Complex Engineering Structures Research Articles

Feedforward backpropagation artificial neural networks for predicting mechanical responses in complex nonlinear structures: A study on a long bone

Feedforward backpropagation artificial neural networks (ANNs) have been increasingly employed in many engineering practices concerning materials modeling. Despite their extensive applications, how to achieve successfully trained ANNs is not thoroughly explained in the literature, nor are there lucid discussions to delineate influential parameters obtained from analyses. Long bones are composite materials possessing nonhomogeneous and anisotropic properties, and their mechanical responses exhibit dependency on numerous variables. Material complexity hinders researchers from arriving at a consensus in implementing an optimal constitutive model or encourages them to adopt a simple constitutive model including many simplifying assumptions. However, such exceptional features and engineering challenges make long bones materials worth investigating, enriching our comprehension of complex engineering structures using novel techniques where traditional methods may present limitations. This paper reports on the prediction of loading, displacement, load and displacement simultaneously, and strains using feedforward backpropagation ANNs trained with experimental recordings. The technique was used to find optimum network structures (architectures) that encompass the best prediction ability. To enhance predictions, the influence of several elements such as a network training algorithm, injecting noise to datasets prior to training, the level of injected noise which directly affects model fitting and regularization, and data normalization prior to training were investigated and discussed. Essential parameters influencing decision making in identifying well-trained and well-generalized ANNs were elaborated. A considerable emphasis in this study was placed on examining the generalization ability of the already trained and tested ANNs, thus guaranteeing unbiased models that avoided overfitting. Gaining favorable outcomes in this study required three years of performing experiments and data collection before establishing the networks. The subsequent training, testing, and determination of the generalization of more than 60,000 ANNs are promising and will assist researchers in comprehending mechanical responses of complicated engineering structures that exhibit peculiar nonlinear properties.

Modeling and Simulation Analysis of the Temperature Field of High Speed Missile Cabin

A temperature field analysis method is developed for the cabin of high-speed missile. The high fidelity three-dimensional model of the thermal protection system is build based on the finite element method, including structure and equipments inside the cabin. The model can express the heat conduction path, radiation relationship and the heat capacity of the equipment. The aero-heating and heat transfer are solved simultaneously. The convection coefficient relevant to experiment is used to simulate the heat transfer of the gas in the cabin. It can be used to large-scale engineering calculation for the thermal protection system of high-speed aircraft. The numerical example of a head cabin for high-speed missile shows that the obvious regional characteristics of the surface temperature outside the cabin is presented, which reflects the coupling effect of aero-heating and cabin structure. The temperature of the equipment in the cabin rises due to radiation and convection heat transfer. Heat capacity of the equipment and natural convection in the gap have obvious influence on the rate and amount of temperature rising. The developed APDL command stream can integrate commercial software of CAD and CAE. It is suitable for large and complex engineering structure because of the advantages such as high computational efficiency and strong portability.

Recent advances in reliability analysis of aeroengine rotor system: a review

PurposeTo provide valuable information for scholars to grasp the current situations, hotspots and future development trends of reliability analysis area.Design/methodology/approachIn this paper, recent researches on efficient reliability analysis and applications in complex engineering structures like aeroengine rotor systems are reviewd.FindingsThe recent reliability analysis advances of engineering application in aeroengine rotor system are highlighted, it is worth pointing out that the surrogate model methods hold great efficiency and accuracy advantages in the complex reliability analysis of aeroengine rotor system, since its strong computing power can effectively reduce the analysis time consumption and accelerate the development procedures of aeroengine. Moreover, considering the multi-objective, multi-disciplinary, high-dimensionality and time-varying problems are the common problems in various complex engineering fields, the surrogate model methods and its developed methods also have broad application prospects in the future.Originality/valueFor the strong demand for efficient reliability design technique, this review paper may help to highlights the benefits of reliability analysis methods not only in academia but also in practical engineering application like aeroengine rotor system.

