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Buckling restrained braces (BRBs) which are generally composed of a steel core and a encasing(buckling restrainers) are utilized to resist lateral forces in high seismic regions since BRBs exhibit high energy dissipation capacity, ductility and stiffness. The steel core carries both compressive and tensile forces. During the compression, the core starts buckling and the encasing tries to prevent this buckling. However, due to the unbonding layer/gap between the encasing and steel core, the steel core eventually buckles and contacts with the encasing. Buckling phenomenon is also associated with the initial imperfection and gap size. In this study, the effects of the initial imperfectionof steel core, gap size (1-5 mm)and friction coefficient (0.01-0.5)between the encasing and steel core on the behavior of BRBs are investigated. Pursuant to this goal, numerical analyses using a finite element tool ABAQUS were conducted. A total of 19 numerical models were developed and monotonically loaded. Initial imperfection was implemented to the models using buckling mode shapes.The results revealed that increasing gap size leads to a reduction in load-carrying capacity. It is recommended to keep gap sizes between 1 and 2 mm. On the other hand, initial imperfection does not significantly affect load-carrying capacity and global behavior. However, it was also observed that the fluctuations in load increase as the amplitude of the mode shape and gap size increase. Moreover, the friction coefficient should be kept between 0.01 and 0.05; otherwise, undesired behaviors can be observed.

Sandwich plates consist of a total of three layers, with a thick core layer between two thin face layers. The face layers provide resistance to bending, while the core layer provides resistance to shear. General purpose finite element softwares are one of the most suitable and widely used analysis methods to investigate the behavior of structures. Many design parameters can be easily examined by using these analysis programs. In this study, the buckling behavior of sandwich square plates simply supported on four sides, whose ratio of core layer thickness to face layer thickness is between 7 and 9, was investigated using a general purpose finite element software. The effect of thickness variation was investigated by varying the face and core layer thicknesses of sandwich plates with a constant total thickness. At the same time, the materials of the face and core layers were changed and the most suitable design for the buckling behavior was revealed. For this purpose, 110 analyzes were made with 2 different face materials, 5 different core materials, 11 different thickness ratios. According to the results obtained from the analysis, the maximum critical buckling load was calculated as 282.108 N/mm2 in the sandwich plate with steel face and PVC H200 core. The most suitable design of sandwich plates against buckling was determined by presenting the results with graphics. [ABSTRACT FROM AUTHOR]

In this article, the optimum stacking sequence with maximum buckling load factor of a plate made of M91/IM10 unidirectional prepreg material, which has a very high strength compared to the materials used in the aerospace industry, is obtained by genetic algorithm method. The composite plate in question is simply supported at 4 edges and subjected to biaxial in-plane compressive loads. With the computer code developed using the genetic algorithm method, stacking sequences that provide maximum buckling strength at certain fiber angle ranges and certain number of layers for various load cases and various plate aspect ratio combinations are obtained. The laminate is assumed to be symmetrical and balanced. The results are compared with the results obtained from graphite/epoxy composite material, which has been studied in the literature. The comparison reveals that a plate made of M91/IM10 prepreg material can provide the same buckling performance with lighter structures than graphite epoxy. [ABSTRACT FROM AUTHOR]

Due to technical developments and wider range of applications in the steel structures, significance of the research on structural stability problems become forward. Lateral torsional buckling is a major problem especially for doubly symmetric I-shaped steel members subjected to flexure about their strong axis. If these members are not appropriately braced against lateral deflection and twisting, they are under the risk of failure by lateral torsional buckling prior to the reach their load carrying capacity. In this study, elastic lateral torsional buckling behavior of doubly symmetric I-shaped steel members under linear moment gradient is investigated considering a proposed method, several design standards and codes, approaches from the literature and finite element analysis. Proposed method herein is based on finite difference solution of lateral torsional buckling differential equation considering linear moment gradient. Different unbraced member lengths and various end moment values are considered in order to compare and evaluate these approaches in terms of critical moment and moment modification factor. Analysis results show that lateral torsional buckling is a key issue for doubly symmetric I-shaped steel members that are under flexure and it is reflected satisfactorily with the proposed method considering the design codes and standards, approaches from the literature and finite element analysis results.

