Search

This study proposed a novel application of Neural Network AutoRegressive eXogenous (NNARX) model in predicting nonlinear behaviour of riverbank erosion rates which is difficult to be achieved with good accuracy using conventional approaches. This model can estimate complex river bank erosion rates with flow variations. The NNARX model analysed to a set of primary data, 60% (203 data for training) and 40% (135 data for testing), which were collected from Sg. Bernam, Malaysia. A set of nondimensional parameters, known as functional relationship, used as an input to the NNARX model has been established using the method of repeating variables. The One-Step-Ahead time series prediction plots are used to assess the accuracy of all developed models. Model no. 6 (5 independent variables with 10 hidden layers) gives good predictive performance, supported by the graphical analysis with discrepancy ratio of 94% and 90% for training and testing datasets. This finding is consistent with model accuracy result, where Model no. 6 achieved R2 of 0.932 and 0.788 for training and testing datasets, respectively. Result shows that bank erosion is maximized when the near-bank velocity between 0.2 and 0.5 m/s, and the riverbank erosion is between 1.5 and 1.8 m/year. On the other hand, higher velocities ranging from 0.8 to 1.3 m/s induces erosion at a rate between 0.1 and 0.4 m/year. Sensitivity analysis shows that the highest accuracy of 91% is given by the ratio of shear velocity to near-bank velocity followed by boundary shear stress to near-bank velocity ratio (88.5%) and critical shear stress to near-bank velocity ratio (88.2%). It is concluded that the developed model has accurately predicted non-linear behaviour of riverbank erosion rates with flow variations. The study's findings provide valuable insights in advanced simulations and predictions of channel migration, encompassing both lateral and vertical movements, the repercussions on the adjacent river corridor, assessing the extent of land degradation and in formulating plans for effective riverbank protection and management measures.

The main objective of this study is to analyse the effect of the non-linear behaviour of the soil on the seismic response of a foundation by taking into account the soil-structure interaction. The foundation is square-shaped, and rigid, resting on the surface of a homogeneous semi-infinite soil, and solicited only by the incident harmonic wave SH. However, for higher deformations (during strong earthquakes), the behaviour of the soil will be characterised by a nonlinear behaviour law. The phenomenon of soil nonlinearity due to the seismic excitation imposed on the soil is reflected in the curve of reduction of the normalised shear modulus G/Gmax and the curve of increase of the normalised hysteretic damping coefficient ξ/ξmax as a function of the unit shear deformation γ/γr. This behaviour is obtained by the equivalent linear method with the Masing model implemented in the one-dimensional (1D) computational code Caldynasoil. In this study, first, determine the nonlinear behaviour of a soil profile stressed by different levels of seismic accelerations applied at the bedrock level. The Caldynasoil computational code was used to find the variations of the nonlinear dynamic properties of the soil profile for different levels of seismic loading. Secondly, integrating the nonlinear dimensionless properties of the soil in a three-dimensional computational code Fonvib_Wave based on the boundary elements method combined with the theory of thin layers (BEM-TLM) in the frequency domain allows calculating the nonlinear displacements of a surface foundation. The obtained results represent the influence of the nonlinear behaviour of the soil on the vibration modes of a rigid foundation subjected to a shear wave SH as a function of the dimensionless frequency a0, and the angles of incidence θV and θH. The conclusions that may predict from this research have shown the importance of the influence of the nonlinear behaviour of the soil and the angles of incidence of the SH wave on the response of the soil-foundation system compared to the linear case. [ABSTRACT FROM AUTHOR]

Current seismic regulations neglect the influence of multiple seismic events on the seismic response, which, as already recognized in the literature, may influence the seismic behavior of reinforced concrete structures. Symmetrical and asymmetrical low-rise reinforced concrete frames are investigated here via nonlinear time-history (NLTH) analysis considering multiple earthquake events, as well as under a respective single seismic event, for comparison purposes. The two horizontal directions, as well as the vertical one, of the ground excitation are considered in the dynamic analysis, assuming the elastoplastic action of reinforced concrete sections under heavy loading. A simple ratio is defined to express the geometrical in-plane asymmetry of the buildings. The nonlinear response outcomes of the time-history analyses are appropriately plotted by using unitless parameters for an objective estimation of the structural behavior under multiple earthquakes. The dimensionless response results and plots are presented and discussed in view of the relative geometrical asymmetry of the 3D frames. The effect of the multiple seismic events, as well as the one of a simple geometrical symmetry/asymmetry, is identified and discussed in the presented plots resulting from the dynamic analysis. Thus, practical remarks are presented regarding the significance of the in-plane symmetry/asymmetry of frames for improvements in the provisions of the current seismic regulations to develop safer structures. [ABSTRACT FROM AUTHOR]

