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The object of this study are thin-walled rectangular plates with a central cut-out under uniform compression. The load is applied to the shorter and at the same time free-supported edges of the plate. The plates are made of carbon-epoxy laminate. A numerical modal analysis is performed for a number of cases where the plate with a central notch is longitudinally reinforced with isotropic strips fixed on the opposite sides of the plate. The main purpose of this study is to investigate the effect of the proposed design solutions on the buckling mode and buckling loads corresponding to the lowest buckling mode. The knowledge of these parameters will enable optimal design of elastic plate elements with predefined mechanical properties and designed mode of buckling. The eigen-problem was solved by numerical analysis using the finite element method. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental program into buckling, ultimate and post-ultimate behaviour of thin-walled cold-formed steel lipped channel members subjected to eccentric compression about minor axis. Tested specimens are subjected to compression with a wide range of both positive and negative eccentricities. Thus the evolution of the plastic mechanisms and the use of them to characterise the ultimate strength is examined by the experimental tests. [ABSTRACT FROM AUTHOR]

The bifurcation buckling load can be determine solving a linear eigenproblem of buckling. If the structure is not perfect, the effect of bifurcation doesn’t occur. So, how to estimate a value of the lowest buckling load of the real structure? A methodology for determination of the lowest buckling load of a real structure with initial imperfection using a post-buckling path is presented. The investigation is performed for a Z-column made of carbon-epoxy laminate. The amplitude of initial imperfection is small less than half of the walls thickness. The column is simply supported on both ends. All calculations are performed by the finite element method and Koiter’s method. A plate model of the thin-walled structure has been applied. First, an eigenvalue buckling problem is solved to determine bifurcation loads. Next, post-buckling equilibrium paths for the plate structures are determined to calculate the lowest approximate bifurcation loads by the P-w and P-w2 methods, the inflection point method and the Koiter’s method. The presented methodology is correct, when the uncoupled buckling is considered. The numerical results were verified in experimental tests. A Aramis system was applied. A static compression test was performed on a universal testing machine. Specimens were obtained with an autoclave technique. Tests were performed at a constant velocity of the cross-bar equal to 2 mm/min. The compressive load was less than 150% of the bifurcation load. [ABSTRACT FROM AUTHOR]

The bent beam may lose overall or local stability of the web or compression belt depending on the type and manner of load, shape and geometric features of the cross-section, length, support conditions or indirect spring constraints. The purpose of this article is to determine the critical moment of loosening for purlins using three sections, namely IPE 140, CE 140 and Z300×94×86×30×2.5, assuming their cross-sectional values are as close as possible to each other. In order to determine the bearing capacity of the cross-section of the beam, it is necessary to determine the critical moment of the deflection ie the loss of flat bending form with twisting with respect to the longitudinal axis. Only for the case of constant load torque is known an analytical solution in closed form [1–3]. Other waveforms of bending moments are included in the analytical formula by the factor C1 [5]. For complex support conditions, you can use numerical programs to calculate the finite element method. For more detailed description of the beam, you must model the shell elements. [ABSTRACT FROM AUTHOR]

Since the real structure is not perfect, the geometric imperfections are present. In this case, the bifurcation buckling load overestimates the buckling load. This problem is particularly interesting in experimental studies, because the amplitude of imperfection and its mode can differ for each sample. In this paper, a methodology for determination of the lowest buckling load of a thin-walled plate structure with imperfection using a load–axial shortening plot was presented. The proposed approach can be applied, when the post-buckling path is stable, only. It was shown that the load corresponding to an alternation in rigidity of the real structure on the load-axial shortening plot determines the buckling load with high accuracy. The P-w² method and the inflection point method were applied, as well, to verify the obtained results. First, numerical calculations were performed by the finite element method and Koiter’s method using Byskov-Hutchinson’s formulation. The imperfections were defined explicitly. Other parameters of the system, such as boundary conditions, loads, geometrical dimensions were free from inaccuracies. A plate model of the thin-walled structure was applied. An eigenvalue buckling problem of perfect structures was solved to determine bifurcation loads and their eigenmodes. Then nonlinear problem of buckling was solved by Koiter’s perturbation method for one mode approach or the finite element method employing Newton-Rawson’s method. The load - axial shortening plots were made to analyse an influence of the imperfection amplitude on an approximate value of the lowest buckling load. The uncoupled local buckling was considered. Detailed computations were conducted for short Z-column made of general carbon-epoxy laminate under uniform compression. The Z-column was simply supported on both ends. Finally, the numerical results were verified in experimental tests using Aramis system. A static compression test was performed on a universal testing machine. Tests were performed at a constant velocity of the cross-bar equal to 2 mm/min. The compressive load was less than 150% of the bifurcation load. A very good agreement between the results attained with both the methods for solving the nonlinear problem was obtained. [ABSTRACT FROM AUTHOR]