In this paper, the thermal buckling loads of elliptical thin plates made of functionally graded material (FGM) with thicknesses that vary parabolically are examined. The aim is to study the effect of parabolic thickness variations in the directions of both axes on the thermal buckling of FGM plates. In the analyses, the boundaries are assumed to be simply supported and clamped. Rayleigh-Ritz method is applied to solve the partial differential equations. The Poisson’s ratios of the plates are kept constant, but their moduli of elasticity and thermal expansion coefficients are assumed to vary functionally in the thickness direction due to the material characteristics of FGMs. The study is carried out for several plate aspect ratios. Thermal buckling results of elliptical FGM plates with parabolically varying thicknesses are determined and the critical temperatures of those plates are obtained.

The aim of this research is to examine the mechanical buckling behavior of multi-layered functionally graded beams in the axial direction. Numerical buckling analyses were performed using finite element software called ANSYS. Each beam configuration is suggested to be three layers prepared using various percent volume fractions of Zirconia (ZrO2) and Aluminum (Al) materials. The levels of layers and layer positions of the beams were evaluated according to Taguchi’s L9 (33) orthogonal array technique. Layers were determined as control factor and so nine numerical analyses were performed under clamped-clamped boundary conditions. The first mode shapes of the axially layered functionally graded beams were demonstrated in order to detect the most affected layers as visually. Analysis of signal-to-noise ratio was applied to obtain the optimum levels of layers. Analysis of Variance (ANOVA) was employed to solve the layers with significant impacts and their percent contributions on numerical results. The maximum buckling load was determined using various positions of layers with the optimum levels obtained based on Taguchi methodology.

Reinforced concrete (RC) structures in earthquake prone regions are designed to achieve the seismic performance objectives. In end regions of RC members, longitudinal reinforcing bars may develop buckling due to high compressive strains under reversed cyclic loadings. The performance based assessment for RC structures should rely on analytical models which can account for the effect of rebar buckling on the nonlinear response. This study extends a previously proposed nonlinear truss modeling approach for modeling RC elements whose response is affected by rebar buckling. Nonlinear truss model includes diagonal truss elements accounting for biaxial effects in compression and tension stiffening for concrete elements in the horizontal and vertical directions. The truss elements representing reinforcing steel are provided with a uniaxial material model which can explicitly account for inelastic buckling and fracture of rebars. The modeling approach is validated with experimental test results on one RC beam considering mesh size effects on the response. Numerical model computed strength degradation in moment-drift ratio response of the beam in accordance with the experimental results.

Aim of this study is to determine the cross sectional geometries of beams which have better response to buckling with the usage of same amount of filament. These beams have the same cross sectional area and length. Thus, design points were sorted freely without the consideration of the amount of filament, printing time and energy consumption. Length of beams and applied forces were kept constant for each design point, besides that basic cross sectional geometries were changed for each design series. These geometries were selected as, circle, rectangle, equilateral triangle, rhombus (diamond), ellipse and rounded rectangle. Moreover four different printing material were taken into consideration for comparison according to buckling. Depending on 6 different cross sectional shape, 101 cross sectional area and 4 material, totally 2424 design alternatives were built. Firstly, mathematical model of these designs were constructed, then they were tested by using finite element method (FEM) and regression analysis. All model branches were compared to each other with the statistical analysis. As a result of all analyses, design alternatives were sorted according to mechanical strength.