This paper is concerned with the calibration and validation of a numerical procedure for the analysis of pile performance in soft clays during seismic soil–pile–superstructure interaction (SSPSI) scenarios. Currently, there are no widely accepted methods or guidelines. Centrifuge and shaking table model tests are often used to supplement the available field case histories with the data obtained under controlled conditions. This paper presents a new calibration method for establishing a reliable and accurate relationship between full-scale numerical analysis and scaled laboratory tests in a 1g environment. A sophisticated approach to scaling and validating full-scale seismic soil–structure interaction problems is proposed that considers the scaling concept of implied prototypes as well as "modelling of models" techniques that can ensure an excellent level of accuracy. In this study, a new methodology was developed that can provide an accurate, practical, and scientific calibration for the relationship between full-scale numerical analysis and scaled laboratory tests in the 1g environment. The framework can be followed by researchers who intend to validate their seismic soil–structure interaction findings. [ABSTRACT FROM AUTHOR]

Solving dynamics problem in the frequency domain gives significant advantages compared with solutions fully computed in the temporal domain, but history-dependent nonlinear behaviour is an obstacle to employ that strategy. A hybrid approach is proposed to solve the nonlinear behaviour in the temporal domain, while the mechanical equilibrium is solved using a frequency strategy coupled with model-order reduction methods. In order to employ the fast Fourier transform (FFT) robustly for the transient regime, artificial numerical damping is used. The reduced-order hybrid temporal-frequency approach is investigated for two- and three-dimensional applications; it appears as a robust and proficient technique to simulate structures under transient dynamic loadings until failure. [ABSTRACT FROM AUTHOR]

It is known that bomb-laden vehicles target many buildings as a result of terrorist activities. The effects of such attacks must be reduced and structures must be protected against blast effects. In high seismic hazard regions, buildings are designed to be earthquake resistant. One of the methods used to dampen earthquake effects on structures is base isolation. Base isolation is effective in distributing blast loads to the structure, similar to seismic loading. In this study, the effects of this distribution on the structure will be evaluated. The scope of the study encompasses the numerical estimation of explosive loads at different distances according to the explosive material carrying capacity of various vehicles and their effects on structures. Linear and nonlinear analysis methods were used to compare the dynamic behaviour of school buildings designed with and without base isolators. The Turkish Building Earthquake Code (2018), which includes the maximum seismic loads, was used in the design of the isolators. Numerical analysis was performed using SAP2000 software based on the finite element method. The blast loads were applied to the floors of the building using the direct integration method in the time domain. FEMA standards were used to determine the blast loads and the performance was evaluated in comparison with the numerical analysis results. As a result of the study, it was concluded that structures with base isolators are efficient in reducing the effects of an explosion at certain distances and these distances will affect the design of the shelter walls. [ABSTRACT FROM AUTHOR]

The collaborative robot market has experienced rapid growth, leading to advancements in compliant actuation and torque control. Magneto-rheological (MR) clutches offer a hardware-level solution for achieving both compliance and torque control through adjustable coupling between the input and output of the MR clutch. However, the presence of frequency-dependent magnetic hysteresis makes controlling the output torque challenging. In this paper, we present a comparative study of six widely used hysteresis models and propose a computationally efficient algebraic model to address the issue of hysteresis modeling and control of the output torque of rotary MR clutches. We compare the estimated torques with experimental measurements from a prototype MR clutch, to evaluate the computational complexity and accuracy of the model. Our proposed algebraic hysteresis model demonstrates superior accuracy and approximately two times less computational complexity than the Bouc–Wen model, and approximately twenty times less memory requirement than neural network-based models. We show that our proposed model has excellent potential for embedded indirect torque control schemes in systems with hysteresis, such as MR clutches and isolators. [ABSTRACT FROM AUTHOR]

The unique properties of Shape Memory Alloys (SMAs) have motivated researchers to use them as primary reinforcement in reinforced concrete (RC) structures. In this study, the applicability of using external unbonded SMA bars to retrofit RC beam-column joints (BCJs) is investigated. A three-dimensional finite element model, which simulates the suggested retrofitting technique, is first developed, and validated using ABAQUS software. The model is then further simplified and utilized to conduct a parametric study to investigate the behaviour of SMA retrofitted RC BCJs. Results of the parametric study are used to perform multiple linear regression analysis. Simple equations, which can be used to calculate the length and amount of SMA bars required to retrofit a RC BCJ, are then developed.

