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One of the benefits of using corrugated web girders is the increase of lateral‐torsional buckling resistance. Different approaches have been presented to obtain the value of the critical moment as a function of the cross‐section geometry. Previous research works consider that the increase in buckling resistance must be accredited to a higher warping constant. The paper presents a systematic finite element numerical analysis of girders with different corrugated web shapes. Bending with respect to the weak axis shows that corrugated web implies higher moment of inertia. Torsion analysis results clearly demonstrate that the increase of torsion resistance is mainly due to higher torsional constant. The paper compares the elastic critical moment values obtained by using finite element elastic buckling analysis with the values provided by theoretical expressions introducing equivalent section properties. Results show that the equivalent section properties approach provides values very close to those obtained using finite elements. Finally, the paper presents closed form expressions to directly compute approximate equivalent section properties of any girder with corrugated web, which compare very satisfactory with those values obtained with finite element buckling analysis. [ABSTRACT FROM AUTHOR]

The geometry and mechanical behavior of concrete bridge towers are complex. Hence, it is important to generate a rational mechanical analysis model for structural design. The method of strut‐and‐tie models (STMs) is an effective way to analyze disturbed regions (D‐regions) such as the anchorage zones of cables in bridge towers. This paper provides a detailed analysis of the elastic stress distribution on the bridge tower of a cable‐stayed bridge with two cable planes. The vertical component of the stay cable force was considered for the analysis. Additionally, two different STMs of the bridge tower were developed with the load path method using different horizontal spacings of the stay cables. Based on the minimum energy principle, the optimal STMs of the two different STMs were generated. A detailed calculation method for the configuration of the optimal STMs is presented. In the paper, computational expressions of the internal force for the tie members in the two STMs are also proposed. Overall, this study demonstrated the strong applicability of the proposed STMs for a bridge tower in a cable‐stayed bridge with two cable planes. This can be considered an effective simplified method in the structural design of bridge towers. Furthermore, the study established that the influence of the horizontal distance between stay cables on the mechanical response‐behavior of the structure should be considered in the design of concrete bridge towers. [ABSTRACT FROM AUTHOR]

The current paper resumes the design of a steel lattice transmission tower carried out in the framework of the RFCS‐funded research project ANGELHY. The scope of ANGELHY is the establishment of analysis methods for lattice towers and the development of design rules for steel and hybrid angle sections, as well as built‐up members composed of angles. In Europe, the design of transmission towers for overhead electrical lines can be carried out according to EN 1993‐3‐1: 2006 or for electrical lines exceeding 1 kV according to EN 50341‐1: 2012. Both standards prescribe linear elastic global analyses for the design of steel lattice towers. In the current paper, the linear elastic design of the suspension transmission tower according to the German National Annex of EN 50341‐1:2012 is presented. In a first step, common typologies of lattice transmission towers used in Europe are described. In a second step, the chosen tower typology is explained in detail. The Danube tower represents the widest spread tower typology in Europe. Finally, the detailed design procedure of the tower according to EN 50341‐1:2012 is presented. The design is carried out with the software TOWER – Version 15.0 from Power Line Systems. [ABSTRACT FROM AUTHOR]

When slender parts of plated structural members are under compression the local buckling may govern resistance of the whole structure. In addition to that, holes in those slender parts may reduce the resistance even more. Knowing that holes in different positions of steel structural members are very common, a simple but as precise as possible calculation method of critical buckling force would be beneficial for engineers. In order to create such a method, which would take the influence of the holes into account, an extensive analysis campaign of elastic buckling of thin plates with holes has been carried out. The finite element method was used for the calculations, and analysis of the obtained results derived to a simple calculation expression. The influence of different positioning and diameters of holes on elastic local buckling force is analyzed in the paper, and the developed calculation equation is presented. The proposed calculation method/ equation can be used by engineers in order to easily predict the elastic buckling coefficients and the critical forces of plates with round holes under compression. In order to add more value for engineers, the factors which have influence on the critical buckling force are commented. Also, recommendations for further development and possible extensions of the method are given in the paper. [ABSTRACT FROM AUTHOR]

The paper considers elastic anisotropic nano‐sheet with nanotopography and containing embedded nanocavities under time‐harmonic in‐plane wave motion. The mechanical model is based on the classical elastodynamic theory for the anisotropic bulk solid and the nonclassical boundary conditions along its boundary derived by Gurtin and Murdoch. A localized constitutive equation for the half‐plane boundary is considered in the frame of surface elasticity theory. The computational tool is an efficient direct displacement boundary element method (BEM) based on the frequency‐dependent elastodynamic fundamental solution for elastic generally anisotropic material. To show the versatility of the proposed methodology, wave propagation in an elastic anisotropic heterogeneous nano‐sheet with nanorelief presented by hill‐canyon nanotopography is studied. The simulations illustrate the dependence of the wave field on the material anisotropy, on the surface elasticity properties, on the nanorelief peculiarities, on the nanocavities existence and their dynamic interaction, and on the incident wave characteristics. The obtained results reveal the potential of the developed mechanical model based on the boundary integral equations in the frame of surface elasticity theory to produce highly accurate results by using strongly reduced discretization mesh in comparison with the domain‐based methods. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model for the elastic analysis of single floating piles subjected to axial dynamic loads, that is based on treating the soil surrounding the pile as a Tajimi‐type viscoelastic continuum. The pile and the soil column underlying the pile tip are modelled using one‐dimensional rod theory, and this allows obtaining an elegant solution that requires solving a system of linear equations, instead of complicated integral equations. Closed‐form expressions are derived for the dynamic stiffness at the pile head, and the frictional resistance along the pile shaft. The presentation concludes with a discussion on the main mechanisms that govern the inertial response of floating piles, and an investigation on the sensitivity of the dynamic stiffness and of the frictional resistance to the main geometrical and material problem parameters. [ABSTRACT FROM AUTHOR]

