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This article explores the possibility of optimizing geometry and mass of a beam based on the conditions for ensuring local buckling. The subject of the study is a box-shaped beam with non-linear walls. This type of beam is unpopular because it has not been studied properly. This fact only indicates its novelty. However, researches and experiments prove that this type of beam is superior to current types of beams in terms of local buckling. This indicates relevance of further research and use of beams with non-linear walls in structures, where local stability is the main aspect in choosing the geometric dimensions of the beam. To optimize this type of beam, a numerical experiment was performed by using the finite element method in ANSYS. The experiment confirmed the possibility of geometric optimization with maintaining similar performance of local stability. The results of this study are obtained formulas. The first formula is required to find the local buckling stresses of box-shaped beams with optimized non-linear walls. This formula was found by approximating the results of a numerical experiment using the least squares method in a MathCAD. The second formula is required to find benefit in mass when using optimized geometry.

Background and Objectives: Scleral buckling and pars-plana vitrectomy are therapeutic options for the treatment of rhegmatogenous retinal detachment. Comparative studies still support the value of scleral buckling in phakic eyes. Nevertheless, the number of sceral buckling procedures may be continuously decreasing over time. The study aims to analyse the incidence of scleral buckling procedures for the treatment of patients with retinal detachment in Germany over time., Material and Methods: The numbers of scleral buckling procedures (OPS 5-152) and rhegmatogenous retinal detachment (ICD H33.0) in Germany are analysed on the basis of data from the quality reports published by the Federal Joint Committee and secondary analyses of the DRG-based billing system (DRG-Statistik) of the Federal Statistical Office between 2006 and 2017., Results: Based on the quality reports, numbers of scleral buckling procedures performed between 2006 and 2017 dropped by 49% from 8841 to 4510. During this period of time, the number of rhegmatogenous retinal detachments, identified by the ICD code H33.0, rose by 102% from 11 507 to 23 314. A decrease in scleral buckling procedures of 42% between 2006 and 2017 was also observed in the DRG Statistics. Regional and age-dependent subgroup analyses suggests that there are both regional and age-dependent differences in the practice of scleral buckling., Conclusions: Our analysis clearly illustrates that scleral buckling procedures are now less commonly performed in Germany than in 2006. However, the total of ~ 4500 billed procedures in 2017 in Germany shows that scleral buckling is still an important and current therapeutic option in the treatment of retinal detachment., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Georg Thieme Verlag KG Stuttgart · New York.)

Buckling techniques are used for rhegmatogenous (break-induced) retinal detachment. The aim is to achieve a functional closure of the retinal breakwith permanent retinal attachment by scleral indentation and coagulation of retinal holes. The surgery is primarily extraocular. The use of different buckling methods depends on various factors. The success rates are high at 54 - 97% after the initial procedure, but decrease as the macula is detached. When the possibilities of the scleral buckling procedures are exhausted, pars plana vitrectomy is the next therapeutical option. In recent years, however, there is a trend to primarily address even a simple rhegmatogenic retinal detachment with vitreous surgical methods., Competing Interests: Honorierte Referententätigkeit für die Firmen Bayer, Novartis, Alimera., (Georg Thieme Verlag KG Stuttgart · New York.)

For many decades, scleral buckling surgery was the only reasonable surgical procedure in eyes with primary rhegmatogenous retinal detachment. In recent years, primary vitrectomy has apparently become the treatment of choice, although evidence from comparative clinical trials is missing. In this article, data from clinical trials and indications for buckling surgery are presented., Competing Interests: Nein., (Georg Thieme Verlag KG Stuttgart · New York.)

Background: The effect of the surgeon on the outcome of surgical treatment for rhegmatogenous retinal detachment (RRD) has previously been analysed in a few studies only. In the prospective multicentre SPR study, scleral buckling (SBS) and primary vitrectomy (PV) were compared in RRD with medium complexity in a randomised fashion. In this study, we examined the surgeon factor on the outcome of RRD surgery within the SPR study., Material and Methods: An analysis of the surgeon as a factor on the functional outcome (logMAR visual acuity), primary anatomic success (retinal reattachment central to the aequator without any additional retina-affecting surgery including laser, cryo and macular pucker surgery) and final anatomic success (retinal reattachment one year postoperatively) was carried out., Results: Overall, 416 phakic patients (209 SBS, 207 PV) and 265 pseudophakic patients (133 SB, 132 PV) were recruited by 45 surgeons in 25 centres. In the phakic group, the mean functional outcome of individual surgeons was between 0.2 and 0.74 (mean, 0.41, SD 0.41). This difference reached statistical significance (p = 0.0398). In the pseudophakic subgroup, the mean functional outcome was between 0.09 and 0.64 (mean, 0.42, SD 0.49) without reaching a statistical significance (p = 0.0715). Primary success per surgeon varied between 41.67 % and 90.00 % (mean, 63.16 %) in the phakic subgroup and 33.33- 80.95 % (mean, 61.75 %) in the pseudophakic subgroup. Final anatomic success was achieved in 92.86 - 100.00 % (mean, 97.96 %) in the phakic subgroup and 80.00 - 100.00 % (mean, 95.44 %) in the pseudophakic subgroup. There was no statistically significant correlation between surgeon and anatomic outcomes., Conclusion: In the phakic subgroup, a statistically significant correlation between surgeon and functional success could be demonstrated for RRD with medium complexity. This correlation was not interrelated to the surgical method. Functional outcome in pseudophakic patients and anatomic outcomes in both subgroups of phakic and pseudophakic patients showed no statistically significant correlation between surgeon and anatomic success., (Copyright Georg Thieme Verlag KG Stuttgart . New York.)