This paper is concerned with the calibration and validation of a numerical procedure for the analysis of pile performance in soft clays during seismic soil–pile–superstructure interaction (SSPSI) scenarios. Currently, there are no widely accepted methods or guidelines. Centrifuge and shaking table model tests are often used to supplement the available field case histories with the data obtained under controlled conditions. This paper presents a new calibration method for establishing a reliable and accurate relationship between full-scale numerical analysis and scaled laboratory tests in a 1g environment. A sophisticated approach to scaling and validating full-scale seismic soil–structure interaction problems is proposed that considers the scaling concept of implied prototypes as well as “modelling of models” techniques that can ensure an excellent level of accuracy. In this study, a new methodology was developed that can provide an accurate, practical, and scientific calibration for the relationship between full-scale numerical analysis and scaled laboratory tests in the 1g environment. The framework can be followed by researchers who intend to validate their seismic soil–structure interaction findings.

The complexity of biaxial tests and analysis of their results makes it difficult to study the interlaminar shear properties of fibre-reinforced composites, particularly under through-thickness compression, which occurs in thick-walled composite elements. The improvements in experimental methods to study the features of the nonlinear behaviour of composites under biaxial loading is now an important and relevant task in the development aircraft structural elements made of carbon fibre-reinforced polymers. This study aimed to develop a new experimental approach for the reliable determination of the interlaminar shear properties of laminates under through-thickness compression using a standard testing machine. An appropriate V-notched specimen was developed based on the configuration of well-known Iosipescu and butterfly-shaped specimens. The approach is demonstrated using woven carbon/epoxy laminates. Both the preliminary assessment of the stress fields under combined compression/shear loading and the analysis of fracture mechanisms were performed with finite-element modelling in a three-dimensional formulation. The digital image correlation (DIC) method was used to obtain experimental, full-field deformations of the specimens and to estimate the uniformity of the strain distribution in the gauge section. The stress–strain curves were obtained under biaxial loading, and the corresponding features of the composite failure behaviour were analysed in detail. It was found that the maximum compression strain on the stress–strain curves, in some cases, corresponded to the discontinuity in the composite structure. In these cases, the disproportionate changes in through-thickness strains in the gauge section of the specimens were recorded at the maximum load. With the increase in through-thickness compression stresses, the difference between the shear strength values, determined by the maximum load and the maximum compressive strain, increased by up to 20%. It was shown that the assessment of the composite strength at maximum load at the design stage significantly increased the risk of premature failure of the composite elements during exploitation. [ABSTRACT FROM AUTHOR]

Representative modelling of reinforced concrete (RC) components in underground structures is essential for accurate assessment of structural performance (deformations and internal forces) within numerical simulations. This paper examines the implications of selecting different structural modelling approaches within the seismic (dynamic) finite element analysis of a buried structure of complex shape, using the CMS (Compact Muon Solenoid) Detector Cavern of the Large Hadron Collider in Geneva, Switzerland, as a case study. Two alternate modelling approaches were employed to model the cavern lining: (i) a composite continuum approach, with the concrete and embedded reinforcement being explicitly modelled; and (ii) the use of a nonlinear elasto-plastic plate element. The pre-earthquake ground initial conditions were determined through simulation of the construction and detector installation operations consistent with field measurements from extensometers and internal survey of floor deformations. The results demonstrate the importance of adopting a non-linear continuum modelling approach in representing the RC lining under strong shaking events to avoid under-prediction of seismic actions at locations of potential seismically induced damage. Such an approach will be essential in 3D problems where multi-axial dynamically varying stresses are applied on the RC section. Finally, it offers a realistic approach in representing structures of complex shape and that contains volume and thick elements. • Composite-continuum approach for modelling reinforced concrete accurately simulated beam and column tests. • Composite-continuum and elasto-plastic plate approaches accurately simulated construction-induced lining deformations. • Plate elements underestimated seismic actions under strong shaking in critical regions. • Elasto-plastic plates cannot be used to model thick concrete elements (e.g. inverts). • Composite-continuum approach offers more realistic modelling of complex underground structures. [ABSTRACT FROM AUTHOR]