Effect of Pylon Shapes on Seismic Response of a Long-Span Steel Box-Girder Cable-Stayed Bridge

In recent decades, the demand for complex and economical engineering structures with great aesthetics has been on the rise and the cable stayed bridges also take their share of this interest. Besides many advantages cable-stayed bridges are quite flexible, hence susceptible mainly to dynamic actions such as impact loads, wind effects and seismic excitations. In this context, this study focused on the effect of A and H shape reinforced concrete pylons on the seismic behavior of a long span steel triple box-girder cable-stayed bridge that was presumed to be located in an earthquake-prone region in Turkey. The 3D models of the bridge were constructed using SAP2000 software and the time history analysis have been carried out considering cable sag, large displacement effects. The seismic responses of the bridges are compared in terms of axial force on cables, deflections on the pylons and the deck

Development of modern technology of rice cultivation on rice engineering irrigation systems in the Krasnodar Territory

Rice irrigation systems are complex engineering structures, the main task of creating favorable conditions for growing rice. This situation poses a challenge for the workers of the rice-growing sector in Russia to create effective and modern engineering irrigation systems that will reduce the anthropogenic load and generally improve the ecological and reclamation situation in the ecosystem of the rice irrigation system. Consequently, our research on the development of new rice engineering systems is relevant, and their widespread implementation will strengthen the food security of Russia. The developed technology of rice cultivation has shown its effectiveness on the rice irrigation system at LLC “Chernoerkovskoye” of the Slavyansky District of the Krasnodar Territory. The effectiveness of the proposed technology was expressed in improving the reclamation state of soils, reducing the irrigation rate by more than five times, increasing the biometric indicators of rice plants and the quality of the resulting rice grain. The research carried out makes it possible to “level” the gap between scientific and technical achievements in the construction of irrigation systems and their practical implementation in production, facilitating the exchange of new experience and improving the professional level of workers in the agro-industrial complex. In turn, the accumulation of production experience will make it possible to update the regulatory and technological framework for rice production to make timely management decisions and obtain guaranteed high yields of high-quality rice grain.

Novel Fatigue-Damage Sensor for Prediction of Remaining Fatigue Lifetime of Mechanical Components and Structures

In this paper, a novel Internet of Things (IoT) fatigue damage sensor is presented to predict the fatigue damage accumulation level and residual fatigue life of critical mechanical and structural components. The intelligent radio-frequency identification (RFID)-integrated fatigue sensor system has special designed breakable mini beams with multiple parallel oriented geometry and symmetric U-type stress concentrated notches. The fatigue sensing beams with different stress and fatigue lifetime levels are designed to estimate the fatigue damage accumulation and remaining fatigue life of unidirectional and multidirectional structural or mechanical elements, including composite structures. The fatigue damage sensor attached on a real structure goes through the same fatigue life experience of critical structural elements or mechanical components from the beginning of service life or any point in the service life to the end of service life. A fatigue sensor with five parallel symmetric U notched mini beams with different fatigue lifetimes (10% N, 25% N, 50% N, 70% N, 85%–90% N) normalized to the total life (N) of a structure are considered to predict the remaining fatigue lifetime of a real structure using the cumulative damage Miner’s rule. The mini fatigue sensor beams attached to the surface of a structure are designed to fail, depending on their fatigue life, earlier than the total fatigue lifetime of the structure, like a fatigue fuse system. The fatigue damage sensing beams fail gradually while passing through the same fatigue cycles as a structural member. When the service lifetime of a real monitored structure is very close to the total fatigue life, the critical maximum lifetime (80%–90% N) notched mini sensor beam breaks and issues an alarm that the service life of the real structural part is approaching its fatigue strength limit and the end of its service life. The smart fatigue damage sensor is wireless-enabled, which makes it possible to check the health status of the sensor over a sensor network as often as one likes. Since the wireless distributed fatigue sensor network system monitors the fatigue health conditions of structures periodically or on demand, the data collected on the sensor network system can be used not only for condition-based fatigue life prediction but also for sensor-based predictive fatigue maintenance and the development of new fatigue design tools for fatigue-sensitive complex and large engineering structures or mechanical systems.

Coupling of non-conforming trimmed isogeometric Kirchhoff–Love shells via a projected super-penalty approach

Penalty methods have proven to be particularly effective for achieving the required C1-continuity in the context of multi-patch isogeometric Kirchhoff–Love shells. Due to their conceptual simplicity, these algorithms are readily applicable to the displacement and rotational coupling of trimmed, non-conforming surfaces. However, the accuracy of the resulting solution depends heavily on the choice of penalty parameters. Furthermore, the selection of these coefficients is generally problem-dependent and is based on a heuristic approach. Moreover, developing a penalty-like procedure that avoids interface locking while retaining optimal accuracy is still an open question. This work focuses on these challenges. In particular, we devise a penalty-like strategy based on the L2-projection of displacement and rotational coupling terms onto a degree-reduced spline space defined on the corresponding interface. Additionally, the penalty factors are completely defined by the problem setup and are constructed to ensure optimality of the method. This method is particularly suited for spline spaces of moderate degrees p=2,3, where the projection is computationally efficient and the condition number related to our choice of parameters does not yield a significant deterioration of the solution accuracy. To demonstrate this, we assess the performance of the proposed numerical framework on a series of non-trimmed and trimmed multi-patch benchmarks discretized by non-conforming meshes. We remark that only water-tight geometries have been considered in this work. We systematically observe a significant gain of accuracy per degree-of-freedom and no interface locking phenomena compared to other penalty-like approaches. Lastly, we perform a static shell analysis of a complex engineering structure, namely the blade of a wind turbine.