Summary: This work studies the dynamics of the Negative Stiffness Bilinear Elastic (NSBE) oscillator. Such a mathematical idealization can be used to describe deformable rocking systems equipped with restraining tendons or with curved extensions of their bases. First, this paper establishes the characteristic quantities of the bilinear system to make it equivalent to the actual rocking structures. Then, it proceeds by proposing a simpler "equivalent" system that can be used to study the behavior of the NSBE. The equivalent system is not some linear elastic oscillator but a bilinear elastic system with zero stiffness of the second branch: the Zero Stiffness Bilinear Elastic (ZSBE) system. ZSBE is useful because it needs one parameter less than NSBE to be defined. Next, "Equal Displacement" and "Equal Energy" rules that provide estimates of the maximum displacement of the NSBE based on the response of the ZSBE are defined. The concept is similar to the RμΤ relations that provide estimates of the response of bilinear yielding systems based on the response of an equivalent linear elastic system, with one major difference: it does not resort to a linear elastic system but to the ZSBE. The proposed methodology is applied on the FEMA P695 ground motions scaled at three different levels. The results show that ZSBE is a good proxy of NSBE and, hence, indicate that an exhaustive study of the ZSBE is useful for the design of rocking structures. [ABSTRACT FROM AUTHOR]

In this paper, we present the model of continuum mechanics for an analysis of the size‐dependent elastic state of the wrinkled thin film coating with the nanosized thickness. For this purpose, we formulate the two‐dimensional boundary value problem for the film‐on‐substrate system under plane strain conditions in terms of the complex variable. To analyse the effect of surface and interface elasticity, the surface and interphase domains are modelled as negligibly thin layers adhering to the bulk phases without slipping. The algorithm of deriving the expressions for the stress tensor components in the first‐order approximation of the boundary perturbation method is described. Based on this algorithm, the influence of the size of the wrinkles, film‐to‐substrate stiffness ratio and film thickness on the stress concentration in the film is examined. [ABSTRACT FROM AUTHOR]

This paper presents an analysis on the elastic characteristics of luffa and palm natural fiber composites (NFC) with epoxy and ecopoxy matrixes, taking into account the impact of fiber volume fractions. Furthermore, longitudinal modulus, transverse modulus, shear modulus, and Poisson's ratio were predicted using representative volume elements (RVEs) with chopped random and unidirectional fiber arrangements. However, analytical approaches such as rule of mixture, Chamis, Halpin–Tsai, and Nielsen were considered for validating and comparing the findings of finite element analyses. Hence, it was found that increasing fiber volume fraction increased the elastic properties of palm/epoxy, palm/ecopoxy, and luffa/epoxy NFCs, but decreased that of luffa/ecopoxy NFC. Addition of palm fibers in ecopoxy and epoxy had stronger effect than luffa on enhancing the elastic properties of the final structure. However, greatest elastic characteristics observed through analytical and numerical models were obtained for ecopoxy matrix with 0.5 palm fibers. A strong agreement was observed between the results obtained from analytical approaches and RVE unidirectional model. Chamis model exhibited higher outcomes compared to the considered analytical techniques, while Halpin–Tsai model showed the least values. [ABSTRACT FROM AUTHOR]

Summary: Local mechanical properties of submicron features are of particular interest due to their influence on macroscopic material performance and behaviour. This study is focused on local nanomechanical measurements, based on the latest Atomic Force Microscopy (AFM) mode, where the peak force set point is finely controlled at each pixel. After probe calibration, we evaluate the impact of spring constant of two AFM hand‐crafted natural full diamond tips with steel cantilevers, used for mapping. Based on the fast capture of the cantilever deflection at each pixel and real time force curve analysis in the elastic region, AFM local measured contact moduli mappings of the silica beads (>50 GPa) incorporated in an epoxy resin matrix, are compared with those determined using classical instrumented nanoindentation tests. Our analyses show that with the two AFM probes, without local residual deformation, the high moduli of the silica beads measured with this advanced AFM mode are within the standard deviation of the values determined by classical nanoindentation. Lay Description: The knowledge of material properties at the nanometer scale is a key parameter for well understanding and determining the behavior of material at macroscopic scale. In this paper, we compare two methods (an advanced mode and a classical one) based on the analysis of probes in interaction with the surface of studied material. We focus on a latest developed mode for determining local mechanical properties with a very high spatial resolution. For the advanced mode, we also consider two different hand‐crafted probes. Our analyses show that with the high spatial resolution advanced mode, local mechanical properties are well determined. We also highlight the impact of the properties of the used probes for this advanced mode. In a final step, the power of the presented investigation lies in the fact that it does not modify the topography of the surface. [ABSTRACT FROM AUTHOR]