The collaborative robot market has experienced rapid growth, leading to advancements in compliant actuation and torque control. Magneto-rheological (MR) clutches offer a hardware-level solution for achieving both compliance and torque control through adjustable coupling between the input and output of the MR clutch. However, the presence of frequency-dependent magnetic hysteresis makes controlling the output torque challenging. In this paper, we present a comparative study of six widely used hysteresis models and propose a computationally efficient algebraic model to address the issue of hysteresis modeling and control of the output torque of rotary MR clutches. We compare the estimated torques with experimental measurements from a prototype MR clutch, to evaluate the computational complexity and accuracy of the model. Our proposed algebraic hysteresis model demonstrates superior accuracy and approximately two times less computational complexity than the Bouc–Wen model, and approximately twenty times less memory requirement than neural network-based models. We show that our proposed model has excellent potential for embedded indirect torque control schemes in systems with hysteresis, such as MR clutches and isolators.

It is known that bomb-laden vehicles target many buildings as a result of terrorist activities. The effects of such attacks must be reduced and structures must be protected against blast effects. In high seismic hazard regions, buildings are designed to be earthquake resistant. One of the methods used to dampen earthquake effects on structures is base isolation. Base isolation is effective in distributing blast loads to the structure, similar to seismic loading. In this study, the effects of this distribution on the structure will be evaluated. The scope of the study encompasses the numerical estimation of explosive loads at different distances according to the explosive material carrying capacity of various vehicles and their effects on structures. Linear and nonlinear analysis methods were used to compare the dynamic behaviour of school buildings designed with and without base isolators. The Turkish Building Earthquake Code (2018), which includes the maximum seismic loads, was used in the design of the isolators. Numerical analysis was performed using SAP2000 software based on the finite element method. The blast loads were applied to the floors of the building using the direct integration method in the time domain. FEMA standards were used to determine the blast loads and the performance was evaluated in comparison with the numerical analysis results. As a result of the study, it was concluded that structures with base isolators are efficient in reducing the effects of an explosion at certain distances and these distances will affect the design of the shelter walls.

Spatial variability of tensile strength, widely existing in concrete gravity dams due to the influence of long construction period and heterogeneous construction quality, has a profound impact on the nonlinear behaviour of structures. In this paper, a method to simulate the random field of the tensile strength of concrete gravity dams based on the random field theory is proposed. A typical non-overflow dam section of the Guandi gravity dam is taken as an example, artificial seismic waves with similar response spectra and natural seismic waves with different magnitudes are selected for the comparative analysis. Based on the concrete damage plasticity (CDP) model and incremental dynamic analysis (IDA) method, the damage characteristics, failure modes, probability density evolution processes, and fragility curves obtained from gravity dams with homogenous and random fields of tensile strength are compared with each other. The differences among waves and realisations of random fields are also investigated. It is seen that the spatial variability of tensile strength aggravates the damage degree, decreases the continuity of local damaged areas, and increased the failure probability of global dams. It reveals that the random characteristics affect the dams' nonlinear behaviour directly. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a theoretical meso-model describing the nonlinear behaviour of filament wound glass–polyester composite structures based on a progressive damage and failure analysis. This model has been implemented in the finite element modelling software Abaqus through the user material subroutine and then validated by experimental investigations. Numerical results have been compared with experimental data obtained from a set of tests on representative specimens using the strain measurement technique.

The nonlinear behavior of a soil–foundation interface due to mobilization of the ultimate capacity and the consequent energy dissipation may be utilized to alter seismic demands of a structure. However, current design practice does not account for the nonlinear behavior of soil–foundation interface primarily due to the absence of reliable nonlinear soil–structure interaction (SSI) modeling techniques. The objective of this study is to simulate the performance of multi-story building-foundation systems through a Winkler-based approach. Opensees finite element framework is employed for simulation. Four typical 4, 8, 12 and 16-story steel moment resisting frame (MRF) buildings on three hypothetically soft, medium and hard soil sites with shear wave velocities less than 600m/s subjected to actual ground motion records of varied hazard levels are modeled with and without SSI. It is observed that the performance level of models supported by flexible foundation, particularly in an intense earthquake event, may alter significantly in comparison to fixed-base structures. Moreover, for MRFs on soft soil, the nonlinear foundation is found to have a significant effect on the force and displacement demands. This is indicating the necessity for consideration of flexible foundation behavior in the modern design codes in order to accomplish an economic yet safe structural design.

