Search

The collocation boundary element method, as developed and taught in the traditional books, suffers from severe inconsistencies, partly responsible for the method's lack of clarity and broader applicability (not to mention the uncontrollable proliferation of misleading alternatives that only add to more confusion). This has been recently corrected, as summarized in this review paper, in which we report the proposition of a convergence theorem for the general, just consistent, three-dimensional isoparametric formulation of potential and elasticity problems (https://doi.org/10.1016/j.enganabound.2023.01.017), and also introduce the not interchangeable concepts of nodes and loci, for boundary displacements and tractions in elasticity, respectively, as well as of points, for domain sources. We have implemented, for both two-dimensional potential and elasticity problems, real-variable (https://doi.org/10.1016/j.enganabound.2023.01.015, https://doi.org/10.1016/j.enganabound.2023.03.026) and—still better—complex-variable (https://doi.org/10.1016/j.enganabound.2023.04.024) codes for generally high-order, curved elements, which effortlessly enable evaluations with numerical precision that is only machine-limited and only resorts to the problem's mathematics—plus Gauss–Legendre quadrature of all integrals' regular parts. (Ad hoc mechanical interpretations, "regularizations," interval subdivisions, special quadrature formulas, or variable transformations are neither strictly speaking correct nor generally applicable nor required.) Despite the singular kernels that enter diverse forms of Somigliana's identity (as for evaluating stress results at a domain point), problem-unrelated singularities do not come up in a mathematically consistent formulation and implementation: singularities are just man-made. A few examples of highly challenging topological issues are presented. We show that fracture mechanics problems may be dealt with seamlessly, and we manage to objectively assess a problem's topological consistency, precision, accuracy, and round-off errors related to a given mesh discretization and software-conditioned computational digits. [ABSTRACT FROM AUTHOR]

A 2 D Boundary Element Method (BEM) formulation, based on the representative volume element (RVE) concept, simulates the mechanical behavior of experimentally tested concrete under compression. A step-by-step parametric identification is presented. Considering different modeling for the fracture process at ITZ (Interfacial Transition Zone), the experimental results are captured when this phenomenon is modeled only around bigger aggregates. Besides, the size and quantity of the aggregates do not have great influence on the concrete mechanical behavior and the insertion of porosity in the mortar domain is very important. The proposed numerical model is efficient, robust, and accurate. [ABSTRACT FROM AUTHOR]

Two different models have been proposed to explain how the endpoints of chromatin looped domains (‘TADs’) in eukaryotic chromosomes are determined. In the first, a cohesin complex extrudes a loop until it encounters a boundary element roadblock, generating a stem-loop. In this model, boundaries are functionally autonomous: they have an intrinsic ability to halt the movement of incoming cohesin complexes that is independent of the properties of neighboring boundaries. In the second, loops are generated by boundary:boundary pairing. In this model, boundaries are functionally non-autonomous, and their ability to form a loop depends upon how well they match with their neighbors. Moreover, unlike the loop-extrusion model, pairing interactions can generate both stem-loops and circle-loops. We have used a combination of MicroC to analyze how TADs are organized, and experimental manipulations of the even skipped TAD boundary, homie, to test the predictions of the ‘loop-extrusion’ and the ‘boundary-pairing’ models. Our findings are incompatible with the loop-extrusion model, and instead suggest that the endpoints of TADs in flies are determined by a mechanism in which boundary elements physically pair with their partners, either head-to-head or head-to-tail, with varying degrees of specificity. Although our experiments do not address how partners find each other, the mechanism is unlikely to require loop extrusion.

The use of reinforced concrete walls has become popular in Latin America as a structural system for the construction of residential buildings. However, this system is characterized by a low ductility capacity, compromising its seismic performance during the last strong earthquakes. This study uses three real buildings composed of reinforced concrete walls located in a high seismic region and soil type D, designed based on the Colombian building code. Nonlinear models of these three buildings were generated to evaluate the seismic response under actual ground motions. The three buildings were then redesigned using seismic isolation and the same analysis procedure was carried out to obtain the seismic response of the isolated buildings, comparing the results with those of the fixed base. The results show that the seismically isolated buildings exhibited a higher seismic performance, moving from a life safety performance level of the fixed-base buildings to an immediate occupancy performance level. In addition, the isolated buildings required up to 50% less reinforced steel and up to 100% fewer boundary elements compared to the fixed-base buildings, while keeping the architectural and building advantages of the wall structural system. [ABSTRACT FROM AUTHOR]

