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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.

Purpose – The vibration of the rails is a significant source of railway rolling noise, often forming the dominant component of noise in the important frequency region between 400 and 2000 Hz. The purpose of the paper is to investigate the influence of the ground profile and the presence of the train body on the sound radiation from the rail. Design/methodology/approach – Two-dimensional boundary element calculations are used, in which the rail vibration is the source. The ground profile and various different shapes of train body are introduced in the model, and results are observed in terms of sound power and sound pressure. Comparisons are also made with vibro-acoustic measurements performed with and without a train present. Findings – The sound radiated by the rail in the absence of the train body is strongly attenuated by shielding due to the ballast shoulder. When the train body is present, the sound from the vertical rail motion is reflected back down toward the track where it is partly absorbed by the ballast. Nevertheless, the sound pressure at the trackside is increased by typically 0–5 dB. For the lateral vibration of the rail, the effects are much smaller. Once the sound power is known, the sound pressure with the train present can be approximated reasonably well with simple line source directivities. Originality/value – Numerical models used to predict the sound radiation from railway rails have generally neglected the influence of the ground profile and reflections from the underside of the train body on the sound power and directivity of the rail. These effects are studied in a systematic way including comparisons with measurements.

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]

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.)

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]