The current investigation aims at enhancing the buckling characteristics of basalt fiber-reinforced composites by incorporating nano clay (NC) particles into the epoxy matrix system. Basalt fiber-reinforced composite laminates containing different NC concentrations (0.0%, 0.5%, 1.0%, 1.5%, 2.0% and 3.0%) by weight have been manufactured by vacuum-assisted resin transfer molding method and subjected to axial and lateral compression loadings to determine the effects of NC particles on buckling properties. Also, the influences of NC particles on material structure were examined by analysis with SEM micrographs of buckled samples. The results demonstrate that introduction of NC particles has significant effects on both axial and lateral buckling behaviors. Compared to pure samples, the highest improvements obtained for axial and lateral critical buckling loads were 48.1% and 39.56%, respectively, from the sample having 1% NC. Further increasing amount of NC particle content have exhibited reductions in critical buckling loads. This can be explained by poor interfacial bonding as a result of agglomerations and exfoliation of nanoparticles at epoxy/basalt interfaces in certain areas. According to obtained results, the application of NC inclusion has proved to be compatible with structure of basalt fiber-reinforced composites and they might be used together for applications requiring high buckling resistance. [ABSTRACT FROM AUTHOR]

In this article, the buckling of carbon nanotube (CNT) patterned cylindrical shells subjected to axial compressive load is presented within the framework of shear deformation theory (SDT). The material properties of nanocomposites change as a linear function depending on the thickness coordinate. The basic equations of cylindrical shells with CNT pattern are derived based on Donnell type shell theory and the critical axial load expression is obtained within the framework of SDT by applying Galerkin method. The effects of transverse shear deformations on the critical axial load of functionally graded CNT patterned cylindrical shells are investigated by changing CNT patterns, volume fraction ratio and shell parameters. [ABSTRACT FROM AUTHOR]

In this study, the buckling of variable cross-section columns under axial load is investigated by the Complementary Functions Method (CFM). Columns whose cross-sectional properties change continuously throughout the element are modeled according to the Timoshenko beam theory. By using the internal force-strain relations and equilibrium equations, a set of first-order ordinary differential equations governing the buckling behavior is obtained. The effects of different taper values and length/thickness ratios on the buckling load along the element are investigated for different boundary conditions. The calculated dimensionless buckling loads are tested with the available values in the literature and the results obtained from the Abaqus finite element program. The applicability of the CFM to the elastic buckling problem of variable cross-section columns has been demonstrated. [ABSTRACT FROM AUTHOR]

Objectives: To compare the results of scleral buckling surgery with and without use of operating microscope for primary rhegmatogenous retinal detachment (RRD). Materials and Methods: This comparative study consisted of 74 eyes of 74 patients who underwent scleral buckling for primary RRD. Group 1 consisted of 35 patients (17 male and 18 female) who were operated using operating microscope and Group 2 consisted of 39 patients (19 male and 20 female) who were operated without operating microscope. Patients with post-equatorial breaks, retinal breaks greater than 90°, proliferative vitreoretinopathy (≥C2), and those with follow-up period of less than sıx months were excluded from the study. The two groups were compared based on age, sex, etiology, anatomic success, and surgical complications (scleral perforation, iatrogenic retinal breaks, vitreous hemorrhage, buckle malposition, and vortex vein damage). Results: Mean age was 64.11±7.91 years (range, 55-79 years) in Group 1 and 65.20±6.15 years (range, 56-80 years,) in Group 2. Mean age and gender were not statistically significantly different between the groups (p=0.508 and p=0.990, respectively). Etiological causes were revealed as myopia, peripheral retinal degeneration, pseudophakia, aphakia, trauma, and idiopathic. Etiological causes were not significantly different between the two groups (p>0.05, for all). Surgical complication rates were higher in Group 2, however, the differences were not statistically significant (p>0.05, for all). Anatomical success rates was similar between the two groups (80% in Group 1 and 79.5% in Group 2, p=0.956). Conclusion: The results of scleral buckling surgery with and without use of operating microscope were not significantly different; However, operating microscope should be used especially in presence of risk factors for scleral complications. (Turk J Ophthalmol 2014; 44: 175-8)