This paper presents mechanics-based modeling methodologies to predict the shear strength of squat walls incorporating boundary elements. Developed with the intention of surmounting the limitations of empirical models that are prevalent in the structural engineering community, these approaches are composed of an iterative analytical method and simplified design equations. Conforming to experimental observations, a failure criterion is established to determine the web crushing and shear compression of each wall component. Upon validating the methodologies against 123 test data compiled from the literature, detailed responses of the wall system are examined to comprehend the behavior of the web and the compression and tension boundary elements subjected to lateral loading. Model outcomes indicate that the overall strength of the squat walls is distributed to the web and the boundary elements by 58% and 42%, respectively, signifying that the contribution of the boundary elements should not be ignored, unlike the case of most customary models. In contrast to the provision of published design specifications, both horizontal and vertical reinforcing bars affect the shear strength of the web concrete. The growth of compressive principal strains, which dominate the failure of the members, is a function of the reinforcement ratio. According to statistical evaluations, the proposed models outperform existing models in terms of capacity prediction. The effects of major parameters are articulated from a practical standpoint. [ABSTRACT FROM AUTHOR]

It is well known that boundary integral equations are exact mathematical representations of the governing differential equations of a boundary value problem when the integrals are written over a closed-shape boundary representation (B-representation) of the domain, usually reffered to as a watertight Brepresentation. However, practical geometric design technics (namely, NURBS surfaces) often do not render a watertight B-representation. Non-watertight geometric models with small gaps and overlaps are often generated in the design stage of projects. Based on a proposed surface-independent discretization approach, the present study investigates how unsought gaps affect the response of boundary element models of linear elasticity problems. The developed surface-independent discretization is applied to discretize multiplepatches NURBS B-representation geometries. Linear triangular and quadrilateral elements are adopted to discretize the independent surfaces. Generalized discontinuous elements at the edges of the visible areas of the NURBS parametric spaces are detected by a Level Set function. An offset collocation strategy is adopted for the nodes at the edges of the visible part of the parametric spaces. Thus, singularities and near singularities due to collocation are avoided in the BEM equations. The influence of gaps in the convergence of the L2-norm of boundary displacement error is verified in a 3D example with an available analytical solution. A second example with available numerical solution is analyzed with a non-watertight BEM discretization for qualitative boundary field validation. Finally, a non-watertight B-representation geometry of a crane hook is analyzed. The obtained results have pointed out that, as long as the gaps (and overlaps) are small enough, BEM models built up from non-watertight geometries may produce valuable solutions for practical purposes. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) walls containing openings are usually stiffened by boundary elements (or boundary flanges) in the form of columns on one or both sides. Both thickness and longitudinal reinforcement ratio of such boundary members generally exceed those of enclosed walls. Such boundary elements also contribute to an improvement in the strength of enclosed walls. As a result, the strength of RC walls with openings with boundary elements is higher than those without them. In this paper, an analytical approach based on the softened strut-and-tie model is proposed to evaluate the shear strength of RC walls with a central opening and enclosed by boundary elements. The combined behavior of the wall and boundary elements under a simultaneous bending moment and axial loading is considered in the sectional analysis to calculate neutral axis depth for evaluating strut capacity. Shear strength predictions through the proposed approach showed reasonable accuracy when verified against the test data from eleven RC walls with a single central opening. Comparisons are also made with strength estimations based on American and Japanese code provisions. Finally, a simplified equation for the evaluation of neutral axis depth is presented to enable design engineers to conduct preliminary design of RC walls with openings that are enclosed by boundary elements. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the reliability of testing idealized prisms to simulate failure mechanisms in RC walls. In-plane cyclic tests on three flexural walls with different transverse reinforcement detailing and axial tests on three rectangular RC prisms idealized as wall boundary zones are conducted and the experimental responses are discussed in this paper. The results confirmed that idealized rectangular RC prisms are susceptible to failure due to the development of global out-of-plane (OOP) instability. These investigations revealed that strain distribution along the height is a key parameter influencing the failure mechanism observed in wall boundaries and idealized prism specimens. [ABSTRACT FROM AUTHOR]