The paper deals with a nonlinear analysis of load-displacement curves of the von Mises planar truss. The model with hot-rolled steel members IPE 200 was solved. A nonlinear solution was applied which enabled the monitoring of individual buckling shapes of the von Mises planar truss in the course of pre-critical and post-critical behaviour. Symmetric and asymmetric shapes of buckling were identified. Further, there was determined by computation the value of vertical displacement of top joint, which corresponds to critical internal force in the von Mises planar truss, at which the model passes from precritical behaviour to the post-critical one. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an effective approach to numerical investigation of the debonding process in composite laminates under quasistatic loading with usage of the cohesive zone model. It is based on contact interaction of the coinciding reference surfaces of two interconnected shell-layers. The cohesive zone model is intended to define a stick area where potentially the debonding can occur. This approach was realized in the ANSYS® commercial software and was verified on the test models, which usually apply to experimental investigation of the fracture process. Both the buckling phenomenon and postbuckling behavior of the ply separation are considered in thin-walled laminated plate under 4-point bending. By using the proposed approach, the defect propagation is investigated, which is caused by the ply separation buckling. [ABSTRACT FROM AUTHOR]

The study investigates the behaviour of short, thin-walled laminated C-columns under eccentric compression. The tested columns are simple-supported. The effect of load inaccuracy on the critical and post-critical (local buckling) states is examined. A numerical analysis by the finite element method and experimental tests on a test stand are performed. The samples were produced from a carbon-epoxy prepreg by the autoclave technique. The experimental tests rest on the assumption that compressive loads are 1.5 higher than the theoretical critical force. Numerical modelling is performed using the commercial software package ABAQUS®. The critical load is determined by solving an eigen problem using the Subspace algorithm. The experimental critical loads are determined based on post-buckling paths. The numerical and experimental results show high agreement, thus demonstrating a significant effect of load inaccuracy on the critical load corresponding to the column's local buckling. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental studies on the determination of the deformed state of an I-beam. A step-like character is established on the "load-deflection" diagram at bending deformation of an I-beam. It is shown that stages I and II are conditioned upon the deformation behavior of a steel vertical wall of the beam. Stages III and IV are determined by the geometry of the sample and the type of the deformation effect. The presence of stage III is conditioned upon slow buckling of an I-beam shelf under the place of the applied load. A correlation between the distribution of local plastic deformation foci on the lateral surface of the steel I-beam and stages I and II on the deformation curve in the "load-bending" coordinates is established. It has been revealed that the transition from the elastic stage I and the parabolic stage II is accompanied with a change from the chaotic distribution of local plastic deformation foci to the laminated one with a well-defined stratification of compressive and tensile plastic deformations in the upper and lower sides of the I-beam at the macro-scale level. [ABSTRACT FROM AUTHOR]

Due to the experimental value of the imperfect structure pipeline under the external load is far below the linear theoretical calculation value, the nonlinear large deflection theory was adopted. The stability of imperfect structural pipelines was studied by theoretical research and numerical simulation considering bending deformation and initial imperfections. The difference of critical load between numerical simulation and theoretical value was analyzed. It can be found: By numerical simulation, the critical load of the simulation fit with the nonlinear large deflection theory well. Compared with linear theory, the nonlinear large deflection theory described the stability of imperfect structures more accurately. [ABSTRACT FROM AUTHOR]

This study investigates the modes of failure of the insulated sandwich wall panel (ISWP). A specimen of ISWP with dimension of 1220 mm width x 56 mm thickness x 1770 mm length was tested under in-plane lateral cyclic loading. Experimental work was carried out to determine the lateral strength capacity of ISWP starting with a small percentage of ±0.01% drift and was increased gradually by 0.1% drift until the maximum strength capacity was achieved. The maximum in-plane lateral strength recorded was 5.6 kN at ±1.6% drift. The maximum vertical displacement measured was 15.54 mm at ±1.8% drift (positive direction) and the maximum lateral displacement is 33.8 mm (positive direction). Experimental results also demonstrate that the ISWP did not suffer any damage on the surface of wall but major failure modes observed were buckling of the wall frame since the ISWP was protected by the aluminium frame along the edge of the ISWP. However, there were some failure occurred at the connection joint of ISWP to foundation and uplift the bottom corner of ISWP. [ABSTRACT FROM AUTHOR]

