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Lattice structures are an important class of architected cellular solids and structures with high potential for multifunctional and lightweight applications. Novel technologies such as additive manufacturing have vastly extended the design freedom to develop such architectures. In this work, a reliable theoretical model for optimizing unit cell design against buckling is developed for two different cell architectures: pyramidal and tetrahedral. The model's accuracy was evaluated through extensive finite element analysis and compared to existing methods available in the literature. [ABSTRACT FROM AUTHOR]

Marine unbonded flexible pipes serve as the most essential equipment in offshore oil and gas exploration and exploitation. Axial compressive loads during installation or in service in the complex marine environment usually lead to buckling failure. A flexible pipe is a composite structure with multiple functional layers, of which the tensile armor layer plays a key role with regard to the response of the pipe subjected to axial loads. In this paper, a simplified three-dimensional finite element model is developed, focusing on the tensile layer and replacing the carcass layer, pressure sheath layer, and pressure armor layer by a cylindrical rigid body to reduce computational expense. By using this model, the buckling failure modes of the tensile armor layer (in particular the birdcaging phenomenon) are analyzed. Several key parameters that affect the stability of the flexible pipe under axial compression and torsion are emphasized, and their effects on its axial and torsional stiffness are compared and discussed. The results show that both the lay angle of the steel wires and the interlayer friction coefficient have a significant influence on the axial and torsional stiffness of the pipe, whereas the damaged length of the outer sheath has virtually no effect.

This paper presents experimental and numerical studies on compression behaviour of equal-leg steel angles with bolted connection and subjected to local defect at the bolt hole. To simulate corrosion, a mechanical cutting method was used in the experimental test to increase the diameter of bolt holes, and a total of 18 steel angles were investigated in the study. The parameters considered included the slenderness and the diameter of bolt holes. The slendernesses of steel angles were 80 and 140, and the diameter of bolt holes ranged from 21.5 to 27.5 mm. Additionally, numerical models were established for the steel angles. The accuracy of the numerical model was verified by comparing experimental data with numerical results. Based on the validated numerical model, a parametric analysis was conducted to quantitatively assess the influences of the slenderness and the diameter of bolt holes on the load capacity of specimens against global buckling. Experimental and numerical results showed that the defect at the bolt hole affected the load capacity of specimens when the diameter of the bolt hole was increased to 27.5 mm and the slenderness was not greater than 100. [ABSTRACT FROM AUTHOR]

Buckling failure of layered rock slopes due to self-weight is common in mountain areas, especially for high and steep slope, and it frequently results in serious disasters. Previous research has focused on qualitatively evaluating slope buckling stability and rarely studied the whole process from bending deformation to forming landslide. In this work, considering the tensile and compressive characteristics of rock, the simulation of high and steep slope bucking failure evolved in Bawang Mountain, was conducted by numerical manifold method. The buckling deformation mechanism and progressive failure process of Bawang Mountain high steep slope were studied. The reliability of the numerical method was verified by the comparison of theoretical calculation and field measurement data. The results show that numerical manifold method can accurately simulate high and steep slope buckling failure process by preforming interlayer and cross joints. The process of slope buckling deformation and instability failure can be divided into minor sliding-creep deformation, interlayer dislocation-slight bending, traction by slope toe-sharp uplift, accelerated sliding-landslide formation. Under the long-term action of selfweight, the evolution of slope buckling from formation to landslide is a progressive failure process, which mainly contains three stages: slight bending deformation, intense uplift deformation and landslide formation. [ABSTRACT FROM AUTHOR]

The purpose of this research is to examine the mechanism of connecting rod failure on a 110 cc 4-stroke motorcycle that exhibits plastic deformation at the connecting rod neck. Visual inspection, chemical composition testing, metallographic testing, hardness testing, and numerical simulation are the analytical techniques employed. The connecting rod material is classified as SAE-AISI 4140 steel based on the findings of the chemical composition test. The results of the metallographic tests revealed the presence of a martensite phase in the microstructure. The connecting rod material's average hardness value, as determined by the Vickers technique of hardness testing, is 500 HV. Similarity between the buckling failure mode, which happens when the load absorbed by the connecting rod exceeds the normal load and occurs in the vicinity of the maximum stress point, may be shown from stress analysis (von Mises) and buckling mode analysis (eigenvalue buckling). The history of riding motorcycles that have been altered by adding compression to get the required speed without taking the strength of the connecting rod components into account further supports this conclusion. [ABSTRACT FROM AUTHOR]

By experimental methods, 26 specimens were designed to conduct elastic and elastic–plastic buckling tests on cylindrical shells containing cracks. This study discusses the influence of factors such as the length–diameter ratio, the diameter–thickness ratio, the crack length, the inclination of the crack, etc., on the buckling load. Additionally, finite element models were established to compare with experimental results. For the PMMA cylindrical shell, the results showed that as the length–diameter ratio of the cylindrical shell increased, the buckling load first decreased and then increased. For the 6063 aluminum alloy cylindrical shell, with increasing length–diameter ratio, diameter–thickness ratio, and crack length of the cylindrical shell, the buckling load decreased accordingly. However, concerning the crack inclination, as the crack inclination increased, the buckling load increased accordingly. This indicates that the larger the crack inclination, the higher the load capacity of the cylindrical shell containing cracks. Through finite element simulations of cylindrical shells with cracks, it was found that through compressive mechanical properties, both elastic and elastic–plastic buckling loads yielded results that are closer to the experimental results. Additionally, the inclusion of contact effects in numerical simulations further improved the agreement with the experimental results, and the variation trend of the buckling load in the finite element simulation was consistent with the experimental results. The research findings provide valuable references for the assessment of load capacity in structures containing cracks. [ABSTRACT FROM AUTHOR]