Copyright of bāb Journal of FSMVU Faculty of Architecture & Design is the property of bab Journal of FSMVU Architecture & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Canterbury earthquake royal commission report highlighted that, despite being well-detailed, several reinforced concrete (RC) shear walls did not achieve their anticipated ductility capacities. In order to enhance the performance of such walls during future seismic events, the report recommended the use of concentrated and confined rebars at the wall toes coupled with high reinforcement ratios within the wall to initiate secondary cracks and extend the inelastic wall regions, thus minimizing the corresponding seismic demands. In this respect, the current study evaluates the seismic performance of RC walls with flanged and boundary element configurations compared with their typical rectangular counterparts, when different reinforcement ratios are incorporated. Specifically, the study presents a detailed analysis of six three-story half-scaled RC shear walls tested under quasi-static cyclic loading representing different seismic demands. The six walls were originally tested in two phases, where each phase had three different wall types (i.e., rectangular, flanged, and boundary element configurations). Walls in both phases had the same overall dimension and cross-section area; however, Phase II walls had 2.4 times the vertical reinforcement ratios used in Phase I walls. Following a summary of the experimental program and results, the current study presents the analytical results of the walls in terms of their load-strain relationships, curvature profiles, stiffness degradation trends, energy dissipation capacities, and equivalent viscous damping ratios. A comparison between the theoretical and experimental curvatures is also presented for the test walls at different drift levels. The results show that flanged and boundary element walls had low yield curvatures and high ultimate curvatures which resulted in enhancing their displacement ductility capacities. Flanged and boundary element walls also exhibited higher stiffness degradation rates when compared with their rectangular counterparts, leading to reduced seismic demands. Moreover, flanged and boundary element walls with high vertical reinforcement ratios (1.58%–1.63%) had higher energy dissipation capacities than their counterparts with low vertical reinforcement ratios (0.66%–0.69%). However, rectangular walls with low vertical reinforcement ratios (1.17%) showed higher ultimate curvature capacities than rectangular walls with high vertical reinforcement ratios (2.80%). Overall, the results demonstrate that future editions of relevant design standards (e.g., CSA A23.3 and ACI 318-19) should consider assigning different seismic design parameters (e.g., ultimate compressive strains, equivalent viscous damping ratios, and ductility-related modification factors) for RC shear walls based on their end configurations that can significantly alter the performance of such walls under seismic events. [ABSTRACT FROM AUTHOR]

Some reinforcements used in the manufacturing of composites parts by Liquid Composite Molding (LCM) processes have a dual-scale nature, which supposes flow imbalances between the tows and channels at the mesoscopic scale, which in turn, cause uncontrolled defects (voids, dry points, among others) and could considerably affect the global flow behavior during the filling of cavities at a macroscopic scale. In the present work, a new approach to conducting filling simulations of dual-scale fibrous reinforcements at a mesoscopic scale is proposed. This consists of imposing a pressure gradient across the Representative Unitary Cell, and considering Stokes-Darcy coupling conditions between the porous and the free-fluid sub-domains to determine the filling of the former ones. Contrarily to the traditional approach, where a uniform pressure is assumed for the channels, and only the porous media fluid is modeled, the present approach allows considering the fluid motion at channels, flow-direction dependent capillary pressure, air compression and dissolution, and vacuum pressure, as well as capturing several phenomena of the evolution of intra-tow bubbles, namely, compression, mobilization at constant volume and migration from tows towards the channel. The velocity vectors and streamlines in the tows and channel subdomains, when these phenomena take place, are analyzed as well. [ABSTRACT FROM AUTHOR]

We consider the non-symmetric coupling of finite and boundary elements to solve second-order nonlinear partial differential equations defined in unbounded domains. We present a novel condition that ensures that the associated semi-linear form induces a strongly monotone operator, keeping track of the dependence on the linear combination of the interior domain equation with the boundary integral one. We show that an optimal ellipticity condition, relating the nonlinear operator to the contraction constant of the shifted double-layer integral operator, is guaranteed by choosing a particular linear combination. These results generalize those obtained by Of and Steinbach [Is the one-equation coupling of finite and boundary element methods always stable?, ZAMM Z. Angew. Math. Mech.93 (2013), 6–7, 476–484] and [On the ellipticity of coupled finite element and one-equation boundary element methods for boundary value problems, Numer. Math.127 (2014), 3, 567–593], and by Steinbach [A note on the stable one-equation coupling of finite and boundary elements, SIAM J. Numer. Anal.49 (2011), 4, 1521–1531], where the simple sum of the two coupling equations has been considered. Numerical examples confirm the theoretical results on the sharpness of the presented estimates. [ABSTRACT FROM AUTHOR]

For the first time, a nonlinear interface problem on an unbounded domain with nonmonotone set-valued transmission conditions is analyzed. The investigated problem involves a nonlinear monotone partial differential equation in the interior domain and the Laplacian in the exterior domain. Such a scalar interface problem models nonmonotone frictional contact of elastic infinite media. The variational formulation of the interface problem leads to a hemivariational inequality, which lives on the unbounded domain, and so cannot be treated numerically in a direct way. By boundary integral methods the problem is transformed and a novel hemivariational inequality (HVI) is obtained that lives on the interior domain and on the coupling boundary, only. Thus for discretization the coupling of finite elements and boundary elements is the method of choice. In addition smoothing techniques of nondifferentiable optimization are adapted and the nonsmooth part in the HVI is regularized. Thus we reduce the original variational problem to a finite dimensional problem that can be solved by standard optimization tools. We establish not only convergence results for the total approximation procedure, but also an asymptotic error estimate for the regularized HVI. [ABSTRACT FROM AUTHOR]

