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A simple analytical model for calculating the nonlinear deformations of a corrugated core (fluting) during out-of-plane compression is developed. The results from the analytical model are compared to a more comprehensive finite-element model and to experiments. A connection between the boundary conditions and the damage state of the corrugated board is discussed. Including a modified set of boundary conditions gives an almost perfect match of the initial stiffness to the experimental results, indicating that the core might be significantly damaged as a result of the manufacturing process. Possibly, the strength of corrugated boards might be increased about 20% if one could avoid damaging the fluting during the manufacturing process. DOI: 10.1061/(ASCE)0733-9399(2007)133:11(1171) CE Database subject headings: Structural analysis; Finite element method; Deformation; Corrugating.

High-rise structures with large aspect ratios are subjected to unexpected motions under wind excitation. Structural vibrations induced by vortices in the wake were captured by aeroelastic real-time hybrid simulation (aeroRTHS) in the companion paper. An effective and practical method is critical for explaining the mitigation of adverse wind loading impact upon these structures. Analyzing the performance of structural control devices against wind excitation in an aeroelastic wind tunnel test often is time- and cost-intensive. In this paper, aeroRTHS testing is extended to include (1) a vibration control device numerically added to the numerical substructures and tested to mitigate the cross-wind oscillation in the aeroRTHS framework; and (2) the use of 128 pressure sensors installed on two side faces of a physical building model in a boundary layer wind tunnel (BLWT) at the University of Florida Natural Hazards Engineering Research Infrastructure Equipment Facility (UF NHERI EF) to provide a more complete description of the wind-force distributions imparted on nine building configurations both with and without a tuned mass damper (TMD) at various constant wind speeds. Wind-force distribution was characterized in the time domain in terms of time histories of equivalent forces and displacements, and envelopes of wind forces. Frequency response analysis was conducted based on power spectral densities of input equivalent wind forces and output structural dynamic response. Results from the aeroRTHS tests demonstrated that the aeroRTHS method is capable of investigating aeroelastic structures with passive mitigation devices. The aeroRTHS tests in the wind tunnel demonstrated that the augmentation of buildings with TMDs is an effective way to attenuate the cross-wind vibration in tall buildings. [ABSTRACT FROM AUTHOR]

The special collection on the EMI Conference Student Competition Finalist Papers is available in the ASCE Library (https://ascelibrary.org/jenmdt/emi student finalist papers). This online collection is comprised of invited papers based on the paper/poster winners and finalists of the student paper/poster competitions that take place every year during the annual Engineering Mechanics Institute (EMI) Conference, starting from the 2020 EMI conference. [Extracted from the article]

Some of the papers by the discussers were cited by the authors in the original paper, but it is not necessary to cite those EKF papers published many years ago. The proposed UKF-UI by the authors in the original paper was a direct extension of the classical UKF; therefore, it was capable of structural damage detection using partial structural responses. In contrast, the UKF-UI by the authors in the original paper provided the recursive identification of a joint structural system and unknown inputs, so it is a real-time identification approach like the classical UKF method. Differently, the authors of the original paper proposed an approach of simultaneous identification of joint structural systems and unknown inputs for large structural systems using the unscented Kalman filter with unknown input (UKF-UI) method. [Extracted from the article]

This paper presents the mathematical derivation and numerical implementation of a novel regularized density-driven damage mechanics (D3M) model for simulating failure in concrete members. The novel idea behind the derivation of the approach is that damage is described as a function of the local change in material density. This choice is justified by the fact that the development of local damage directly corresponds to a reduction in local density since undamaged cementitious composites inherently have a higher density than the fluid or gas that occupies damaged regions. For this reason, devising numerical approaches that can predict the material behavior as a function of density could open up new possibilities for the prediction of the nonlinear behavior of concrete structures, as well as the derivation of novel testing procedures for the evaluation of strength by means of direct and indirect measures of density. In this context, a three-phase mesoscopic representation of concrete material is used, where coarse aggregate, mortar, and the interfacial transition zone are explicitly modeled to obtain a realistic representation of the material internal structure. The manuscript first presents the mathematical derivation of the model, with emphasis devoted to the regularization of the computational implementation. This paper then proceeds to demonstrate that the novel regularized D3M is insensitive to the mesh size chosen to represent the three material phases while also predicting realistic compression-to-tension strength ratios and damage patterns at failure. In addition, a parametric study is carried out to illustrate the effect of the relevant mechanical parameters on the observed response. Finally, the proposed model is validated by comparison with experimental results of 3-point bending tests on plain concrete beams of various sizes, also demonstrating that the regularized D3M is capable of predicting size effect in concrete members. [ABSTRACT FROM AUTHOR]

Photogrammetry has gained the interest of professionals and researchers for activities related to construction projects' progress monitoring via attaining precise 3D point models. However, the precision of the generated models is directly linked with the precise scaling of the point cloud to ground truth dimensions (GTDs). Available scaling-up procedures for the close-range photogrammetry technique are complex, time consuming, and require human intervention, which adds the risk of error in the scaled-up model dimensions. Such a scenario creates hesitation among industry professionals toward implementing point cloud technologies. This paper devises an automated scaling-up methodology to overcome the said concerns by considering the construction progress monitoring theme. The intact process of automated scaling up of point cloud model to GTDs is controlled by two main parameters, that is, Python-based modules and designed ArUco-supported controlled markers. Remarkable outcomes are achieved with less than 1% scaled-up error compared with GTDs, which will improve the confidence of industry professionals toward point cloud technologies. Photogrammetry applications have been adopted in several domains and the optimum usage of attained models can be executed with 3D replicas having precise details of surface features and geometry. Therefore, to attain 3D point cloud models with ground truth dimensions (GTDs), or actual dimensions of the targeted object the practitioners mostly follow the markers/ground control points (GCPs) technique (minimum three GCPs/markers), manual scaling, or georeferencing data. However, the accuracy of traditional GCPs/markers' technique and manual rescaling is dependent on the experience of the site staff/operator, and error chances may increase with the increasing number of GCPs/markers, whereas the georeferencing data-based technique is more technical and complex. Therefore, this paper developed an automated system for scaling up 3D point cloud models to GTDs with minimal human involvement. The system works with the help of specialized designed markers known as ArUco-supported controlled markers (ASCM). Only one ASCM marker is placed beside the targeted object for imaging; the devised system detects the marker in the images and rescales the developed point cloud model following the designed strategy. The system has high accuracy and can easily be implemented for scaling up close-range photogrammetry models in any domain. [ABSTRACT FROM AUTHOR]

Determining whether to invest in a project is a complex and challenging decision. This project investment decision relies heavily on its promised strategic goals (i.e., target benefits) stated in its business case and which are expected to be realized following project completion. However, in many cases, the proposed project benefits are far greater than those that the project realistically can achieve, leading to the risk of projects being funded erroneously. The construction management literature has offered approaches such as reference class forecasting (RCF) to rectify unrealistic project estimates. This paper identifies weaknesses in the current approaches, exposes their inefficiency, and proposes a step-by-step stratified approach as an effective alternative to detect, measure, and rectify unrealistic estimates of project benefits, and utilizes the proposed approach on a light rail construction project. The contribution of this approach is that each project benefit target can be rectified differently, based on the measurable levels of deviation from more-realistic estimates. This paper advances the construction management literature by enabling managers to set realistic project goals in the project front end, increase the reliability of estimates in the project business case, and improve the quality of project investment decisions. The decision to fund a construction project is impacted by information included in business cases and proposals, such as the estimated project cost and expected goals. However, such information often is unrealistic or exaggerated (to make the project more attractive for funding), which negatively impacts investment decisions made by senior executives. As a result, projects can be funded erroneously, causing a waste of resources and potential failure to achieve its unrealistic expectations. Because the existing literature offers little guidance for how to ensure that project goals are realistic, this paper developed and illustrates a step-by-step process for measuring and rectifying the gap between proposed and realistic project goals to alert senior executives when a proposed project is unlikely to meet its proposed goals. [ABSTRACT FROM AUTHOR]