In this paper, according to the characteristics of bedding slope deformation and buckling failure of slab cracked rock mass in Xinjiang Tianchi Energy South open-pit Coal Mine, with the help of slope radar monitoring means, by transforming the prediction of landslide failure process into the judgment of gradual failure of slope rock mass, the internal relationship between slope radar slope surface displacement rate and slope deformation and buckling failure is analyzed, and based on elastic plate theory, the relationship between slope buckling failure length and anchorage parameters is discussed. The results show that the radar displacement rate of slope surface shows an obvious downward trend in the strong bending uplift stage before the failure of slab cracked rock mass due to the expansion of tension cracks and the exposure of bottom sliding surface; the inflection point at which the radar displacement rate on the slope surface drops to the minimum value can be used as the graphical criterion of slope failure and the time node of critical sliding early warning; when the anchor row spacing is less than the ultimate length of slope buckling failure, the anchor bolt（cable） can effectively improve the flexural stiffness of plate cracked rock mass, and the treatment effect of plate cracked rock mass buckling failure is remarkable.

Based on the energy equilibrium, the computational formula of critical buckling length of multi-layer rock slope is derived. Considering interlayer and cross joints, the numerical manifold method is used to simulate the buckling evolution process of Malvern hills slope in New Zealand, and the theoretical calculation and numerical simulation results are compared with the field measured data. The results show that numerical manifold method can accurately simulate slope buckling failure process by preforming interlayer and cross joints. The process of slope buckling deformation and instability failure can be divided into interlayer dislocation-slight bending, slope toe traction-sharp uplift and accelerated sliding-landslide formation. Under the long-term action of self-weight, the evolution of slope buckling from formation to failure mainly includes three stages: initial bending, sharp bending and landslide formation. The angle between cross joint and slope normal is defined as β. Among the four kinds of cross joints with the angle β of 0°, 15°, 30° and 45°, the slope with 45° cross joint is most prone to slipping and bending deformation, the degree of buckling is the largest, and the number of time steps of slipping and bending is the least. When β is in the range of 30°−45°, the numerical simulation results are in good agreement with the reality.

To evaluate the performance of wheel coupler formwork support components, the bearing capacity of the horizontal bar, the shear capacity of the wheel, the shear capacity of the sleeve, and the stability bearing capacity of the single- and double-layer vertical poles were investigated through systematic full-scale tests. The feasibility and correctness of the experiment were verified by comparing the results with those of a finite element analysis. The results demonstrated that the weak point of the horizontal bar was the bearing capacity of the weld at the connection between the socket and the horizontal bar. Preventing buckling failure of the weld at the connection between the horizontal bar and the socket was critical to ensure the bearing capacity of the horizontal bar. Under the action of a shearing force, the wheel underwent buckling failure of the welding seam at the connection between the wheel and the vertical pole. With a decreasing number of connecting horizontal bars on the wheel, the shear capacity of the wheel decreased significantly. The shear failure mode of the sleeve was buckling failure. The connection weld did not undergo buckling failure during the load-bearing process, which was basically meeting the serviceability state. The failure of a single-layer vertical pole was typical with lateral displacement buckling, while the double-layer vertical pole did not undergo buckling with lateral displacement. [ABSTRACT FROM AUTHOR]

Current stability evaluation methods are unable to consider the progressive developing process of the bulking landslide and lack progressive evaluation method. Based on the strain‐softening constitutive model and energy conservation theory, this study proposes a progressive evaluation method for buckling landslide stability considering the shear mechanical characteristics of the slip zone with large displacement, enabling progressive evaluation of landslide stability as the buckling landslide deforms. Proposed method was validated based on the good agreement between evaluation result and observation from the critical displacement of Baiyangou landslide in the Three Gorges Reservoir area in China, as a case study. The results also suggest a displacement distribution along the slip zone presenting a two‐step growth feature from the front edge to rear edge; in contrast, the shear strength distribution presents a two‐step decline feature. In addition, the parameter sensitivity analysis of slip zone and slide mass of buckling landslide shows that buckling landslide stability is directly proportional to the thickness of slip zone and elastic modulus of slide mass and inversely proportional to the length of slide mass. [ABSTRACT FROM AUTHOR]

