for each variation of these parameters: the ultimate in-plane capacity, the elastic buckling capacity, and the ultimate elastic-plastic buckling capacity.In order to check the input data and to provide concise display of the results, a graphic postprocessor was developed as part of the research. The program NISPLOT uses colour graphics to generate plots of the nodes, element mesh, the deflected shape, and stress patterns of the loaded plates. The plots were reduced to black and white for this paper. Key words: girders, holes, steel, ultimate capacity, buckling.
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Guo, Shengshan, Jianxin Liao, Hailong Huang, Hui Liang, Deyu Li, Houqun Chen, Aijing Zhang, and Yifu Tian. "The Effect of Shear Sliding of Vertical Contraction Joints on Seismic Response of High Arch Dams with Fine Finite Element Model." Advances in Civil Engineering 2020 (August 7, 2020): 1–12. http://dx.doi.org/10.1155/2020/4353609.
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The contraction joints of arch dams with and without shear keys are simplified to be with no-slip condition and with relative sliding condition, respectively. Based on the Lagrange multiplier method, a contact model considering the manner of independent cantilever dead load type with no-slip condition and relative sliding condition is proposed to model the nonlinearities of vertical contraction joins, which is special to the nonlinear analysis of arch dams considering the manner of dead load type. Different from the conventional Gauss iterative method, the strategy of the alternating iterative solution of normal force and tangential force is employed. The parallelization based on overlapping domain decomposition method (ODDM) and explicit message passing using distributed memory parallel computers is employed to improve the computational efficiency. An existing high arch dam with fine finite element model is analyzed to investigate the effect of shear sliding of vertical joints on seismic response of the arch dam. The result shows that the values of maximum principal tensile stress under relative sliding condition are significantly greater than those under no-slip condition.
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Sae Siew, James, Olivia Mirza, and Sakdirat Kaewunruen. "Nonlinear Finite Element Modelling of Railway Turnout System considering Bearer/Sleeper-Ballast Interaction." Journal of Structures 2015 (April 20, 2015): 1–11. http://dx.doi.org/10.1155/2015/598562.
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Rail turnouts are built to enable flexibility in the rail network as they allow for vehicles to switch between various tracks, therefore maximizing the utilisation of existing rail infrastructure. In general, railway turnouts are a safety-critical and expensive feature to a rail system as they suffer aggressive operational loads, in comparison to a plain rail track, and thus require frequent monitoring and maintenance. In practice, great consideration is given to the dynamic interaction between the turnouts components as a failed component may have adverse effects on the performance of neighbouring components. This paper presents a nonlinear 3D finite element (FE) model, taking into account the nonlinearities of materials, in order to evaluate the interaction and behaviour of turnout components. Using ABAQUS, the finite element model was developed to simulate standard concrete bearers with 60 kg/m rail and with a tangential turnout radius of 250 m. The turnout structure is supported by a ballast layer, which is represented by a nonlinearly deformable tensionless solid. The numerical studies firstly demonstrate the importance of load transfer mechanisms in the failure modes of the turnout components. The outcome will lead to a better design and maintenance of railway turnouts, improving public safety and operational reliability.
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Bao, Yulin, and Ernest J. Barenberg. "Three-Dimensional Nonlinear Stability Analysis of Tangent Continuous Welded Rail Track Under Temperature and Mechanical Loads." Transportation Research Record: Journal of the Transportation Research Board 1584, no. 1 (January 1997): 31–40. http://dx.doi.org/10.3141/1584-05.