The use of boundary elements in the analysis of exterior acoustic problems poses challenges at specific frequencies, since fictitious eigenfrequencies may arise at the internal resonances of cavities, leading to inaccurate results or even unstable behavior. To filter out these fictitious eigenfrequencies, a scheme based on the combined Helmholtz integral equation formulation (CHIEF) can be used to prevent the so-called non-uniqueness problem, although it requires additional equations and points. The BEM formulation final accuracy will, however, depend on the correct choice of these points. Here, a strategy to help in defining good approximations for the position and number of such points is proposed, based on an optimization process which maximizes the system matrix's smallest singular value. The accuracy of the method for exterior radiation problems is investigated using different examples. With low computational cost and simple implementation, the two proposed algorithms automatically circumvent the non-uniqueness problem, aiding the implementation of more stable BEM codes. [ABSTRACT FROM AUTHOR]

Noise barriers are common noise mitigation measures usually implemented near roads or railways, with proven efficiency. This work presents a study of a porous concrete material incorporating expanded clay as aggregate, to be used on the sound-absorption layer of noise barriers. A theoretical material model is calibrated using experimental data and then used to estimate the diffuse field sound absorption from the normal incidence sound absorption estimation/measurement. Validation of such estimation is performed by comparing to reverberant room measurements. Numerical simulations are carried out using the boundary element method (BEM) and the CNOSSOS-EU calculation method to assess the performance of different types of barriers incorporating this material. L-shaped and vertical barriers are tested, as well as low-height and conventional (taller) barriers, employed in the context of a railway noise scenario. Different results are obtained by the two methods, mainly due to the different underlying physical principles. Good insertion loss values may be obtained using both conventional and low-height noise barriers together with the porous concrete material if a careful choice of its location within the barrier is made. [ABSTRACT FROM AUTHOR]

MultiFEBE integrates multiple finite element and boundary element models for solving linear static and time harmonic multi-domain interaction problems within the field of computational mechanics. It allows to couple bounded or unbounded two- and three-dimensional continuum inviscid fluids, elastic solids or poroelastic media with beam and shell structural elements. This paper summarizes the models and numerical methods implemented in the code, and illustrates its use and capabilities through the computation of the dynamic response of the support structure of an offshore wind turbine fixed to the seabed through a jacket structure and three suction caissons.

This article describes a novel and accurate implementation of finite element method-boundary element method (FEM-BEM) coupling based on Argyris element (AE), for the $C^{1}$ solution of axi-symmetric magnetostatic problems in open boundary domains. The aim of the work is twofold: 1) to provide novel, easy, and accurate way to compute the basis functions that is strongly not affected by accuracy errors and 2) to give a clear mathematical and numerical description of the FEM-BEM coupling based on AE. The first goal is achieved by shifting to the origin the physical triangular elements and computing the basis function in the shifted coordinate system. Second, AE-based FEM-BEM coupling relies on the boundary integral equations (BIEs) for poloidal flux and its partial derivatives of both first and second order, accurately computed by combining the analytical formula based on elliptic integrals together with high degree Gaussian cubature. The application of the proposed method to an advanced plasma equilibrium magnetic configuration, typical of magnetic confinement fusion (MCF) (i.e., snowflake configuration), highlights that, even in case of coarse triangulation, satisfactory results can be achieved, and the error on the boundary conditions (BCs) is well below machine working precision. [ABSTRACT FROM AUTHOR]

Steel plate shear walls (SPSWs) are among the most desirable load-bearing systems, which have been used wildly in various structures. Recently, designers have tended to SPSWs with only beam connections showing several problems. In the present research, several SPSWs with various types of connection conditions between infill plate and boundary elements, and various stiffness of boundary elements have been studied. The result illustrates that by having the full connection between infill plate and boundary elements, at least a 33% interconnected infill plate to columns could eliminate the significant loss of fundamental factors in SPSWs connected to beam only. Furthermore, increasing the stiffness of columns has more effect on the performance of SPSWs in comparison with beams. [ABSTRACT FROM AUTHOR]

