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A steel brace is effective to retrofit old reinforcement concrete (RC) buildings by increasing the horizontal load capacity of structures. However, concrete cracks that easily occur in the surrounding RC members under tension initiate early strength degradation, so this research aimed to develop a new self-centering brace (SCB) with the compression-only capacity such that no tension force is developed in the brace or to the adjoining RC members. Original SCBs have been developed to reduce the residual deformation of structures with a symmetrically flag-shaped hysteretic response. By altering the force transfer mechanism in the original SCB, a compression-only self-centering brace (C-SCB) can be developed under a symmetrically reversed cyclic loading, providing an alternative for the RC building retrofit. This paper first introduces the mechanics and deformation mechanism of the proposed C-SCB. A test program is then conducted on the cyclic tests of a buckling-restrained energy dissipating bar (EDB) to evaluate the energy dissipation. A 3,695-mm-long C-SCB is composed of posttensioning high-strength steel tendons, steel compression members, and buckling-restrained EDBs for the energy dissipation. The C-SCB in tests showed a good compression-only self-centering capability up to an axial displacement of 31 mm, with a maximum axial force of 1,530 kN. No damage of the steel tendons, compression members, or EDBs was found after three phase tests. Finite element analysis further validated the compression-only hysteretic response and mechanics of the C-SCB in a symmetrically reversed cyclic loading. [ABSTRACT FROM AUTHOR]

In the process of horizontal well construction, the working environment in the well is very complicated. It is difficult to determine the actual deformation and force of the coiled tubing in the wellbore from the load change at the wellhead along. In addition, the coiled tubing wrapped around the reel and entering the wellbore through the injection head may cause an initial residual bending. In this paper, the mathematical model of the coiled tubing under axial load during buckling deformation is established, and the analytical solution with the time term is derived by reasonable simplification of the model. The effect of residual bending on the post-sinusoidal buckling of the coiled tubing in the horizontal well was investigated using the separation variable method. The effect of residual bending variations on the well wall contact forces is analyzed. The research shows that the initial parameter Г is the main factor influencing the post-sinusoidal buckling of the coiled tubing with residual bending. The larger the parameter value Г, the greater the effect of the residual bending on the post-sinusoidal buckling deformation of the coiled tubing, and the earlier the critical point of the mixed sinusoidal-helical buckling of the coiled tubing appears. The compression velocity of the coiled tubing has a significant effect on the well wall contact force. The faster the compression, the greater the contact force. By introducing the time term and the separation variable, this paper provides a new method and theoretical basis for further study of the process of entering sinusoidal-helical buckling of the coiled tubing with initial residual bending. [ABSTRACT FROM AUTHOR]

Buckling of axially loaded beams is discussed in the context of Λ-fractional analysis and mechanics. An axially compressed cantilever beam is considered in the Λ-fractional space, and the critical load is defined. The variational buckling problem of the simply supported beam is considered in the Λ-fractional space. It is pointed out that the Euler–Lagrange equation corresponding to the minimization of the total energy function with the Weierstrass–Erdmann conditions is only acceptable. The Λ-fractional buckling elastic curve of a simply supported beam is presented. That elastic curve is transferred into the initial space. The post-critical buckling deformations are defined in the context of globally stable equilibrium deformations. [ABSTRACT FROM AUTHOR]

The classical theory of elastic critical buckling stress works well for slender columns and thin flat plates under compression; however, the situation is different for longitudinally compressed thin-walled circular cylindrical shells, and the issue has plagued us despite considerable efforts over the last 100 years. We noticed that all such buckling analyses thus far, both linear and nonlinear, in terms of the main philosophy, inherited and were confined to Euler's pioneering solution for the slender column model that focuses on the longitudinal buckling deformation mode and should be classified as the 'longitudinal open-loop' eigenmode because the deformations of the two longitudinal ends are physically independent of each other. In view of this, for an ideal linear-elastic buckling model of a thin-walled perfectly circular cylindrical shell under uniform longitudinal compression on the foundation of the longitudinal open-loop eigenmode solution, it is also necessary to consider a 'circumferential closed-loop' eigenmode simultaneously to physically avoid violating the reality of its ideal periodic deformation on the entire perimeter and to mathematically redefine the biunique and precise relationship for each distinct eigenmode by the critical circumferential wavelength. Originating from such a case study, the mathematical uniqueness issue hidden in the general solution of the Donnell equation is further discussed. The authenticity of the competing eigenmode characterized by the Koiter circle is also discussed. Furthermore, a preliminary attempt was conducted to interpret the discrepancy between theoretical and experimental buckling loads, mainly initiated by the characteristic type of longitudinally generated circumferential local inward displacement in initial geometric imperfections, using the insights herein. [ABSTRACT FROM AUTHOR]

This article addresses the problem of determining the solicitation and deformation of beams with geometric imperfection, also called real beams under a compression action. This calculation is performed by applying the Finite Transfer Method numerical procedure under first-order effects with the entire compression action applied instantaneously and applying the action gradually under second-order effects. The results obtained by this procedure for real sinusoidal or parabolic beams are presented and compared. To verify the potential of the numerical procedure, the first and second-order effects of a beam with variable section are presented. New analytical formulations of the bending moment and the transverse deformation in the beam with sinusoidal imperfection subjected to compression are also obtained, under first and second-order analysis. The maximum failure load of the beams is determined based on their initial deformation. The results of solicitation and deformation of the real beam under compression are compared, applying the analytical expressions obtained and the numerical procedure cited. The beams under study are profiles with different geometric characteristics, which shows that it is possible to obtain maximum failure load results by varying the relationships between lengths, areas and slenderness. The increase in second-order bending moments causes the failure that originates in the beam, making it clear that this approach reproduces the buckling phenomenon. The article demonstrates that through the Finite Transfer Method the calculation of first and second-order effects can be addressed in beams of any type of directrix and of constant or variable section. [ABSTRACT FROM AUTHOR]

A full-scale, two-tiered steel buckling-restrained braced frame (BRBF) was tested to evaluate experimentally the seismic behavior of steel multitiered BRBFs, namely, column stability response, column seismic demands, and tier deformations under a loading protocol representing earthquake ground motions. The test specimen consisted of diagonal braces oriented in opposing directions in the two adjacent tiers to create the most critical multitier response. The test frame was designed in accordance with the 2010 AISC Seismic Provisions as a lateral load-resisting system of a single-story building. The frame was subjected to a three-phase loading protocol consisting of lateral displacement time histories corresponding to a far-field ground motion record and a near-field ground motion record applied sequentially achieving total frame drifts in excess of 3.5%, followed by a final monotonic lateral displacement corresponding to 4.5% story drift. The test frame exhibited a stable response despite a non-uniform distribution of frame inelastic deformation between the tiers, which induced significant in-plane bending moments in the columns. Flexural bending, combined with a large axial compression force, led to partial yielding in the columns. Large deformation demands were also observed in the BRB yielding in tension and attracting the majority of frame lateral deformation. On the basis of test results, a displacement-based analysis approach was proposed to relate column in-plane bending and flexural stiffness to relative inelastic tier deformations. [ABSTRACT FROM AUTHOR]