For thin elastic structures submerged in heavy fluid, e.g., water, a strong interaction between the structural domain and the fluid domain occurs and significantly alters the eigenfrequencies. Therefore, the eigenanalysis of the fluid-structure interaction system is necessary. In this paper, a coupled finite element and boundary element (FE-BE) method is developed for the numerical eigenanalysis of the fluid-structure interaction problems. The structure is modeled by the finite element method. The compressibility of the fluid is taken into consideration, and hence the Helmholtz equation is employed as the governing equation and solved by the boundary element method (BEM). The resulting nonlinear eigenvalue problem is converted into a small linear one by applying a contour integral method. Adequate modifications are suggested to improve the efficiency of the contour integral method and avoid missing the eigenvalues of interest. The Burton-Miller formulation is applied to tackle the fictitious eigenfrequency problem of the BEM, and the optimal choice of its coupling parameter is investigated for the coupled FE-BE method. Numerical examples are given and discussed to demonstrate the effectiveness and accuracy of the developed FE-BE method. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The redistribution of moment within a statically indeterminate reinforced concrete beam at the ultimate limit state occurs through variations in the flexural rigidities and through the formation of hinges. The phenomena of moment redistribution (MR) is used to increase the efficiency of reinforced concrete design by allowing moments to be transferred away from critical cross sections thereby resulting in lower design moments. To allow for this effect in design, two main approaches are adopted. The first is to perform an elastic analysis and then to adjust the resulting distribution of moment using a codified MR factor. The second is to apply a plastic analysis allowing for the formation of hinges, and to calculate the rotational requirements at the hinges from first principles. This paper uses fundamental plastic analyses to derive closed‐form expressions for the hinge rotational requirements for full MR (that required to achieve the theoretical maximum applied load within the beam based on the moment capacity of sections within the beam). These closed‐form solutions are then used to quantify the maximum load on a beam when the rotational capacities at a hinge are less than the rotational requirements for full MR (partial MR). Closed‐form solutions are then used to derive MR factors which do not require semimechanical calibration. [ABSTRACT FROM AUTHOR]

We derive a one‐dimensional model for an elastic shuttle, that is, a thin rod with rounded ends and small fixed terminals, by means of an asymptotic procedure of dimension reduction. In the model, deformation of the shuttle is described by a system of ordinary differential equations with variable degenerating coefficients, and the number of the required boundary conditions at the end points of the one‐dimensional image of the rod depends on the roundness exponent m∈(0,1). Error estimates are obtained in the case m∈(0,1/4) by using an anisotropic weighted Korn inequality, which was derived in an earlier paper by the authors. We also briefly discuss boundary layer effects, which can be neglected in the case m∈(0,1/4) but play a crucial role in the formulation of the limit problem for m ≥ 1/4. [ABSTRACT FROM AUTHOR]

This paper extends previously developed models to account for the influence of the column and the foundation masses on the behavior of top-heavy deformable elastic cantilever columns rocking on a rigid support surface. Several models for energy dissipation at impact are examined and compared. A novel Vertical Velocity Energy Loss model is introduced. Rocking uplift and overturning spectra for the deformable elastic cantilever model excited by sinusoidal ground motions are constructed. The effects of non-dimensional model parameter variations on the rocking spectra and the overturning stability of the model are presented. It is shown that the remarkable overturning stability of dynamically excited large cantilever columns is not jeopardized by their deformability. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This article describes in detail the research on the elastic properties of carbon nanotube reinforced composite materials and graphene‐carbon nanotube (G‐C) reinforced composite materials. Several different composite material models were established using finite element software ABAQUS to study the influence of the inclination angle, quantity and volume fraction of carbon nanotubes and graphene on the elastic modulus of reinforced composites. The results show that as the volume fraction of graphene and carbon nanotubes increases, the Young's modulus and shear modulus of the reinforced composite material increase significantly. In addition, the tilt angle and quantity of graphene and carbon nanotubes will also affect the elastic properties of the composite material. The Young's modulus E and the shear modulus G decrease with the increase of the inclination angle, and increase with the increase of the number of graphene and carbon nanotubes. [ABSTRACT FROM AUTHOR]

Summary: This paper investigates the seismic response of multi‐storey cross‐laminated timber (CLT) buildings and its relationship with salient ground‐motion and building characteristics. Attention is given to the effects of earthquake frequency content on the inelastic deformation demands of platform CLT walled structures. The response of a set of 60 CLT buildings of varying number of storeys and panel fragmentation levels representative of a wide range of structural configurations subjected to 1656 real earthquake records is examined. It is shown that, besides salient structural parameters like panel aspect ratio, design behaviour factor, and density of joints, the frequency content of the earthquake action as characterized by its mean period has a paramount importance on the level of nonlinear deformations attained by CLT structures. Moreover, the evolution of drifts as a function of building to ground‐motion periods ratio is different for low‐ and high‐rise buildings. Accordingly, nonlinear regression models are developed for estimating the global and interstorey drifts demands on multi‐storey CLT buildings. Finally, the significance of the results is highlighted with reference to European seismic design procedures and recent assessment proposals. [ABSTRACT FROM AUTHOR]

Using the first‐principles method based on the density functional theory, hydrogen diffusion, electron structure, and mechanical properties of hydrogen impurity in W15V structure are investigated in this paper. It is found that in W‐V lattice the single H atom tends to be located in the tetrahedral interstitial site nearest to V atom with the solution energy of 0.614 eV. The calculation of energy barriers shows that the V doping can be helpful to trap H atoms near the V atom. The analysis of the elastic moduli shows that the V‐alloying can decrease the strength and improve the ductility of pure W. In addition, the H impurity further enhances this situation. Besides, the effect of H impurity on pure W is greater than W15V structure. The results of this study offer a useful database for the research of W‐based alloys for plasma facing materials (PFMs). [ABSTRACT FROM AUTHOR]