In this paper, the effect of openings on global performance of Cold Formed Steel Shear Wall Panels is investigated numerically using the ABAQUS software. A benchmark model is first validated in terms of lateral shear capacity and nonlinear behaviour of the CFS-SWP. The failure mode of the CFS-SWP with opening is identified and validated. Subsequently, a parametric study on the effect of size and position of openings is conducted, in which the opening position is found to have a significant impact on the CFS-SWP performance. The benchmark model can be used for design purposes to evaluate with good accuracy the reduced ultimate strength of individual CFS-SWPs for any size and position of openings.

The minarets, which have a tall and slender structure, are quite vulnerable to dynamic forces, i.e. earthquakes and winds. In mainly concrete minarets, since the bond between the concrete blocks is provided by only mortar, the damages caused by high tensile stresses may emerge. This study aims to simulate the behaviour of the concrete Selimiye minaret damaged during the İzmir (Seferihisar-Samos) earthquake on October 30, 2020. The nonlinear finite element model of the Selimiye minaret is created using the Concrete Damage Plasticity failure model. In the nonlinear time history analyses, the İzmir earthquake records obtained from the Bayraklı station, located the closest to the minaret, are used. The damages occurring in the transition segment of the minaret are verified with the finite element method. This study also aims to strengthen insufficient concrete minarets with an innovative, cost-effective, and better workability method. The proposed strengthening method is based on a Fabric Reinforced Concrete Mixture. Finite element models are strengthened from the inner surface using Fabric Reinforced Concrete Mixture composites reinforced with glass and steel fibers. As a result of the finite element analyses, it is concluded that the concrete minarets can be strengthened from the inner surface with the Steel Fabric Reinforced Concrete Mixture method in safety. In addition, with a parametric study, it has been determined that partial strengthening applications, which are more economical and aesthetic, can be more effective on structural performance than full strengthening applications. [ABSTRACT FROM AUTHOR]

The unique properties of Shape Memory Alloys (SMAs) have motivated researchers to use them as primary reinforcement in reinforced concrete (RC) structures. In this study, the applicability of using external unbonded SMA bars to retrofit RC beam-column joints (BCJs) is investigated. A three-dimensional finite element model, which simulates the suggested retrofitting technique, is first developed, and validated using ABAQUS software. The model is then further simplified and utilized to conduct a parametric study to investigate the behaviour of SMA retrofitted RC BCJs. Results of the parametric study are used to perform multiple linear regression analysis. Simple equations, which can be used to calculate the length and amount of SMA bars required to retrofit a RC BCJ, are then developed. [ABSTRACT FROM AUTHOR]

Impact interactions take place in the process of dynamic behavior in the elements of manipulators and robots. Their precise investigation is an important engineering problem. A model having one degree of freedom with forced excitation and impacts is investigated. A special procedure for more precise calculation of impacts is proposed. Numerical results for various parameters of the investigated system are presented. The advantage of the application of the proposed procedure for more precise calculations of dynamics of this system is indicated. [ABSTRACT FROM AUTHOR]

The complexity of biaxial tests and analysis of their results makes it difficult to study the interlaminar shear properties of fibre-reinforced composites, particularly under through-thickness compression, which occurs in thick-walled composite elements. The improvements in experimental methods to study the features of the nonlinear behaviour of composites under biaxial loading is now an important and relevant task in the development aircraft structural elements made of carbon fibre-reinforced polymers. This study aimed to develop a new experimental approach for the reliable determination of the interlaminar shear properties of laminates under through-thickness compression using a standard testing machine. An appropriate V-notched specimen was developed based on the configuration of well-known Iosipescu and butterfly-shaped specimens. The approach is demonstrated using woven carbon/epoxy laminates. Both the preliminary assessment of the stress fields under combined compression/shear loading and the analysis of fracture mechanisms were performed with finite-element modelling in a three-dimensional formulation. The digital image correlation (DIC) method was used to obtain experimental, full-field deformations of the specimens and to estimate the uniformity of the strain distribution in the gauge section. The stress–strain curves were obtained under biaxial loading, and the corresponding features of the composite failure behaviour were analysed in detail. It was found that the maximum compression strain on the stress–strain curves, in some cases, corresponded to the discontinuity in the composite structure. In these cases, the disproportionate changes in through-thickness strains in the gauge section of the specimens were recorded at the maximum load. With the increase in through-thickness compression stresses, the difference between the shear strength values, determined by the maximum load and the maximum compressive strain, increased by up to 20%. It was shown that the assessment of the composite strength at maximum load at the design stage significantly increased the risk of premature failure of the composite elements during exploitation.