Hat-shaped steel members are widely used in solar greenhouses, due to their low cost, fast construction, and high material efficiency. This study aims to determine the ultimate bearing capacity of a solar greenhouse with the hat-shaped steel under snow loads. The typical solar greenhouse with an 8 m span and 3.8 m ridge height was selected as the research object. The finite element method (FEM) under ANSYS software was used to analyze the instability mechanism and failure modal of the structure under snow loads (uniform and non-uniform snow loads). An investigation was made to clarify the effects of the longitudinal tie bars, initial geometric imperfections, and sectional dimensions on the ultimate bearing capacity of the structure under non-uniform snow loads. Both the material and geometrical nonlinearity were considered in the finite element model. A bilinear kinematic hardening model was adopted for the steel with a yield strength of 235 MPa, Young’s modulus of 206 GPa, and Poisson’s ratio of 0.3. The geometrical nonlinearity was activated using the ‘NLGEOM’ option. To consider the local buckling, the greenhouse skeletons were then modeled with the Shell181 element suitable for the large strains and rotations. Fixed hinge supports were used for both ends of the skeleton. An arc-length method was utilized to trace the nonlinear load-displacement curve, in order to calculate the ultimate bearing capacity of the structure under snow loads. The ultimate bearing capacity of the solar greenhouse with the hat-shaped steel was slightly higher than that of the hollow rectangular section under the same conditions of net section area, upper flange width, web depth, and wall thickness. The solar greenhouse was more sensitive to the non-uniform snow loads, compared with the uniform ones. The ultimate bearing capacity of the hat-shaped steel solar greenhouse under non-uniform snow loads was about 28% of that under uniform snow loads. Therefore, some suggestions were presented for the non-uniform snow loads in the design stage of the solar greenhouse structure. The roof ridge and north roof end were dangerous sections under non-uniform snow loads, which firstly entered the full section yield state. The longitudinal tie bars were expected to effectively improve the ultimate bearing capacity of the greenhouse structure. The ultimate bearing capacity of the structure with the longitudinal tie bars was about 1.25 times that without tie bars. The ultimate bearing capacity was only reduced by 2%, when the initial geometric imperfections amplitude increased from 5 to 20 mm. It infers that the solar greenhouse was not sensitive to the initial geometric imperfection. The cross-section size of a hat-shaped steel was recommended that the ratio of the upper flange width to the lip width, the upper flange width to the lower flange width, and the web depth to the lower flange width were about 4.17, 3.33, and 4.67, respectively, while, the ratio of the web depth to the lip width, and the lower flange width to lip width were less than 9.25 and 1.7, respectively. These findings can provide a strong reference for the solar greenhouse with the open cold-formed thin-walled steel under snow loads. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department 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.)

When a circular tube is under axial compression, it can be developed into specific forming technologies (e.g., tube inversion). However buckling failure is prone to occurring and seriously restricts the successful realization of the forming process or service performance. In this paper the conical convex or concave dies with different semi-cone angles were adopted to change tube end contact conditions and the buckling process, critical buckling force and the buckling waves of AA6061 tube under axial compression were investigated by using finite element simulation combined with experiments. The results show that the buckling deformation, the position where initial buckling wave appears, and the distribution of axial stress in tube blank are quite different when axially compressed on a flat die or a conical convex die (semi-cone angle β = 60°). For the conical convex dies as semi-cone angle increases from 75° to 87.5°, or for concave dies as semi-cone angle decreases from 110° to 92.5°, the axial compressive stress, critical buckling force and critical reduction increase, while the peak of the buckled wave decreases, i.e., occurrence of buckling delays and the buckling becomes more difficult to occur. When β is 90° (flat die), the critical buckling force and reduction reach the peak values.

The development of composite coating with higher dispersive second phase is a crucial goal to achieve its performance against wear. In this respect, an interesting experimental investigation on the behavior of Ni–B–TiO2 sol composite coating towards scratching, sliding and impact loadings was performed. The adhesive strength was determined by progressive scratch test, while the tribological behavior was assessed through rotating and reciprocating sliding tests, as well as the impact-sliding tests. The in-situ formation of TiO2 nanoparticles in Ni–B bath, which is a recently invented technique, significantly improves the scratch response of the composite coating and its abrasive wear resistance. Indeed, the composite coating appears exempt from delamination after both scratch tests and pin-on-disk test, contrary to the pure Ni–B coating. Regarding the impact wear resistance, it was found that the wear severity and damage mechanisms depend strongly on the impact angle, which in turn is controlled by the solicitation type. The SEM observations accompanied with EDS analysis were carried out inside the wear scars to clearly understand the relationship between the surface damage and the contact angle.

The Winkler foundation model is widely used in soil calculation for the analysis of buckling failure of super-long piles. The model regards the foundation soil as an elastic body composed of discrete spring elements with the continuity of the foundation soil ignored, which is inconsistent with the actual engineering. In this paper, the double-parameter foundation model which conforms to the actual deformation characteristics of soil is introduced. The model uses two independent parameters to reflect the characteristics of the foundation soil, and the shearing effect between the soil springs is considered to reflect the continuity of foundation soil. Based on this, the total potential energy function of the pile-soil system is established. According to the principle of stationary potential energy and the variational method, the analytical solution of the buckling critical load of the pile foundation can be calculated by the m-method and the combination method respectively. The results of the example show that the error between the calculated method and the test piles is within 5%, which indicates that the double-parameter can accurately reflect the reaction behavior of the foundation soil during the buckling failure of super-long pile in the actual engineering. Meanwhile, the soil resistance model of the combination method is closer to the actual pile body constraint. [ABSTRACT FROM AUTHOR]