This paper presents a theory for the buckling of short beams considering cross-sectional distortions due to transverse shear (i.e., shear warping), based on the consistent linearization of a geometrically nonlinear planar beam. The proposed deformation field considers the warping amplitude as an independent kinematic field, and the hyperelastic material assumes that the stresses normal and tangent to the deformed cross section are linear with respect to their work-conjugate finite strains. An approximate closed-form solution to the resulting quartic equation for the critical load is provided to facilitate practical implementation. Theoretical differences giving rise to distinct buckling theories for higher-order shear beams are discussed in terms of (1) the assumed deformation field, (2) variational consistency, and (3) material constitutive relation. The proposed formulation is applied to evaluate the stability of infinite strip unbonded fiber-reinforced elastomeric isolators (FREIs) with moderate-to-high shape factor, for which shear warping is expected to have a major influence due to the flexural flexibility of the fiber reinforcement. A homogenization procedure is described to obtain effective isolator rigidities considering rubber compressibility and fiber extensibility. Next, a finite element parametric study of the buckling of unbonded infinite strip FREIs is presented, and the results are used as a benchmark to evaluate the adequacy of the proposed and existing formulations. The theory presented herein and its approximate solution exhibit the best match with the numerical results, and the latter is deemed adequate for practical application. [ABSTRACT FROM AUTHOR]

The moving deformation of the strata and the redistribution of stope stress after mining show asymmetrical characteristics, which do not conform to the symmetrical structural characteristics of the original rock beam fracture. To further analyze the deformation of rock beams and the asymmetry law of stope pressure distribution after strata caving, the detailed process of instability and deformation of composite rock beams before failure was revealed through similar material simulation, theoretical analysis, and numerical simulation. Through similar simulation experiments, the structural characteristics of strata caving were observed. After excavation, the caving angle near the open-off cut side of the model is greater than that on the stop-mining line side. The maximum bending moment of the rock beam is located at the open-off cut side. The rock beam fracture is located on the partial open-off cut side in the middle of the rock beam. The rock beam on the open-off cut side is easy to shear slip and not easy to hinge. The rock beam in front of the advancing direction of the working face is easily hinged. Based on the structural characteristics of strata caving, considering the thickness of the composite rock beam, the two-hinged arch mechanical model for rock beam fracture is established. On this basis, the key parameters of rock beam instability and fracture such as limit load, additional horizontal stress, limit break distance, and break position are analyzed. Based on the deformation characteristics of two hinged arches, the caving structure and the asymmetric distribution mechanism of stress redistribution during the deformation of overburden in stope are explained. Finally, the deformation of rock beam and the asymmetry of stress distribution in stope are verified by numerical calculation. The results show that the concentrated stress value of the coal pillar at the open-off cut side is greater than that in front of the working face. There is a pressure relief area behind the working face, and the pressure relief area has a certain range. The range of stress concentration area, pressure relief area, and stress value tend to be stable, and only the range of the original rock stress zone expands when the working face is advanced to a certain distance. The asymmetric distribution of compaction stress in goaf is related to the buckling deformation of strata. [ABSTRACT FROM AUTHOR]

The compression load of straight bars, for which the cross-sections are smaller compared to their length, causes a phenomenon of bending along the longitudinal axis. Upon reaching a certain level, called the critical level of the stresses, the bending deformations begin to increase beyond the bearing limit of the bar. It yields instantly, due to an unstable elastic deformation state, although the material's resistance limit has not been exceeded. The irreversibility of the phenomenon is dangerous especially for the railway tracks and is not fully mastered by calculation methods. They can eventually establish the level of the critical demand, which has values specific to each rail configuration. It is accepted that for loads lower than this level, buckling of the respective rail does not occur. The longitudinal tension in the railway tracks occurs due to the expansion caused by their heating under the action of the sun's rays, but also due to the friction between the rails and the train wheels. This paper proposes the realization of a study model of the buckling of the railway tracks. This model is represented by an assembly, built in the SOLIDWORKS application for which a Buckling simulation was made. The imposition of two distinct temperatures on the rails and crossties is the source of the model's request. The increase in the temperature of the component parts of the assembly causes their expansion, so implicitly the appearance of some longitudinal deforming forces, specific to the buckling phenomenon. [ABSTRACT FROM AUTHOR]

Floating liquefied natural gas (FLNG) cryogenic hoses can be employed for the transmission of liquefied natural gas (LNG). Usually, U-shaped metal bellows can be applied as the inner lining of FLNG cryogenic hoses. In installation, positioning and other working conditions, torsion is one of the main loads, and torsional buckling instability is a major failure mode of U-shaped metal bellows of FLNG cryogenic hoses. In the current research, the buckling instability of bellows under torsional loads has been investigated in detail, the mechanical mechanism of deformation in torsional buckling mode of bellows has been analyzed and the influence of the structural design parameters on the stability performance has been summarized. It was seen that the axis of the bellows was presented as a spiral line shape during the torsional buckling stage. At the same time, the torsional buckling properties of toroid and spiral bellows were analyzed. The obtained results showed that the torsional buckling stability of the spiral bellows was weaker than that of the toroid bellows and increase of the spiral angle of the spiral bellows intensified this trend. In addition, the post-buckling analysis of U-shaped bellows under torsional loads was carried out by means of experiments and finite element simulation. It was shown that the results obtained from finite element (FE) analysis in this research presented a relatively accurate critical torque value and a consistent buckling instability mode, compared with the experimental results. On this basis, the effects of common defects such as thickness thinning on the torsional stability of bellows were investigated. Considering the geometric defect of thickness thinning, the error of FE analysis was reduced further, and it was found that the defect could significantly decrease the stability of the bellows. The above analysis results could provide a reference for structural design and post-buckling analysis of bellows. [ABSTRACT FROM AUTHOR]

Buckling phenomenon is a common failure mode for composite materials under the effect of compressive loading which is mainly investigated in two stages as pre – buckling and post – buckling. At the pre – buckling phase, the deformations take place temporarily in elastic range. However, load carrying capacity of a member can be increased by regarding the post – buckling process. Therefore, it is important to determine the final and maximum load carrying ability of the structure. Since, at the end of the post – buckling, the body cannot carry load and crippling failure takes place. In this review article, crippling behavior of the composite structures is investigated. After describing the crippling phenomenon, this study mainly investigates both experimental and theoretical points of views. In this scope, affecting parameters such as stacking sequence, geometrical properties and boundary conditions are determined. Then, the improved theoretical approaches are stated. The compatibilities of the test results are assessed with theoretical studies. [ABSTRACT FROM AUTHOR]

This research is concerned with the free vibration and buckling analysis of carbon nanotube-reinforced beams (CNT-RBs) using a novel high-order shear deformation theory (HSDT). The current HSDT is modeled by a trigonometric function without a shear correction factor, and the displacement field has only four variables. Several different carbon nanotube distributions, including two uneven CNT distributions (X-CNT and O-CNT), are considered. The mixture rule is applied to express the effective material properties of carbon nanotube-reinforced beams. The CNTR beams are rested on two springs and a shear layer (Kerr foundation). Hamilton's principle is employed to derive the governing equations, which are then solved using the Navier technique. The current theory and several parameter effects are studied and validated in comparison to benchmark studies and theories. The main purpose of this study is to enhance understanding of high-order shear theories, such as third order, sinusoidal, exponential, etc. In this context, our theory yields excellent results when compared to other theories. The difference between our theory and the exact solution is so minimal that it is superior to other theories. The second part of the study focuses on investigating the distribution of carbon nanotubes to enhance understanding. This knowledge can assist panel manufacturers in determining the appropriate distribution shape. Our results indicate that the third distribution (X-CNT) significantly influences mechanical behavior, unlike the first and second distributions (UD-CNT and O-CNT). [ABSTRACT FROM AUTHOR]