A continuous stirred tank reactor (CSTR) is a standout nonlinear system among the most essential units of chemical industries. In this article, an Elman neural network is designed to analyse the characteristics of nonlinear behaviour of the CSTR system. The data generated employing the state-space model of CSTR are used to train the designed Elman neural network controller and the controller parameters are optimally tuned by the proposed hybrid swarm intelligencebased optimization algorithm. Two different hybridizations have been developed, including DPSO, DGSA and hybrid DPSO-DGSA and successfully employed in controller tuning. The significance of the proposed controller is validated by a comparative analysis made with conventional methods and the performance is experimentally demonstrated using MATLAB software. [ABSTRACT FROM AUTHOR]

Manipulators and robots find a number of applications in agricultural engineering. They are used in pipe robots for transportation of materials. Also pipe robots are applied for cleaning of internal surfaces of the pipes. Impact interactions take place in the process of dynamic behavior in the elements of manipulators and robots. Their precise investigation is an important engineering problem. A model having one degree of freedom with forced excitation and impacts is investigated. The values of coefficient of restitution and coefficient of viscous damping have basic effect to the dynamic behavior of such systems. In this paper the investigations of the dependence of regions with single valued regimes of motion from the coefficient of restitution and from the coefficient of viscous damping are performed. This paper is devoted to numerical experiment: the model of the system is presented in detail as well as the parameters for which calculations were performed are indicated. The presented graphical relationships enable to choose the regimes suitable for operation of elements of manipulators and robots. They are applicable in the process of design of pipe robots. [ABSTRACT FROM AUTHOR]

Unstable friction-induced vibrations are considered an annoying problem in several fields of engineering. Although several theoretical analyses have suggested that friction-excited dynamical systems may experience sub-critical bifurcations, and show multiple coexisting stable solutions, these phenomena need to be proved experimentally and on continuous systems. The present work aims to partially fill this gap. The dynamical response of a continuous system subjected to frictional excitation is investigated. The frictional system is constituted of a 3D printed oscillator, obtained by additive manufacturing that slides against a disc rotating at a prescribed velocity. Both a finite element model and an experimental setup has been developed. It is shown both numerically and experimentally that in a certain range of the imposed sliding velocity the oscillator has two stable states, i.e. steady sliding and stick–slip oscillations. Furthermore, it is possible to jump from one state to the other by introducing an external perturbation. A parametric analysis is also presented, with respect to the main parameters influencing the nonlinear dynamic response, to determine the interval of sliding velocity where the oscillator presents the two stable solutions, i.e. steady sliding and stick–slip limit cycle. [ABSTRACT FROM AUTHOR]

Offshore steel trestles (OSTs) are commonly used to construct sea-crossing bridges. Presuming OSTs to be elastic to hydrodynamic hazards during their service lifetime is economically unacceptable due to their use as a temporary facility. In order to enhance operational safety and also reduce building costs, a nonlinear analysis framework is developed based on pushover approach and is applied to assess the nonlinear response of OSTs subjected to wave and current loads. The framework yields a nonlinear response curve that supplies structural nonlinear behaviors, capacities and plasticity development as functions of wave height. The dynamic amplification, current speed, loading direction, marine growth and soil-structure interaction (SSI) on the nonlinear response of the example OST under wave and current loads are then investigated. The results show that the structurally vulnerable positions of OST are located at the bottom of the piles and the joints connecting the brace to the pile. [ABSTRACT FROM AUTHOR]

A mechanical model has been presented for analysis of plates resting on extensible geosynthetic reinforced granular fill lying on soft soil improved by stone columns. Foundation has been idealised as a plate and geosynthetic layer as rough elastic membrane. Granular fill, soft soil and stone columns has been idealised respectively as Pasternak shear layer, Kelvin–Voigt elements and Winkler springs and their nonlinear behaviour has been considered. Deformation compatibility condition at interface of geosynthetic and granular fill has been considered. An iterative finite difference scheme with proper boundary conditions has been used to solve governing differential equations and the system of simultaneous equations so obtained, have been solved using LU decomposition method. Response of plate in terms of deflection and bending moment and tension mobilized in geosynthetic has been presented in non-dimensional form. Influence of type of geosynthetic (extensible and inextensible) in reducing the settlements in conjunction with stone columns has been presented and the significance of each parameter influencing the plate response has been studied by means of detailed parametric study. [ABSTRACT FROM AUTHOR]