There are significant levels of concern about both the safety assessment and financial evaluation of the whole hydropower system, especially at early project stages. In addition, there is a variety of reliable and accurate methods for analysis, design, and optimization of steel pressure liners in hydropower plants. Several countries have developed specific regulations and codes for the design, installation, and safety evaluation of under-pressure piping, as well as estimates of the potential risks associated with failure. This paper reviews the current methodologies and codes available for design and safety assessment of either unstiffened or stiffened pressure steel liners in hydropower plants. After examining the main guidelines and practical conclusions drawn from recent research in the field of liners subjected to either internal or external pressure, this article then discusses the relevant regulations and codes. The scope of this work is to summarize the advantages, disadvantages, and main characteristics of the existing design criteria, analysis methods, and other issues related to steel liners. Afterwards, this paper compares the main reliable formulations and modelling techniques, even the most recent or sophisticated ones. Lastly, we draw some conclusions regarding their accuracy and scope of applicability. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the behaviour of a braced steel frame with a proposed system: anticompression brace system (ABS) subjected to cyclic lateral loads. The ABS is proposed to deal with common brace buckling problems. In the study, split-K braced steel frames: with ABS and with ordinary brace system (OBS) were used as speciments. Cyclic loading tests were conducted to evaluate the performance of the proposed system in preventing the brace to buckle and to obtain the behaviour of the frame with ABS compared to the frame with OBS under cyclic quasistatic loading. From the cyclic tests, it was observed that the proposed system worked in preventing the braces to buckle, hence, the aimed state, “buckling prevention” was achieved. The results of the study also show that the frame with ABS had a lower initial stiffness compared to the frame with OBS, nevertheless, after exceeding drift ratio of 0.85% based on raw data or 0.64% based on fitted-curves, the frame with ABS exhibited good behaviour through lower degradations in stiffness and cyclic strength relative to the frame with OBS that experienced sudden and greater degradations.

To evaluate the performance of wheel coupler formwork support components, the bearing capacity of the horizontal bar, the shear capacity of the wheel, the shear capacity of the sleeve, and the stability bearing capacity of the single- and double-layer vertical poles were investigated through systematic full-scale tests. The feasibility and correctness of the experiment were verified by comparing the results with those of a finite element analysis. The results demonstrated that the weak point of the horizontal bar was the bearing capacity of the weld at the connection between the socket and the horizontal bar. Preventing buckling failure of the weld at the connection between the horizontal bar and the socket was critical to ensure the bearing capacity of the horizontal bar. Under the action of a shearing force, the wheel underwent buckling failure of the welding seam at the connection between the wheel and the vertical pole. With a decreasing number of connecting horizontal bars on the wheel, the shear capacity of the wheel decreased significantly. The shear failure mode of the sleeve was buckling failure. The connection weld did not undergo buckling failure during the load-bearing process, which was basically meeting the serviceability state. The failure of a single-layer vertical pole was typical with lateral displacement buckling, while the double-layer vertical pole did not undergo buckling with lateral displacement.

• FE models were established to examine the behavior of buckling propagation and crossover. • The influences of geometry and material property of pipes and arrestors on the failure mode and crossover pressure were numerically explored. • Four machine learning models were developed to predict the failure mode, crossover pressure, and arresting efficiency, respectively. Integral buckle arrestors are regarded as the most effective arresting devices, which can provide an obstruction to a propagating buckle thereby protecting downstream pipelines. In the present study, numerical frameworks were established to reproduce the phenomenon of buckling propagating and crossing under hydrostatic pressure, and a strong consistency between measurements and predictions was achieved. The stress levels and deformation configurations of the assembly were carefully examined for two different failure modes. Then, broad parametric analyses on the crossover pressure were performed covering key material properties and geometries. After that, machine learning techniques were developed and used for predictions of failure modes, crossover pressure, and arresting efficiency, respectively. Four algorithms, including Random Forest, Multi-layer Perceptron, K-Nearest Neighbors, and Support Vector Machine, were implemented using a dataset with seven variables. The prediction performance was evaluated by standard statistical metrics, and it was found that Multi-layer Perceptron model exhibited the better prediction accuracy for both classification and regression problems. Additionally, the existing experimental results were also used to verify the reliability of the machine learning model. The results demonstrate that the machine learning techniques can offer relatively accurate predictions for both flattening and flipping failure modes. [ABSTRACT FROM AUTHOR]

Buckling failure is a special form of a landslide, and it has been little debated in the literature so far. There have been few studies conducted on this type of slope failure, and the corresponding reinforcement measure research has also been rarely conducted. Therefore, it is nearly impossible to provide systematic guidance for the reinforcement and monitoring of such a slope. In this study, a new type of slope test system is developed, and the reinforcement effect of double-row piles was studied using simplified laboratory tests. Under the conditions of no pile and piles, load tests on the sliding body were carried out, and the ultimate loads that can be borne by the slope sliding body under these two conditions were analyzed. The multivariate information evolution of stress, displacement, and pile deformation under these two conditions were studied using multiple monitoring methods. The results showed that anti-slide piles can significantly improve the ability of the sliding body to withstand external loads. For the condition of no piles, 4 kN/m (20.55 kPa) was the critical value and the critical load the slope could bear reached 10 kN/m (51.38 kPa) after the installation of piles. The first row of piles withstood more load than the second row of piles, and double-row pile reinforcement can effectively improve the anti-slip safety reserve. In addition, monitoring of the deformation of the slope and anti-sliding piles should focus on the position of the sliding body and the slip face. Based on the results of laboratory tests, on-site field monitoring was then conducted on the target slope, including displacement monitoring at different positions on the slope before and after anti-slide pile construction, deformation monitoring of anti-slide piles, and rock stress monitoring around anti-slide piles. Monitoring results showed that the slope deformation and rock mass stress tended to be stable after anti-sliding pile construction, and the anti-slide piles were conducive to a safe state. The results of this study provide a useful reference for the reinforcement and monitoring of buckling failure in an actual slope. [ABSTRACT FROM AUTHOR]

There are significant levels of concern about both the safety assessment and financial evaluation of the whole hydropower system, especially at early project stages. In addition, there is a variety of reliable and accurate methods for analysis, design, and optimization of steel pressure liners in hydropower plants. Several countries have developed specific regulations and codes for the design, installation, and safety evaluation of under-pressure piping, as well as estimates of the potential risks associated with failure. This paper reviews the current methodologies and codes available for design and safety assessment of either unstiffened or stiffened pressure steel liners in hydropower plants. After examining the main guidelines and practical conclusions drawn from recent research in the field of liners subjected to either internal or external pressure, this article then discusses the relevant regulations and codes. The scope of this work is to summarize the advantages, disadvantages, and main characteristics of the existing design criteria, analysis methods, and other issues related to steel liners. Afterwards, this paper compares the main reliable formulations and modelling techniques, even the most recent or sophisticated ones. Lastly, we draw some conclusions regarding their accuracy and scope of applicability.