This paper presents a new discretize-then-optimize (DTO) method for dynamic force inversion in a two-dimensional (2D) linear elastic, damped solid based on Runge–Kutta (RK) explicit time integration. Previous literature on DTO modeling for force or material inversion has predominantly focused on inversion methods based on Newmark implicit time integration. However, because implicit time integration may not be suitable for a problem with a large number of degrees of freedom [e.g., third-dimensional (3D) wave problems], there is a need to study an alternative DTO force-inversion formulation that centers around the RK explicit time integration, leveraged by a diagonal mass matrix. This paper attempts to fill this gap and present the full detail of the new RK-DTO formulation for dynamic force inversion. Our computational examples demonstrate that the new RK-DTO inversion simulator effectively reconstructs moving dynamic forces on the upper surface of the solid. It excels in efficiency when dealing with a higher number of degrees of freedom (DOFs) and maintains accuracy even with increased DOFs and observation durations. A smaller sensor spacing enhances the accuracy of the inverted force profile in the RK-based inversion. The presented inversion method can effectively identify the profiles of dynamic moving loads even when measurement data include noise or when the values of material properties are not deterministic. [ABSTRACT FROM AUTHOR]

Various papers have presented different methods for computations of mechanics and kinematics of discrete structural systems. However, little has been done in comparing and benchmarking the seismic response from two different discrete-system-models with experiments. This paper presents a detailed seismic performance comparison between two models—level set discrete element method (LS-DEM) and Logiciel de Mécanique Gérant le Contact (LMGC90), calibrated with shake table experiments conducted on four concrete-block configurations. Theories of both models are thoroughly explained and compared. The simulation results are benchmarked against experimental data. Finally, the principal results and significance of this benchmarking effort is discussed. [ABSTRACT FROM AUTHOR]

This paper compares three approaches for predicting the bridge response under moving vehicles. The first approach represents the vehicle as a concentrated moving load, while the second and third approaches simulate the vehicle using single (1-dof) and two (2-dof) degrees of freedom models, respectively. The vehicle–bridge models have been implemented following a finite-difference formulation. These models have been validated against the experimental displacement response of a mid-span prestressed reinforced concrete bridge. Parametric analyses have been conducted to investigate the impact of road roughness on the discrepancies between the models' predictions. An increasing level of road roughness, modeled according to ISO-8608, tends to conceal the mutual differences between the models' outcomes. Furthermore, a Monte Carlo simulation has been employed to fit the probability distributions of two indicators, comparing the bridge displacement responses in three roughness scenarios and considering variable velocity and vehicle characteristics. The primary objective is to assess whether there are scenarios where vehicle–bridge interaction modeling becomes indispensable for accurately estimating the vehicle's effect on the bridge response. The paper presents expressions for four probability density functions of the chosen metric, facilitating the comparison between the 1-dof and 2-dof models with the concentrated load approach. [ABSTRACT FROM AUTHOR]

Although welding is one of the essential steel fabrication processes, the American Welding Society expects that the labor shortage in the United States will reach a deficit of 360,000 welders by 2027. Developing an automatic robotic welding system could potentially alleviate the labor shortage and provide better welding quality. As a first step, this paper designs a system pipeline that can automatically detect different welding joints and plan and track the joints' trajectory with the initial point alignment in real time. There are rare studies that could achieve automatic initial point alignment in real time because the laser stripe's deformation is not obvious at the narrow weld. In this study, the target joint's endpoints were detected once the joint was detected on live video. Then, the joint trajectory was planned, and the robotic arm automatically aligned with the initial point and tracked the planned trajectory while scanning. The results demonstrate the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, for the first time, isogeometric analysis (IGA) and nonlocal theory are used to investigate the free vibration and transient response of bidirectional functionally graded porous (BFGP) curved nanobeams with elastic boundary conditions (BCs) and variable nonlocal parameters. Different from traditional boundary conditions, where a curved beam's beginning and end positions are connected by an elastic system of straight and torsion springs, this allows for greater flexibility in controlling the stiffness of the springs to obtain arbitrary boundaries. One thing that sets this research apart from others is the hypothesis that the mechanical characteristics of the materials, including nonlocal parameters, are supposed to change according to Voigt schemes in the direction of thickness, length, and porosities of the beam. On the basis of higher-order shear curved beam theory, Hamilton's principle is used to develop the curved nanobeam's equations of motion. The accuracy of the proposed model is established by juxtaposing the current study's findings with those of credible papers. A comprehensive examination has been conducted to analyze the impact of input parameters on the free vibration and transient response of BFGP curved nanobeams. Furthermore, the benchmark solutions elucidated in this work might serve as a valuable reference for analyzing the free vibration and transient response of BFGP curved nanobeams in other investigations. [ABSTRACT FROM AUTHOR]

To improve the current manual and iterative nature of clash resolution on construction projects, current research efforts continue to explore and test the utilization of machine-learning algorithms to automate the process. Though current research shows significant accuracy in automating clash resolution, many have failed to provide clear explanation and justification for the selection of their feature and label space. Since this is critical in developing an effective and explainable solution in machine learning, it is crucial to address this research gap. In this paper, the authors utilize an in-depth literature review and industry interviews to capture domain knowledge on how design clashes are resolved by industry experts. From analysis of the knowledge captured, we identified 23 factors considered by experts when resolving clashes and five alternative solutions/options to resolve a clash. Using a pool of industry experts, a modified Delphi approach was conducted to validate the factors and options and to determine a priority ranking. The authors identified 94 industry experts based on a predetermined qualification matrix to take part in the modified Delphi. Twelve participants responded and took part in the first round, and 11 completed the second round. A consensus was reached on all clash factors and resolution options. Factors including "clashing elements type," "constrained slope," "critical element in the clash," "location of the clash," "code compliance," and "project stage clashing element is in" were ranked as the most important factors, while "clashing element material" and "insulation type" were considered the least important. Participants also showed more preference to the "moving the clashing element with low priority in/along x-y-z directions" option to resolve clashes. These identified factors and options will be utilized to collect specific clash data to train and test effective and explainable machine-learning algorithms toward automating clash resolution. [ABSTRACT FROM AUTHOR]

The field of (practical) data-driven approaches that utilize the vibration signature of target systems for developing mathematical models (for computational purposes, control, or anomaly detection for structural health monitoring) is still an active research area, despite the fact that several powerful system identification techniques have been developed in the system dynamics field to analyze such measurements. However, there is still a paucity of comprehensive experimental studies that investigate the range of validity of such identification techniques, particularly those applicable to realistic situations encountered in the structural engineering field, with the focus on detecting, quantifying, locating, and classifying observed changes, especially when there are significant inherent nonlinearities in the reference (undamaged) complex target structure, and where there are unavoidable sources of errors and uncertainties in the measurements and the attendant data analysis procedures. The research team constructed a well-instrumented, reconfigurable test apparatus (resembling a tall building) that allows the introduction of quantifiable levels of composite changes at various locations, orientations, and types of linear and/or nonlinear changes, with the aim of investigating a subset of the aforementioned challenges facing researchers who are interested in assessing the utility of some practical system identification approaches. The primary focus of the identification approach is on a decomposition procedure that is ideally suited for certain types of structures that possess some topological features that can be exploited to enhance the detectability of small changes. A companion paper provides a detailed description of the testbed features and its instrumentation. The present paper focuses on the analysis of some of the very extensive data sets that were created to study the usefulness of some practical dimensionless probabilistic measures that not only provide normalized change indices but also simultaneously attach a confidence level to each of these indices. [ABSTRACT FROM AUTHOR]