In this study, snap-buckling and post-buckling behaviors of fixed beams having initially small circular imperfection subjected to uniformly distributed vertical loads are examined. The effect of a parameter related to the geometry of the initially imperfect beam on the buckling values as well as the deformed shapes of the initially imperfect beam, support reactions and internal forces are investigated. The finite difference method and the displacement-controlled Newton-Raphson method are used for the numerical solution of the nonlinear governing differential equations obtained within the framework of the Euler-Bernoulli beam theory. It is observed that the concerning geometric parameter significantly effects the buckling values, deformed shapes of the initially imperfect beam, support reactions and internal forces. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to compare the surgical impact of scleral buckling (SB) and pars plana vitrectomy (PPV) on the anatomic results and visual recovery in cases of rhegmatogenous retinal detachment with mild vitreous hemorrhage. Materials and Methods: In this study, we included 78 eyes of 78 phakic patients who underwent primary surgery for rhegmatogenous retinal detachment complicated by mild vitreous hemorrhage (38 eyes by SB,40 eyes by PPV);all patients had been followed for longer than 6 months after surgery. The surgical outcome and the rate of complications were retrospectively compared. Mann-Whitney U-test and chi-square test were used for the statistical analysis. Results: The reattachment rate after the first surgery was 78.9% (30/38) in the SB group and 95% (38/40) in the PPV group. The difference between the groups was statistically significant (p=0.035). Unseen retinal breaks in 4 eyes, malpositioned buckle in 2 eyes and insufficient closure of the break in 2 eyes of SB cases, as well as reopening of the original break in 2 eyes of PPV cases were the causes of failure. Visual improvement in the PPV group was significantly better than in the SB group in the third and sixth postoperative months (p

A 68-year-old woman presented to our clinic with a 1-month history of central scotoma and visual loss in her right eye. The best corrected visual acuity (BCVA) was hand motion in her right eye. Fundus examination showed myopic chorioretinal degeneration in association with posterior staphyloma and the retina was slightly elevated throughout the macula. Optical coherence tomography (OCT) revealed retinal detachment involving the posterior pole with a macular hole and staphyloma. The patient underwent pars plana vitrectomy, internal limiting membrane peeling, macular buckling, and perfluoropropane gas tamponade. At 3-month follow-up, her BCVA was improved to counting fingers at 1 meter and flattened retina with closed macular hole was observed by OCT. Myopic macular hole with retinal detachment associated with posterior staphyloma represent a challenge regarding their management and several surgical techniques have been described. Although satisfactory anatomical improvement is achieved in these eyes after surgery, the visual acuity outcomes may be poorer than expected due to the chorioretinal atrophy at the posterior pole.

In this study, free vibration and buckling analyses of functionally graded (FGM) sandwich beams is investigated by Navier's method. Displacement field is defined according to the first order shear deformation theory, and the equations of motion are derived by the Lagrange's principle. Volumetric ceramic ratio is defined by a power-law rule. In the analytical solution, different trigonometric series functions are used for each end conditions considered. Two cases of functionally graded sandwich beams are considered: a) Homogeneous ceramic core and FGM faces (Type A), and b) FGM core and homogeneous faces (Type B). Natural frequencies and buckling loads are obtained for different boundary conditions, power-law indices and slenderness. Numerical results are compared with the available literature, and a good agreement are obtained between the results. [ABSTRACT FROM AUTHOR]

Buckling restrained braces (BRBs) have high energy dissipation capacity and equal tension and compression axial load capacity. Therefore, the application of BRBs has gained popularity in seismic regions. The first studies on BRBs started in Japan in 1970 and since then more studies have been undertaken in other earthquake prone countries. Although the BRBs perform well in component and subassembly tests, they do not perform as well in frame tests because of the interaction between beam-column-gusset plate and BRB. In this study, the component and subassembly test of the BRBs and then BRB frame tests available in the literature are summarized.

Second order effects caused by internal forces in slender systems generate additional internal forces and deflections. Stability problems occur, when the additional internal forces and deflections do not converge (flexural buckling). Furthermore, lateral buckling is also possible due to very small rotations perpendicular to the beam cross-section (lateral torsional buckling). This stability problem has been studied by number of researchers and is one of the main topics in engineering. Except certain types of structures, it is difficult to formulate a closed-form solution. It will be helpful to develop numerical solutions for these systems. In this study, stiffness matrix calculation with respect to both flexural and torsional buckling is presented. Buckling problems in curved or tapered crosssection systems can be analyzed by dividing the beams into finite segments. Within this framework, an application is presented regarding the flexural and lateral torsional buckling in 2nd degree parabolic arches. [ABSTRACT FROM AUTHOR]

Copyright of Teknoloji is the property of Engineering Science & Technology, an International Journal 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.)