In this work, buckling strength assessment of a deck of a double hull oil tanker is carried out using the non-linear finite element code ADVANCE ABAQUS. The comparisons are performed with the Det Norske Veritas (DNV-GL) PULS (Panel Ultimate Limit State) buckling code for the stiffened panels, DNV-GL Classification Notes (CN) No.30.1 and the DNV-GL Ship Rules. The case studied corresponds to axial compression. Two levels of imperfection tolerances are analyzed, in accordance with the specifications in the DNV-GL Instruction to Surveyors (IS) and the DNV-GL Classification Notes No. 30.1. Both “as built” and DNV-GL Rule “net” dimensions are analyzed. The strength values from ADVANCE ABAQUS and PULS are very close. DNV-GL CN 30.1 is in conservative side, but the strength differences between the “as built” and “net” dimension cases are consistent with the finite element analysis results. This paper gives a brief description of the background for the stiffened panel models used in PULS, and comparison against non-linear FE analysis, and DNV-GL Classification Society Rules. The finite element code ADVANCE ABAQUS is employed in a non-linear buckling analysis of a stiffened deck panel on a double skin tanker that is subjected to a Condition Assessment Program (CAP) hull survey. The aim of the analyses has been to validate and compare the buckling capacity estimates obtained from PULS, DNV-GL Classification Notes No.30.1 (CN 30.1) and the DNV-GL Ship Rules.

Because of the high ratio of strength to weight, composite vessels are widely used in maritime and aerospace industries. The way of composite vessels breaking under hydrostatic pressure is assignable by paying attention to the geometry and material's properties. In composite vessels, using of composite stiffeners has high complexity in manufacturing process. On the other hand, due to the low young's modulus of composite materials, usually cannot use of the materials as a stiffener. In this research, effects of using hoop stiffeners on buckling pressure of composite bodies have been studied. In this paper, mechanical manner of a composite body is studied by Finite Element Method (FEM) in two statuses (with metal stiffener and without metal stiffener). According to results, using of a metal hoop stiffener that has 3.6 percents of the composite body weight increases buckling pressure up to 25 percents. Based on results increasing the buckling pressure of composite bodies by mounting steel hoop stiffeners added lower weight to the suite from increasing of thickness of bodies. For verification of numerical results, a composite vessel of GRP (Glass Reinforced Polymer), reinforced by a hoop stiffener mounted on inner surface has been experimentally under hydrostatic pressure to the breaking step. Finally, it was broken by 16 bar pressure. The results showed that the estimated pressure of software has a little difference with the experimental estimation that represents high accuracy of modeling process in the research.

Near-surface buckling of horizontally laminated sedimentary rock has been reported to occur in Ontario, Canada and the Upper Midwestern U.S. where high horizontal in situ stresses occur. Often referred to as 'pop ups', these buckling events typically occur suddenly and are commonly accompanied by a rapid energy release akin to rock bursting. In recent years, this mode of instability has become a concern for surface mining and quarry operations, in particular in cases where the buckling failure creates a connection between an underlying aquifer and the excavation. Despite previous research on the topic of buckling instability, there remains many limitations in development of a design methodology to account for buckling failure. The main objective of this research study is to experimentally investigate a simple buckling failure mode, known as three hinge buckling (THB): buckling that involves rotation of a two-rock block configuration with a central hinge. An experimental testing procedure was developed to reproduce THB at laboratory scale, including the design and fabrication of a new testing apparatus and development of a testing methodology. A preliminary THB test was conducted and the results are presented. A simplified, elastic block numerical model was developed using the distinct element method code 3DEC in order to provide insight into the laboratory experiment. Overall, this newly-developed test was able to reproduce the THB failure experimentally in the laboratory and to provide an opportunity to observe the brittle buckling failure to obtain valuable, quantifiable information about the failure process. [ABSTRACT FROM AUTHOR]

The buckling of a gold thin film deposited on a rigid substrate has been numerically investigated by means of static molecular dynamics simulations. Three different regimes of deformation have been identified depending on the values of the adhesion energy of the film on its substrate (Γ int). For low adhesion energy, the buckling and gliding through dislocation emission into the interface have been observed. For intermediate values of Γ int , the dissociation of the interfacial dislocations into the film leads to the formation of a Lomer–Cottrell lock that stops the buckle extension, promoting thus the propagation of a crack accompanied by the emission of dislocations. It results in the formation of a twin. For large values of Γ int , the kinking of the interfacial crack has been evidenced along with dislocation nucleation at its tip leading to twins again. Finally, the different evolutions of the film have been summarized in a "behavior" diagram displayed in the plane of applied strain and adhesion energy variables. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office 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.)