Cement-stabilized macadam is a type of heterogeneous and discontinuous material. To study the mesomechanical behavior of cement-stabilized macadam particles, a discrete-element model of cement-stabilized macadam is constructed according to the random distribution theory and certain porosity and gradation. The constitutive relations of contact between particles may be linear contact, linear bonding, and linear parallel bonding. The stress–strain, crack propagation, particle velocity, stress transfer, and force chain distribution of cement-stabilized macadam were analyzed after comparing the results of simulated uniaxial compression with laboratory tests. The results of uniaxial compression calculations for cement-stabilized macadam were in good agreement with the experimental data. At the beginning of loading, the upper/lower particles moved toward the middle; at the peak loading stage, the particle movement was mainly in the vertical direction; and at the final of loading, the particles mainly moved to the sides. With the increase in loading, the contact force between particles became larger and larger. At the loading peak, the contact force between particles reached the maximum value, and the normal and tangential contact forces of particles were not evenly distributed. Microcracks at each stage were mainly vertical cracks, most of which were located at 70–110°. In this paper, the uniaxial compression test of cement-stabilized macadam was dynamically simulated using discrete-element theory, and the mesoscopic structure and dynamic variation process of parameters were analyzed. It provides references for the study of damage of heterogeneous and discontinuous quasi-brittle materials. [ABSTRACT FROM AUTHOR]

Very recently, an innovative mesh-free method, the so-called line element-less method (LEM), has been proposed to determine the response of plates under uniformly distributed edge moments. However, the previous formulations do not solve the problem related to plates with reentrant angles. In this paper, an innovative formulation is introduced to evaluate the deflection function of a simply supported plate possessing reentrant angles at the boundary and loaded by uniformly distributed edge moments. Framed in the LEM, this formulation consents to obtain a plate deflection function, implementing a simple algorithm within Mathematica software. Compelling savings in terms of time and computational costs are achieved, since there is no need to discretize the domain or the contour. Finally, the accuracy of the proposed results is highlighted by a good match with those achieved by classical methods and the finite-element method. [ABSTRACT FROM AUTHOR]

The paper proposes a spectral decomposition–based approach for implementing a multisurface coupled damage–plasticity model for concrete subjected to fire. The multisurface approach enables distinct flow rules to be used for plastic flow in compression and tension. The spectral decomposition–based procedure enables, for general multiaxial loading, the Jacobian for the return mapping algorithm to be determined analytically without the need for finite difference approximations or additional nested iterations. The proposed approach, developed in the context of a general multisurface plasticity model subject to the small strain assumption, is specialized to the case of a combined Drucker-Prager and Rankine yield surface, and can account for situations where the eigenvalues of the stress tensor are degenerate. It is verified by solving finite element models for concrete structural components subjected to high temperature under a wide variety of mechanical loads. The simulation results, obtained using a sequentially coupled approach, are found to closely match established experimental results. [ABSTRACT FROM AUTHOR]

The paper presents a modified differential quadrature method (DQM) to solve buckling problems of beams and rectangular plates. The proposed method addresses the problem of applying multiple boundary conditions at each boundary point by developing a novel approach that constructs basis functions satisfying multiple boundary conditions. The weighting coefficient matrices of high-order derivatives in the DQM can then be calculated directly from the basis function, and additional equations about boundary conditions can be avoided. The method is first applied to derive the basis functions of beams with various boundary conditions and to solve beam buckling problems. Then, the method is extended to the buckling of rectangular plates, where the plate deflection is assumed as the sum of multiplications of two basis functions for beams with the corresponding boundary conditions. To verify the accuracy of the proposed method, several examples are presented, and very good agreement is observed between the results obtained by the proposed method and those reported in the literature as well as those obtained by the finite element method. [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach to analyze the seismic stability of rock slopes using the stress characteristics method (SCM). Based on a prescribed factor of safety (FS), the slope profile (SP) is forthrightly determined without involving any optimization technique. A theoretical model is developed to execute the seismic analysis by coupling the SCM with the modified pseudo-dynamic (MPD) approach. The SCM obliterates the necessity of predefined slope geometry and slip surfaces in the analysis, whereas the MPD approach captures more credible nonuniform seismic inertia forces during earthquake excitation. The generalized Hoek–Brown criterion is employed to model the nonlinear strength characteristics of the rock mass. With different recommended values of FS, chart solutions comprising SPs are presented to readily evaluate the seismic stability of rock slopes. A comprehensive parametric analysis is conducted to interpret the behavior of obtained SPs under the influence of various input parameters. The overall slope angle of the present curvilinear SPs is found to be in close agreement with that of traditional linear SPs reported in the literature. Moreover, the legitimacy of the current methodology for designing open pit mines and assessing the safety status of existing rock slopes is showcased through different case studies along with a numerical simulation of the derived SPs. [ABSTRACT FROM AUTHOR]

Pipeline guided wave inspection is an efficient tool for determining the defect location. However, quantifying the defect size remains a challenging task. This paper proposes a quantification method for corrosion-like defects in pipelines based on the multifrequency identification of nondispersive torsional guided waves. First, a theoretical scattering model describing the T(0,1) wave's interaction with a simplified corrosion-like defect is introduced. Subsequently, a multifrequency identification method is proposed, enabling the inverse quantification of defect parameters by a defined spectral defect index (SDI). To implement this approach, a pseudo pulse-echo configuration is devised, which contains two rings of piezoelectric transducers attached on the pipeline's outer surface. Finite-element (FE) models are employed to test the performance of the proposed method for both axisymmetric and nonaxisymmetric defects, and an analysis of the robustness of the method is also conducted. The results show that this method has good accuracy even for signals with a very low signal-to-noise (SNR) ratio. Furthermore, an FE model is developed to validate the feasibility of this method for long-distance detection considering attenuation effect. Finally, experimental validation of the proposed method demonstrates close agreement between predicted and actual defect sizes, showing its potential for practical applications. [ABSTRACT FROM AUTHOR]

We consider in this paper the general properties of laminates designed to be isotropic in extension and in bending and with a coupling between the in- and out-of-plane responses. In particular, we analyze the mathematical properties of the tensors describing the elastic and thermal behavior and the mechanical consequences of these properties. The polar formalism for planar tensors is used in this study. By this approach, it is easy to put in light some interesting, qualitative, mechanical, and mathematical facts concerning coupled isotropic laminates and to appreciate the fundamental differences, from the mathematical and mechanical point of view, between hybrid laminates, i.e., composed by layers of different materials, and laminates made of identical plies. [ABSTRACT FROM AUTHOR]

Shape sensing refers to the deformation reconstruction of structures using measured surface strain. However, there is currently a lack of research on the shape sensing of large deformations, especially for beam structures. To address this issue, this paper proposes a new method called the rotation angle approximation (RAA) for reconstructing large deformations of beam structures. This method utilizes theoretical and actual curvatures to create a least-squares error functional. By minimizing this functional, the rotation angles of the corresponding beam can be obtained, avoiding the accumulation of errors that occurs when using traditional computation methods. The deformed shapes can be predicted utilizing the boundary conditions and the rotation angles along the beam. This method can reconstruct the large deformation of a beam without requiring prior knowledge about the material properties or external loads. The accuracy and effectiveness of this method were validated through numerical simulations and experiments. The results indicate that this method can accurately predict the different deformations of a beam induced by various loading conditions. [ABSTRACT FROM AUTHOR]