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Results from applications of the three-dimensional continuous welded rail (CWR) track model ILLIBUCKLE to a tangent CWR track with nonlinear resistance and lateral geometric imperfections are presented. Stability analysis is made of the tracks under temperature and mechanical loads by using temperature lateral-displacement curves. Tangent CWR track stability is highly sensitive not only to ballast lateral resistance and geometric imperfections of the the initial track but also to the vertical rotational stiffness in rail-pad fastener systems and vehicle lateral loads. It is concluded that not only the peak values but also the initial slope and the limit resistance in the ballast lateral-resistance curve obtained from a single-tie push test are important in evaluation of track stability. With regard to vertical rotational stiffness in a rail-pad fastener system, track stability is not significantly affected by the nonlinearities, but it is affected by the initial slope. Effects of the combination of mechanical and thermal loads on tangent track stability are presented. The reduction of ballast lateral resistance due to the uplift of rail tie under vehicle vertical loads as well as the magnitude of vehicle lateral loads significantly decrease track stability. A 1400-kg vehicle lateral load can buckle tangent CWR track under a rail-temperature increase as low as 56°C (100°F) under unfavorable conditions.
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Sayed-Ahmed, Ezzeldin Y., and Nigel G. Shrive. "Numerical analysis of face-shell bedded hollow masonry walls subject to concentrated loads." Canadian Journal of Civil Engineering 22, no. 4 (August 1, 1995): 802–18. http://dx.doi.org/10.1139/l95-090.
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A nonlinear elastoplastic finite element model has been developed for face-shell bedded hollow masonry walls subject to in-plane concentrated loads. The model takes into account geometric and material nonlinearities as well as damage due to progressive cracking. Behaviour of the masonry components subject to compressive states of stress is modelled using the theory of plasticity, and cracking is modelled using both discrete and smeared cracking approaches. The model is generated on a SUN SPARC 10/31 workstation using the preprocessor of the finite element program ANSYS; the finite element solution is obtained using the ABAQUS program on the Fujitsu VPX 240/10 and IBM RS/6000 workstation. A brief summary of the numerical modelling and the iterative procedures is discussed. Results from simulated tests of seven-course high wallettes subject to concentrated loads are used to verify the behaviour of the numerical analyses. The methodology, when combined with substructuring, allows analysis of substantially larger walls than would more typical 3-D analyses. The model can be used to check existing design rules and develop more rational design methods for hollow masonry subject to concentrated load. Key words: masonry, hollow concrete masonry, finite element modelling, cracking, failure, strength enhancement factor, concentrated loads.
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Markovic, Zoran, Slobodan Stupar, Mirko Dinulovic, Ognjen Pekovic, Predrag Stefanovic, and Dejan Cvetinovic. "Assessment results of fluid-structure interaction numerical simulation using fuzzy logic." Thermal Science 20, suppl. 1 (2016): 235–50. http://dx.doi.org/10.2298/tsci160111083m.
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A fuzzy approximation concept is applied in order to predict results of coupled computational structure mechanics and computational fluid dynamics while solving a problem of steady incompressible gas flow through thermally loaded rectangular thin-walled channel. Channel wall deforms into wave - type shapes depending on thermal load and fluid inlet velocity inducing the changes of fluid flow accordingly. A set of fluid - structure interaction (FSI) numerical tests have been defined by varying the values of fluid inlet velocity, temperature of inner and outer surface of the channel wall and numerical grid density. The unsteady Navier-Stokes equations are numerically solved using an element-based finite volume method and second order backward Euler discretization scheme. The structural model is solved by finite element method including geometric and material nonlinearities. The implicit two-way iterative code coupling, partitioned solution approach, were used while solving these numerical tests. Results of numerical analysis indicate that gravity and pressure distribution inside the channel contributes to triggering the shape of deformation. In the inverse problem, the results of FSI numerical simulations formed a database of input variables for development fuzzy logic based models considering downstream pressure drop and maximum stresses as the objective functions. Developed fuzzy models predicted targeting results within a reasonable accuracy limit at lower computation cost compared to series of FSI numerical calculations. Smaller relative difference were obtained when calculating the values of pressure drop then maximal stresses indicating that transfer function influence on output values have to be additionally investigated.
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SHANMUGAM, N. E., and B. LAKSHMI. "EFFECT OF KEY PARAMETERS ON STRENGTH OF IN-FILLED STEEL-CONCRETE COMPOSITE COLUMNS." International Journal of Structural Stability and Dynamics 05, no. 02 (June 2005): 217–39. http://dx.doi.org/10.1142/s0219455405001520.