Copyright of Teknoloji is the property of Engineering Science & Technology, an International Journal 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.)

In this study, the thermal buckling analysis of the non-homogenous shallow spherical shell is investigated. Firstly, the analytical modeling of non-homogenous material properties and appropriate thermal expansion coefficient which vary continuously through the thickness direction is made. In the formulation of the problem, Kirchhoff-Love's first order shell theory is used and Hooke's law is taken into account for stress-strain relations. By using Donnell-Mushtari-Vlasov's (DMV) assumptions and linear stress-displacement relation, the stability equations depending on three displacements are obtained. Stability equations are solved for the simply supported boundary condition and analytical expression for the dimensionless critical uniform temperature rise is found. In numerical computations, the effects of variations of the elasticity modulus and appropriate thermal expansion coefficient as a power function according to thickness direction and variation of the geometric parameters of the sphere on the critical uniform temperature rises are examined as. To test the validity of this study, the obtained results are compared with counterparts in the open literature. [ABSTRACT FROM AUTHOR]

In this study, the critical buckling loads of natural fiber reinforced glass fiber composite specimens with different stacking sequences kept in seawater were experimentally investigated. Jute and glass fabrics as fiber and epoxy resin as matrix were used to produce the composites in different configurations. Alkali treatment was applied to jute fabrics in order to increase the amount of adhesion between the reinforcement and the matrix. Composite specimens were subjected to buckling test kept in seawater and room conditions for two months (60 days). Critical buckling loads of natural fiber reinforced composite specimens were determined in the direction of the data obtained as a result of the tests. As a result of the experimental study, it was seen that sea water influenced the buckling strength of natural composites in the negative direction. When the symmetric and antisymmetric composites were compared, it was observed that the critical buckling stress in the specimens with antisymmetric (02g/902j)us kept in Mediterraneanseawater was lower than those with symmetric sequence(02g/902j)s. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate IS/OS and ELM junction and restauration with spectral-domain optical coherence tomography (SD-OCT), anatomical and functional outcome after scleral buckling surgery (SBS) in macula-off rhegmatogenous retinal detachment (RRD). Materials and Methods: Medical charts of 81 eyes, who underwent SBS for macula-off RRD were retrospectively analysed. Reattachment success rates, pre- and postoperative visual acuity (VA) were examined. Postoperative SD-OCT images were obtained at 6. month to evaluate the status of photoreceptor IS/OS and ELM junction. OCT characteristics were correlated with final VA. Risk factors influencing postoperative VA were evaluated by using linear multivariate logistic regression. P values <0.05 were considered statistically significant. Postoperative at 12. month VA was examined, IS/OS and ELM restauration was evaluated with SD-OCT in 76 eyes. Results: The primary anatomic success rate was 93.8% (76 eyes), final success rate was 98.8% (80 eyes). Preserved ELM (p=0.003) and IS/ OS integrity (p=0.029), drainage of subretinal fluid (p<0.0001) were significant independent factors for influencing postoperative VA favourable. Duration of detachment >6 days (p=0.04), two/three retinal breaks (p<0.0001) and severe IS/OS disruption (p<0.0001) were significant independent risk factors for a poor postoperative VA. Severe IS/OS disruption was the most important risk factor for poor postoperative VA. Posoperatively at 12 months in 64% and 52% of eyes IS/OS and ELM restauration with increase in VA was detected Conclusion: IS/OS and ELM-integrity may be important independent predictors of postoperative VA. Severe IS/OS disruption may be the most important risk factor for poor postoperative VA. IS/OS and ELM restauration may permit increase in VA. [ABSTRACT FROM AUTHOR]