This paper investigates the large displacement post-buckling behavior of a column with central brace using the elastica solution. The method is able in predicting the buckling load and in tracing the exact post-buckling paths, both primary and secondary paths. Depending on the brace stiffness, different shapes of symmetrical and anti-symmetrical post-buckling paths can be shown to exist. Whilst previous work reported only one threshold value of brace stiffness, the results also show the existence of infinite number of threshold values, each indicates a change in the post-buckling behavior. [ABSTRACT FROM AUTHOR]

The stability of compression members is typically assessed through buckling curves, which include the influence of initial geometric imperfections and residual stresses. Alternatively, the capacity can be obtained more directly by carrying out a second order analysis using equivalent bow imperfections that account for both geometric imperfections and residual stresses. For design by second order elastic analysis, following EN 1993‐1‐1 recommendations, the magnitudes of the equivalent bow imperfections can either be back‐calculated for a given member to provide the same result as would be obtained from the member buckling curves or taken more simply as a fixed proportion of the member length. In both cases, a subsequent linear axial + bending cross‐section check is required. For design by second order inelastic analysis, there are currently no suitable recommendations for the magnitudes of equivalent bow imperfections and, as demonstrated herein, it is not generally appropriate to use equivalent bow imperfections developed on the basis of elastic analysis. Equivalent bow imperfections suitable for use in design by second order inelastic analysis are therefore established in the present paper and shown to yield reliable results when compared to benchmark results and current design guidance. [ABSTRACT FROM AUTHOR]

This paper addresses a linear elastic methodology for analysis of thin‐walled steel frames. The analysis is based on structural meaningful displacement modes that considerably reduce the number of degrees of freedom needed compared to a similar analysis using shell finite elements. The methodology allows the use of an adequate reduced number of higher order displacement modes. The methodology uses advanced beam elements to model the major structural elements within the frame and advanced joint elements to model the connections between the beam elements. Each joint element is a super element modeled by use of other finite elements such as shell elements. This allows the user to model virtually any geometry of the connection. Furthermore, the advanced beam element is formulated based on a linear combination of structural meaningful displacement modes belonging to each individual beam. Since the methodology is based on displacement modes of the (advanced) beams, it is possible to extract and identify critical displacement patterns for the frame as well as for each beam and joint within the frame. This gives the designer an in‐depth understanding of the behavior of the frame and hence a powerful tool to optimize its design. [ABSTRACT FROM AUTHOR]

A semi-analytical method for calculating the response of single piles and pile groups subjected to lateral loading is developed in this paper. Displacements anywhere in the soil domain are tied to the displacements of the piles through decay functions. The principle of virtual work and the calculus of variations are used to derive the governing differential equations that describe the response of the piles and soil. The eigenvalue method and the finite difference technique are used to solve the system of coupled differential equations for the piles and soil, respectively. The proposed method takes into account the soil surface displacement along and perpendicular to the loading direction and produces displacement fields that are very close to those produced by the finite element method but at lower computational effort. Compared with the previous method that considered only the soil displacement along the loading direction, accounting for the multi-directional soil displacement field produces responses for the piles and soil that are closer to those approximated by the finite element method. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY A new finite heterogeneous element consisting of sliced microstructures (FHES) is applied in a multi-scale technique. The FHES represents a heterogeneous material with microscopic constituents without homogenization or microscopic finite element analysis. A representative volume element extracted from a heterogeneous structure is thinly sliced. Each slice is modeled as a combined spring to calculate properties of the FHES. Each FHES has the same number of nodes as an ordinary finite element, and the macroscopic analysis cost is the same as that for ordinary finite element analysis. However, the FHES retains information about the microscopic material layout (i.e., the distribution of a material's property) in itself that is lost during homogenization. In the proposed approach, materials are not homogenized. The FHES does not have a constant (homogenized) material property and can 'change stiffness' depending on its deformation behavior. This reduces error due to coarse-graining and allows us to calculate the macroscopic deformation behavior with sufficient accuracy even if a large gradient of strain is generated in the macroscopic field. The novelty of the research is the development of rational heterogeneous finite elements. The paper presents the theory behind the FHES and its practical application to a linear elastic problem. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper discusses an existence result for energetic solutions of rate-independent damage processes and the temporal regularity of the solution. We consider a body consisting of a physically nonlinearly elastic material undergoing small deformations and partial damage. The present work is a generalization of [16] concerning the properties of the stored elastic energy density as well as the suitable Sobolev space for the damage variable: While previous work assumes that the damage variable z satisfies z in W1, r(Ω) with r > d for Ω ⊂ ℝd, we can handle the case r > 1 by a new technique for the construction of joint recovery sequences. Moreover, this work generalizes the temporal regularity results to physically nonlinearly elastic materials by analyzing Lipschitz- and Hölder-continuity of solutions with respect to time. [ABSTRACT FROM AUTHOR]

In this paper, a simple and effective method is presented to deal with elastic-plastic problems of annular disks with a nonlinear strain-hardening material behaviour under external pressure. The governing equation is derived from the deformation theory of plasticity, von Mises' yield criterion, and the nonlinear strain-hardening stress-strain relation. The truncated Taylor's expansion is employed to solve the governing equation. A comparison is made among the proposed method, existing analytical approaches and finite element method for annular disks with constant and variable thickness under external pressure. Excellent agreement is found between the proposed approach and finite element analysis. [ABSTRACT FROM AUTHOR]