This study evaluated two fundamental assumptions about the geometry of the wood cell wall to develop a mechanistic characterization of wood behavior at the scale of wood structural components. This paper used a three-step homogenization scheme implemented through homogenization techniques and finite-element analyses to evaluate a multilayered cell wall and a simplified single-layer method. Both earlywood and latewood geometries were considered. A three-part sensitivity analysis assessed the influence of wood constituent proportions, microfibril angle, and cellulose crystallinity on cell wall stiffness. Sensitivity to constituent ratios was evaluated through a Monte Carlo simulation of 1,000 sampled points and correlation analysis. Sensitivity to microfibril angle and cellulose crystallinity was evaluated through parametric characterization. The investigation found that both methods provided an accurate assessment of wood stiffness when compared with experimentally determined values. Care should be taken when modeling higher densities of wood, and use of either method in higher order models should be determined by the resolution of input data and computational needs. [ABSTRACT FROM AUTHOR]

Overland flow from inundation events (IEs) such as hurricanes or tsunamis produce destructive loading conditions on nearshore structures. The magnitude of this loading and its associated impact can be substantially reduced by the existence of natural and/or anthropogenic obstacles, such as planted vegetation patches or neighboring structures. This paper examines the shielding effects offered by onshore coastal vegetation to nearshore structures, by establishing a numerical framework in combination with statistical computing methods to explore how vegetation properties, such as density and, more important, geometry relative to a row of shoreline infrastructure elements, impacts the resultant IE loads and subsequently the structural vulnerability. Computational fluid dynamics (CFD) simulations are first conducted to predict the intensity measures (IMs) of interest (momentum flux, free surface elevation, water pressure, and depth-averaged velocities, as well as base shear forces) on the shoreline structures for different excitation intensities (wave heights) and vegetation configurations. This information is used to develop a predictive model for the IMs using surrogate modeling techniques in order to expedite the succeeding risk assessment process. Gaussian process (GP) regression is specifically adopted as the surrogate modeling technique here, since it can accommodate noise in the training observations (CFD numerical errors) and quantify the associated predictive uncertainty (originating from the surrogate model) with minimal additional computational complexity. The spatial correlation between some of the examined IMs is explicitly addressed at the GP calibration stage. The developed predictive model is then used to estimate the structural vulnerability, with the surrogate model prediction errors explicitly considered when calculating the probability of exceedance for the different damage states, as warranted in such a vulnerability setting. Comparisons among different vegetation configurations, including the bare earth case, support an in-depth exploration of the impact of vegetation geometry on the shielding effects it can offer. Two case studies are examined, demonstrating applicability of the proposed framework for both system- and component-level vulnerability assessments. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the horizon size on failure due to strain and damage localization in the case where peridynamics is a nonlocal theory by its own, which corresponds to most bond-based peridynamics models. Two constitutive relationships are discussed: the microelastic brittle model and a progressive damage model. The usual practice with the microelastic brittle model is to fit the microelastic constant for a given horizon size so that elasticity is recovered. At the same time, the fracture energy provides the critical bond stretch. This methodology yields an indirect determination of the tensile strength of the material, that goes to infinity as the horizon size trends to zero. With the damage model, the stretch at the inception of damage can be obtained from the tensile strength. Then, a simple one-dimensional case of wave propagation and interactions in a bar is considered. For fixed values of the horizon, convergence with a refinement of the discretization is checked. The energy dissipated upon fracture is found to be a linear function of the horizon. It is also a function of the softening response. The horizon cannot be chosen arbitrarily, unless the softening parameter is adjusted to fit the fracture energy, like in the crack band model. Surprisingly, such a methodology is very seldom mentioned in the current literature dealing with fracture modeled by peridynamics. [ABSTRACT FROM AUTHOR]

The realistic modeling of vibratory energy harvesters is necessary to ensure their reliable performance when subjected to random excitation. However, the hysteretic behavior of piezoelectric materials and the nonlocality of fractional electrical components make the numerical estimation of their stochastic response computationally challenging. This paper proposes an iterative method based on equivalent linearization and stochastic averaging for estimating the stationary probability density function of the output voltage amplitude of vibratory energy harvesters modeled as a hysteretic oscillator with fractional electrical components subject to a broadband stochastic process. By estimating the average of hysteretic terms, one can find an amplitude-dependent linear governing equation for the output voltage, from which one can determine a stochastic differential equation governing the evolution of the output voltage amplitude. We obtain the stationary solution of the corresponding Fokker–Planck equation in a semianalytical form, and we include comparisons with pertinent Monte Carlo simulation data to show that the estimated probability density functions are accurate and obtained at a minimal computational cost. [ABSTRACT FROM AUTHOR]

The aim of this paper is to explore the mechanical characteristics of lattice-based airless tires made by three-dimensional (3D) printing technology under a large-deformation regime. The proposed airless tires are designed and fabricated based on the hexagonal lattice geometries under two different orientations. Experimental tests are conducted to investigate the effects of geometrical parameters and the types of lattices on the radial responses of airless tires. A finite-strain beam element is also established to simulate airless tires under various loading states, including radial, longitudinal, torsional, slipping, and rolling conditions. In this respect, a finite-element formulation is developed based on finite-strain hyperelasticity and solved by implementing an iterative Newton–Raphson scheme. Numerical and experimental results confirm that the proposed finite-strain beam element can be used for the analysis of airless tires with complicated lattice geometries under various nonlinearities, such as geometrical, material, and contact phenomenon. The numerical illustrations emphasize the effects of geometrical parameters of lattices and loading parameters on the behavior and mechanical properties of airless tires. The effects of lattice orientations, thickness, number of unit cells, and the coefficient of Coulomb friction between the tire and the ground, as well as loading direction, are investigated. Their implications on the responses of the airless tires with the same weight are highlighted, and pertinent conclusions are outlined. It is also shown that the proposed mathematical model can be used in future efforts for analysis, optimization, and design of lattice-based airless tires with complex geometries. This paper is a numerical/experimental research of the 3D printed lattice-based airless tires under various real loading cases such as radial, longitudinal, torsional, slipping, and rolling conditions. The proposed airless tires are designed/fabricated based on two different orientations of hexagonal lattice geometries. The material used for modeling and fabrication of these airless tires is rubber-like materials (hyperelastic), which can have many reversible deformations. The results show that under real loading conditions, the links of the lattice experience instabilities, such as buckling and snap. It should be mentioned that these instabilities are quite important in practical applications that are investigated in the present work in detail. Moreover, the behavior of lattice-based airless tires under each loading condition is divided into linear behavior and nonlinear behavior. Linear behavior of an airless tire can be predicted by the present model for different geometrical parameters (such as length, thickness, among others). Unlike linear behavior, nonlinear behavior highly depends on load and deformation histories. Therefore, each case needs the optimization and design of lattice-based airless tires. [ABSTRACT FROM AUTHOR]