In order to improve the resilience of structures subjected to strong earthquakes, a buckling-plate self-centering friction damper (BPSCFD) with low post-yielding stiffness is proposed, which consists of a group of post-buckling plates and a self-centering variable friction mechanism. The damper is intended to not only reduce the peak and residual deformation of structures, but also to limit the additional internal force of the structural elements. Through theoretical derivation and finite element simulation, the hysteretic damping and self-centering characteristics of BPSCFDs are studied. In order to examine the seismic performance of the BPSCFDs, the dampers are employed to retrofit a double-columns bridge bent, and the corresponding elastic-plastic time history analysis is conducted. The results show that the force-displacement relationships of BPSCFDs with different parameter combinations are characterized by typical flag-shaped self-centering hysteretic loops and low post-yielding stiffness, and the dampers can effectively reduce the peak and residual deformation of the bridge bent without increasing the peak acceleration and base shear. The research results could supply a guideline for the design and application of the damper. [ABSTRACT FROM AUTHOR]

Reduced beam section (RBS) connections are ductile connections that have been widely used in steel structures. Because of the reduction of web resistance, local buckling usually occurs under large deformations and is associated with decreased strength. In addition, the complex deformation of beams prevents determining the residual strength, hence posing a challenge in postearthquake repairs. In this study, a buckling-restrained system (BRS) including steel channels and a mortar was proposed for deformed RBS regions to provide lateral support on buckled plates so as to recover the connection strength. Two full-scale RBS connections with various cutting ratios were first tested, and then the connection was repaired with BRS loaded again. The test results indicated that the repaired connections were loaded at a drift angle of up to 4% without fracture or strength deterioration. The negative strength increased by approximately 18%, and the maximum strength was similar to that of the original connection, indicating that the column-to-beam flexural strength ratio of the connection did not change. The strain at the heat-affected area also did not increase and rather decreased because of the additional support of the restraint. The dissipated energy capacities of the repaired specimens were approximately 92% and 87% of the values of the original specimens. These results confirmed that BRS provided sufficient lateral resistance and helped recover the connection performance. • This paper proposed a new postearthquake repair method for recovering the performance of the locally buckled reduced beam section connections. • Two full-scale connection specimens with different cutting ratios were prepared and tested. • The results indicated that the method notably enhanced the strength of the locally buckled connection, and the maximum strength was similar to that of the original connection, indicating that the column-to-beam flexural strength ratio of the connection did not change. • The strain at the heat-affected area also did not increase, and the dissipated energy capacities of the repaired specimens were closed to the values of the original connections. • The repair method does not require field cutting, welding works, and temporally support structures. [ABSTRACT FROM AUTHOR]

The out-of-plane buckling behavior of arches is closely related to the element torsional behavior. The traditional 12-degree-of-freedom second-order element stiffness matrix which uses a simplified element torsional stiffness GJ/ L (where G is the shear modulus, J the St. Venant torsion constant, L the element length) may significantly underestimate the out-of-plane buckling loads of funicular arches. This paper presents a simple and effective exact matrix stiffness method (MSM) for the out-of-plane buckling analysis of funicular arches. The developed MSM uses a 14-degree-of-freedom second-order element stiffness matrix of three-dimensional beam-columns considering both torsion and warping deformations. The out-of-plane buckling analysis of funicular arches is performed by using the global structural stability stiffness matrix, which combines the transformed second-order element stiffness matrices. The proposed MSM with the exact 14-degree-of-freedom second-order element stiffness matrix for the out-of-plane buckling analysis is verified by comparing with some classical solutions of funicular circular and parabolic arches with box sections and I-sections. Further discussions show that the 14-degree-of-freedom second-order element stiffness matrix may be reduced to a simplified 12-degree-of-freedom form only by deriving the exact element torsional stiffnesses, which could be significantly larger than GJ/ L for members with large cross-sectional torsional stiffness parameters (especially open cross-sections). [ABSTRACT FROM AUTHOR]

• Buckling strength of metamaterial is designed by deep learning and improved compared with benchmark models, validated by 3D printing and compression testing. • The optimization proceeds to transition in dominant buckling mode from in-plane to out-of-plane deformation, converging the eigenvalue of 2nd mode to 1st mode. • The mechanism of superior buckling strength shows that thickness of horizontal beam does not significantly affect buckling strength and post-buckling behavior. Metamaterials are specially engineered materials distinguished by their unique properties not typically seen in naturally occurring materials. However, the challenge lies in achieving lightweight yet mechanically rigid architectures, as these properties are sometimes conflicting. For example, buckling strength is a critical property that needs to be enhanced since buckling can cause catastrophic failure of the lightweight metamaterials. In this study, we introduce a generative machine learning based approach to determine the superior geometries of metamaterials to maximize their buckling strength without compromising their elastic modulus. Our results, driven by machine learning based design, remarkably enhanced buckling strength (over 90 %) compared to conventional metamaterial designs. The simulation results are validated by a series of experimental testing and the mechanism of the high buckling strength is elucidated by correlating stress field with the metamaterial geometry. Our results provide insights into the interplay between shape and buckling strength, unveiling promising avenues for designing efficient metamaterials in future applications. [ABSTRACT FROM AUTHOR]

In this article, the vibration and buckling of a double-layer Graphene sheet (DLGS) coupled with a piezoelectric nanoplate through an elastic medium (Pasternak and Winkler models) are investigated. DLGS are subjected to biaxial in-plane forces and van der Waals force existing between each layer. Polyvinylidene fluoride (PVDF) piezoelectric nanoplate is subjected to an external electric potential. For the sake of this study, sinusoidal shear deformation theory of orthotropic plate expanded with Eringen's nonlocal theory is selected. The results indicate that nondimensional frequency and nondimensional critical buckling load rise when the ratio of width to thickness increases. Furthermore, incrementing the effect of elastic medium parameter results in increasing the stiffness of the system and, consequently, rising nondimensional frequency and critical buckling load. [ABSTRACT FROM AUTHOR]

In this article, the thermal buckling behavior of orthotropic circular bilayer graphene sheets embedded in the Winkler-Pasternak elastic medium is scrutinized. Using the nonlocal elasticity theory, the bilayer graphene sheets are modeled as a nonlocal double-layered plate that contains small scale effects and van der Waals (vdW) interaction forces. The vdW interaction forces between the layers are simulated as a set of linear springs using the Lennard-Jones potential model. Using the principle of virtual work, the set of equilibrium equations are obtained based on the first-order shear deformation theory (FSDT) and nonlocal differential constitutive relation of Eringen. Differential quadrature method (DQM) is employed to solve the governing equations for simply-supported and clamped boundary conditions. Finally, the effects of the small scale parameter, vdW forces, aspect ratio, elastic foundation, and boundary conditions are considered in detail. [ABSTRACT FROM AUTHOR]