Artificial intelligence is gaining increasing popularity in structural analysis. However, at the structural system level, the appropriateness of data representation, the paucity of data, and the physical interpretability of results are rarely studied and remain profound challenges. To fill such gaps, a physics‐informed model named StructGNN‐E (i.e., structural analysis based on graph neural network [GNN]–elastic) based on the GNN architecture, which is capable of implementing the elastic analysis of structural systems without labeled data, is proposed in this study. The systems with structural topologies and member configurations are organized as graph data and later processed by a modified graph isomorphism network. Moreover, to avoid dependence on big data, a novel physics‐informed paradigm is proposed to incorporate mechanics into deep learning (DL), ensuring the theoretical correctness of the results. Numerical experiments and ablation studies demonstrate the unique effectiveness of StructGNN‐E against common DL models, with an average accuracy of 99% and excellent computational efficiency. Due to its differentiability, StructGNN‐E is promising for bidirectionally linking structural parameters and analysis results, paving the way for a new end‐to‐end structural optimization method in the future. [ABSTRACT FROM AUTHOR]

Two theories may be used to analyze overdamped variable-head (slug) tests in aquifer materials. The first theory assumes that the solid matrix strain has a negligible influence. The second theory takes into account some elastic and immediate strain. Something is wrong with these theories because they yield different hydraulic conductivity values. This paper explains what is wrong after establishing the strain-stress elastic equations for a slug test in 2 ideal conditions: plane strain and spherical symmetry. The equations show that the radial contraction (or elongation) and tangential elongation (or contraction) yield a null volumetric strain. As a result, the conservation is described by the Laplace equation, which is used by the first theory. This first theory is the only one to yield correct solutions. The diffusion equation, with storativity, which is used by the second theory, is physically ill founded for slug tests in aquifers. This new proof scientifically confirms previously raised doubts and experimental proofs that the second theory is ill founded. [ABSTRACT FROM AUTHOR]

The geometric non-linear behaviour of thin axisymmetric circular plates on an elastic foundation is studied in the paper by using a boundary integral equation approach. A plate analogue procedure is suggested to simplify the solution. With such simplification, the foundation reaction can be arbitrary functions of plate deflection, rotation and curvatures. The boundary integral equation of thin plates and the fundamental solution of a biharmonic equation are employed for both bending and plane stress analysis. A number of numerical examples are given in the paper to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The paper is concerned with the equilibrium theory of elastic materials with voids. An analogue of the Phragmén-Lindelö principle for a semi-infinite right cylinder composed of a homogeneous and anisotropic material is presented. The paper studies the asymptotic behaviour of solutions measured by the cross-sectional work function. The work-function to within a rigid body displacement either decays faster than a certain decreasing exponential function or grows faster than a growing exponential function. A uniqueness result is also derived. [ABSTRACT FROM AUTHOR]

A Eurocode‐compliant design approach was developed for the design of thin‐walled cold‐formed steel sections which combines the AISI S100‐16‐Direct Strength Method (DSM) with the design provisions of EN 1993‐1‐3. The new design approach transfers the cross‐sectional resistance determined acc. to DSM based on numerical elastic buckling analyses on the gross cross‐section into the global member verification acc. to EN 1993‐1‐3. Additional factors were introduced to optimize the new approach, e.g., to account for the effects of the nonlinear stress distribution in cross‐sections subject to local and/or distortional buckling. Within the framework of the German research project FOSTA P1328/IGF 19964, an extensive series of tests on differently shaped, perforated, and unperforated cold‐formed sections in compression and bending were conducted which serve to analyze the buckling phenomena and the load‐bearing capacity and to validate the new design approach. In addition, a numerical model was developed, calibrated to the tests, and used for further parametric analyses on the load‐bearing capacity of cold‐formed sections. [ABSTRACT FROM AUTHOR]

Web holes are commonly seen in cold‐formed steel channel sections to accommodate the technical services. The presence of the web holes has resulted in the reduction of the sectional capacities of the cold‐formed steel sections and has been considered in the design according to the American Specification AISI S100‐16 using a new approach in the design called the Direct Strength Method (DSM). This article, therefore, will use this design method to investigate the sectional capacities of perforated channel sections under compression or bending with the variation of hole sizes in relation to those of gross channel sections. Elastic buckling analysis – a compulsory requirement for application of the DSM – can be conducted using a module CUFSM software program recently developed by the American Iron and Steel Institute. The investigated channel sections are taken from the availably commercial sections. The obtained sectional capacities are seen as the opposite trends for local and distortional buckling modes, although a downtrend of the sectional capacities is found in general with the increase of hole dimensions. It was found that perforated channel sections with smaller hole height and longer hole lengths were recommended to obtain the optimum section capacities in terms of the same web hole area, but the opposite trend was seen for these sections under bending with long hole lengths. [ABSTRACT FROM AUTHOR]

In United States practice, the strength of composite columns is assessed with available strengths that are computed considering member length effects. This approach has advantages; however, developing axial compression‐bending moment interaction diagrams that account for member length effects is not a straightforward task. Current methods result in unconservative error for highly slender members with large bending moments. While it is theoretically possible to develop more accurate interaction diagrams, a simpler approach, and one which more directly addresses the cause of the unconservative error, is to improve the accuracy of the stiffness used in the elastic analyses to determine required strengths. In this work, new recommendations are developed for this stiffness for steel‐concrete composite columns. The recommended stiffness is a function of required axial compression and bending moment, which increases accuracy and enables improved available strength calculations, resulting in more efficient designs. [ABSTRACT FROM AUTHOR]