This study presents results from cyclic testing on various configurations of a recently developed pressurized sand damper in which a steel sphere is moving within a cylindrical tube filled with sand that is under pressure. The experimental campaign investigated the effects of the key design parameters of the damper, namely, the effect of the clearance between the moving sphere and the cylindrical tube and the effect of the overall length of the damper to its force output. The recorded force–displacement loops when normalized to the strength of the pressurized sand damper reveal remarkable order with stable behavior and confirm that the force output is nearly rate-independent. The paper also presents recorded force–displacement loops where the sphere mounted on the piston rod is replaced with a bolt where only the bolt head and nut are protruding from the moving piston rod. With this configuration, the pinching behavior of the pressurized sand damper at longer strokes is suppressed without generating large forces at longer strokes. The increasing need for structures to meet acceptable performance levels during earthquake and wind excitation has led to the development of various high-performance design and retrofit strategies. Supplemental damping is a widely accepted response-modification strategy for structures where energy is dissipated in dedicated, specially designed energy dissipation devices. Motivated by the recent failures and displacement limitations of existing energy dissipation devices, this paper examines the behavior of an innovative, reliable, long-stroke, low-cost energy dissipation device in which a steel sphere is moving within a cylindrical tube filled with sand that is under pressure. One of the novel aspects of the proposed pressurized sand damper is that it dissipates energy through the hysteretic behavior of sand that can be enhanced by controlling the externally exerted pressure on the sand. The experimental campaign investigates the effects of the key design parameters of the damper, namely, the effect of the clearance between the moving sphere and the cylindrical tube in association with the effect of the overall length of the damper to its force output. [ABSTRACT FROM AUTHOR]

Cables are used for engineering applications such as transport systems that involve mobile cables suspended between supports for carrying attached vehicles. Because of the inherent cable's flexibility and the modification of dynamics properties during movement, such systems are sensitive to self-sustained oscillations under steady-state conditions. To provide an understanding of such vibratory excitation sources and a design method to prevent operating problems, this paper proposes a real case study of a chairlift and the development of an original model. The aim is to highlight the mechanisms responsible for the dynamic response amplification of the cable line. The method is based on a reduction of the complete dynamic model to a single mode, which localizes the vibration energy along the cable loop. The reduced model thus obtained takes the form of a Mathieu–Hill parametric excitation oscillator. The stability study reveals zones of instability in which the dynamic system response increases. The approach is then validated on the real case study by positioning the chairlift's operating points in the stability diagram according to different configurations. Operating points are determined using the signal of the evolution of the static tension of the cable during the movement of the vehicles. Based on the case study, a general methodology for modifying design parameters is proposed to avoid undesirable line dynamics. [ABSTRACT FROM AUTHOR]

In recent decades, the outcrossing rate method has gained popularity for structural time-dependent reliability assessments (TRA). Despite numerous efforts, developing a general analytical outcrossing rate method for a nonstationary non-Gaussian performance function to estimate the failure probability within the forecast time interval remains a significant challenge. This paper introduces an analytical outcrossing rate method for non-Gaussian cases, named the three-moments-based outcrossing rate (TMO) method. The outcrossing rate is formulated based on the third-moment outcrossing rate with no assumption of the correlation between the performance function and its derivative process, allowing for a comprehensive understanding of the performance characteristics of a structure. Following the development of the proposed outcrossing rate, a TRA methodology is established to evaluate the failure probability of the nonstationary non-Gaussian performance function. Notably, the TMO method only requires statistical moments of the nonstationary non-Gaussian performance function, which are easy to calculate, facilitating efficient implementation. Three numerical examples are presented to demonstrate the applicability, efficiency, and accuracy of the proposed TMO method. It can be concluded that the proposed TMO method provides an accurate and useful approach for TRA in engineering applications. [ABSTRACT FROM AUTHOR]

When cables use many wires packed in a hexagonal pattern wrapped by bands around the surface, effective stiffness plays an important role in structural integrity and safety. This paper studies cylindrical wires packed in a hexagonal lattice tightened up by wrapping bands. When a transverse load is applied, the stress transferred through the contacts between the wires can be represented by a center-center force network with the Hertz contact theory. When yielding is considered in the contact zone, an elastoplastic contact model is developed. The Singum model simulates the singular forces by the stress between continuum particles. The effective stress-strain relationship changes with the stress of the wrapping bands and exhibits isotropic behavior in the cross section. Therefore, the overall elastic behavior of the cable is transversely isotropic with a tailorable stiffness in the cross section by the wrapping force. This method is general for mechanical modeling of packed parallel wire cables, and its application to bridge cable testing and repair with development length prediction is underway. Practical Applications: This study introduces a novel approach, the Singum model, for analyzing the overall mechanical properties of packed wire cables, which are crucial for ensuring structural integrity and safety in various engineering applications. By investigating the effective transverse stiffness of packed wire cables through a combination of theoretical modeling, finite element analysis (FEM), and experimental tests, this research provides valuable insights into optimizing cable design and performance across diverse engineering applications such as cable domes, electric transmission lines, tramways, cable-stayed bridges, and suspension bridges. The findings highlight the significant impact of wrapping force on the effective stiffness of packed cylinders, offering engineers a means to tailor the stiffness of cable cross sections for specific requirements in these applications. This study provides a robust framework for advancing the understanding and optimization of packed wire cable systems in engineering practice with reasonable assumptions and simplifications, which can be tailored for specific materials or applications. [ABSTRACT FROM AUTHOR]

The mesoscale structure generated in concrete plays a significant role in the mechanical properties and local failure behavior of mesoscale concrete. This work proposes a novel rigid-block discrete-element method (RB-DEM) for concrete modeling with random mesoscale structure. The results of the uniaxial compression using the RB-DEM demonstrated satisfactory agreement with experimental data. The RB-DEM does not only show satisfactory performance in simulation but also it is simple to use. The RB-DEM model can be built from any finite-element mesh generator, either open source codes or commercial software, which are readily available. The interfacial transition zone (ITZ) is modeled directly by assigning the weakened contact model or parameter at the interface between aggregate and mortar. The effects of ITZ parameters, aggregate volume fraction, and geometric shape on the stress–strain curve and crack propagation are discussed. This work provides a novel and efficient tool for the mesoscale fracture simulation of concretelike material considering the relatively large time-step of the DEM. Concrete is one of the most common building materials, and its mechanical properties and crack evolution under pressure are extremely important for practical engineering construction. With the development of computer performance, scholars have used software or code to simulate experiments to improve efficiency and save costs (this is known as numerical simulation). This paper proposes a novel method named rigid-block DEM to simulate uniaxial compressive strength test of concrete, and the results were highly similar to the actual experimental results. This method can help researchers further study the influence of various concrete parameters on its performance. Compared with the traditional methods, the rigid-block DEM has abundant advantages such as simple model generation and high calculation efficiency, which provides a valuable reference for the future numerical simulation of concrete, and has certain guiding significance for engineering construction. [ABSTRACT FROM AUTHOR]

In the two-dimensional (2D) example consisting of 12 nodes excluding four nodes representing supports, the authors used horizontal acceleration responses at seven nodes, rotational acceleration responses at five nodes, plus one displacement response for data fusion to identify the structure. Al-Hussein and Haldar ([1], [3]) used these examples to verify the method they proposed, known as unscented Kalman filter with unknown input and weighted global iteration (UKF-UI-WGI). In Al-Hussein and Haldar ([3]), the discussers wrote "However, the authors (indicating discussers for this discussion) Al-Hussein and Haldar ([2]) observed that the traditional UKF procedure may not be able to identify a large structural system using such short duration responses." The authors need to clarify how the displacement response time history would be measured along with acceleration time history avoiding any data latency-related problem. [Extracted from the article]