PURPOSE AND DESCRIPTION OF THE COMPRESSOR STATION

All work on the construction of pumping and compressor stations is usually divided into two groups of zero cycle work and ground cycle work. The work of the zero cycle includes the preparation of the construction site, earthworks, work on the construction of foundations for buildings, pumping units and technological equipment, work on the construction of underground pipelines and utilities. The work of the ground cycle includes work on the construction of buildings for pumping and compressor shops and auxiliary buildings, installation work on installation and fixing on the foundations in the design position of pumping units. Compressor stations (CS) have been installed along the pipeline route to maintain a certain flow rate of the transported gas and to ensure optimal pressure in the pipeline. A modern compressor station is a complex engineering structure that provides the basic technological processes for the preparation and transportation of natural gas. Keywords: compressor stations, gas pipeline, building structure, Booster compressor stations.

Evidence-theory-based structural reliability analysis with epistemic uncertainty: a review

Epistemic uncertainty widely exists in the early design stage of complex engineering structures or throughout the full-life cycle of innovative structure design, which should be appropriately quantified, managed, and controlled to ensure the reliability and safety of the product. Evidence theory is usually regarded as a promising model to deal with epistemic uncertainty, as it employs a general and flexible framework, the basic probability assignment function, which enables the quantification and propagation of epistemic uncertainty more effective. Due to its strong ability, evidence theory has been applied in the field of structural reliability during the past few decades, and a series of important progresses have been achieved. Evidence-theory-based reliability analysis thus provides an important means for engineering structure design, especially under epistemic uncertainty, and it has become one of the research hotspots in the field of structural reliability. This paper reviews the four main research directions of evidence-theory-based reliability analysis, and each one is focused on solving one critical issue in this field, namely, computational efficiency, parameter correlation, hybrid uncertainties, and reliability-based design optimization. It summarizes the main scientific problems, technical difficulties, and current research status of each direction. Based on the review, this paper also provides an outlook for future research in evidence-theory-based structural reliability analysis.

Multiaxial fatigue assessment of complex steel connections: A case study of a vertical-lift gussetless truss bridge

Civil engineering structures grow more complex as engineers push innovation boundaries. Load complexity, costs, construction and maintenance efficiency, among other things, can lead to unique designs that are often excluded in current design codes and evaluation standards. Fatigue-induced damage is currently one of the most common damage types experienced by ordinary and complex civil engineering structures subjected to cyclic loading such as bridges. However, current fatigue evaluation and design standards provide limited guidance on how to approach complex welded connections. Uniaxial and multiaxial methods for the evaluation of fatigue life using strains histories are compared for the assessment of a welded gussetless truss connection of the Memorial Bridge, a vertical-lift bridge connecting Portsmouth, NH and Kittery, ME. As expected, using both approaches result in sufficient remaining fatigue life. However, it is demonstrated that commonly used uniaxial fatigue analysis methods can be insufficient in complex structures that experience variable amplitude, multiaxial, and non-proportional loading. Multiaxial non-proportional stresses experienced by a complex connection can cause a decrease in remaining fatigue life estimates. This paper presents assessment tools and a method for the evaluation of fatigue life of complex welded connections using strain time histories.

Компьютерная модель асинхронного гребного электропривода с тремя обмотками на статоре

Object and purpose of research. This paper discusses electric propulsion system of leader icebreaker. Its purpose was to develop mathematical and computer-based model of electric propulsion drive powered by asynchronous motor with three stator windings for further investigation of steady, transitional, asymmetric and emergency operation scenarios of electric power and propulsion system for the leader icebreaker. Materials and methods. Hardware and methods for computer-based simulation of complex engineering structures. Main results. Development of the mathematical model representing asynchronous motor with three windings in phase coordinates. Computational studies on direct startup of 15 MW propulsion motor, as well as on steady and transitional operational conditions of ship electric power system consisting of 36 MW synchronous genset, two-winding transformers and electric propulsion drive with 15 MW asynchronous motor in phase coordinates with three stator windings and three-level frequency converter. Calculation of voltage non-sinusoidality ratio for MSB buses with operation of 15 MW propulsion motor driven by 36 MW synchronous genset. Conclusion. Mathematical model of asynchronous motor suggested in this paper could be used to calculate steady and transitional operation scenarios of marine power systems with frequency-controlled three-winding asynchronous motor, as well as to calculate electromechanical and electromagnetic processes and refine frequency control algorithms. This is especially relevant because each of the asynchronous electric machines used in the electromechanical assemblies of leader icebreaker propulsion motors has three stator windings, and this icebreaker is the first experience of applying a 15 MW marine electric drive.