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This paper is concerned with the detailed study on the behavior of steel tubular columns in-filled with concrete. Moment–curvature–thrust relationships are generated for column cross-sections by an iterative process. Nonlinear equilibrium equations which include geometric and material nonlinearities are solved by an incremental-iterative numerical scheme based on generalized displacement control (GDC) method. The analytical model is used to investigate the effect of various parameters that could influence the behavior and ultimate load. Column end restraints are also considered as one of the parameters. The variables selected for the study cover a wide range of parameters arising from various loading conditions and column geometries.
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Eremina, Tatiana, Dmitry Korolchenko, and Denis Minaylov. "Experimental Evaluation of Fire Resistance Limits for Steel Constructions with Fire-Retardant Coatings at Various Fire Conditions." Sustainability 14, no. 4 (February 9, 2022): 1962. http://dx.doi.org/10.3390/su14041962.
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The experimental evaluation of fire resistance limits for steel constructions with fire-retardant coatings consists of a lot of experiments on the heating of steel structures of buildings by solving a heat engineering problem at various fire conditions. Building design implies the assessment of compliance of actual fire resistance limits for steel constructions with the required limits. Fire resistance limits for steel constructions are determined for “standard” temperature mode, and this can lead to overestimated fire resistance and underestimated heat influence for a real fire. Estimation of the convergence for “standard” temperature mode and possible “real” fire mode, as well as of the compliance of actual fire resistance limits with real fire conditions, was realized in the following stages: mathematical modeling of real fire development by the field model in software package Fire Dynamics Simulation (FDS) with various fire loads and mathematical modeling of steel construction heating for the standard temperature mode obtained by modeling “real” fire modes (the finite difference method of solving the Fourier heat conduction equation at external and internal nonlinearities was used for modeling the process of steel structure heating with the implementation in the ANSYS mechanical software package). Experiments of the assessment of fire-protective paint’s effectiveness were carried out for standard temperature mode and obtained by modeling “real” fire modes. The equivalent fire duration dependence on fire load type was determined. This dependence can be taken into account in determination of fire resistance limits for steel constructions in warehouse building roofing. Fire-protective paint effectiveness was estimated for “standard” temperature mode and various other temperature modes.
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Lu, Naiwei, Yang Liu, Mohammad Noori, and Xinhui Xiao. "System Reliability Assessment of Cable-Supported Bridges under Stochastic Traffic Loads Based on Deep Belief Networks." Applied Sciences 10, no. 22 (November 13, 2020): 8049. http://dx.doi.org/10.3390/app10228049.
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A cable-supported bridge is usually a key junction of a highway or a railway that demands a higher safety margin, especially when it is subjected to harsh environmental and complex loading conditions. In comparison to short-span girder bridges, long-span flexible structures have unique characteristics that increase the complexity of the structural mechanical behavior. Therefore, the system safety of cable-supported bridges is critical but difficult to evaluate. This study proposes a novel and intelligent approach for system reliability evaluation of cable-supported bridges under stochastic traffic load by utilizing deep belief networks (DBNs). The related mathematical models were derived taking into consideration the structural nonlinearities and high-order statically indeterminate characteristics. A computational framework is presented to illustrate the steps followed for system reliability evaluation using DBNs. In a case study, a prototype suspension bridge is selected to investigate the system reliability under stochastic traffic loading based on site-specific traffic monitoring data. The numerical results indicated that DBNs provide an accurate approximation for the mechanical behavior accounting for structural nonlinearities and different system behaviors, which can be treated as a meta-model to estimate the structural failure probability. The dominant failure modes of the suspension bridge are the fracture of suspenders followed by the bending failure of girders. The degradation of suspenders due to fatigue-corrosion damage has a significant effect on the system reliability of a suspension bridge. The numerical results provide a theoretical basis for the design on cable replacement strategies.