This research aims to establish the semi-analytical approach for nonlinear dynamic buckling and vibration responses of functionally graded graphene platelet reinforced composite (FG-GPLRC) circular plates and spherical shells subjected to time-dependent radial pressure and thermal loads. The higher-order shear deformation theory with von Karman’s nonlinearities and the nonlinear viscoelastic foundation model is used to establish the expression of the fundamental equations of considered structures. The shells and plates are considered with clamped and immovable edge, and shallow curvature of the shells is applied. The Lagrange function is applied to establish the total energy of structures, and the potential function of viscous damping of the viscoelastic foundation is expressed using the Rayleigh dissipation function. The motion equation of the structures can be formulated using the Euler–Lagrange function. The dynamic responses are obtained using the numerical method, and the critical dynamic buckling loads are obtained using the dynamic buckling criterion of Budiansky–Roth. The large effects of material parameters, geometrical parameters, and nonlinear viscoelastic foundation on dynamic responses of considered structures are investigated and discussed in many numerical examples. [ABSTRACT FROM AUTHOR]

In this paper, under the condition of bidirectional stress, the buckling deformation of the side plate in a rectangular concrete-filled steel tube (CFST) column has been studied in detail. We have conducted a theocratical analysis, an experimental validation and a finite element simulation to investigate the influences of the height-width ratios and Nominal Poisson's ratios on the buckling form of the side plate, and we also try to explain the change of buckling form between unidirectional and bidirectional stress, both of them can provide a good reference and basis for design and application of the CFST column. The specific work can be summarized as follows: Firstly, a theoretical analysis has been conducted to study the buckling coefficient solution method of the thin plate under the conditions of axial compress and transverse tension. Then, under the conditions of the unidirectional and the bidirectional stress, a comparative study is carried out to investigate the changing relationship of the buckling coefficient (k) of the side plate; the results indicate that the buckling characteristic is changed due to the bidirectional stress, meanwhile, the buckling coefficient and the number of buckling half-wave will increase. Furthermore, the existing outcomes and the numerical simulations are adopted to study the relevance between the number of the elastic buckling half-wave in the side plate and the corresponding height-width ratio of the component; the results indicate that the former is larger than the latter. Finally, based on the obtained, the buckling relationship curve, the conclusion can be drawn as follows: when the bidirectional stress has been applied to the side plate, there is an equal interval between the different buckling half-waves; meanwhile, the interval shows a quadratic function reduce trend with the increase of nominal Poisson's ratio. [ABSTRACT FROM AUTHOR]

This work aims to reveal the in-plane-compressive characteristics of Glass Fibre based single face corrugated Structure Sheet (GFSS) by developing a loading holder of the both ends of the panel of GFSS in the direction of the cross machine direction. A grooved end-support device was developed and exmined. In order to set stably and quickly a straight panel of GFSS on the compressive-testing apparatus, the width and the depth of the holder's groove were varied against the geometrical size of the panel, and the stability and reproducibility of compressive deformation of the panel was experimentally investigated. When changing the height of the panel and reinforcing the both ends of the panel by dipping instant adhesives, the deformation behavior and the buckling strength was characterized in three modes: a short height crushing without lateral deflection, a small lateral deflection mode as the intermediate state, and a triangle-like folding as a long height crushing. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on the evaluation of the seismic performance of a new hybrid buckling restrained brace (HyBRB) under cyclic load. Detailed design steps adopted for the HyBRB design are reported in this paper. The analytical method for estimation of critical loads corresponding to buckling mode formation of the steel core inside the restrainer has been presented. The design targets achieved for the HyBRB are ease of inspection of the detachable BRB core to facilitate replacement of the steel core after a seismic event, if necessary, and enhanced energy-dissipation capacity through restrained buckling about both weak and strong axes of the core. The proposed HyBRB has displayed stable hysteretic behavior with good energy-dissipation capacity in low to high levels of the core strain range. Permanent deformation about the strong axis of the core was observed on unfastening of the restrainers, although restrained buckling of the core was observed about the weak axis in lower displacement amplitudes. Analytical simulation was carried out using a phenomenological model to simulate the experimental behavior. The simulated axial force-deformation hysteresis loops were found to be in close agreement with those obtained from experimental investigation. [ABSTRACT FROM AUTHOR]

• Comparing between the finite element simulation and the actual buckling is aneffective way to determine the loading forms of the buckling. • The casing can lead to the redistribution of deformation and the concentration of deformation of pipelines. • The variation of ground load will lead to buckling deformation of road crossing pipeline. • A small deformation of pipeline will evolve into serious buckling due to the change of ground load and geological disaster. As one of the main forms of pipeline deformation and failure, buckling poses a threat to the service safety of pipelines, seriously leads to oil and gas leakage, pipeline shutdown and environmental pollution. It not only brings huge economic losses, but also leads to fire, explosion and other accidents, which threaten the property and life safety of the country and people. Therefore, it is necessary to study the buckling deformation mechanism and failure rule, so as to lay a foundation for the evaluation and protection of pipeline buckling deformation. In this paper, theory and finite element simulation method has been used to study the buckling failure mechanism of the pipeline crossing road. The form and magnitude of the local load causing pipeline buckling are obtained through theory and vilified by the finite element simulation. The analysis results show that the boundary conditions and stiffness of the pipe are locally changed by the casing, and the deformation of the pipe is concentrated under the external load, such as road load and seismic wave, which leads to buckling. Therefore, the existence of casing will affect the deformation distribution of pipeline, and it is necessary to optimize the design and protect it in practical engineering to avoid buckling caused by deformation concentration. [ABSTRACT FROM AUTHOR]

Large deformations can easily occur when tunneling through weak surrounding rock with high underground stresses. Under high-stress environments, the surrounding rock stores a large amount of strain energy, and the strain energy stored in the soft and weak surrounding rock enclosure is dissipated through the large traveling plastic deformation. Therefore, the effective use of the surrounding rock's bearing capacity and energy dissipation is a feasible solution to the large deformation problem. Based on the energy principle, this study designs a high compressibility, large stroke energy-dissipation element, which transforms the traditional support into energy-dissipation support and solves the problem of large deformation by reasonably utilizing the "displacement" of the surrounding rock. The experimental results showed that the steel plate assembled structure had an initial peak value of about 15 MPa, a constant resistance of about 2 MPa with a large stroke, and a compression rate of more than 75%, with good post-compression flexural peak characteristics. Elastic–plastic buckling analyses of defective steel plate composite structures were carried out using finite element analysis software, and the deformation and force characteristics of a variety of steel plate composite structures after buckling under actual field conditions were investigated. Based on the 3D laser scanning system, the thickness of the upper and lower steel plates of the steel plate composite structure was set to 1 cm, the height of the vertical plate was set to 28 cm, and the thickness was set to 8 mm. The original rigid supporting method was converted into one of compression support by circumferentially embedding the steel plate composite structure into the initial support structure. The resulting support configuration offered a high safety factor because the pressure of the surrounding rock was released by the deformation of the steel plate composite structure. [ABSTRACT FROM AUTHOR]