In this paper results of the analysis of the load-bearing capacity of steel trapezoidal sheets and optimization of cross-section based on requirements signalized by producers were presented. Consequently optimal criterion was assumed as maximal covering width and maximal bearing capacity with simultaneous minimization of costs and minimal waste of metal sheet used for profiling. Parametric optimization included 8 cross-section variants of trapezoidal sheets with a height of 136 mm and of 152 mm, thickness (0.7 mm, 1.0 mm and 1.5 mm) and various width of the plane elements of the cross-section. Moreover, different number of intermediate stiffeners was taken in to account. Furthermore, for one variant of the most optimal geometry of the trapezoidal sheet, a numerical experiment was carried out using the finite element method with the use of the advanced MES code implemented in the Abaqus Standard program. Numerical analyses have shown that the type of analysis has a significant impact on the obtained results, therefore it is necessary to conduct laboratory tests to verify the numerical model. [ABSTRACT FROM AUTHOR]

The paper presents the weight optimization process of the main steel truss that supports the Slatina Sport Hall roof. The structure was loaded with self-weight, dead loads, live loads, snow, wind and temperature, grouped in eleven load cases. The optimization of the structure was made using genetic algorithms implemented in a Matlab code. A total number of four different cases were taken into consideration when trying to determine the lowest weight of the structure, depending on the types of connections with the concrete structure (types of supports, bearing modes), and the possibility of the lower truss chord nodes to change their vertical position. A number of restrictions for tension, maximum displacement and buckling were enforced on the elements, and the cross sections are chosen by the program from a user data base. The results in each of the four cases were analyzed in terms of weight, element tension, element section and displacement. The paper presents the optimization process and the conclusions drawn. [ABSTRACT FROM AUTHOR]

The paper is devoted to a three-layer circular plate consisting of two facings and a core with variable mechanical properties. The simply supported plate is subjected to pressure. The mathematical model of the plate is formulated, in particular the field of displacements. The nonlinear hypothesis is proposed. Basing on the principle of the total potential energy the system of equilibrium equations is derived. Then the system is solved using the method of Bubnov-Galerkin. The maximal deflections, normal stresses and shear stresses are calculated. [ABSTRACT FROM AUTHOR]

In this paper the stability of a cantilever two-member column subjected to an unintentional eccentric partially follower load is discussed. The main member of the column is comprised of two parallel aluminium rods, whereas the second auxiliary member in the form of a piezoceramic rod is offset from the centroidal axis of the first member. The column has one end fixed to the ground and all rods at the second end are joined by an ideally rigid mounting head. The unintentional eccentricity of the external force results from imprecise manufacturing or improper assembling processes of loading heads. Eccentric loading makes the column to bend and that phenomenon may be counteracted by implementation of the piezoelectric actuation to the auxiliary rod. Application of the electric field to the piezoceramic material induces in the system, dependently on the direction of the field, an additional internal compressive or tensile force. This force, acting along the auxiliary rod being offset from the host column, may counterbalance the bending moment resulting from the eccentricity of the external load. The problem has been formulated by using the principle of stationary value potential energy in which the electro-mechanical coupling of the piezoceramic material has been taken into consideration. It has been shown through the numerical calculations that type and amount of the external force, its eccentricity, as well as the piezoceramic rod offset and amount of induced force has a great impact on the internal forces distribution. Moreover, it has been shown that column’s lateral deflection, being a result of applied external force, depending on the amount of that force and the eccentricity direction with respect to the system centroid may be minimized or even completely removed. [ABSTRACT FROM AUTHOR]

The paper deals with the design, experimental analysis and numerical optimization of tensegrity dome models. Two structures are analyzed - a Geiger system dome (preliminary dome), with PVC-U bars and PA6/PP/PET tendons and a Fuller system dome (target dome), with wooden bars and steel cables as tendons. All used materials are experimentally tested in terms of Young's modulus and yield stress values, the compressed bars are also tested for the limit length demarcating the elastic buckling from plastic failure. The data obtained in experiments is then implemented in SOFiSTiK commercial software FE model. The model's geometrical parameters are considered uniform random variables. Geometrically and materially nonlinear analysis is carried out. Based on the obtained structural response (displacements), a Monte Carlo simulation - based approach is incorporated for both structural design point formulation and the SLS requirements fulfillment analysis. Finally, an attempt is made to erect the Fuller dome model in order to compare the numerical results of an experimentally-derived model with the in situ measurements of an actual structure. [ABSTRACT FROM AUTHOR]