This paper presents a stochastic analysis of the size effect on the nominal strength of quasibrittle structures with a large preexisting notch. This type of scaling behavior has been extensively studied within a deterministic framework. Little attention is paid to stochastic analysis, which is essential for reliability-based analysis and design of engineering structures. Stochastic finite element simulations are performed to study the failure of geometrically similar beams of different sizes. The numerical analysis uses a continuum damage model, in which the tensile strength and fracture energy are modeled by homogeneous random fields. Different correlation lengths are considered as a parametric study. The analysis yields the size effects on the mean and coefficient of variation (CoV) of the nominal structural strength. It is shown that the size effect on the mean strength agrees well with the Bazant size effect model. The simulation predicts a strong size effect on the CoV of the nominal strength. Small-, intermediate-, and large-size asymptotes are derived analytically for the scaling behavior of the strength CoV. Based on these asymptotes, an approximate scaling equation is proposed for the CoV of nominal strength. The effect of the correlation length on the simulated failure behavior is discussed. [ABSTRACT FROM AUTHOR]

Architected materials are a new class of materials that interlink practices in architecture and structural engineering to produce materials by conjugation of several simple materials through the interplay between geometry and material properties. Tensegrity structures are composed of struts and cables held in a state of self-stress. With a high strength-to-weight ratio, they provide opportunities for deployable and transportable bridges. Although tensegrity structures are indeterminate, cable damage is challenging to predict and detect a priori, which is aided by a resilient architected material segment as a structural health indicator. The technology of 3D printing complements the development of architected material. Computational studies have shown the effect of coordination number and cross-linking density on the stretch behavior of polymer networks for microscopic deformation scale. This paper presents the relationship between various parameters of multilayered randomized architected material (MLRAM) and its tensile behavior. The randomization of link orientation is to address the unknown direction of the critical force in the strut. A computational model calibrated through experimental testing was developed that mimics the tensile behavior of MLRAM. Using this model, the variation in the tensile behavior in terms of peak tensile capacity and postpeak behavior of MLRAM can be studied for various geometries with specific parameters. From the study, it is observed that the tensile capacity and stiffness of the MLRAM increase with a higher coordination number. The recent advancement of additive manufacturing and 3D printing have provided researchers with the scope to study the feasibility of many difficult geometries and its properties. This is one such study that develops and investigates the tensile properties of a newly developed multilayered randomized architected material (MLRAM). The tensile properties were determined experimentally for centimeter-scale 3D-printed models and a computational model was proposed to replicate the behavior in the linear static region. This novel study provides a preliminary idea of a new concept of architected material that can be extended to a three-dimensional concept in the future. First, the model helps researchers investigate various geometry and design materials with properties as required for specific applications. This proposed MLRAM extended into a three-dimensional material also has the potential to act as visual damage detection indicators that can be incorporated in highly redundant structural systems such as tensegrity structures. [ABSTRACT FROM AUTHOR]

The behavior of axisymmetric cylinders under various surface loading has remained the topic of research for many years. Most of the solutions presented in the literature are load-specific. Therefore a general solution is sought to satisfy any boundary conditions prescribed on any surface. This paper presents a general solution to satisfy a wide combination of boundary conditions prescribed on the curved as well as on the flat ends of a cylinder. A hollow cylinder was considered, composed of transversely isotropic material. The formulation is based on the variational principle, resulting in a set of coupled governing equations and associated boundary conditions. The solutions to the coupled governing partial differential equations are obtained by systematically decoupling them, followed by the method of separation of variables and the Frobenius method. All the boundary conditions are satisfied by making use of either the Fourier or the Fourier–Bessel transformation. The solutions for various test cases were validated by comparing them against three-dimensional solutions obtained using finite-element analysis. The solution for the solid cylinder was obtained by considering the limiting case of the internal radius approaching Zero. [ABSTRACT FROM AUTHOR]

Vortex-induced vibration (VIV) is a critical problem for high-rise buildings. Thus, accurate prediction of aerodynamic damping becomes a key problem in the wind-resistant design of high-rise buildings. A common feature of the existing aerodynamic damping models is that most of their model parameters are functions of wind velocity. Such a feature leads to the inconvenience of users because the parameters need to change from case to case. This paper proposes an aerodynamic damping model that is a function of structure responses only. That means it does not need to adjust its parameters in different wind speeds. A single-degree-of-freedom aeroelastic square section high-rise building model with different structural damping ratios is tested in a wind tunnel for the analytical modeling. According to the identified aerodynamic damping coefficients and its relation with response amplitudes, the nonlinear aerodynamic damping model is proposed. It is a polynomial-type function of the instantaneous velocity and displacement of the structure. The results show that predicted responses, by using one set of model parameters, are in good agreement with the experiment data in the whole tested wind speed range. These results suggest that the proposed aerodynamic model can be a generic model for prediction of wind-induced vibration. [ABSTRACT FROM AUTHOR]

Existing research indicates that free water has a considerable influence on the dynamic mechanical properties of concrete, which is not considered in commonly used concrete models. This paper presents a high-fidelity constitutive model according to the Karagozian&Case model (K&C model) to capture the free water effect on the high dynamic properties of concrete structures. In this study, the new failure surfaces, equation of state and dynamic increase factor, which are in good agreement with experimental data, are put forward to consider the free water effect on concrete properties. On the other hand, a modified damage accumulation is introduced to better predict the soften stage of the stress-strain curve. The model is implemented into the livermore software technology corporation—dynamic nonlinear analysis (LS-DYNA) hydrocode through the user-defined materials subroutine. Numerical single element tests are first carried out to calibrate the parameters of the proposed model, where the numerical predictions are in good consistency with the test data. The perforation and penetration tests on concrete targets with different saturation are then simulated to verify the accuracy of the proposed model. Additionally, the influence of free water on the ballistic performance of concrete is investigated, and it is found that the presence of free water reduces the penetration resistance of concrete target. [ABSTRACT FROM AUTHOR]

Stress and deformation analysis of a cavity in an infinite/finite medium is a fundamental applied mechanics problem of interest in multiple physics and engineering disciplines. This paper develops a complete semianalytical solution for the cylindrical cavity expansion in nonassociated Mohr–Coulomb materials, by using the graphical approach and Lagrangian formulation of the cavity boundary value problem (through tracing the responses of a single material point at the cavity wall). The novelty of the new solution framework lies not only in the relaxation of the stringent intermediacy assumption for the vertical stress as usually adopted in the previous analyses, but also in the comprehensive consideration of nonhydrostatic initial stress conditions via arbitrary values of K0 (the coefficient of earth pressure at rest defined as the ratio between the horizontal and vertical initial stresses). The essence of the so-called graphical method, i.e., the unique geometrical analysis and tracking of the deviatoric stress trajectory, is fulfilled by leveraging the deformation requirement that during cavity expansion the progressive development of the radial and tangential strains must maintain to be compressive and tensile, respectively. With the incorporation of the radial equilibrium condition, the problem is formulated to solve a single first-order differential equation for the internal cavity pressure with respect to a pivotal auxiliary variable, for all the distinct scenarios of K0 being covered. Some selected results are presented for the calculated cavity pressure-expansion curve and limit cavity pressure through an example analysis. The definitive semianalytical solution proposed will be not only substantially advancing the current state of knowledge on the fundamental cavity expansion theory, but also able to serve as a unique benchmark for truly verifying the correctness and capability of the classical cornered Mohr–Coulomb constitutive model built in commercial finite element programs. [ABSTRACT FROM AUTHOR]