Unbonded flexible pipes have become widely employed in marine environments with the development of the offshore oil and gas exploration industry. Such pipes are subject to complex loads, which may lead to significant failure. Tensile armor layers are key components of these flexible pipes, and radial buckling failure may occur under high compressive or other combined loads. In this paper, a simplified numerical model of the flexible pipe is developed using the finite element (FE) method, and the main failure modes of the tensile armor layers are simulated. This simplified model is an improvement over those employed in previous studies on tensile armor failure. Several parameters that have important effects on pipe stiffness are investigated. The results show that an increase in the winding angle of the tensile armor wires as well as the damage to the outer sheath of the flexible pipe will decrease the compressive stiffness significantly. The presence of friction between adjacent layers will increase the stiffness to a small extent while the external hydrostatic pressure enhances its axial stiffness greatly and improve the stability of the pipe. These results may be used as a reference in the development and engineering applications of flexible pipes. • A simplified numerical model of the flexible pipe is developed using the finite element (FE) method. • The main failure modes of the tensile armor layers are simulated via the FE model. • Parameters that play important effects on the stiffness of flexible pipe are investigated. • Both the winding angle of the tensile armor wires and the damage to the outer sheath of the flexible pipe affect the stiffness significantly. • Both the friction between adjacent layers and the external hydrostatic pressure increase the stiffness. [ABSTRACT FROM AUTHOR]

This study investigates the load-bearing behavior of timber members subjected to combined compression and bending based on the guidelines of the standard Eurocode 5. In this context, two design approaches are stated to account for flexural buckling: the effective length method and the second-order analysis. Although Eurocode 5 states that second-order analysis can be carried out to check the stability of beam-columns, it does not mention how to formulate this analysis. This study investigates this case in order to develop alternative interaction formulae to check the stability of timber members subjected to simultaneously acting axial compression and bending moments with risk of buckling failure. The second-order analysis advanced in this article can be an alternative tool to be used by the structural engineer to assess the stability of axially loaded members subjected to the risk of flexural buckling failure. [ABSTRACT FROM AUTHOR]

Recent developments in composite manufacturing have been resulted in formation of newly-known 3D integrated weft-knitted fabrics which can be used as the composites' reinforcing materials. In this paper, the compression-resistivity of 3D composite panels reinforced with these newly designed 3D textile-preforms from E-glass fibers has been studied. Following this research, the composites mechanical functionality under flatwise and edgewise compression loadings was evaluated. Using VIP method, three groups of glass/epoxy composite with different core thicknesses and structural geometries were prepared. It was concluded that the compressive strength of the flat-wisely loaded samples would significantly decrease by increasing the thickness. Moreover, changing the composites' geometrical shape leads to some changes in failure mode; in this regard, the produced single-decker U-shaped panels only suffer from the pure buckling failure, while the double-decker U-shaped panel failed due to a combination of facing bending stress, core shear stress, and buckling failure. Thickness changes are not as effective as structural geometry changes on the panels' compress-resistivity under edgewise compression. As compared with the conventional 3D woven sandwich composites, it was approved that mechanical functionality of the produced 3D integrated weft-knitted spacer panels is completely improved so that they can be considered as good alternatives especially in building constructions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology 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.)

Abstract The ultimate strength of stiffened panels under compressive loads is assessed by numerical simulations, in order to compare with tests made to investigate the influence on the ultimate strength of varying pit location, pit diameter and pit depth. The validated model is them used for a numerical study on the influence of pitting on the residual ultimate strength of stiffened panels by a series of non-linear finite element analysis. The parameters of pit position, diameter, number, depth, and corroded volume loss will be investigated for the stiffened panels subjected to axial compressive load with initial deformations. It is found that the pits will induce the buckling failure of stiffened panels. All parameters discussed in this paper have significant influence on the residual ultimate strength of the pitting corroded stiffened panel. A formula was derived by introducing the reduction of plate slenderness and column slenderness. Highlights • The collapse mechanics of pitted stiffened plates are investigated numerically compared with tests. • A series of FEAs were conducted to study the influence of pit damage. • Pits can induce the buckling and reduction of ultimate strength of stiffened panel. • A formula is introduced considering the reduction of the plate slenderness ratio and column slenderness induced by pits. [ABSTRACT FROM AUTHOR]

Lightweight lattice structures are an important class of cellular structures with high potentials for multi-functional applications. Considering load-bearing requirements, truss buckling is one of the main failure mechanisms for low density and slender lattice structures. Critical buckling loads can be increased by modifying the profile of a truss. In this paper, we present a shape design method to optimize the critical buckling loads for lattice cores with free-form trusses. The free-form truss is represented by Fourier series and implicit surfaces, having smooth truss diameter variations and truss joints. The optimized truss profile is obtained by solving a parametric shape optimization problem with Fourier series coefficients as design variables. The method is used for designing optimized 1D columns and 3D Kagome lattice cores for sandwich panels. The numerical results predict 26.8% and 20.4% improvements of the critical buckling loads for 1D columns and 3D Kagome lattice cores compared to their uniform counterparts of the same mass, respectively. The optimized structures include complex smooth and curved geometries that are well suited for additive manufacturing because of the greater design freedom. Finally, the initial and optimized lattice cores are additively manufactured and tested. The experimental results validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The investigation of a tribo-contact dynamic, friction and wear prediction are the main objectives of the materials tribology. In this paper, the external dynamic of a friction process is investigated by means of a definition of the dynamic characteristics of tribological objects. According to the automatic control theory, the dynamic system of tribological objects is a subject of a parametric identification. In the simplest case, these parameters are a damping coefficient and a free frequency (natural oscillation frequency). The proposed method allows the use of an amplitude-frequency response for the estimation of dynamic coefficients of a friction interaction. In addition, this approach makes it possible to evaluate the surface characteristics of tribological pairs (for example, asperity) and to determine the bifurcational components of a friction. This method is the basis of the processes investigations of evolution tribological characteristics. [ABSTRACT FROM AUTHOR]