• Knowledge gained about sampling extraction for very thick brick masonry structures. • Core testing method performed for multi-wythe brick masonry infrastructure. • Comparable mechanical properties obtained from cores and rectangular samples. • Stiffer compressive behaviour and weaker flexural bond properties closer to water. The present work aims at providing insights on the material characterization of multi-wythe masonry infrastructure, in particular exploring a through-thickness effect of mechanical properties and benchmarking the core testing as an efficient slightly-destructive testing method. An experimental campaign was carried out to characterize shear, compressive and bond properties of a 1.2-m thick bridge's pillar constructed in 1882 in the city of Amsterdam (the Netherlands). Both cores and rectangular samples (e.g. prisms, triplets, couplets) were extracted across different locations in the wall thickness to evaluate the effect of exposure to environment conditions and to verify the capability of core testing methods. Results show that the masonry close to the water side (external) showed higher values of elastic modulus and lower values of flexural bond properties with respect to masonry inside the pillar. As for the capability of core testing on multi-wythe masonry, generally cores would present similar compressive/shear properties compared with rectangular samples. Besides, bond patterns and dimensions of cores showed negligible effect on compressive properties; However, this needs to be extensively verified by considering other masonry typologies. Overall, the study provides a first insight on the mechanical properties of multi-wythe masonry urban infrastructure and knowledge regarding the sampling and testing strategy for these structures. In turn, this will increase the knowledge on multi-wythe masonry, which is limited in literature, and will support the assessment of many infrastructure in typical Dutch canal cities by providing input for calculation methods. [ABSTRACT FROM AUTHOR]

This study proposed a novel application of Neural Network AutoRegressive eXogenous (NNARX) model in predicting nonlinear behaviour of riverbank erosion rates which is difficult to be achieved with good accuracy using conventional approaches. This model can estimate complex river bank erosion rates with flow variations. The NNARX model analysed to a set of primary data, 60% (203 data for training) and 40% (135 data for testing), which were collected from Sg. Bernam, Malaysia. A set of nondimensional parameters, known as functional relationship, used as an input to the NNARX model has been established using the method of repeating variables. The One-Step-Ahead time series prediction plots are used to assess the accuracy of all developed models. Model no. 6 (5 independent variables with 10 hidden layers) gives good predictive performance, supported by the graphical analysis with discrepancy ratio of 94% and 90% for training and testing datasets. This finding is consistent with model accuracy result, where Model no. 6 achieved R 2 of 0.932 and 0.788 for training and testing datasets, respectively. Result shows that bank erosion is maximized when the near-bank velocity between 0.2 and 0.5 m/s, and the riverbank erosion is between 1.5 and 1.8 m/year. On the other hand, higher velocities ranging from 0.8 to 1.3 m/s induces erosion at a rate between 0.1 and 0.4 m/year. Sensitivity analysis shows that the highest accuracy of 91% is given by the ratio of shear velocity to near-bank velocity followed by boundary shear stress to near-bank velocity ratio (88.5%) and critical shear stress to near-bank velocity ratio (88.2%). It is concluded that the developed model has accurately predicted non-linear behaviour of riverbank erosion rates with flow variations. The study's findings provide valuable insights in advanced simulations and predictions of channel migration, encompassing both lateral and vertical movements, the repercussions on the adjacent river corridor, assessing the extent of land degradation and in formulating plans for effective riverbank protection and management measures., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)

This study proposes two new emulator circuits of floating (grounded) flux‐controlled incremental/decremental memristor, based on modified z‐copy current–voltage differencing transconductance amplifier (VDTA). The circuits use only one VDTA as an active element, a single grounded capacitor and a variable number of grounded resistors, which benefit from the integrated circuit. Furthermore, it can utilise metal–oxide–semiconductor (MOS) capacitance instead of the external capacitor in the circuit. It does not consist of any multiplication circuit block to obtain non‐linear behaviour of the memristor. The parameters of the proposed memristor emulator can be tuned electronically by changing the biasing current of the VDTA. Change of the transconductance gain of the VDTA provides an advantage in the form of the externally controllable memristor. Through the simulation program with integrated circuit emphasis (SPICE) simulation which was carried out on the basis of 0.18 μm complementary MOS technology and experimental results using two MAX435 commercial devices as an active element, all theoretical assumptions and conclusions were reached in different operating frequencies, the capacitance value and process corner. The simulation test results have shown that the maximum frequency is 50 MHz. [ABSTRACT FROM AUTHOR]