The large fluctuation of uncertain parameters introduces a great challenge in the stability analysis of structures. To address this problem, a novel stochastic residual error based homotopy method is proposed in this article. This new method used the concept of homotopy to reconstruct a new governing equation for stochastic elastic buckling analysis, and the closed‐form solutions of the isolated buckling eigenvalues and eigenvectors are obtained by the stochastic homotopy analysis method. On this basis, a pth order origin moment of the stochastic residual error with respect to the elastic buckling equation is defined. Then, the optimal form of the homotopy series can be determined automatically by minimizing the pth order origin moment, which overcomes the disadvantage of highly relying on sample values of the existing homotopy stochastic finite element method. Moreover, the proposed method is developed to deal with the stochastic closely spaced buckling eigenvalue problem. Three mathematical examples and three buckling eigenvalue examples, including a variable cross‐section column, a 7‐story frame, and a Kiewitt single‐layer latticed spherical shell, are performed to illustrate the accuracy and effectiveness of the proposed method by comparing with the existing methods when dealing with large fluctuation of random parameters. [ABSTRACT FROM AUTHOR]

A series of Ni‐Mn‐Zn mixed spinel ferrite doped with Sm3+ ions is prepared by using sol‐gel auto‐combustion technique. Single phase cubic spinel structure of all the samples is confirmed by using XRD analysis. Incorporation of Sm3+ ions in Ni‐Mn‐Zn ferrites increases the lattice parameter from 8.4105 to 8.4134 Å. Williamson – Hall (W‐H) and strain size plot (SSP) analysis confirms the tensile‐type strain induced in the crystal lattice, which increases with the addition of Sm3+ ions. Average crystallite size estimated from Scherrer equation is found in the range 21.7–24.9 nm, which in good agreement with the results obtained from W‐H and SSP analysis. Infrared spectra recorded in the range 350–800 cm−1 reveals the characteristic features of spinel ferrites. Higher frequency band ν1 is observed near 580 cm−1 and lower frequency band ν2 is observed near 380 cm−1. By using the IR data, elastic constant (stiffness constant) and elastic moduli (Young's modulus, bulk modulus, and rigidity modulus) are estimated. Debye temperature obtained from Anderson formula ranging from 535 to 562 K and from Waldron equation ranging from 676 to 713 K with the substitution of Sm3+ ions. [ABSTRACT FROM AUTHOR]

In the present article the two‐dimensional hybrid equilibrium element formulation is initially developed, with quadratic, cubic, and quartic stress fields, for static analysis of compressible and quasi‐incompressible elastic solids in the variational framework of the minimum complementary energy principle. Thereafter, the high‐order hybrid equilibrium formulation is developed for dynamic analysis of elastic solids in the variational framework of the Toupin principle, which is the complementary form of the Hamilton principle. The Newmark time integration scheme is introduced for discretization of the stress fields in the time domain and dynamic analysis of both the compressible solid and quasi‐incompressible ones. The hybrid equilibrium element formulation provides very accurate solutions with a high‐order stress field and the results of the static and dynamic analyses are compared with the solution of the classic displacement‐based quadratic formulation, showing the convergence of the two formulations to the exact solution and the very satisfying performance of the proposed formulation, especially for analysis of quasi‐incompressible elastic solids. [ABSTRACT FROM AUTHOR]

Analyzes the approximate estimation formulae of the transient creep C integral and creep J integral for the elastic-power law creeping cracked body under constant displacement. Application of approximate analytic method; Concept of finite element method; Consideration of elastic-power law creeping material by the elastic strain rates.

In this paper, the existing Displacement Discontinuity Method (DDM) for three-dimensional elastic analysis with boundary discretized into triangular elements, which is purely based on analytical integrals, is extended from the constant element to the square-root crack edge element. In order to evaluate the singular integral when the receiver point falls into the remitter element, i.e., the observed point (x,y) ∈Δ, a part analytical and part numerical integration procedure is adopted effectively. The newly developed codes prove valid in estimating the Stress Intensity Factor (SIF) KI. Furthermore, for the sake of keeping the advantages of high-speed and high-accuracy in developing the numerical system, a novel method to realize pure analytical integration of influence function is found by the aid of symbolic computation technology of Mathematica. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Seismic events in recent years have underlined the need to quickly classify the built heritage in terms of seismic performances. The capacity of a structure can be assessed by means of inelastic analyses, requiring sophisticated numerical procedures. The simplified method herein proposed only requires use of common analyses such as the elastic structural analysis and the rigid‐plastic analysis. For this reason, it lends itself well to be used in the immediate aftermath of an earthquake, not requiring any static or dynamic non‐linear analyses. The proposed methodology has been set up by means of a large parametric analysis, carried out on 420 frames designed according to 3 different approaches: the first one is the Theory of Plastic Mechanism Control (TPMC), ensuring the design of structures showing global collapse mechanism (GMRFs), the second one is based on the Eurocode 8 design requirements (SMRFs) while the third is a non‐seismic design, based on design for vertical loads (OMRFs). [ABSTRACT FROM AUTHOR]