Submarine pipeline is one of the most popular research filed that many researchers focus on solving the issue of buckling of pipeline. The snaked laying is an effective method to control the lateral buckling. The scour below offshore pipeline may affect the efficiency and performance of the snake lay pipeline. The objective of this study was to investigate the effect of scour hole on the buckling of seawater pipelines. A three-dimensional numerical model developed to investigate the effect of scour below offshore pipeline subjected to wave and current by using Abaqus software and Aqua Module. The results indicated that vertical deformation of straight pipeline increased by increasing scour hole depth. This value changed 4.85 cm to 32.87 for holes 11 to 200 cm respectively, but these parameters of the snake lay pipelines were not affected by the presence of scour hole. Moreover, the effective axial force of snacked lay pipelines reduced 5 times in comparison to straight pipeline by applying wave and current. The results indicated that the value of stress of snaked-lay pipeline was independent on scour hole depth. Therefore, this pipeline was effective method to limit and control buckling even in the presence of scour below it. [ABSTRACT FROM AUTHOR]

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For this study, the geological engineering features and possible failure modes of the Dabenliu quarry slope in the Jinping-I Hydropower Station were qualitatively analyzed before a method for setting viscous boundary and an algorithm for modeling pre-stressed cables were embedded into a DDA (Discontinuous Deformation Analysis) computer code to analyze the deformation of the slope under seismic loading. Our simulation results revealed that the middle and upper parts of the slope slipped along the bedding joints (interlayer shear zones) and that the lower part buckled and collapsed after the slope was excavated. This is a typical slipping–buckling failure mode characterized by upper-slipping followed by lower-buckling. Based on the distribution of the simulated internal force of the anchor cables, the reinforcement scheme was adjusted by strengthening the support for the middle and lower parts of the slope, whereas the length and pre-stress of the anchor cables were reduced for the upper part of the slope. The adjusted reinforcement scheme can ensure the stability of the slope under the action of a magnitude 7 earthquake, and the slope may lose stability with no evident collapse under the action of a magnitude 8 earthquake. Finally, the simulation results were verified via a comparison with the monitoring data regarding the slope. [ABSTRACT FROM AUTHOR]

Rail vehicles generate huge longitudinal impact loads in collisions. If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body, the risk of car body structure damage and train derailment will increase. Herein, a four-stage rigid–flexible coupling finite element model of the coupler is established considering the coupler buckling load. The influence of the coupler buckling load on the train longitudinal–vertical–horizontal buckling behavior was studied, and the mechanism of the train horizontal buckling instability in train collisions was revealed. Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically. The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision. If the strength of the two sides of the car body structure in the lateral direction is asymmetrical, the deformation on the weaker side will be larger, and the end of the car body will begin to deflect under the action of the coupler force, which in turn causes the train to undergo sawtooth buckling. [ABSTRACT FROM AUTHOR]

This work investigates the interplay between viscoelasticity and instabilities in soft particulate composites undergoing finite deformation. The composite is subjected to in-plane deformation at various constant strain rates, and experiences microstructural buckling upon exceeding the critical strain level. We characterize the dependence of the critical strain and wavelength on the applied strain rate through our numerical analysis. In the simulations, we employ the single and multiple-branch visco-hyperelastic models. We find that the critical strain and wavelength – characterized by the single-branch model – show a non-monotonic dependence on the strain rate, reaching a maximum at a specific strain rate. Remarkably, different buckling patterns (with different critical wavelengths) can be activated by changing strain rates. The space of admissible buckling modes widens in composites with higher instantaneous shear modulus. In the composites characterized by the multiple-branch model, the critical strain function exhibit multiple local maxima following a superposition of the single-branch responses. Typically, the branch with a larger relaxation time has a more significant effect on the critical strain. Moreover, the local maximum (of the critical strain function) is amplified by increasing the strain–energy factor of the corresponding branch term. Finally, we perform the experiments on the 3D-printed particulate soft composite characterized by a broad spectrum of relaxation times. The comparison of the experimental and simulation results demonstrates the ability of the numerical model to predict the critical buckling characteristics. [ABSTRACT FROM AUTHOR]

To simplify the construction of traditional self-centering buckling-restrained braces (SC-BRBs) and achieve efficient recovery function, an innovative type of single-tube self-centering buckling-restrained braces (ST-SC-BRBs) is proposed. The ST-SC-BRBs only require one outer tube for the prestressed system. The detailed structure and working principle of the ST-SC-BRBs are described, and it is emphasized that the restrained steel tube should be checked as a compression-bending member to ensure its overall stability. Low-cycle fatigue tests are conducted on scaled models of one traditional BRB and two ST-SC-BRBs. The results show that the residual deformation of the ST-SC-BRBs is significantly reduced compared to that of the traditional BRB, with comparable energy dissipation capacity. The ST-SC-BRB works stably with a full hysteresis curve and an obvious "flag-shaped" pattern within the inter-story drift ratio of 2%. The self-centering ratio is the key factor affecting the recovery effect of the ST-SC-BRB. To achieve smaller residual deformation, the self-centering ratio is suggested to be greater than 1. Overall, the ST-SC-BRB presents a more simplified and effective approach to constructing a recoverable functional structure. • A new type of single-tube self-centering buckling restrained brace (ST-SC-BRB) is proposed. • Axial low-cycle tests show that the ST-SC-BRB structure achieves significantly reduced residual deformation. • The self-centering ratio of the ST-SC-BRB is the key factor affecting its self-centering effect. [ABSTRACT FROM AUTHOR]

• A modified concrete damaged plasticity model is proposed considering the deformation and mechanical characteristics of LRS FRP-confined concrete. • The 3D finite element analysis of longitudinal reinforcement buckling in LRS FRP-confined RC columns is realized. • The effect of longitudinal reinforcement buckling on member is illustrated by the FEA results. • The factors affecting the buckling of longitudinal reinforcement are studied, and an empirical formula for determining the failure of members by the buckling of longitudinal reinforcement is proposed. Large rupture strain (LRS) FRPs have great potential to be used for seismic retrofit of RC columns because of its high rupture strain (i.e., > 5%) that provides better confinement effects. However, in FRP-confined RC columns, the longitudinal reinforcements may buckle before the LRS FRP rupture, especially in the case of large stirrup spacing. This study aims to present a 3D finite element (FE) model for simulating the buckling effect of longitudinal reinforcements in LRS FRP-confined RC columns. A modified concrete damaged plasticity model (CDPM) is proposed to consider the deformation and mechanical characteristics of LRS FRP-confined concrete. Removal of failed concrete elements is considered to facilitate the buckling of longitudinal reinforcements in LRS FRP-confined RC columns. The FE analysis accuracy was verified by comparisons with test results. The factors affecting the buckling of longitudinal reinforcements were discussed through an extensive parametric study. Empirical formulas for the stress and strain values at which the longitudinal reinforcement starts to soften were developed. An empirical formula for the ultimate axial strain of LRS FRP-confined RC columns determined by longitudinal reinforcement buckling was also obtained by regression analysis. [ABSTRACT FROM AUTHOR]