Since the battery is the most crucial part of an electric vehicle, its safety level has attracted researchers. This work focused on the computational approach of several batteries using non-linear finite elements. The battery types simulated were Lithium-Iron-Phosphate (LFP) 18650, which were produced in a laboratory. A mechanical load simulation scenario follows a condition when an electric vehicle experiences a collision. Here, the battery pack was axially and laterally crushed. The simulation approach is carried out using the LS-DYNA software. The mechanical properties of the battery are obtained from several experimental approaches. Finally, the battery cell is crushed from the axial and lateral directions with a non-linear finite element approach based on the obtained mechanical properties. This parameter will be used in the future to predict the failure of the battery pack due to dynamic loads. [ABSTRACT FROM AUTHOR]

The objective of the paper is to analyze the influence of initial imperfections on the behaviour of thin-walled girders welded of slender plate elements. In parallel with experiments, one of the ultimate load tests was computer modelled. In so doing, the girder was modelled, using the geometrically and materially non-linear variant of the shell finite element method, by the ANSYS program. The shape changing during loading process is often accompanying with sudden „snap-through" i. e. rapid curvature change. [ABSTRACT FROM AUTHOR]

The crash behavior of Cold Rolled Mild Steel (CRMS) closed form thin section was studied by conducting compressive tests at loading velocities of 5 mm/min and 1000 mm/min. The numerical simulations were conducted for the same experimental conditions to understand the deformation shape, peak forces and energy absorption capacity of sections at different impact velocities. The simulation results correlated well with the experimental results. [ABSTRACT FROM AUTHOR]

Weighing measurement platforms are devices designed for weighing goods in warehouses, production halls and other closed and open facilities. The subject of the analysis was a series of weighing platforms being an alternative to the structures currently offered on the market, qualitatively new in terms of specific and added features. [ABSTRACT FROM AUTHOR]

The Modular Test Stand for Fatigue Testing of Aeronautical Structures is presented in the paper. Several different fatigue tests can be executed at the same time by means on this stand. In this way authors intend to diminish cost of fatigue test and makes it affordable for low cost projects e.g. student projects. Authors describe an essential assumptions and limitations as well as design phase where they tried to meet them. [ABSTRACT FROM AUTHOR]

The aim of this study is to show the advantage of Functionally Graded Material (FGM) as a coated layer and bond coated (under coated) layer in new coated beam structures. Three pattern coated such as Homogeneous Coated (HC), Functionally Graded Coated (FGC), and Homogeneous- Functionally Graded Coated (H-FGC) were considered. The static analysis of three different coated beam with non-uniform cross-section is emphasized for this study. The classical beam theory with several boundary conditions under uniformly transverse loading is analyzed by using Ansys software. In FGM layer of beams, changes of material properties are assumed based on layerwise method. The material properties in each layer differ as a sigmoid function along the thickness coordinate in order to analyze the composite. And also Poisson’s ratio is considered constant across the thickness of coated beams. The deflections and stresses of coated beams are evaluated and under discussion based on two different material parameters. The results are showed that the H-FGC pattern has minimum deflection like the HC pattern. In the H-FGC pattern, the stress distribution at the interface of coated layer with substrate layer gradually change as well as the stress in the ceramic coated layer has not increased. [ABSTRACT FROM AUTHOR]

A method is proposed to predict the fatigue life and residual strength of fiber reinforced composites subjected to variable amplitude (VA) loadings. Based on a recently developed two-parameter residual strength model, the damage accumulation rule is based on the “equivalent strength approach” allowing to account for the variable loading without any simplifying assumption. The cycle-by-cycle effects can be easily recovered on the basis of strength degradation kinetics and the approach reliability is checked on the basis of a series of constant amplitude (CA) literature data. The approach allows correcting the imperfections of Miner’s rule and its unreliability when applied to fiber composites and to build on a solid foundation a numerical procedure for fatigue calculations under spectrum loadings. High-Low (H-L) and Low- High (L-H) three-block sequences of loadings have been simulated highlighting the basic concepts of the proposed damage rule. The analytical predictions reveal that the sequence and interaction of events has a strong influence both on the rate of damage accumulation and fatigue life. [ABSTRACT FROM AUTHOR]

It is common in full-scale laboratory tests to simulate live or transient loads of secondary importance with generic weights, even if the load being simulated is uniform in nature. For many simple structures, such as beams or plates, calculation of appropriate substitute load is rather straightforward. The paper deals with somewhat more difficult case of orthotropic plates, which are common solutions for fire resistant roofs. The main load of these structures in tests according to EN 1363:2012 [1] is temperature, but uniform load must also be included in the tests. A numerical algorithm is proposed to beforehand calculate an applicative load, which preferably would not impair neither favour the test specimen. A FEA model of the roof specimen is built and optimisation algorithm seeks for the solution, taking into consideration all of the arbitrarily formulated constraints for the load distribution and a set of independent objective functions. In the paper, few such objective functions, appropriate in this kind of tests, are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we propose an approach for the determination of the resistance area boundaries for a locomotive cab under possible ad hoc (non-regulated) loads. This limiting surface (boundaries of the area) for the incoming parameters determines the area of safe operation for a locomotive cab. If the parameters of the locomotive and the obstacles are below this limiting surface, the protection of personnel and cab equipment will be provided. [ABSTRACT FROM AUTHOR]