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Murtazaliev, G. M., and M. M. Payzulaev. "NONLINEAR BEHAVIOR CALCULATION ALGORITHM FOR THIN-WALLED SYSTEMS." Herald of Dagestan State Technical University. Technical Sciences 46, no. 2 (August 28, 2019): 176–84. http://dx.doi.org/10.21822/2073-6185-2019-46-2-176-184.
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Objectives The emergence of modern high-strength materials leads to the creation of thin-walled structures in various fields of technology. To obtain the necessary information about their behavior under load, one should analyze all the characteristic features encountered at all stages of their loading - at the initial (initial) stage of their operation, taking into account one or more types of nonlinearities, find possible critical states and, depending on the type of stability loss, study the nature of the initial stage of postcritical deformation. Based on an algorithm combining approximate analytical and numerical methods, the article solves the model problem — studying the behavior of a thin-walled spherical shell under load.Method. The study is based on solving the nonlinear problem of determining the stress-strain state at the initial - axisymmetric stage of work; critical (bifurcation) load values; analysis of the nature of post-bifurcation behavior. The work uses a variant of the general theory of stability and postcritical behavior of structures previously developed by V.T. Coiter.Result. The solution of such a general problem associated with discontinuous phenomena is carried out on the basis of mathematical ideas formulated in the theory of branching solutions of nonlinear equations. The values of the coefficients characterizing the initial stage of the post-bifurcation behavior of the shells and, from a practical point of view, the relations between the critical and limiting values of the loads are obtained. It is shown that depending on the area of the shell surface part loaded by the distributed load, the nature of the initial stage of postcritical deformation changes not only quantitatively, but also qualitatively.Conclusion. The most effective in solving problems associated with discontinuous phenomena are combinations of approximate analytical ones - catastrophe theory and numerical methods that do not require complex, timeconsuming and significant amounts of computation. Analysis of the initial stage of the postbifurcation behavior of structures allows us to assess the degree of danger of reaching a critical state, which is achieved by taking into account the values of the corresponding reliability coefficients in the calculations.
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Bluhm, Gore Lukas, Keld Christensen, Konstantinos Poulios, Ole Sigmund, and Fengwen Wang. "Experimental verification of a novel hierarchical lattice material with superior buckling strength." APL Materials 10, no. 9 (September 1, 2022): 090701. http://dx.doi.org/10.1063/5.0101390.
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Recently, a systematic approach for the design of lattice materials with extreme buckling strength has led to optimized hierarchical lattice materials with unprecedented load carrying capacity. This is obtained at the cost of a small decrease in linear stiffness. However, the superior buckling resistance of such optimized hierarchical lattice materials has so far only been predicted numerically. In fact, concerns have been raised regarding the validity of the employed linear buckling analysis and potential risk of catastrophic failure due to the coalescence of multiple critical buckling modes. This work aims at refuting these concerns by designing and testing manufacturable novel hierarchical lattice materials with superior buckling strength. Thereby, the basis is provided for wide applications of these high-performing materials in mechanical design. A novel hierarchical material is generated for this work by combining the mentioned design procedure with a requirement on the minimum feature size to ensure manufacturability. For addressing the raised concerns, the optimized material design, together with a reference material, is realized with the help of additive manufacturing and experimentally tested in uniaxial compression. The obtained results are compared to numerical simulations considering geometrical and material nonlinearities, and an overall good agreement is found between experimental and numerical results. This confirms an increase in buckling resistance and post-buckling load carrying capacity by a factor of more than three compared to the regular reference lattice structure. Hence, the buckling superiority of this novel type of architected materials is clearly demonstrated.
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Stitic, Andrea, Anh Nguyen, Aryan Rezaei Rad, and Yves Weinand. "Numerical Simulation of the Semi-Rigid Behaviour of Integrally Attached Timber Folded Surface Structures." Buildings 9, no. 2 (February 25, 2019): 55. http://dx.doi.org/10.3390/buildings9020055.