This present study consists to analyze the mechanical buckling and the free vibration stabilities of antisymmetric cross-ply and angle-ply laminated composite plates using a refined high order shear deformation theory of four variables against five in other high order theories. Among the advantages of this new theory it takes into consideration the shearing effect in the calculation of deformation without the need for shear correction factors and giving rise to a variation of the shear stresses along the thickness and satisfying the zero shear stresses condition in faces of the plate. The laminate resting on the Pasternak elastic foundation, including a shear layer and Winkler spring, are considered. The equations of the motion are derived from Hamilton's principal. The closed form solution of simply supported rectangular plates has been obtained by using the Navier method. In addition, the effects of various parameters of the laminated composite plate on static buckling and dynamic are presented. [ABSTRACT FROM AUTHOR]

The contradiction of high subducting plate rate (ranging from 4 to 9 cm/yr on Earth's surface) and low slab sinking rate (about 1 and 2 cm/yr in lower mantle) calls for significant slab deformation in the middle mantle. However, mechanisms that can account for both the deformation and the rate discrepancy have not been fully explored. Here, using 2‐D numerical models that incorporate grain size evolution, we propose a new slab deformation mode, slab segmentation and stacking, to accommodate the differential slab sinking rates. Our results show that the segmented slab due to faulting and grain‐size reduction may further break off and stack over itself as it encounters the high‐viscosity lower mantle. Stacked slabs slowly sink in the lower mantle, while periodic slab tearing hinders upward stress transmission, allowing shallow plates to subduct at a higher rate. This discovered mode also provides an alternative explanation for slab thickening in the lower mantle. Plain Language Summary: According to observations and analysis, the velocities of plates entering the trench are much higher than the slab sinking rate in the lower mantle. Inconsistent velocities at the slab's two ends must be accommodated by slab deformation or accumulation in the middle mantle to ensure mass conservation. We have considered three different deformation modes: slab buckling, horizontal deflection, segmentation and stacking. Compared to the diffusive plastic weakening in the mode of slab buckling, previous studies have shown that slab faulting and grain size evolution can induce stronger localized weakening within slabs. Our study goes a step further by finding that the segmented slab can break off and stack over itself periodically when it encounters the lower mantle. This allows the slab to deform more easily in the mantle transition zone, enabling the plate to subduct at a higher rate while keeping the lower‐mantle slab sinks at a low rate. We also find that this mode of slab deformation can equally well explain the thickening of the slab in the lower mantle. Key Points: The discrepancy between the subducting plate rate and lower mantle slab sinking rate calls for slab accumulations in the middle mantleSimple buckling explains the accumulation but is not sufficient to accommodate the rate discrepancyThe mode of slab segmenting, breaking off, and stacking is a possible solution to the slab accumulation and rate discrepancy [ABSTRACT FROM AUTHOR]

During the operation of the drill string, it displays a degree of flexibility. Simultaneously, its dynamic properties, influenced by complex stress conditions, manifest nonlinearity and uncertainty. A comprehensive investigation into the dynamics of flexible drill strings is imperative for deep well drilling. This paper presents a model that simulates random interactions between a flexible drill string and the borehole wall, simplifying the actual drill string model using analogous principles. Dynamic simulation software is utilized for analysis, and an indoor experimental setup has been established. The results reveal that with a constant weight on bit (WOB), higher drill string rotational speeds correlate with increased susceptibility to buckling deformation. Additionally, the critical time for deformation onset exhibits a nearly linear relationship with rotational speed. Maintaining a constant rotational speed, an increase in WOB enhances the likelihood of buckling deformation. The experimental findings suggest a correlation between the drill string's rotation frequency and the WOB. [ABSTRACT FROM AUTHOR]

The general theory of slender structure buckling by Grabovsky and Truskinovsky (Cont. Mech. Thermodyn. 19(3–4):211-243, 2007), (later extended in J. Nonlinear Sci. 26(1):83–119, 2016 by Grabovsky and the author), predicts that the critical buckling load of a thin shell under dead loading is closely related to the Korn's constant (in Korn's first inequality) of the shell under the Dirichlet boundary conditions resulting from the loading program. It is known that under zero Dirichlet boundary conditions on the thin part of the boundary of positive, negative, and zero (one principal curvature vanishing, and one apart from zero) Gaussian curvature shells, the optimal Korn constant in Korn's first inequality scales like the thickness to the power of −1, − 4 / 3 , and − 3 / 2 respectively. In this work we analyse the scaling of the optimal constant in Korn's first inequality for elliptic shells that contain a finite number of points where both principal curvatures vanish. We prove that the presence of at least one such point on the shell leads to the scaling drop from the thickness to the power of −1 to the thickness to the power of − 3 / 2 . To our best knowledge, this is the first result in the direction for constant-sign curvature shells, that do not contain a developable region. In addition, under the assumption that a suitable trivial branch exists, we prove that in fact the buckling deformation of such shells under dead loading, should be localized at the vanishing curvature points, as the shell thickness h goes to zero. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach to scrutinize the creep buckling of the super-heating pipes in boilers subjected to external pressure in high temperature environment. It is well known that once buckling occurs, cylindrical shells will collapse instantly. As the load carrying capability of the cylindrical shell decreases sharply upon the occurrence of the buckling, the proposed analysis is based on the consideration that the creep will have a significant influence on the material properties only in the pre-buckling stage. According to the creep aging theory, the influence of the creep deformation on the mechanical response of the super-heating pipes is defined by introducing two parameters--the reduced Young's modulus and the reduced Poisson's ratio. The nonlinear constitutive relation for creep deformation of the super-heating pipes in high-temperature environment is established based on the deformation theory in mechanics of plasticity. Governing equations for creep buckling of super-heating pipes in boilers are derived by considering the extra change of curvature due to the initial curvature of the super-heating pipes. MATLAB programs are developed based on the analytical expression for super-heating pipes with simply supported boundary conditions at the two ends and are tested against the available experimental results and the finite element prediction from ABAQUS software. It is found that the components of the creep strain caused by the stress at high temperature far exceeds those of the elastic strain. As a results of that, the creep buckling load of the super-heating pipes is much lower than its elastic buckling load. From this study, an explicit expression to compute the creep buckling load is provided which facilitates engineer to easily predict the residual life of the super-heating pipes at different servo temperature and servo time. • Two parameters are defined to demonstrate the influence of the creep deformation on the buckling of the super-heating pipes. • The nonlinear constitutive relation for creep deformation of the super-heating pipes is established. • The extra change of curvature due to the change in initial radius of the super-heating pipes is taken into consideration. • The buckling load of the super-heating pipes is greatly reduced once upon the occurrence of the creep deformation. [ABSTRACT FROM AUTHOR]

Welding deformation occurs due to non-uniform thermal expansion, thermal contraction, restraint, and phase transformation in a metal by a local welding heat source. This causes problems such as low buckling strength and the reduced workability of the production process. Correcting welding deformations in stainless steel using heat—such as by linear heating—causes metal sensitization, which should be avoided. Herein, welding deformation was reduced by applying tension stress instead of correcting the deformation by heating. A deformation-prevention jig was used to reduce welding deformation during the manufacturing of a cylinder made of STS304 by laser welding. The tensile stress was induced by pushing the cylinder shell outward using the deformation-prevention jig. A thermo-elastoplastic analysis was performed to investigate the effects of the magnitude of the tensile stress on welding deformation. Furthermore, the parametric results—which indicated a reduction in welding deformation—were verified through experiments. The thermo-elastoplastic analysis suggested that deformation did not occur when the magnitude of tensile stress was approximately 50% of the yield stress of the base metal. Moreover, the deformation was experimentally reduced by 11–20% when a tensile stress of 30 MPa was applied to the cylinder, compared with that in the absence of tensile stress. [ABSTRACT FROM AUTHOR]