Finite element model updating of composite with adhesive jointed structure under built-up internal stress

Highly complex engineering structures such as the body-in-white of a car consist of hundreds of different parts that are assembled using various types of joints such as welded and adhesive joints. The finite element method has been used extensively in various engineering fields to predict and analyze the dynamic behavior of assembled structures. However, despite the use of well-characterized individual subcomponent models, the predicted results frequently differ from measured results. This is believed to be because of the invalid assumptions of the joint model such as the material properties and other uncertainties associated with the assembly. This study investigated the use of a model updating method (MSC Nastran SOL 200) to identify the invalid assumptions and uncertainties in adhesive jointed composite structures and to minimize the difference between predicted and measured results. Results revealed that the stresses built-up in a structure during the assembly process are permanently retained in the structure after the adhesive is completely cured and that they cause a local stress stiffening effect, which is believed to affect the resonance frequencies of the structure. Introducing the effect of the stresses as an updating parameter in the model updating process increases the prediction accuracy.

Experimental and Numerical Study on the Mechanical Behavior of Composite Steel Structure under Explosion Load.

Most engineering structures are composed of basic components such as plates, shells, and beams, and their dynamic characteristics under explosion load determine the impact resistance of the structure. In this paper, a three-dimensional composite steel structure was designed using a beam, plate, and other basic elements to study its mechanical behavior under explosion load. Subsequently, experiments on the composite steel structure under explosion load were carried out to study its mechanical behavior, and the failure mode and deformation data of the composite steel structure were obtained, which provided important experimental data regarding the dynamic response and mechanical behavior of the composite steel structure under explosion load. Then, we independently developed a parallel program with the coupled calculation method to solve the numerical simulation of the dynamic response and failure process of the composite steel structure under explosion load. This program adopts the Euler method as a whole, and Lagrange particles are used for materials that need to be accurately tracked. The numerical calculation results are in good agreement with the experimental data, indicating that the developed parallel program can effectively deal with the large deformation problems of multi-medium materials and the numerical simulation of the complex engineering structure failures subjected to the strong impact load.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ И ВЫБОР ТЕХНОЛОГИИ УСТРОЙСТВА ОГРАЖДАЮЩИХ МЕТАЛЛИЧЕСКИХ КОНСТРУКЦИЙ ПРИ СТРОИТЕЛЬСТВЕ ПОДЗЕМНЫХ СООРУЖЕНИЙ

Urban motor transport complex engineering structures, the construction of which is carried out for a long time, and the cost is often tunnels of structures. Despite this, urban tunnels remain in demand as a means of solving transport problems, especially for large cities, in areas with dense urban development or an established architectural appearance, the violation of which is unacceptable. The construction of tunnels makes it possible to increase the throughput of highways, especially in places of large intersections, one of the diverting high-intensity transit traffic flows underground, making them invisible on the surface and thus not disrupting the existing historical appearance of the area.

Construction of risk diagnosis mode database for South to North Water Transfer Project

There are complex and diverse engineering structures in the Middle Route Project of South to North Water Transfer. In order to ensure the normal operation of the project during the operation period. By analysing and summarizing the possible dangerous situations, it can effectively improve the emergency response ability of relevant management departments. In this paper, typical structures and risk databases are built based on the method of entity relationship graph. Using the related factors in the history risk databases, the engineering factors, environmental factors and human factors are sorted out to subdivide the entities. The relationship between risk factors and typical structures is carried out by risk codes, so as to build a complete engineering risk database.

A Critical Review of Nonlinear Damping Identification in Structural Dynamics: Methods, Applications, and Challenges.