Full textAbstract:
Timber folded surface structures assembled using semi-rigid multiple tab and slot joints (MTSJ) have been shown to form feasible structural systems with high load bearing potential. However, for their further development and use on large building scales, a pertinent model for prediction of their structural behaviour has yet to be developed. This paper focuses on simplified numerical methods for accurately modelling the semi-rigid structural behaviour of bidirectional timber folded surface structures with multiple tab and slot connections. Within this scope, the structure behaviour is considered to be in the elastic stage. Three practical methods of analysis for such structural systems are presented. The first two approaches use the Finite Element Method (FEM), where the theory of plates and shells are applied. In the first method, the MTSJs are modeled using strip element models, while, in the second strategy, spring models are used. The third modeling strategy elaborates on the new macroscopic mechanical models, referred to as macro models. Sets of one-dimensional (1D) elements are used to represent the mechanical behaviour of the entire system. Both linear and geometric nonlinear analysis are performed for all three modeling strategies. The numerical results are then validated against the large scale experiments. Comparison of the strip and spring element model results have shown that the strips represent more accurately the experimentally obtained values. Concerning the macro modelling approach, very good agreement with both detailed FE modelling approaches, as well as experimental results, were obtained. The results indicate that both linear and nonlinear analysis can be used for modelling the displacements within the elastic range. However, it is essential to include geometric nonlinearities in the analysis for accurate modelling of occurring strains as well as for displacements when considering higher load levels. Finally, it is demonstrated that including semi-rigidity in the numerical models is of high importance for analysing the behaviour of timber folded surface structures with MTSJ.
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Cai, Zhicheng, and Xiang Yuan Zheng. "Nonlinear Whirling Motion of Monopile Offshore Wind Turbines Subjected to Harmonic and Seismic Base Excitations." International Journal of Structural Stability and Dynamics 19, no. 02 (February 2019): 1950009. http://dx.doi.org/10.1142/s0219455419500093.
Full textAbstract:
The triggering mechanism and the vibration patterns of the nonlinear whirling motion of monopile offshore wind turbines subjected to unidirectional base excitations are investigated both theoretically and experimentally via a 64:1 scaled model of the prototype NREL-5MW monopile offshore wind turbine. For motion, two nonlinear coupled integro-differential equations containing cubic nonlinearities due to curvature and inertia are solved by both analytical and numerical methods. Harmonic and random seismic base excitations with different amplitudes and frequencies are considered in the analysis to understand the instability mechanism. Extensive shake table tests show that the experimental results have good qualitative agreements with the theoretical results, and as observed in eight load cases, the nonlinear whirling motions of nacelle do exist and tend to be induced by large harmonic excitations with structural resonant frequency.
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Hinman, John, Vong Toan, and Steve Thoman. "Seismic Retrofit of 1958 Carquinez Bridge." Transportation Research Record: Journal of the Transportation Research Board 1624, no. 1 (January 1998): 54–63. http://dx.doi.org/10.3141/1624-07.
Full textAbstract:
The 1021-m (3,350-ft) long steel through truss bridge carrying the east-bound lanes of Interstate 80 across the western end of the Carquinez Strait about 40 km (25 mi) north of San Francisco opened to traffic in 1958. It was the first major highway bridge in the United States to use high-strength (T1) steel, the first to use welded built-up members, and the first to use high-strength bolted connections. These “firsts,” combined with the size of the bridge and the traffic demands, presented a formidable challenge to the retrofit design team. The retrofit objective was to prevent collapse of the bridge during an earthquake with an expected mean return period in the range of 1,000 to 2,000 years. Under this noncollapse criterion, significant damage to the bridge, such as yielding and buckling of members, was considered acceptable. It was important, then, that a measure of acceptable damage be defined and that the postyield behavior of the structure be both very predictable and very ductile. A preliminary design was prepared based on an elastic analysis with geometric non-linearities. The retrofit design was then examined by incorporating material nonlinearities into the model; adjustments to the retrofit design were required in some isolated areas. Design issues that the team addressed included connections for loads as high as 60 to 50 kN (13,500 kips); local buckling of thin-walled, high-strength members; postyield behavior of major load-carrying steel members; rocking of rigid A-frame tower assemblies; and an expansion joint for an 8-ft movement rating.