We consider the thermoelastic wave equation in three dimensions with transparent boundary conditions on a bounded, not necessarily convex domain. In order to solve this problem numerically, we introduce a coupling of the thermoelastic wave equation in the interior domain with time-dependent boundary integral equations. Here, we want to highlight that this type of problem differs from other wave-type problems that dealt with FEM–BEM coupling so far, e.g., the acoustic as well as the elastic wave equation, since our problem consists of coupled partial differential equations involving a vector-valued displacement field and a scalar-valued temperature field. This constitutes a nontrivial challenge which is solved in this paper. Our main focus is on a coercivity property of a Calderón operator for the thermoelastic wave equation in the Laplace domain, which is valid for all complex frequencies in a half-plane. Combining Laplace transform and energy techniques, this coercivity in the frequency domain is used to prove the stability of a fully discrete numerical method in the time domain. The considered numerical method couples finite elements and the leapfrog time-stepping in the interior with boundary elements and convolution quadrature on the boundary. Finally, we present error estimates for the semi- and full discretization. [ABSTRACT FROM AUTHOR]

Two different models have been proposed to explain how the endpoints of chromatin looped domains ('TADs') in eukaryotic chromosomes are determined. In the first, a cohesin complex extrudes a loop until it encounters a boundary element roadblock, generating a stem-loop. In this model, boundaries are functionally autonomous: they have an intrinsic ability to halt the movement of incoming cohesin complexes that is independent of the properties of neighboring boundaries. In the second, loops are generated by boundary:boundary pairing. In this model, boundaries are functionally non-autonomous, and their ability to form a loop depends upon how well they match with their neighbors. Moreover, unlike the loop-extrusion model, pairing interactions can generate both stem-loops and circle-loops. We have used a combination of MicroC to analyze how TADs are organized, and experimental manipulations of the even skipped TAD boundary, homie , to test the predictions of the 'loop-extrusion' and the 'boundary-pairing' models. Our findings are incompatible with the loop-extrusion model, and instead suggest that the endpoints of TADs in flies are determined by a mechanism in which boundary elements physically pair with their partners, either head-to-head or head-to-tail, with varying degrees of specificity. Although our experiments do not address how partners find each other, the mechanism is unlikely to require loop extrusion., Competing Interests: XB currently employed by a biotech company; however, this author's experimental contributions to the paper were done prior to taking the biotech job, WK, MF, AK, SL, ML, PS, JJ No competing interests declared, (© 2024, Bing, Ke, Fujioka et al.)

The load-penetration curve in elastic nanoindentation of an elastic micropolar flat by a diamond spherical punch is analyzed. The presented results are obtained by a specifically developed numerical tool based on a judicious combination of the conventional boundary element method and strong form local point interpolation method. The results show that the usual linear relationship between the material depression and the square of the radius of the contact area is also valid in this case of micropolar elastic material. It is also shown that the relation between the indentation stress (applied load over the contact surface) and the indentation strain (ratio of contact radius by the punch radius) is linear. The proportionality coefficient which is none other than the indentation stiffness varies with the coupling factor of the micropolar elastic medium. A relation between the indentation stiffness of a micropolar solid and that of a conventional solid with the same Young modulus and Poisson ratio is derived.

Some fibrous reinforcements used in the manufacturing of parts by Liquid Composite Molding (LCM) have a dual-scale nature, which supposes flow imbalances between the tows and channels at mesoscopic scale, which in turn, cause uncontrolled defects (voids, dry points, among others) and could considerably affect the global flow behavior during the filling of cavities at macroscopic scale. In the present work, a new approach to conduct filling simulations of dual-scale fibrous reinforcements at mesoscopic scale is proposed. This consists of prescribing a pressure gradient along the Representative Unitary Cell, and imposing Stokes-Darcy matching conditions between the tows and the channel sub-domains to determine the filling of the former ones. Contrarily to the traditional approach, where a uniform pressure is assumed for the channels and only the porous media fluid is modeled, the present one allows considering the fluid pressure gradient at channels (fluid motion), air compressibility and dissolution, flow-direction dependent capillary pressure, and vacuum pressure, as well as capturing several phenomena involved in the dynamic evolution of intra-tow voids, namely, compression, mobilization at constant volume and migration from tows towards channel. The velocity vectors and streamlines in the tows and channel subdomains, when these phenomena take place, are analyzed as well.