Piles are one-dimensional (1D) beam–column elements used to support tall buildings, onshore and offshore structures, bridges, wind turbines, etc. In practice, piles are commonly designed using the Euler–Bernoulli Theory. However, this theory is only considered appropriate for long, slender piles because it neglects the contribution of the shear deformation on the pile response. The effect of the shear deformation might be of importance in short, rigid and large-diameter piles such as monopiles, and it should be considered in the analysis. In geotechnical engineering, studies addressing this effect and its interaction with the surrounding soil are scarce and very limited. The aim of this work is to conduct a parametric study to investigate the influence of the shear deformation, semi-rigid connections and pile/soil stiffness ratio on the head deflection, head rotation and first-mode of critical load of an embedded pile. For this purpose, the well-known commercial FE software SAP2000 is employed. Four examples are presented to show the effect of the shear deformation on reinforced concrete (RC) and hollow circular piles embedded in either homogeneous or non-homogeneous soil. For lateral deformation analysis, it is found that deflections and rotations at the pile head considerably increase when the shear deformation is taken into account and they are of most significance at low values of pile/soil stiffness ratios. For buckling analysis, Timoshenko's theory shows that the critical load notably increases as the stiffness of the surrounding soil increases and, regardless of the soil/pile stiffness ratio, it rapidly decreases as the shear stiffness of the pile decreases. • The effects of shear deformation on the lateral response of piles are investigated. • The effects of shear deformation on the critical load of piles are examined. • The influence of the soil inhomogeneity in conjunction with the effect of shear deformation is examined. • Ranges of pile/soil stiffness ratios where shear deformation are of significance are provided. • Results from Timoshenko's and Euler–Bernoulli's beam theories are discussed. [ABSTRACT FROM AUTHOR]

In recent years, trenchless horizontal directional drilling (HDD) technology has developed rapidly towards the direction of large pipe diameter and long span. During construction, the buckling deformation and large drag torque of the drillstring (DS) are the key problems restricting the development of the HDD technology. In order to understand the buckling deformation law of the DS in horizontal directional drilling engineering, as well as the transfer and the distribution of the drag torque, and the relationship between the buckling deformation and drag torque, the dynamic model of the DS system in drilling engineering is applied to HDD engineering. The dynamics model of HDD at a long distance (5200 m) is established and calculated. The research indicates (1) when the buckling deformation of the DS is small, priority should be given to reducing the friction and torsion at the bending position; (2) excessive inlet thrust is the main reason for the buckling deformation of the DS, and the smaller the hole diameter, the more serious the buckling deformation; (3) severe buckling deformation of the DS will lead to an increase in the frictional resistance at the deformed part, and even local self-locking, resulting in the inability to continue to increase the weight on bit (WOB). The research results preliminarily reveal the relationship between DS buckling deformation and drag torque in ultra-long distance HDD engineering and point out the phenomenon law of drag torque and buckling deformation, which has reference value for the development of HDD technology. [ABSTRACT FROM AUTHOR]

Negative-stiffness mechanical metamaterials that can achieve bandgap tuning are a novel area of intense interest, enabling vibration control as well as a wide range of mechanical properties. In this paper, a negative-stiffness mechanical metamaterial consists of beam elements that can be reconfigured for large deformations and the bandgap can be tuned by its deformation behavior. The deformation process of the proposed negative-stiffness metamaterial under uniaxial compression, as well as the band structure and vibration characteristics of the metamaterial under different deformation states are analyzed by a combination of numerical simulation and experiment. The research results show that the proposed negative-stiffness metamaterial suffers from buckling instability and large deformation during uniaxial compression., and has different band structures and band gap ranges under different deformation states. Thus, bandgap tuning can be achieved by the deformation of negative stiffness metamaterials. Furthermore, negative stiffness metamaterials with different angles exhibit different results in bandgap tuning. Finally, the performance of vibration transfer is verified by experiments. This study may provide a new avenue for the related research and design of negative-stiffness mechanical metamaterials with bandgap tuning capabilities. [ABSTRACT FROM AUTHOR]

Thin-walled parts are widely used in the aerospace industry, where the milling deformation of the parts caused by their thin-walled draping and extremely large size ratio characteristics as well as high material removal rate has been the most common quality issue that greatly affects the assembly performance and operation safety of aerospace equipment. Hence, effective management of milling deformation for a thin-walled part will significantly improve its quality, which, however, is still made difficult by the lack of a real-time deformation perception, optimization, and control method. To bridge this gap, a novel online optimal control method of milling deformation for thin-walled parts is proposed by incorporating digital twins into the milling process of thin-walled parts. To this end, a reference framework of the milling process digital twin (MPDT) for thin-walled parts are designed, where the autonomous operation logic of MPDT for online optimal control of milling deformation is further clarified. On that basis, three key enabling technologies of MPDT are introduced from the perspective of multidimensional high-fidelity MPDT modeling, knowledge-driven low-latency milling deformation simulation, and online optimal control of milling deformation, which provide an insight into the industrial implementation of MPDT. Eventually, a MPDT prototype system is implemented, where its application and evaluation results demonstrate the feasibility and effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

We conducted an isogeometric analysis (IGA) to evaluate the performance of automobile structural member deformation and crash. In automobile crash analysis, ensuring the accuracy of the acceleration, velocity, and load in time series, as well as the structural deformation behavior, is important. To maintain the aforementioned consistency, accurately reproducing the bending and buckling of structural members is indispensable. In this study, we firstly computed the bending and buckling of structural members using IGA and validated its performance by comparing the results with those of a conventional finite element analysis and experiments. In addition, we utilized IGA for the crash analysis of an automobile body. [ABSTRACT FROM AUTHOR]