In 1744, the critical buckling load with the assumption of uniform cross-section without weight of column were computed by Euler. Whenever an economical solution is required, the weight of column must be considered for solution of buckling analyses. In literature, the critical buckling load and asymptotic behaviour of heavy column in condition of atmosphere have inverstigated for ten different support types. When this literature is examined, it is stated that the differential equations of for four different suppport types in condition of water is similar to condition of atmosphere. However, the differential equations of other four different suppport types in condition of water is different from to condition of atmosphere. And it is stated that the critical buckling load these different suppport types in condition of water is not calculated from condition of atmosphere. The goals of this paper are to develop self weight buckling of column at its top fixed and lower end fixed-roller supported in condition of water. This paper, presents a analytical method for calculating the critical buckling load of the heavy column.

Commercial utilization of the nuclear energy becomes possible through the controlled fission reaction that occurs within the nuclear reactors. Controlled realization of the fission reaction depends on the neutron number staying constant. This is called criticality condition. In the simplest approximation, the neutrons that trigger the fission reaction can be separated into two groups as low energy thermal neutrons and high energy fast neutrons. This is named two group neutron diffusion theory. In this work, the reactor radius that satisfies the criticality for a given reactor composition has been determined by solving the two group criticality equation numerically. In this manner, the effects of changes in principal and alternate buckling on critical reactor radius have been elucidated in a detailed way. [ABSTRACT FROM AUTHOR]

Nanotechnology is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale smaller than 1 micrometer, normally between 1-100 nanometers, as well as the fabrication of devices on this same length scale. Nanotechnology cuts across many disciplines, including colloidal science, chemistry, applied physics, materials science, and even mechanical and electrical engineering. Carbon NanoTube (CNT) is a new form of carbon, configurationally equivalent to two dimensional graphene sheet rolled into a tube. It is grown now by several techniques in the laboratory and is just a few nanometers in diameter and several microns long. They are the stiffest and strongest known fibers and have unique electrical properties. An ideal nanotube can be thought of as a hexagonal network of carbon atoms that has been rolled up to make a seamless cylinder. In classical elasticity theory the stress tensor at a given point depends linearly on the strain tensor of the same point. Thus, local elastic theory contains no information about the long range forces etween atoms i.e., there is no internal length scale. On the other hand, the theory of nonlocal continuum mechanics assumes that the stress state at a given reference point is considered to be function of the strain states of all points in the body. Properties of materials at the nanoscale differ fundamentally from those of their bulk counterparts. Carbon nanotubes are one of the structural elements that are used in nanotechnological applications widely. In this study, they are envisioned as hollow cylindrical bars of graphitic carbon at the nanoscale. For these reasons nonlocal theory is more capable to display the mechanical behaviour of materials at the nanoscale. Carbon nanotubes hold substantial promise for the development of nanotechnology. However, thorough understanding of the mechanical behavior of carbon nanotubes is essential. Currently, theoretical treatment of buckling of carbon nanotubes has relied on the use of classical continuum mechanics models, such as the elastic shell model or the Bernoulli-Euler beam bending model. Although classical continuum models are relevant to some extent, and efficient in computation for models at large length scales, the applicability of these classical continuum models at small length scales is questionable. Multiple recent experimental results have shown a significant size-effect in mechanical properties when the dimensions of the specimen or the probed material volume become small. The classical continuum theories lack the capability of representing such effects since they do not include any internal length scale. Consequently, these theories are expected to fail when the specimen size become comparable with the internal length scale(s) of the material. Several modifications of the classical elasticity formulation have been proposed to address this deficiency. They are of nonlocal or gradient type and, as a common feature, include one or several intrinsic length scales. Nonlocal elasticity theory was proposed to account for the scale effect in elasticity by assuming the stress at a reference point to be a function of strain field at every point in the body. When the structure considered falls into the nanometer range, nonlacality parameter ? has a significant influence on the outcomes of this study. In some cases, the ratio of local and nonlocal buckling loads can be 1.4. The buckling of carbon nanotubes has been studied by molecular mechanics in literature. In this paper the method of initial values is used in the frame of nonlocal elasticity. This method gives the values of the displacements and stress resultants throughout the rod once the initial displacements and initial stress resultants are known.… [ABSTRACT FROM AUTHOR]