Fiber-reinforced elastomeric isolators (FREIs) have been proposed as a cost-effective solution for expanding the use of seismic isolation to normal-importance structures. By using lightweight fiber reinforcement and eliminating the attachment plates, FREIs reduce cost while improving the isolation efficiency and reducing tensile stresses in the rubber. However, the flexural flexibility of the fiber allows cross-sectional distortions (i.e., warping) to occur, which significantly impacts the stability of these devices. This paper evaluates the buckling of rectangular, circular, and annular FREIs, taking into account shear warping effects. A planar buckling theory previously proposed by the authors is adapted for the three-dimensional problem, and effective warping rigidities and warping-related areas are derived for the above bearing geometries, accounting for rubber compressibility. To assess the adequacy of the proposed buckling theory and derived warping properties in predicting the buckling of FREIs, a parametric finite element study is conducted. The critical load predictions of the proposed analytical formulation are found to be in excellent agreement with those of the numerical simulations. It is shown that traditional estimations of the buckling load that neglect warping are significantly unconservative. Finally, design recommendations and resources are provided for practice-oriented applications. [ABSTRACT FROM AUTHOR]

Posttensioned rocking systems have gained attention, as they limit damage to the primary structure and simplify repairs after extreme events. The literature on posttensioned rocking walls is extensive; however, much of it is focused on numerical modeling and exploration of complex system level behavior. The present paper focuses on an analytical study of the amplitude-dependent frequencies of posttensioned flexible rocking walls. A simplified analytical model is introduced to investigate the interplay between rocking wall deformation and rocking. The study borrows analysis tools from the study of nonlinear normal modes (NNMs) and includes unforced and forced dynamics. A finite element model is also used for comparison with the static and dynamic response from the analytical model. The work shows that the unforced dynamics are able to predict peak response of forced vibration and furthermore illustrate the transition in behavior from fixed-base to flexible rocking walls. In addition, coexisting steady-state solutions were observed from the forced response. The NNMs of flexible rocking walls may aid earthquake/wind engineers in tailoring rocking systems to improve performance in the same way linear modal analysis is used in practice. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on how the crack-parallel stress affects the fracture properties of fiber-reinforced concrete (FRC) using the gap test—a new simple fracture test invented and used for concrete at Northwestern University in 2020. First, it was conducted for plain concrete and was successfully applied to cross-ply carbon-fiber composite and to aluminum. An advantage of this test is that it is unambiguous because the test setup changes from one statically determinate configuration to another. The gap test, combined with the standard notched three-point-bend test, is now applied to geometrically scaled FRC specimens to determine how the fracture energy, Gf , and the effective size, cf , of the fracture process zone (FPZ), are changed by the crack-parallel stress, σxx. For σxx equal to about 2/3 of the standard uniaxial compression strength, the increase in Gf is 64% and 78% for the two FRCs, respectively, which is large but not as large as the 126% increase observed in tests of plain concrete. This indicates that the fiber reinforcement mitigates the effect of σxx , while introducing some degree of ductility into the fracture process. The compressive σxx also increases the effective size of the FPZ by about 81% and 64% while such increase is 134% in plain concrete. Because crack-parallel stresses are ubiquitous in practice, the implications for design are significant. [ABSTRACT FROM AUTHOR]

Extreme waves pose one of the major threats to marine structures. Furthermore, their non-stationary nature makes proper stochastic analysis of their responses a challenging problem. To address this issue, this paper proposes a method based on a novel linear filter wave model incorporated into the dimension-reduced probability density evolution equation (DR-PDEE). The linear filter system is capable of simulating random background waves conforming with the Joint North Sea Wave Project (JONSWAP) spectrum of any arbitrary sea state by adjusting the parameters of filters directly related to the parameters of the JONSWAP spectrum without reidentification. In particular, by conducting the digital filtering, wave kinematics at different depths below the sea surface can be reproduced conveniently, and therefore only one filter is adequate for the depthwise wave kinematics field. Extreme ocean waves are treated as the superposition of background waves and extreme crests according to the constrained quasi-determinism method, with randomness from both parts. Incorporating the filter into the equation of motion of the offshore structure of interest leads to an augmented high-dimensional stochastic system with multiple random variables. The DR-PDEE then is employed to reduce the dimensions of the equation governing the evolution of probability density of responses of the original complex system to two. Solving the DR-PDEE using the path integral method yields the probability function of the response at each time step. A numerical example involving the response of a National Renewable Energy Laboratory (NREL) 5-MW spar-type floating offshore wind turbine (FOWT) subjected to extreme waves was studied to assess the reliability of the proposed method. The method provides an effective tool for the determination of the stochastic extreme response of offshore structures, and provides a foundation for further dynamic analyses. [ABSTRACT FROM AUTHOR]

Importance ranking of rock properties is important in allocating investigation resources, and then performing probabilistic analysis efficiently. Traditional global sensitivity analysis (GSA) can be employed to perform this ranking; however, it neglects (1) the epistemic uncertainties in the probability models and their parameters due to small sample sizes of inputs, and (2) the mutual dependence of inputs. This paper overcomes these limitations by introducing a stratified Bayesian multimodel inference (BMMI) coupled with moment independent GSA to estimate the imprecise sensitivity indexes (SIs) with complex copula-dependent inputs. The methodology initially identifies candidate marginal models and the uncertainties in their parameters by BMMI, which is employed to construct a model set comprising an ensemble of marginals estimated via the reweighting approach. Subsequently, this model set is used to quantify the uncertainties in the copula-based dependent structure using BMMI. The final step is to estimate the inaccurate SIs using the Monte Carlo–based moment independent GSA framework, which propagates an ensemble of joint densities to represent the overall uncertainty. The methodology is generalized in a way that it can be used for any number of complexly dependent inputs and eliminates the need to estimate conditional probability density functions (PDFs) and a precise copula otherwise required in mapping-based and traditional GSA. The methodology is demonstrated for two slopes, i.e., an infinite soil slope (two inputs) and a rock slope (four inputs). The methodology was accurate for both examples, and more informative than traditional GSA because it estimates the bounds of SIs reflecting the effect of epistemic uncertainties associated with dependent inputs with their point estimates from traditional GSA lying in their bounds. [ABSTRACT FROM AUTHOR]

The morphological origin of sand shear modulus at small strains (Gmax) remains poorly understood. This paper introduces spherical harmonic analysis to define multiscale particle morphologies of two typical natural sands: calcareous sand (CS) and Fujian sand (FS). Three distinct scale levels were taken into consideration: general form (large), local roundness (medium), and surface roughness (small). The 3D printing technique was employed to produce uniformly graded sand analogs with independent control of grain shape. Bender element tests were subsequently conducted on these analogs after isotropic consolidation in triaxial apparatus to obtain their shear wave velocities and small-strain shear moduli. The results highlight the substantial enhancement of Gmax through irregular particle morphologies within uniformly graded sand. Notably, the general form (large scale) emerges as the primary morphological determinant of the enhanced Gmax. Parameters of Hardin's equation—material coefficient A and stress exponent N —are demonstrated to reflect the comprehensive Gmax pattern and its sensitivity to confining stress, respectively. The reduction of N with diminishing overall regularity indicates the weakening effect of morphological irregularity on Gmax 's sensitivity to confining stress. Remarkably, the medium-scale level yields the lowest N value, emphasizing the pivotal role of local roundness as the predominant morphological factor in this effect. [ABSTRACT FROM AUTHOR]