• Integrate the soft hyperelastic material into the main structure of Helmholtz resonator (HR) to design a star-shaped soft Helmholtz absorber, whose acoustic characteristics can be tuned by harnessing its post-buckling deformation. • Combine two star-shaped HRs with different wall-thickness to design a ventilated and mechanically tunable absorber to achieve asymmetric sound absorption and perfect sound absorption by applying specific and respective compression loads. • The sound absorption of the proposed pair of HRs can be real-time tuned effectively and repeatedly by mechanical loading and unloading. Helmholtz resonator (HR) has always been an important part of artificial sound-absorbing materials, most of which however cannot be tuned in real time and hence have a limited scope of applications. In this work, we integrate for the first time the soft hyperelastic material into the main structure of HR to design a star-shaped soft Helmholtz absorber. The soft HR exhibits different post-buckling deformation behavior when its wall-thickness varies, which further yields different acoustic characteristics. By combining two star-shaped HRs with different wall-thickness, we are able to achieve asymmetric sound absorption when specific and respective compression loads are applied to the two HRs. In addition, high sound absorption at various frequencies can be obtained via different combinations of the applied loads. Due to the perfect capability of reversible large deformation of soft hyperelastic materials, the sound absorption of the proposed pair of HRs can be real-time tuned effectively by mechanical loading and unloading. In other words, the acoustic switch controlled by mechanical load can be realized. The proposed soft absorber has an obvious practical application value, and also provides an important illustration for the design of soft and tunable acoustic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Wrinkling is a typical failure mode of sandwich structures with thin skins, where the bending deformation of face skins occurs simultaneously in conjunction with transverse stretching deformation of core layer. To analyze the three-dimensional (3D) deformation of wrinkling, a model is required to possess a capability describing completely different deformations at each ply. Therefore, by utilizing the Chebyshev polynomial at each layer of sandwich panels, this paper focuses on proposing a higher-order model to individually illustrate deformations of the skins and the core. By means of the proposed model, a refined triangular element has been constructed. By analyzing the stability of a sandwich plate without stiffeners, the finite-element formulation has been verified by comparing it to the quasi-3D elasticity solutions. In addition, it is anticipated that wrinkling failure can be effectively restrained by designing the stiffener layout. To this end, the influence of stiffener layouts on wrinkling behaviors of sandwich plates has been investigated in detail, and it is found that the capability of resisting the wrinkling deformation can be obviously improved by designing reasonable stiffener layouts. Moreover, the translation between buckling and wrinkling behaviors of sandwich panels with different stiffeners has been also explored, which can help to better understand wrinkling deformation mechanism. In summary, the proposed model can be used to design a reasonable arrangement of stiffeners to resist the wrinkling failure of sandwich panels. [ABSTRACT FROM AUTHOR]

Significant inelastic deformations induced in structural systems lead to structures possibly possessing some degree of permanent lateral deformation following major seismic events. These permanent deformations have led to considerable research being conducted over the past 20 years into developing structural systems that exhibit self-centring behaviour. For a structural system such as the concentrically braced frame (CBF), for which the dissipating mechanism is the tensile yielding and compressive buckling of the diagonal steel tubular members, these residual deformations present a problem when considering the structure's overall resilience to the seismic loading both during and after an event. This paper describes the numerical modelling of a novel self-centring, concentrically braced frame (SC-CBF) system that combines a conventional CBF with a self-centring arrangement to produce a structure that possesses the desirable lateral load-resisting capacity of the CBF but which also re-centres when subjected to many cycles of large inelastic brace deformation. First, an experimental test programme for the SC-CBF is briefly described, followed by a numerical model to capture the SC-CBF's characteristics during cyclic loading. This numerical model is validated using the experimental test data, showing that the experimental and numerical simulation data match rather well. This development presents a platform upon which further research through experimental testing and numerical simulation can be conducted. The proposed SC-CBF system can then be developed into a viable lateral load-resisting system that will provide a more resilient system than the current conventional CBF. [ABSTRACT FROM AUTHOR]

During the development of shale gas, one of the major challenges is the casing deformation (CD) in the horizontal section due to the geological activity. Recently, the casing deformation before hydraulic fracturing (CDBF) occurred in multiple shale gas wells in L block in China. In this paper, based on the theory of tubular mechanics, the relationship between casing buckling and CDBF caused by casing running in is analyzed qualitatively and quantitatively. It is found that the buckling deformation caused by running the casing string process is not sufficient to prevent the tool (Φ99 mm bridge plug). On the other hand, the mechanism of CDBF is systematically analyzed based on the actual field data and finite element (FE) method. In order to analyze the CDBF mechanism, the comparison between the actual casing trajectory and the reservoir rock (S#1, S#2, S#3 and M#1) in horizontal section in H2 platform is carried out, and the preliminary CDBF mechanism is proposed. Then, two groups of FE models are established to reduce the CD process to verify the preliminary mechanism. It is found that the numerical simulation results (high stress section length from FE model) are in good agreement with the actual CD logging results. Based on the analytical results, the corresponding mitigation measures are proposed based on the analysis of the CDBF mechanism. Our work could offer a detailed theoretical basis and reference of CDBF for shale gas well application. [ABSTRACT FROM AUTHOR]

To investigate the mechanical deformation characteristics of the 'Segment-SCC-Steel Tube' combined bearing lining structure under internal and external pressure, the loading device and monitoring system for the stability analysis of the full-scale lining were proposed. The effect of cracked encased concrete and local external pressure on the instability mode of thin-walled steel pipes was explored by full-scale model experiment and three-dimensional FEM numerical simulation. The influence of SCC (Self-Compacting Concrete) and stiffening rings on the stability of steel pipes subjected to external pressure was discussed. The results show that SCC cracks occur and intensify with increasing internal pressure. The external water acts directly on the steel tube through cracking, resulting in wavy deformation, and the gap between the SCC and steel tube further increases. When calculating the critical external pressure for the steel pipe, the constraint of encased concrete can be ignored, and only the constraint effect of the stiffening ring can be considered. Therefore, the Von Mises formula was used to predict the critical external pressure between the stiffening rings with high accuracy. In addition, the stiffening ring can mitigate the crack propagation of nearby SCC. The steel tube remained in the elastic stage under internal pressure. In the full-scale experiment, the external pressure could not continue to rise after reaching 0.65 MPa. Nevertheless, the amplitude of the buckling wave continued to increase. It is considered that the steel pipe is in an unstable state, and the failure mode is dominated by single-lobe buckling. • According to the performance of the 'Segment-SCC-Steel Tube' lining structure, the influence of cracked encased concrete and local external pressure on the buckling mode of steel pipes is investigated. • The loading device of the full-scale model test is proposed for the external pressure stability analysis of the 'Segment-SCC-Steel Tube' lining structure, and the monitoring system combining distributed optical fiber and traditional vibrating wire sensors is established. • The mechanical deformation characteristics of the SCC and Steel Tube lining under internal and external pressure are revealed, and the influence of SCC and stiffening rings on the stability of steel pipes under external pressure is discussed. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for removing out-of-plane deformation in stretched metal interconnects by adding a fractal structure to the original meander shape and using an optimized fabrication stack. In thermoformed electronics, in cases where copper is used as conductor, the twisting of meander-shaped structures caused by excessive mechanical stress can cause a non-uniform surface, delamination of the metal interconnect from the substrate, and in some cases, a short circuit to the adjacent tracks. Typically, designers of stretchable electronics use various shapes and widths of the copper interconnect to tackle this issue. Using conventional meander shapes such as horseshoes and U-shapes is not universally practical, especially when stretching is higher than 30 percent leading to significant out-of-plane buckling. Limiting this out-of-plane buckling by reducing the track width is not always applicable, as a minimum width is needed from a technology and conductivity perspective. The presented approach is inspired by computational and experimental studies of multiple meander shapes and fabrication methods. A geometry- and fabrication-based approach is presented, reducing the mechanical stress of almost all possible meander shapes by increasing the meander's path length to accommodate the metal track's produced torque during stretching. An analytical approach is provided for calculating the optimal meander parameters and the optimal fabrication stack is achieved based on simulation results. Experiments and finite element modeling for a case study show the improvement in the stress distribution and reduction of out-of-plane buckling. [ABSTRACT FROM AUTHOR]