Deflections are among the most complex aspects of reinforced concrete behavior. Furthermore, deflection control is increasingly a governing criterion in design, especially in the case of two‐way members such as flat slabs or edge‐supported slabs. However, simple and theoretically sound and adequately verified methods for calculating deflections of two‐way reinforced concrete members have been lacking. Therefore, in this study, a novel method is proposed for deflection control of two‐way slabs. The method is an extension of the ζ‐method (as defined by Eurocode 2 and the fib Model Code 2010) of interpolating deflections between the uncracked and fully cracked state. As a basis, the method uses elastic deflections that are obtained through linear elastic analyses in finite element software. The elastic deflection is then adequately transformed based on the properties of a representative section, to account for cracking, shrinkage and creep according to a modified version of the ζ‐method. Finally, the method is validated against available experimental results from literature, obtaining satisfactory precision and accuracy. The method proposed in this study aims at providing an easy‐to‐use tool for designers carrying out deflection control of two‐way reinforced concrete slabs. [ABSTRACT FROM AUTHOR]

For elastodynamic problems in an elastic half-space, the idea of describing the displacement variation on the free ground surface outside the region being studied with the fundamental solution in a full space is presented in the paper. Then a corresponding mapped infinite boundary element is constructed for the problems of anti-plane motion. The computed results show that such an element can be applied effectively to obtain high-precision solutions. [ABSTRACT FROM AUTHOR]

An isoparametric plate shell element of 16 nodes and 40 degrees of freedom is developed in this paper directly from 3-D elastic theories. In order to overcome the difficulties caused by straightforward use of a 3-D formulation, the relative displacement method is introduced. For curved shell elements, the use of the orthogonal curvilinear co-ordinate system greatly reduces the computer effort. The new element can conveniently solve shell problems with variable thicknesses and also easily link with other finite elements using displacement d.o.f. such as 8-node to 21-node 3-D elements. Numerical examples demonstrate the efficiency of the element. [ABSTRACT FROM AUTHOR]

This paper proposes a method for tracking an object contour in a sequence of images. In this method, a contour model is defined by elastics. The contour tracking problem is formulated as an optimization problem to find the position that minimizes both elastic energy of its model and the potential energy derived from the edge potential image that includes a target object contour. The contour model is updated sequentially according to the tracking result in the previous frame. In the proposed approach, the contour model not only moves toward the object contour in the current frame, but also preserves the shape of the tracked contour in the previous frame. Therefore, the proposed method makes it possible to establish object tracking even when complex texture and occluding edges exist in or near the target object. Moreover, in this method, since smooth potential fields extending over a long distance are generated by distance transformation, unlike conventional methods, long-range motion tracking can be performed. An algorithm is newly presented which efficiently solves energy minimization problems. The validity and usefulness of the proposed method is shown with some experimental results. [ABSTRACT FROM AUTHOR]

First‐principles calculations using the projected augmented plane wave method have been performed to investigate the structural, elastic, and electronic properties of MgB2C2 under different pressures. The results indicate that the ternary compound MgB2C2 remains mechanically stable under pressure ranging from 0 to 50 GPa. Elastic analysis is performed, and it is found that MgB2C2 always shows obvious intrinsic brittleness under pressure, although there is an increasing trend of ductility, both from BH/GH and νH, with increasing pressure. (100), (010), and (11¯0) planes show strong anisotropy, and the degree of anisotropy decreases with increasing pressure; in the meantime, it is interesting to find that the degree of anisotropy is reduced in the following order of planes 11¯0→100→010 under the same pressure. [ABSTRACT FROM AUTHOR]

We present a new strategy for needle insertion simulations without the necessity of meshing. A diffuse domain approach on a regular grid is applied to overcome the need for an explicit representation of organ boundaries. A phase field function captures the transition of tissue parameters and boundary conditions are imposed implicitly. Uncertainties of a volume segmentation are translated in the width of the phase field, an approach that is novel and overcomes the problem of defining an accurate segmentation boundary. We perform a convergence analysis of the diffuse elastic equation for decreasing phase field width, compare our results to deformation fields received from conforming mesh simulations and analyze the diffuse linear elastic equation for different widths of material interfaces. Then, the approach is applied to computed tomography data of a patient with liver tumors. A three‐class U‐Net is used to automatically generate tissue probability maps serving as phase field functions for the transition of elastic parameters between different tissues. The needle tissue interaction forces are approximated by the absolute gradient of a phase field function, which eliminates the need for explicit boundary parameterization and collision detection at the needle‐tissue interface. The results show that the deformation field of the diffuse domain approach is comparable to the deformation of a conforming mesh simulation. Uncertainties of tissue boundaries are included in the model and the simulation can be directly performed on the automatically generated voxel‐based probability maps. Thus, it is possible to perform easily implementable patient‐specific elastomechanical simulations directly on voxel data. [ABSTRACT FROM AUTHOR]

Summary: In the small strain domain, asphalt mixes (AM) have a linear viscoelastic (LVE) behavior that is strongly dependent on frequency and temperature. The maximum ratio of modulus values can be up to 1000, and traditional elastic analyses are not pertinent. The possibility to characterize AM from frequency response functions (FRFs) was studied. A new optimization process using the finite element method (FEM) has been developed to back‐calculate the LVE properties of AM from FRFs. The numerical optimization process was applied to a reference material with averaged LVE properties determined from tension‐compression tests performed on a wide variety of AM types. The LVE properties were modeled considering the 3‐Dim version of the model 2S2P1D (2 Springs, 2 Parabolic elements, and 1 Dashpot). Reference FRFs for the considered reference material were obtained from FEM simulations. Three different configurations that may be of interest for practical tests were studied at five different temperatures. The proposed numerical optimization method consists in performing separate optimizations at each temperature to obtain the LVE properties for the considered temperature. Then values obtained at each temperature are considered to optimize 2S2P1D and Williams Landel Ferry (WLF) Equation constants to simulate the global LVE behavior of the material. The accuracy of the process was assessed regarding both the calculated FRFs and the complex modulus evaluation. Results indicate that the proposed optimization process converges almost perfectly towards the reference FRFs. The simulated complex modulus values are also in very good agreement with the values of the reference material. [ABSTRACT FROM AUTHOR]