This article proposes a novel numerical model of the dynamic response of large diameter, concrete‐lined circular shafts, embedded in transversely isotropic soils. Excitation is given as time‐harmonic external loads applied to the base of the shaft, or vertically propagating, time‐harmonic pressure waves. The concrete lining is modeled with finite annular plate and cylindrical‐shell finite elements, while the contact tractions at the shaft–soil interface are modeled within a boundary elements framework. The response of the coupled system is obtained by imposing rigorous continuity and equilibrium conditions at the interface. The model yields accurate representation of the energy exchange between shaft and soil, as well as energy propagation through the soil as an unbounded medium. Original numerical results are presented on the response of the shaft and lining for selected geometric and constitutive parameters, frequencies and type of excitation, and anisotropic soil constitutions. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose efficient weak coupling formulations between the boundary element method and the high-order finite element method for solving time-harmonic electromagnetic scattering problems. The approach is based on the use of a nonoverlapping domain decomposition method involving optimal transmission operators. The associated transmission conditions are constructed through a localization process based on complex rational Pad\'e approximants of the nonlocal magnetic-to-electric operators. Numerical results are presented to validate and analyze the new approach for both homogeneous and inhomogeneous scatterers. [ABSTRACT FROM AUTHOR]

The use of boundary elements in the analysis of exterior acoustic problems poses challenges at specific frequencies, since fictitious eigenfrequencies may arise at the internal resonances of cavities, leading to inaccurate results or even unstable behavior. To filter out these fictitious eigenfrequencies, a scheme based on the combined Helmholtz integral equation formulation (CHIEF) can be used to prevent the so-called non-uniqueness problem, although it requires additional equations and points. The BEM formulation final accuracy will, however, depend on the correct choice of these points. Here, a strategy to help in defining good approximations for the position and number of such points is proposed, based on an optimization process which maximizes the system matrix’s smallest singular value. The accuracy of the method for exterior radiation problems is investigated using different examples. With low computational cost and simple implementation, the two proposed algorithms automatically circumvent the non-uniqueness problem, aiding the implementation of more stable BEM codes.

Noise barriers are common noise mitigation measures usually implemented near roads or railways, with proven efficiency. This work presents a study of a porous concrete material incorporating expanded clay as aggregate, to be used on the sound-absorption layer of noise barriers. A theoretical material model is calibrated using experimental data and then used to estimate the diffuse field sound absorption from the normal incidence sound absorption estimation/measurement. Validation of such estimation is performed by comparing to reverberant room measurements. Numerical simulations are carried out using the boundary element method (BEM) and the CNOSSOS-EU calculation method to assess the performance of different types of barriers incorporating this material. L-shaped and vertical barriers are tested, as well as low-height and conventional (taller) barriers, employed in the context of a railway noise scenario. Different results are obtained by the two methods, mainly due to the different underlying physical principles. Good insertion loss values may be obtained using both conventional and low-height noise barriers together with the porous concrete material if a careful choice of its location within the barrier is made.

Aiming at the fault traveling wave on the LCC-MMC HVDC transmission line, this paper analyzed its reflection and refraction characteristics at the DC buses and the fault point, plotted its propagation grid diagrams, obtained the relationship between the polarity of fault traveling wave and the boundary elements, and drew the conclusion that when the impedance of DC filter is far less than the wave impedance of transmission line, the existing fault location methods that need to distinguish these two waves according to their polarities are not applicable to the LCC-MMC HVDC system. On these bases, this paper proposed a modal traveling wave arrival time difference-based location principle for pole-to-ground fault, and a fault traveling wave propagation path ratio-based location principle for pole-to-pole fault, these principles neither need to identify the wave polarity, nor need the wave velocity value. In order to better extract the wave heads and their arrival time, this paper pre-treated the sampling data to make sure all the wave heads are extracted from the same frequency band, then the wave heads and their arrival time can be extracted with the empirical mode decomposition. The simulation results verified the effectiveness of the proposed fault location principle. [ABSTRACT FROM AUTHOR]

This study presents the results of in-plane cyclic tests performed on unreinforced brick masonry walls retrofitted using shotcrete. The experimental study was carried out on three full-scale specimens. One specimen was tested as reference and others were strengthened to the boundaries on one and both sides with two different retrofitting strategies. According to the results, strengthening the wall boundaries on one side of the URM wall resulted less satisfactory. On the other hand, the proposed technique in strengthening the wall boundaries on both sides was effective and extremely improved the behavior of strengthened walls. [ABSTRACT FROM AUTHOR]

Steel plate shear walls (SPSWs) are among the most desirable load-bearing systems, which have been used wildly in various structures. Recently, designers have tended to SPSWs with only beam connections showing several problems. In the present research, several SPSWs with various types of connection conditions between infill plate and boundary elements, and various stiffness of boundary elements have been studied. The result illustrates that by having the full connection between infill plate and boundary elements, at least a 33% interconnected infill plate to columns could eliminate the significant loss of fundamental factors in SPSWs connected to beam only. Furthermore, increasing the stiffness of columns has more effect on the performance of SPSWs in comparison with beams.