Steel constructed are made of thin-walled cylindrical shells. They are widely used in various food and agriculture industries for storing granular solids, liquids, and bulk food. The present research study was completed to determine the structural behavior of thin-walled silo when subjected to wind load. The study included determination of deformational behavior of a large field silo and development of a finite element model. This experimental part of the study comprises a challenging full-scale test on 14.55 m diameter and 23.27 m high steel silo located in the open farm land near Bothwell in the province of Ontario, Canada. The finite element model was then developed for undertaking wind analysis to study the effect of different parameters such as different geometric dimensions, stiffener patterns, and wind girders on the wind-induced buckling strength of steel silos made of corrugated steel. Both linear and geometrically nonlinear buckling analyses were carried out to determine the critical wind speed for corrugated steel silos. The study found that the wind girders, also known as wind rings, significantly increase the buckling strength of the silo. This study found that the critical buckling wind speeds of the field silo specimen have increased by about 44%. Further, the optimum location for the addition of wind rings was found to be near the roof of the silo. [ABSTRACT FROM AUTHOR]

In this research work, the failure reasons of retractable outrigger were analyzed by nonlinear finite element method firstly. Then the actual failure modes and loads were obtained by working condition simulation and destruction test on the two original designs. Both results from analysis and test show that the failure is due to instability of first class retractable outrigger side plate attached with fixed leg. Finally, the front outrigger was strengthened and this optimization was certified to meet bearing requirements through nonlinear finite element analysis and loading test. The method could be used to analyze buckling failure problem of similar structure. [ABSTRACT FROM AUTHOR]

The reason for the failure of the Omo River Bridge that collapsed and partially sank into the river during construction was investigated using standard, structural and analytical finite element model (FEM) and design review procedures according to Eurocode 3. The bridge was initially constructed by a launching construction technique. The span design was based on a Callender- Hamilton bridge type with Warren trusses of the D8M type classification. In all 40 stages were required to put the bridge in place. The bridge collapsed and partially sank into the river during construction, between stages 34 and 35. From in situ inspection, it was observed that the main bridge did not show any significant distress. Moreover, the mode of failure suggested a weak link between the main bridge and the launch nose. The results of the investigation showed that the diagonal link angles in the critical region where the main truss was connected with the launching nose were found to be the most critically loaded members. These members were stressed to their ultimate limit state, causing them to buckle and trigger the sudden collapse of the bridge at the end of launching stage 34. [ABSTRACT FROM AUTHOR]

The reasons that pillars with small width-to-height ratios fail remain unclear. This study established a mechanical model for the buckling failure of a thin pillar subjected to compressive forces to investigate the stability of reserved thin pillars (RTPs) on both sides of mining units during barrier pillar recovery. The critical buckling stress of the thin pillar was obtained using the energy variational method, and its relationship to the aspect ratio (length-to-width ratio) was investigated. The buckling instability of RTPs can be determined by comparing the RTP stress obtained from numerical simulations with the buckling stress derived from the mechanical model. [ABSTRACT FROM AUTHOR]

In this paper, compressive behavior of tubular structures made of aluminum and multilayer carbon fiber reinforced plastic (CFRP) are studied experimentally and numerically. Results show that current evaluation of aluminum tubes using Johnson–Euler method overestimates the critical stress values of the tubular structure because local failure is ignored. A finite element analysis (FEA) model based on Riks method is proposed to re-evaluate compressive performance and failure modes of aluminum tubes. This model is modified for laminated composites by introducing damage model based on Hashin's theory, such as matrix tensile/compressive failure, and fiber tensile/compressive failure. Simulation results of CFRP tubular structure show close agreement with experimental results, but also sensitive to geometric constants. Material failure is primarily the failure mode of tubes with slenderness ratios under 21. A mixed failure mode can be found for slenderness ratios of tubes between 21 and 35. For tubes with slenderness ratios above 35, buckling failure is the primary failure mode. [Display omitted] • Establish evaluation criteria for load carrying capacity of tubular structures. • Analyze compressive behavior of tube by numerical and experimental methods. • Study the large-scale effect in metallic and composite tubular structure. • Design a new compression fixture to test composite tubular specimens. • Examine delamination of composite tubes under axial compressive load. [ABSTRACT FROM AUTHOR]