The aim of the present study is to develop a curvature factor to estimate the ultimate strength and the progressive collapse behaviour of a stiffened curved plate under combined in-plane compression and lateral pressure. Stiffened curved plates are used in various parts of ship and offshore structures, such as bilge structures, columns and the inside structures of offshore semisubmersible rigs. The curvature of a cylindrically curved plate is found to increase the buckling strength and ultimate strength compared with a plate without curvature. Based on the numerical results of a series of nonlinear finite element calculations for all edges with symmetric curved plating with varying parameters such as slenderness ratio, stiffener size, flank angle and amplitude of lateral pressure, an empirical design factor is derived to predict the curvature influence for a fundamental scantling design by rule guidance. The outcomes can be widely referred to in basic designs to decide the required bilge thickness during local scantling. [ABSTRACT FROM AUTHOR]

This study presents a fault location algorithm (FLA) for series compensated transmission lines (SCLs). It is established based on synchronised voltages sampling and Thevenin impedance estimation from both ends of SCL. The method is based on the use of phasor measurement units technology which is aimed to be independent of current measurements. This method includes two subroutines for the faults located on the right‐hand and left‐hand sides of series capacitor (SC). Lumped modelling is considered for SCL with SC equipped with metal–oxide varistor (MOV) arrester. The non‐linear behaviour of SC‐MOV system is investigated in the analysis. The proposed current independent FLA has been thoroughly tested using signals taken from simulations. According to the results, the percentage errors for the fault distances estimation are in proper ranges. [ABSTRACT FROM AUTHOR]

In this paper, the condition of a full-scale concrete bridge subjected to strong earthquakes is evaluated using vibration-based analyses. A new computational toolkit is developed in MATLAB environment for damage identification and long-term monitoring. Two types of parametric and non-parametric analysis methods are carried out on monitoring data. Moreover, a dynamic performance index is proposed based on an AutoRegressive Moving Average with eXogenous excitation (ARMAX) model. This index utilises the response predicted from an ARMAX model to evaluate bridge behaviour during strong earthquakes. Based on the results, a minor but permanent drop of 0.05 Hz in natural frequency of the first transverse and vertical modes is observed after the first strong earthquake. Also, a significant drop in frequency of the first transverse mode is observed during the two strong earthquakes. The results of the index show that the bridge did not follow linear behaviour during the two strong earthquakes as expected from a linear system. A close to flag-shaped force-displacement relationship is also observed during the first strong earthquake that can be an indication of nonlinearity in bridge behaviour. The analysis results illustrate the efficiency of the new monitoring platform for long-term monitoring and management of large datasets. [ABSTRACT FROM AUTHOR]

Abstract Major seismic events have shown that tunnels in cohesionless soils may suffer extensive seismic damage. Proper modelling can be of great importance for predicting and assessing their seismic performance. This paper investigates the effect of lining structural modelling on the seismic behaviour of horseshoe-shaped tunnels in sand, inspired from an actual Metro tunnel in Santiago, Chile. Three different approaches are comparatively assessed: elastic models consider sections that account for: (a) linear elastic lining assuming the geometric stiffness; (b) linear elastic lining matching the uncracked stiffness of reinforced concrete (RC); and (c) nonlinear RC section, accounting for stiffness degradation and ultimate capacity, based on moment-curvature relations. It is shown that lining structural modelling can have major implications on the predicted tunnel response, ranging from different values and distributions of the lining sectional forces, to differences in the predicted post-earthquake settlements, which can have implications on the seismic resilience of aboveground structures. Highlights • The alternative tunnel models exhibit different lining forces along their section. • The locations of the maximum lining forces are identified on the section. • The modelling approach does not affect the ground surface acceleration. • The modelling approach has a significant effect on post-earthquake settlements. [ABSTRACT FROM AUTHOR]

Vehicular traffic can be modelled as a dynamic discrete form. As in many dynamic systems, the parameters modelling traffic can produce a number of different trajectories or orbits, and it is possible to depict different flow situations, including chaotic ones. In this paper, an approach to the wellknown density-flow fundamental diagram is suggested, using an analytical polynomial technique, in which coefficients are taken from significant values acting as the parameters of the traffic model. Depending on the values of these parameters, it can be seen how the traffic flow changes from stable endpoints to chaotic trajectories, with proper analysis in their stability features.