The paper addresses the theoretical framework and the numerical procedure developed to carry out the sectional analysis preliminary to the use of a recently formulated isotropic and homogeneous beam model consistently derived from the Saint Venant solid one. Specifically, in order to ensure the equivalence of the new beam model with the 3D solid one, both in terms of elastic energy and displacements of the beam axis, one requires the evaluation of a symmetric second-order tensor, accounting for the shear deformation, besides the center of twist and the torsional stiffness factor. Common property to such geometrical quantities is to be expressed as integrals of harmonic functions solution of Neumann problems that are defined over the section domain. Hence, with a view towards numerical applications, they are reformulated as integrals defined over the section boundary, assumed to be of arbitrary polygonal shape. The numerical evaluation of the resulting line integrals is obtained by exploiting a recently formulated boundary element approach in which the harmonic potential functions are expressed as polynomials defined on suitably defined subsets of each edge of the section boundary. As an outcome of the extensive numerical tests that have been carried out on compact and thin-walled sections a general criterion, established elsewhere for properly selecting the best combination of polynomial degree and edge discretization, is shown to be successful also for carrying out the shear analysis of beam sections having arbitrary shape. [ABSTRACT FROM AUTHOR]

Excessive lateral deformation of frame structures under seismic action leads to overall dynamic instability. This means that the stiffness of the structures need to be increased. Hence, a less wall frame structure is formed by retrofitting reinforced concrete columns with wing walls (RCCWWs) at specific critical positions of the structure. RCCWWs are widely used in multi-storey and high-rise buildings due to the advantages of relatively flexible layout, higher space utilization, sufficient stiffness provided by wing walls. Nevertheless, the failure mechanism and seismic performance of RC columns would be changed by supplementing wing walls. Past studies and current Chinese code have mainly focused on the application of wing walls to the enhancement of stiffness in the elastic stage of the structure, ignoring crucial factors that affecting the plastic behavior of RCCWWs under cyclic loading, including the lengths of the wing walls, the lengths of boundary elements and stirrups ratio of boundary elements. This paper provides a comprehensive experimental study on the seismic behavior of six RCCWWs specimens which constructed and tested under cyclic loading, examining the effects of the three key factors mentioned above. The damage evolution, the failure mechanism and failure characteristics of RCCWWs is revealed. Test results indicated that RC columns and wing walls can operate better in concert. Simultaneously, the asymmetry of the cross-section causes the damage primarily at the wing walls tips firstly, with less damage observed in the RC columns. RCCWW obviously underwent two-stage failure, the wing wall first failed and lost its bearing capacity, then the RC column held the load individually and dissipated energy until it failed. It is found that the length of the wing wall has extraordinarily significant effect on the bearing capacity and energy dissipation capacity. Increasing the wing walls lengths form 500 mm to 700 mm leads to positive and negative bearing capacity improved by 63 %∼74 % and 16 %∼38 %, respectively. And positive and negative energy dissipation capacity improved by 6 %∼37 % and 2 %∼44 %, respectively. Note that the specification limits of lateral drift ratio (1/50) for frame structures in GB50010-2010 are not applicable to less wall frame structures instead, a more stringent criterion (1/120) is necessary. Finally, a method for estimating the bending moment capacity of RCCWWs is proposed. • Six columns with unilateral wing walls were investigated through quasi-static test. • Two-stage damage evolution process of columns with unilateral wing walls was revealed. • The seismic performance of the specimens with diverse wing walls details was quantified. • The drift ratio for less wall frame structures in "code for seismic design of building" is recommended to 1/120. • A computational model was developed to efficiently estimate the bending capacity of RCCWW. [ABSTRACT FROM AUTHOR]

Laboratory tests demonstrated that reinforced masonry shear walls (RMSWs) can provide sufficient strength and ductility to be considered an efficient seismic force resisting system (SFRS) for mid-rise buildings. The ductility and overall seismic performance of shear walls were increased by providing confinement to the end zones of the walls to form boundary elements (BEs)., which enhanced the ultimate masonry compressive strain and curvature ductility of the walls. Regular stretcher blocks are commonly used in the construction of masonry boundary elements; however, they impose some constraints due to their geometrical characteristics. This study investigated the construction and testing of three half scale specimens of reinforced masonry shear walls with boundary elements (RMSWs+BEs) that were characterized by flexural dominance under reversed cyclic moment and lateral loading. In the lower story panel of a 12-story RMSW building, these walls constitute the plastic hinge zone, which is represented by a plastic hinge wall. In this study, C-shaped masonry units were used instead of stretcher units to construct BEs with different sizes and vertical reinforcement ratios. The findings of this work revealed that employing C-shaped masonry units to construct the BEs was effective in overcoming the construction limits imposed by stretcher units. Additionally, the results of this study demonstrated that when RMSWs+BEs are subjected to quasi-static reversed cyclic loading, they are capable of providing a high level of ductility with minimal loss of strength. • C-shape boundary element blocks were utilized to form the boundary elements. • Specimens were slender walls that represented the plastic hinge of high-rise wall. • Testing of reinforced masonry walls with high aspect ratio. • overcome the constructability limits imposed by using stretcher units • The boundary elements of the walls are different in size and vertical reinforcement. [ABSTRACT FROM AUTHOR]