Thin-walled cylindrical shell is a fundamental engineering structure which has efficient load-carrying capacity. In practical application, this structure is more easily subjected to localized axial compression loads and is prone to buckling. However, until now there is only limited studies on the buckling problems of multi-region localized axial compression loaded cylindrical shells. To elucidate the buckling behaviors of cylindrical shell under such kind of non-uniform loading condition, experimental and numerical studies are carried out in this paper. Twenty cylindrical shell test specimens with different types of localized axial compression loads are fabricated and tested. The corresponding finite element model considering the measured initial geometric imperfections is established for buckling analysis, and good agreement between the numerical and experimental results is validated. Then the buckling failure mode and axial load-carrying capacity of cylindrical shells are investigated in details. Finally, the imperfection sensitivity of thin-walled cylindrical shell under multi-region localized axial compression is discussed. It is found that the number of loading regions and the total loading area have significant effects on buckling failure mode and axial load-carrying capacity of cylindrical shells. The results obtained from experimental and numerical studies can provide some important guidance or suggestions for the design of thin-walled cylindrical shell structures in actual engineering. • Buckling tests of 20 metallic thin-walled cylindrical shell specimens under multi-region localized axial compression loads were performed. • Finite element model for studying buckling behaviors of cylindrical shell were established. • Buckling failure mode and axial load-carrying capacity of cylindrical shell were systematically investigated for the first time. • Imperfection sensitivity of cylindrical shell under multi-region localized axial compression loads was discussed. [ABSTRACT FROM AUTHOR]

• Calculation assuming the equally long beams overestimates the load carrying capacity. • Single beam FE analysis is used to find the optimized lengths within the tolerance. • The load carrying capacity decreases for the optimized beam combination significantly. • The load carrying capacity boundaries determine the field of experimental results. The paper presents an improved algorithm to compute an axial load carrying capacity of the specific multi-beam structure in order to failure avoidance. The former approach based on the finite element method is reduced to determine a relation between the axial load and axial displacement for a single beam, while the time-consuming FE procedure applied on several beams is replaced with a numerical optimization process. The developed approach provides faster and simpler computation of the minimum axial load carrying capacity of the structure considering the beam length tolerances, where the results are in a good agreement with the complex FE analysis. Supporting theoretical and experimental analyses were performed to confirm the correctness of the mentioned method where the load carrying capacity of the multi-beam structure made up of six steel circular beams was analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the P-wave velocities in different directions of sandstone samples under uniaxial compression are measured. The results indicate that the changes in the P-wave velocity in different directions are almost the same. In the initial stage of loading, the P-wave velocity exhibits a rising trend due to compaction and closure of preexisting fissures. As the stress increase, preexisting fissures are closed but induced fractures are not yet generated. The sandstone samples become denser and more uniform. The P-wave velocity remains in a steady state at a high level. In the late stage of loading, the P-wave velocity drops significantly due to the expansion and breakthrough of induced fractures. The P-wave velocity anisotropy index ε is analyzed during the process of loading. It can be observed that the change in the degree of wave velocity anisotropy can be divided into three stages: the AB stage, the BC stage and the CD stage, with a changing trend from decline to incline. In the initial stage of loading, the preexisting fissures have a randomized distribution, and the change is large-scale and uniform. The difference in each spatial point decreases gradually, and synchronization increases gradually. Thus, the P-wave velocity anisotropy declines. As the stress increases gradually, with the expansion and breakthrough of induced fractures, the difference in each spatial point increases. Before failure of rock samples, the violent change region of the rock samples' internal structure is focused on a narrow two-dimensional zone, and the rock samples' structural change is obviously local. Therefore, the degree of velocity anisotropy rises after declining, and it also has good corresponding relation among the AE count, the location of AE events and the degree of wave velocity anisotropy. The projection plane of the main fracture plane on the axis plane is recorded as M plane. Based on the AFF equation, for the CD stage, we analyze the quantitative relationship between the velocity anisotropy index ε and angle θ , which is the difference between the angle of the M plane and the X plane and the angle of the M plane and the Y plane from the theoretical point. The results indicate that 1 ε and cot θ 2 have good negative linear relationship that can be expressed as cot θ 2 = a ∗ 1 ε + b . According to experimental data, the linear fit of 1 ε and cot θ 2 is found, obtaining cot θ 2 = − 0.0472 1 ε + 0.03 , with a linear fit index of 0.908. From an experimental point of view, the linear relationship between 1 ε and cot θ 2 is verified. Through this research, we propose a new method for quantitatively predicting the main fracture occurrence position by P-wave velocity anisotropy. This work has an important significance for understanding buckling failure of rocks. [ABSTRACT FROM AUTHOR]

Bimetal mechanical clad pipe is one of the main measures for anti-corrosion control adopted in oil and gas fields. The liner pipe failure is a key problem that restricting the clad pipe applications. In this paper, a calculation model of clad pipe is established, and the buckling failure of liner pipe under complex loading was investigated. Effects of forming process, working pressure, external environmental loading and structural parameters on the failure mode of liner pipe were studied. The results show that increasing the residual contact pressure in the forming process is helpful to improve the buckling resistance of the liner pipe. The residual stress between liner and outer pipes can make the clad pipes bear a larger bending loads and have a larger critical curvature. Buckling mode "8" of the liner pipe occurs under complex loading. A larger working pressure can reduce the buckling degree and fold amplitude of the liner pipe. The liner pipe is more resistant to buckling in shallow water than in deep water. With the increasing of the wall thickness for liner and outer pipes, buckling resistance of the liner pipe becomes stronger. Finally, prediction formulas for critical curvature and the maximum normalized bending moment of the clad pipe are presented. The research results can provide a theoretical basis for the design, manufacture, and safety evaluation of clad pipe. • Hydroforming process of bimetal mechanical composite pipe is studied. • Buckling mechanism of liner pipe is studied under complex loading. • Effects of forming process, structure, internal and external pressure on liner pipe failure mode are studied. • Critical curvature and maximum normalized bending moment formulas are predicted. [ABSTRACT FROM AUTHOR]