Summary: Glass fiber‐reinforced polymer (GFRP) elastic gridshell is composed of long continuous GFRP tubes and achieves its shape through the elastic deformations during the lifting construction process. However, the complicated mechanical behaviors during the practical forming process are rarely examined in the previous researches. In this research, an innovative approach consolidating the form‐finding analysis and the construction simulation is proposed for the GFRP elastic gridshells. The integrated approach, which is developed with the ABAQUS and Python, is based on finite element analysis and iterative optimization; therefore, the mechanical deformations of gridshell can be accurately taken into account. The procedure of the integrated analysis is comprehensively presented by taking a typical double‐hump gridshell as an example. The form‐finding results (i.e., the flat lattices) derived from the iteration are found to be insensitive to the initial input. The structural behavior indexes (e.g., deflections, support reactions, and sectional stresses) during the lifting construction process are also available in the analysis. Based on the indexes, some general structural features of such gridshells are concluded. The achievements provide novel perspectives for the form‐finding analysis of GFRP elastic gridshells where lifting construction is involved, which is beneficial for the design and analysis of such structures. [ABSTRACT FROM AUTHOR]

Raman and Brillouin spectroscopies enable noninvasive assessment of chemical and elastic properties of biomaterials, respectively. In this report, Brillouin microspectroscopy was used for the time‐resolved analysis of elastic properties of Populus and Geranium leaves, whereas Raman microspectroscopy was employed for the assessment of their chemical variation during drying. Spectroscopic assessment of elastic and chemical properties can improve our understanding of mechanochemical changes of plants in response to environmental stress and pathogens at the microscopic cellular level. This report demonstrates the potential of multimodal optical sensing and imaging of plants as an emerging technique for the quantitative assessment of agricultural crops. [ABSTRACT FROM AUTHOR]

Summary: A new triangular element was created that could be used for the improvement of the accuracy of the constant displacement discontinuity method (CDDM). This element is characterized by three degrees of freedom in the three‐dimensional space as in the classical CDDM approach. The element is based on strain gradient elasticity theory that accounts for the difference of the average value of stress with the local stress at surfaces with large curvature (eg, crack borders, corners, and notches) in elastic bodies. The new element is characterized by a strain gradient term in addition to the two Lamè constants that gives a more representative value of the stresses at the centroid of crack edge elements compared with the classical elasticity solution and thus an accurate stress intensity factor. In this approach, special crack border elements with square‐root radius dependent displacements and numerical integrations are avoided. The extra strain gradient term is calibrated once only on the analytical solution for the penny‐shaped crack. In a verification stage, the accuracy of the computational algorithm for the elliptic and rectangular crack problems is demonstrated. Then, the algorithm, which also accounts for crack closure in compression, is applied for the modeling of crack propagation and crack interaction in uniaxial tension and compression loading. It is illustrated that the numerical predictions are in accordance with experimental evidence pertaining to uniaxial compression of transparent precracked specimens in the lab. [ABSTRACT FROM AUTHOR]

Summary: A complex variable solution is derived for the ground movements around a tunnel considering the lining at different positions in the drilled hole in a linear elastic half‐plane. The soil displacements for three different convergence patterns are presented and compared. It is shown that the surface settlement trough will become flatter and wider when the lining moves upwards; the horizontal displacements are more concentrated in the region below the lining; and the region influenced by displacements is wider. Most calculated settlement troughs can be well represented by Gaussian curves with simple parameters, but the obtained width parameters are larger than the traditional empirical values. The rigorous solution can be used as a simple tool to understand the fundamental mechanism of the lining buoyancy problem and as a benchmark for numerical procedures based on more sophisticated models. The importance of buoyancy effect on the displacement field should be taken into account. [ABSTRACT FROM AUTHOR]

For the seismic design of a structure, horizontal ground shaking is usually considered in two perpendicular directions, even though real horizontal ground motions are complex two-dimensional phenomena that impose different demands at different orientations. While the issue of ground motion dependence on the orientation of the recording devices has been the focus of many significant developments during the last decade, the effects of directionality on the characteristics of the structure have received less attention. This work presents a proposal to calculate the probability of exceedance of elastic spectral displacements accounting for structural typology and illustrates its relevance by means of its application to two case-study buildings. In order to ease its implementation in seismic design codes, a simplification is developed by means of a detailed statistical analysis of the results obtained using four sets of real hazard curves. The framework presented herein is considered to represent an important contribution to the field of performance-based earthquake engineering, permitting improved treatment of directionality effects within seismic risk design and assessment. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An equilibrium problem for an elastic body is considered. It is assumed that the body has a thin elastic inclusion and a thin rigid inclusion. We analyze a junction problem assuming that the inclusions have a joint point. Different equivalent problem formulations are discussed, and existence of solutions is proved. A set of junction conditions is found. We investigate a convergence to infinity and to zero of a rigidity parameter of the elastic inclusion. A delamination of the elastic inclusion is also investigated. In this case, inequality-type boundary conditions are imposed at the crack faces to prevent a mutual penetration between crack faces. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]