Buckling of a column with temperature dependent material properties is investigated. Euler-Bernoulli theory of thin beams is used to derive the element matrices by means of the minimum potential energy principle. Temperature dependency of material properties is taken into account in the formulation. The column is divided into finite elements with the axial degrees of freedom defined at the outer fiber of the column. Column elements have simpler derivations and compact element matrices than those of classical beam-bending element. Some illustrative examples are presented to show the convergence of numerical results obtained by the use of new elements. The results are compared with those of the classical beam-bending element and analytical solution. The new element converges to the analytical results as powerful as the classical beam-bending element. The temperature effects on the buckling loads of the column with temperature dependent material properties are also examined.

Macular holes can develop secondary to pars plana vitrectomy (PPV). We report a case with giant macular hole formation after PPV and scleral buckling. A 66-year-old woman with a history of vitrectomy and scleral buckling due to rhegmatogenous retinal detachment (RRD) in her right eye 5 years ago complained of decrease in visual acuity ever since. Clinical photographs, fluorescein angiography and optic coherent tomography images revealed a very large macular hole of approximately 2465 μm in diameter. This case is an uncommonly large variant of a macular hole secondary to retinal detachment surgery. (Turk J Ophthalmol 2015; 45: 79-80)

The method of differential quadrature developed by Richard Bellman in the 1970s is a numerical solution technique for differential systems by means of a polynomial-collocation approach at a finite number of points. In this paper a global method of generalized differential quadrature is presented to solve the problems on deflection, buckling and vibration behaviour of structural components. Furthermore, the applicability of this method to the deflection analysis of beams due to a point load is also demonstrated. An inherent advantage of the approach is its basic simplicity and small computational effort with easy programmability. Results are obtained for various boundary and loading conditions and are compared with existing exact and numerical solutions by other methods. Numerical examples have shown the accuracy, efficiency and great potential of this method for structural analysis.

In this study, the effects of cold environment and different fiber combinations on lateral buckling behavior of hybrid composite beams were investigated, experimentally. For the lateral buckling tests, 12-layered hybrid composite plates were produced using different combinations of carbon, E-glass and aramid fibers, with an epoxy resin system as the matrix (Araldite LY1564/Aradur 3486). The hybrid composite samples were subjected to lateral buckling test after waiting for 90 days in room conditions, 90 days and 150 days in a cooler, respectively. The lateral buckling behaviors of layered hybrid composite beams were investigated in the direction of the data obtained from the lateral buckling tests. The highest critical lateral buckling load was obtained in the CAG30 specimens with the stacking sequence [(30/-60)3]s. The lowest critical lateral buckling load was obtained in GAC samples with the stacking sequence [(0/90)3]s. It has been observed that critical lateral buckling loads of specimens kept in cold environment increased with critical buckling loads of samples in room conditions. As a result of the study, it was determined that the critical lateral buckling loads of the hybrid specimens kept in the cold environment increased with respect to the critical lateral buckling loads of the hybrid specimens kept in room conditions. [ABSTRACT FROM AUTHOR]

The experiment was carried out to investigate the phenomenon of buckling using simple struts. These results were then compared with the theoretical predictions. Three steel struts of different length were used in the experiment; one of them had fix/pinned-end all the others had pin/pin-end joint. The applied load was placed at different eccentricities for each strut. Six aluminium pin-end struts of varying length were also tested. The measured critical load for each strut was compared against the corresponding Euler and Southwell predictions. For a steel strut, it would be expected that buckling would be symmetrical for left and right eccentricities. However, this was not the case due to imperfections in the struts. The struts buckled with half sine-wave and if one end of the strut was fixed the effective length was reduced and the critical load was increased. In the case of the aluminium struts, due to plastic behaviour in the deformation it was much harder to find the critical load. For steel struts both Euler and Southwell predictions were close to initial estimates of critical load.