In recent decades, nonlinear damping identification (NDI) in structural dynamics has attracted wide research interests and intensive studies. Different NDI strategies, from conventional to more advanced, have been developed for a variety of structural types. With apparent advantages over classical linear methods, these strategies are able to quantify the nonlinear damping characteristics, providing powerful tools for the analysis and design of complex engineering structures. Since the current trend in many applications tends to more advanced and sophisticated applications, it is of great necessity to work on developing these methods to keep pace with this progress. Moreover, NDI can provide an effective and promising tool for structural damage detection purposes, where the changes in the dynamic features of structures can be correlated with damage levels. This review paper provides an overview of NDI methods by explaining the fundamental challenges and potentials of these methods based on the available literature. Furthermore, this research offers a comprehensive survey of different applications and future research trends of NDI. For potential development and application work for nonlinear damping methods, the anticipated results and recommendations of the current paper can assist researchers and developers worldwide to find out the gaps and unsolved issues in the field of NDI.

Robust optimization of engineering structures involving hybrid probabilistic and interval uncertainties

A novel, yet practically feasible, robust optimization approach is proposed in this study for engineering structures involving hybrid uncertainties. Both stochastic and interval uncertain system parameters are incorporated within a single analysis-design computational scheme. The generalized beta distribution is adopted to model the bounded stochastic system uncertainties, which offers the benefit of evaluating the performance of objective function and constraints of the robust optimization. A multi-layered refining Latin hypercube sampling–based Monte Carlo simulation approach is proposed to assess the robustness of the objective function. Furthermore, a new concept, namely, the interval angular vector, is presented to evaluate the robust feasibility of the constraints of the optimization problem. In order to systematically solve the robust optimization problem, a new genetic algorithm is presented in this study which utilizes the order preference by similarity to ideal solution technique so the feasible design vectors can be sorted according to their distances to the negative ideal solution. The effectiveness and applicability of the proposed computational approach are demonstrated by one numeral example and two realistic complex engineering structures including the bucket linkage mechanism of an excavator and the upper beam of a high-speed punching machine.

Indirect reduced-order modelling: using nonlinear manifolds to conserve kinetic energy.

Nonlinear dynamic analysis of complex engineering structures modelled using commercial finite element (FE) software is computationally expensive. Indirect reduced-order modelling strategies alleviate this cost by constructing low-dimensional models using a static solution dataset from the FE model. The applicability of such methods is typically limited to structures in which (a) the main source of nonlinearity is the quasi-static coupling between transverse and in-plane modes (i.e. membrane stretching); and (b) the amount of in-plane displacement is limited. We show that the second requirement arises from the fact that, in existing methods, in-plane kinetic energy is assumed to be negligible. For structures such as thin plates and slender beams with fixed/pinned boundary conditions, this is often reasonable, but in structures with free boundary conditions (e.g. cantilever beams), this assumption is violated. Here, we exploit the concept of nonlinear manifolds to show how the in-plane kinetic energy can be accounted for in the reduced dynamics, without requiring any additional information from the FE model. This new insight enables indirect reduction methods to be applied to a far wider range of structures while maintaining accuracy to higher deflection amplitudes. The accuracy of the proposed method is validated using an FE model of a cantilever beam.

An active meta-layer for optimal flexural wave absorption and cloaking

Flexural wave propagation is common in thin structures and plays a key role in vibrations of structures. Designs of flexural wave absorbers for vibration control have been constantly pursued for decades aiming to find structures that can best balance tradeoffs between small sizes or lightweights and broadband operations. However, their absorption performance has long been evaluated on a case-by-case basis, and the theoretical limit characterizing the relationship between the absorption spectrum and the sample thickness and mass density is missing. In this study, by adopting an inequality as its electromagnetism and acoustics counterparts, the theoretical limit of flexural wave absorption is established. An active meta-layer composed of piezoelectric sensors and actuators with feedback control loops is proposed for optimal wave absorption. We experimentally demonstrate the active meta-layer for optimal broadband wave and vibration control in the beam and acting as skin cloaks of large voids in the plate. The active meta-layer is electrically programmable and scalable without losing stability. The approach proposed sheds light on designs of reconfigurable dynamic control devices and enables alternative solutions for ultrasonic sensing of complex engineering structures.

Study on Relationship between Material Vickers Hardness and Yield Stress of A508 Nuclear Material

It is difficult to directly obtain the mechanical properties of local materials of actual engineering structure (such as welded joints) by traditional mechanical test. Indentation test and ABAQUS finite element test were used in this paper, the relativity between Vickers hardness and yield stress of nuclear material A508 were studied, and a new method of using material surface Vickers hardness to acquire material properties was established. It can be used in the welded lines of nuclear dissimilar metal welded joints to obtain material parameters of mechanical property uneven zone of welded joints, and this new method was supported for complex engineering structure material mechanical parameters.