In the present study, work-hardening behavior under various loading paths of a commercially pure titanium JIS Grade 1 sheet was investigated. The following tension-compression asymmetry was presented. The yield stress was smaller under compression than under tension, whereas the subsequent work-hardening was larger under compression than under tension. When the sheet was subjected to reverse loading from compression to tension, strong Bauschinger effect was exhibited. Thereafter, a concave curve followed by a small stress peak appeared, which was not presented under monotonic tension. Microstructure observations suggested that this characteristic behavior would be owing to the the activities of twinning and detwinning respectively during compression and following tension. [ABSTRACT FROM AUTHOR]

This report involves the modelling of the Milad Tower using the finite element analysis program Strand7. A dynamic analysis was performed on the structure in order to understand the deflections and stresses as a result of earthquake and wind loading. In particular, Linear Static as well as Natural Frequency and Spectral Response solvers were used to determine the behaviour of the structure under loading. The findings of the report highlight that the structure was modelled accurately with the outputs representing realistic values. The report suggests that the design of the beams, columns, slabs and all structural members was sufficient enough to support the tower during maximum loading cases. The governing load case was earthquake loading. [ABSTRACT FROM AUTHOR]

Some new aspects in a classic problem of axial rod compression are presented. For short-term impact the influence of longitudinal waves propagation on the rod instability is investigated. For the long-term compression which considerably exceeds the Euler load, the generalization of the overcritical deformations in the rod from investigated by M.A. Lavrentiev and A.Yu. Ishlinsky in the linear statement to the nonlinear Euler elastics is studied. [ABSTRACT FROM AUTHOR]

We examine the spatial evolution of 3-cycle topologies in the contact networks of 2D and 3D granular media under load experiencing one of two modes of failure at the macroscopic scale: diffused or localised. These mesoscale structures encapsulate kinematical signatures of plastic deformation and thus their destruction or deaths provides a means of tracking or predicting macroscopic failure. A multiscale point pattern analysis quantifies the extent of spatial clustering of these structures within the material throughout loading. In samples undergoing failure through strain localisation, 3-cycle deaths exhibit evidence for spatial clustering well before peak shear stress and shear band nucleation. Detection occurs earlier in the loading history compared to more traditional soil mechanics measures, e.g., porosity maps and particle rotations. Moreover the region of strain localisation is delineated by the spatial distribution of the dying 3-cycle contact topologies. In samples undergoing diffuse failure, no evidence of localisation is detected over short strain intervals suggesting an optimal window size to capture key kinematics, with an aim towards using the spatial behaviour of mesoscopic 3-cycles as a tool to classify macroscopic failure modes. [ABSTRACT FROM AUTHOR]

This presentation is a review of experimental methods for accurately measuring and modeling the anisotropic plastic deformation behavior of metal sheets under a variety of loading paths: biaxial compression test, hydraulic bulge test, biaxial tension test using a cruciform specimen, multiaxial tube expansion test using a closed-loop electrohydraulic testing machine for the measurement of forming limit strains and stresses, combined tension-shear test, and in-plane stress reversal test. Observed material responses are compared with predictions using phenomenological plasticity models to highlight the importance of accurate material testing. Special attention is paid to the plastic deformation behavior of sheet metals commonly used in industry, and to verifying the validity of constitutive models based on anisotropic yield functions at a large plastic strain range. The effects of using appropriate material models on the improvement of predictive accuracy for forming defects, such as springback and fracture, are also presented. [ABSTRACT FROM AUTHOR]

Forming simulations of can end shell have been implemented and compared with the experimental observations of the shell actual forming process. The influences of the loads applied to tools, the clearances between tools, the shapes of the tool profiles and the positions of tools, on the shell forming quality, have then been investigated numerically. The design optimization method based on the numerical simulations has been applied to search optimum design points, in order to reduce the amount of thinning subjected to the constraints of the shell geometric shape and the suppression of wrinkles. The optimization results show that the amount of thinning can be reduced up to 4% by optimizing the forming route, adjusting the clearances and the loads, and modifying the tool shapes. [ABSTRACT FROM AUTHOR]