In typical wall load-bearing reinforced-masonry (RM) buildings, the lateral and vertical forces are resisted by rectangular shear walls. Thus, the walls are subjected to high vertical forces from gravity loads that are expected to limit the displacement and energy dissipation capacities. Moreover, the rectangular RM shear walls have limited lateral stability because of the single vertical reinforcement layer. The intent of this study is to investigate the inelastic cyclic response of RM structural walls subjected to axial compressive stress that results in precompression ratios, P/Agfm′ , higher than 10%. The main objective is to propose practical component-level seismic detailing recommendations to enhance the overall structural performance. In this respect, three half-scale, fully grouted RM shear walls were tested under constant axial load, in-plane fully reversed cyclic loading, and top moment. The tested specimens are flexural dominant to simulate the response of mid and high-rise RM shear walls under strong seismic actions. The walls were designed to have enlarged boundary elements built using C-shaped blocks to evaluate the ability of end zone detailing and confinement to alleviate the impact of the high axial load. The test results demonstrated an overall enhanced structural performance for the three walls. The three specimens attained high ductility levels, high energy dissipation capacity, and failure in the ductile flexural mode. The presence of the well-detailed and confined boundary elements was effective in mitigating the impact of the high axial compression load. Thus, utilizing this type of masonry shear wall increases the competitiveness of masonry buildings as an alternative construction method. [ABSTRACT FROM AUTHOR]

Squat reinforced concrete shear walls with boundary elements (SRCSW-BE) are used in special structures (e.g., nuclear facilities) to resist lateral seismic loads. However, several studies have demonstrated the inaccuracy of the relevant current shear strength prediction expressions (e.g., ASCE/SEI 43-05). Specifically, expressions originally developed based on empirical or experimentally calibrated analytical models (using different datasets) showed discrepancies when their predictions were compared with experimental results from other datasets. This situation is mainly attributed to the complex shear behavior and failure mechanisms of SRCSW-BE in addition to the wide ranges of their interdependent design characteristics. To address this issue, the current study utilizes genetic programming (GP), a form of artificial intelligence, to develop an elegant shear strength prediction expression using a dataset of 254 SRCSW-BE. Guided by mechanics, the key factors governing wall shear strength were first identified, and the GP-based expression was subsequently developed, trained, validated, and tested. The accuracy of the developed GP-based expression was assessed through different performance evaluation measures. The analyses showed that the developed expression can provide better predictions with significantly higher accuracy compared to other shear strength prediction expressions available in relevant design standards and literature. Further robustness assessment also demonstrated the conformity of the GP-based expression with known underlying behavior mechanics of SRCSW-BE, which, along with its elegant form, makes the developed expression adoption-ready by relevant design standards (e.g., ACI 318 and CSA A23.3). Overall, the current study is expected to demonstrate the ability of GP-based approaches in addressing other complex behaviors of structural components/systems and tackling relevant challenges pertaining to the latter's behavior predictions. [ABSTRACT FROM AUTHOR]

The pure boundary element method (BEM) is effective for the solution of a large class of problems. The main appeal of this BEM (reduction of the problem dimension by one) is tarnished to some extent when a fundamental solution to the governing equations does not exist as in the case of nonlinear problems. The easy to implement local point interpolation method applied to the strong form of differential equations is an attractive numerical approach. Its accuracy deteriorates in the presence of Neumann-type boundary conditions which are practically inevitable in solid mechanics. The main appeal of the BEM can be maintained by a judicious coupling of the pure BEM with the local point interpolation method. The resulting approach, named the LPI-BEM, seems versatile and effective. This is demonstrated by considering some linear and nonlinear elasticity problems including multi-physics and multi-field problems. [ABSTRACT FROM AUTHOR]

The problem is the scattering of a plane sound wave at a rough water-air interface. The purpose of this paper is to describe in detail the method and demonstrate its work with simple examples. The main advantage of this approach is that there are no limits on the relation between the shape of the surface and the incident wave, so we can consider large Rayleigh parameter, shading, multiple scattering. The solution of the Helmholtz equation in the form of an integral over the boundary is used only in the inner domain, in the outer domain the separation of variables is used to obtain a nonlocal integral boundary condition on the artificial boundary. [ABSTRACT FROM AUTHOR]