In this study, the post-buckling behavior of shells is investigated using 9-noded isoparametric shell elements. Total Lagrangian approach is used in the formulation and shell material is assumed to be linearly elastic. Non-linear equilibrium equations are solved by arc-length method. Various examples were analyzed to obtain postbuckling behavior of shells. [ABSTRACT FROM AUTHOR]

Potential use of aluminum alloy core material as an alternative to steel in BRBs was investigated. Effectiveness/superiority of such braces that are designed, produced, and tested for the first time in this work, over the available types of BRBs is evaluated. Numerous tensile test specimens (coupons) were prepared in prototype samples according to the prescribed standards. Material test results contain valuable information for choosing the materials to be used in designing and fabricating the BRBs. A strain-gauge placement configuration was also suggested and tested in order to correctly measure the axial strains in the yielding portions of BRB cores. The reasons of why A5083-H111 aluminum alloy materials were preferred in the fabrication of BRB-AC1 and BRB-AC3 specimens were given in detail. Fabrication steps of aluminum alloy BRBs, welding procedures followed, assumed cyclic loading test protocol, instrumentation and data acquisition system used in the tests were described in the scope of this study. Experimentally obtained force-displacement hysteretic curves, tension and compression capacities, dissipated cumulative energies (Eh), cumulative inelastic displacements (η), and effective damping ratios (ξeffb) were calculated and compared. The requirement indicating that tests must involve the highest compression adjustment factor (β < 1.3), ensuring the symmetrical hysteretic curves, was fulfilled. It is concluded that aluminum alloy BRBs (BRB-AC3) with weld-free end connections have superior behavioral values when compared to aluminum alloy BRBs with welded end connections (BRB-AC1). [ABSTRACT FROM AUTHOR]

In the study, two and three-dimensional bending, buckling, and free vibration analysis of homogenous and isotropic rectangular plates are made by the method of differential quadrature. The weighting coefficients for differential quadrature are obtained using the power, Chebyshev and Lagrange polynomials. The governing differential equations (constitutive equations and boundary conditions) are reduced to a linear algebraic equations or a standard eigenvalue equation in terms of the unknown function values at the grid points in the field domain via differential quadrature method. The obtained results are then compared with the other results in the related literature. It is found that the obtained results are suitable in point of view the engineering analysis concept. [ABSTRACT FROM AUTHOR]

In steel structures, beams are usually assembled so as to be under bending about their major axis in order to use the structural material economically. Two major problems take place in design of these steel beams. First problem is exceeding of yield stress at the extreme fiber of the section. External force magnitude for any loading case which causes exceeding of yield stress on a steel beam can be easily calculated. Second problem is loss of stability. In beams which are loaded so as to be under bending about their major axis an equilibrium state is also possible for a certain load magnitude, in which the beam is twisted and buckled about its weak axis. This case is called lateral torsional buckling. Depending on the loading case, yield stress of the structural material and slenderness of the beam, which is related to section properties and length of the element, lateral torsional buckling may occur before the extreme fiber of the section reaches to yield stress. In this case, instead of first yield moment, lateral torsional buckling moment should be considered in design of the beam. In this paper, application of finite differences method for determining elastic critical lateral torsional buckling moment of cantilever I sections which are loaded from shear center is presented. The results are compared with ABAQUS software and it is seen that results obtained from the presented 1D model and ABAQUS software coincide. [ABSTRACT FROM AUTHOR]

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Buckling restrained braces (BRBs) have high energy dissipation capacity and equal tension and compression axial load capacity. Therefore, the application of BRBs has gained popularity in seismic regions. The first studies on BRBs started in Japan in 1970 and since then more studies have been undertaken in other earthquake prone countries. Although the BRBs perform well in component and subassembly tests, they do not perform as well in frame tests because of the interaction between beam-column-gusset plate and BRB. In this study, the component and subassembly test of the BRBs and then BRB frame tests available in the literature are summarized. [ABSTRACT FROM AUTHOR]