The Hermite polynomial model based on the first-four central moments of non-Gaussian distribution is widely applied to simulate non-Gaussian stochastic processes due to its simplicity and efficiency. Although a variety of expressions have been developed to approximate the coefficients of the Hermite polynomial model, unsatisfactory accuracy and limited applicability could still be encountered. Compared to the central moments, probability-weighted moments possess abundant characteristics of probability distribution. In this paper, a new form of Hermite polynomial model is proposed based on probability-weighted moments for simulating non-Gaussian stochastic processes. The coefficients of the Hermite polynomial model can be conveniently determined via a linear system of equations, leading to a wide application range of the model. More importantly, the sample accuracy for simulating non-Gaussian processes can be significantly improved, and the incompatibility problem can be avoided to some extent by using the proposed model. In addition, a fast strategy for determining the Gaussian auto-correlation function is also suggested, which avoids the complicated manipulations of cubic equations of Gaussian and non-Gaussian auto-correlation functions. A classical example is investigated to demonstrate the better accuracy and applicability over conventional Hermite polynomial models for simulating non-Gaussian stochastic processes. Two engineering cases are also investigated to demonstrate practical applications of the proposed model. [ABSTRACT FROM AUTHOR]

Energy harvesting from vortex-induced vibrations (VIV) is gaining more attention in many applied cases. This paper studied the nonlinear dynamics of a tunable VIV-based energy harvester. The energy harvester structure consists of a base-clamped cylinder having an adjustable mass (the tuner) which enables the system to actively synchronize with vortex-shedding frequencies. The Euler-Bernoulli beam theory and the extended Hamilton's principle are used to extract the nonlinear partial differential equations of the distributed model for the cylinder, tuner motion, harvested voltage, and fluctuated lift force. The reduced-order model of the system of equations is derived via the Galerkin method using modified mode shapes. The method of multiple time scales is employed to obtain the approximated analytical solution of the 1:1 internal resonance of the lumped parameter system. The dynamical response of the system is shown by investigating various parameters of the harvester. Additionally, the locus of the points at which the higher orbits of harvested voltage occur is specified for the tuner equilibrium position. The results show the proposed design significantly increases energy harvesting performance by a factor of 900%. This paper is offered as a contribution towards energy harvester design and optimization with the goal of capturing higher energy orbits. [ABSTRACT FROM AUTHOR]

This paper presents a time-dependent analytical solution for undrained elastoplastic response of a porous, fluid-saturated medium to fluid source at the center of an embedded spherical, porous, fluid-saturated inhomogeneity inclusion. The solution considers poroelastic coupling in the inclusion while solving for the surrounding matrix stress using a Lagrangian formulation of the incurring elastoplastic deformations. The solution for plastic deformation of the matrix is obtained using the large deformation theory of plasticity with associated flow rule of either the strain-hardening Drucker-Prager model or smoothed strain-hardening Mohr-Coulomb model. The obtained solution is used as a proxy model to study caprock stress evolution upon fluid injection in subsurface rocks to mimic applications such as CO2 geo-sequestration. Findings indicate that the (poro)elastic models that are predominantly utilized in the existing studies of the subject could substantially underestimate the caprock shear failure threshold. Results obtained from a presented case study show that 0.8% allowance for elastoplastic strain in the caprock could yield up to 100% increase in fluid injectivity of the embedded reservoir. The presented solution may further serve as a rigorous benchmarking tool for verification of related numerical solution schemes. Caprock integrity concerns arise when injecting fluid into an embedded rock formation, e.g., during CO2 geo-sequestration or when withdrawing fluid from a reservoir, e.g., during oil and gas production. This work assesses possible enhancement in the estimated caprock integrity threshold because of plastic deformation beyond elastic limit, yet prior to rock failure. A time-dependent analytical solution for a geometrically idealized model of porous and fluid-saturated reservoir and surrounding caprock is developed for this purpose. Findings indicate that 0.8% allowance in the caprock total elastoplastic strain beyond elastic limit of the rock results in more than a twofold increase in the injectivity of the embedded reservoir. Higher values of plastic strain-hardening parameter or total strain allowance would allow for higher injectivity thresholds. These results underline the necessity for consideration of plastic deformation and stress analysis in studies on caprock integrity analysis. [ABSTRACT FROM AUTHOR]

Though road authorities have well-defined inspection protocols for evaluating bridge serviceability, gaps remain in understanding optimal timing and the impact of maintenance strategies on an individual bridge and its subsystems and, consequently, on the holistic performance of a road network. This paper proposes an innovative model based on system reliability principles that develops optimized bridge maintenance strategies aimed at enhancing the overall reliability of a bridge-dominated road network by considering the quantified impact of bridge component deterioration. Using the first-order second-moment method, we initially determine the reliability index for each bridge based on condition ratings derived from routine inspections as outlined in the bridge inspection manual. Advanced optimization algorithms then formulate the optimal maintenance strategies for the bridge structures. Finally, we gauge the system reliability of the network using Ditlevsen bounds approximation, considering the impact of maintenance actions on varied bridge structural components. The developed model was implemented on a typical bridge-dominated road network in Chongqing, China. The results demonstrate the model has the capacity to quantify the impact of diverse bridge maintenance strategies on the total road network, offering valuable insights for decision makers to design effective, efficient maintenance strategies aimed at extending the lifespan of bridge-dominated road networks. [ABSTRACT FROM AUTHOR]

The production quality assessment of prefabricated laminated slabs (PLS) is required to ensure the installation of components on the construction site. However, existing inspection methods are difficult to realize PLS production quality inspection during the production process, and the inspection speed cannot match the PLS production speed. To address these issues, a deep learning (DL) method based on You Only Look Once version 4 (YOLOv4) is proposed for the quality detection of PLS in production in this research. Five new measures are introduced to improve the performance of YOLOv4. The ResNet50vd backbone and deformable convolution (DCN) are used to enhance the ability of the model to capture the feature information of small targets with drastically changing morphologies in complex contexts. The k-means++ clustering algorithm is used to recalculate anchor box specifications to overcome the challenge of large differences in scales across targets as well as within the same target. Intersection over Union (IoU)-aware loss is used to optimize the loss function to improve the localization accuracy of small targets. Geometric median filtering pruning (FPGM) is used to simplify the network, and the model parameters are reduced to 44.1%, which significantly improves the detection speed of the components. The results show that the improved YOLOv4 can quickly and accurately detect laminated panels, PVC boxes, and steel bars in PLS when IoU=0.75 , which is more suitable for industrial applications, and the model achieves a mean average precision (mAP), F1 score, and FPS of 91.38%, 94.54%, and 22.91 frame rate (f/s) , respectively, which is superior to the comparison method. The proposed method can be directly applied to PLS in production to preemptively detect errors and discrepancies in the components and improve the qualification rate and quality management efficiency of the components, which has a positive effect on the rapid development of industrialized construction. Combined with the actual situation of prefabricated components production, this paper proposes a PLS production quality inspection method that is more in line with the factory production process. The new method was obtained by introducing five improvements to YOLOv4. The improved YOLOv4 can quickly and accurately detect laminated panels, PVC boxes, and steel bars in PLS when IoU=0.75 and is more suitable for industrial applications, and the model achieves a mAP, F1 score, and FPS of 91.38%, 94.54%, and 22.91 f/s , respectively. The proposed method does not require an additional inspection site and can be directly applied to the PLS production line for quality inspection of the PLS in production without interfering with the normal production process of the components and the outgoing process. By changing the posttest inspection to in-test inspection, the method can preemptively detect errors and discrepancies in PLS production and implement remedial measures in a timely manner, which effectively improves the qualification rate of components and the level of production quality management, and reduces the production cost of components. [ABSTRACT FROM AUTHOR]