Purpose: Enhanced depth imaging (EDI) optical coherence tomography (OCT) provides high-definition cross-sectional images of the choroid. Information on alterations in choroidal thickness (CT) after scleral buckling surgery (SBS) and pars plana vitretomy (PPV) are rare., Methods: The medical charts of 44 patients (44 eyes) who underwent SBS versus PPV for macula-off rhegmatogenous retinal detachment (RRD) were retrospectively analysed. Patients with a follow-up ≥ 6 months were included. Postoperative EDI-OCT images concerning CT were evaluated 1 week, 1 month and 6 months postoperatively in 2 groups: group 1: cerclage + cryopexy + subretinal fluid drainage (SRD) + SF6 or air (n = 28 eyes), group 2: PPV + laser photocoagulation + C3F8. Subfoveal CT was compared between the groups and with the non-operated fellow eye., Results: Subfoveal CT in groups 1 and 2 was thicker 1 week postoperatively. There were no significant differences between the groups 2 or when comparing the operated eye with the fellow eye 1 and 6 months postoperatively., Conclusion: There were no differences in subfoveal CT 1 and 6 months after SBS between the eye with macula-off RRD and the fellow eye. Thicker CT 1 week postoperatively after SBS may most likely be induced by scleral buckle reduced blood flow and increased haemostasis in the choroidal circulation and by scleral and choroidal inflammation after cryopexy versus laser photocoagulation after SBS versus PPV., (Georg Thieme Verlag KG Stuttgart · New York.)

Background: After conventional buckling procedures for pseudophakic retinal detachment the primary reattachment rate is 60 to 90% according to literature. Primary vitrectomy may be advantageous in these cases. The purpose of this study was to investigate the spectrum and role of potential side effects like anisometropia and diplopia, to find arguments for or against primary vitrectomy. Also risk factors for pseudophakic retinal detachment were analyzed in our study group, because they may be different from former studies, which were mostly undertake at the time of ec cataract extraction., Patients and Methods: The data from 115 patients (120 eyes) with pseudophakic retinal detachment, who undergone buckling procedure between 1991 and 1996 were retrospectively reviewed. We analyzed the retinal reattachment rate, choroidal detachment, postoperative visual acuity, refraction, occurrence of diplopia, anisometropia and metamorphopsia., Results: The primary retinal reattachment rate was 83.3%. There was a retinal redetachment rate of 16.7%. The primary PVR-rate was 4.2%. After the first reoperation an reattachment rate of 91.6% could be achieved, after the second one an overall rate of 95%. A choroidal detachment occurred in 29.2%. Postoperatively (26.5 months +/- 17.2) we found a cellophane maculopathy in 26.5% with consecutive metamorphopsia in 12.1%. 13 patients (15.9%) complained about diplopia, which had to be corrected by operation in 2 cases and prismatic glasses in 4 cases. Anisometropia could be deserved in 16.4%. The buckling procedures caused refractive changes of -1.80 dpt +/- 1.78 after an encircling band and +0.38 dpt +/- 1.01 after a plombage (average -1.05 +/- 1.86). 20% of patients treated with an encircling band developed anisometropia and only 8.3% of patients with a plombage. Postoperatively the visual acuity raised significantly from 0.3 to 0.6 (median). Best visual recovery could be observed in patients, who underwent only one operation., Conclusions: The primary retinal reattachment rate in pseudophakic retinal redetachment after conventional buckling procedures in our patients are comparable to those in the literature. In spite of phacoemulsification the risk-factors for pseudophakic retinal detachment has not changed. A considerable number of patients complained about postoperative complications like anisometropia and diplopia, which could be avoided by primary vitrectomy. To compare anatomic and functional results of both procedures a randomized prospective study should be undertaken.

Translation abstract A mechanically consistent approach for stability verification of timber beams in compression and bending around the strong axis – part 2: experimental tests and numerical simulationSlender timber beams in bending can be designed using different methods in view of out‐of‐plane stability. Lateral torsional buckling may be verified either using the so called equivalent member method or by means of 2nd order calculations, considering equivalent imperfections. Applying current codes, however, determining the lateral torsional buckling resistance using either of these both methods, leads to different results. In this paper, the background of both verifications is investigated in deep. Moreover, as an alternative approach, a non‐linear calculation with an imperfection shape in affinity to the critical shape was presented in part 1 of this paper. By scaling the curvature, the same results as by the equivalent member method can be achieved. It was shown that plasticity effects can be considered as well. In this part 2, results of lateral torsional buckling tests on glued laminated timber beams are presented, with nearly ideal boundary conditions and load direction remaining vertical through‐out the test. Based on these test first tentative values can be obtained for the imperfection compatible with the alternative lateral torsional buckling approach presented. [ABSTRACT FROM AUTHOR]

Translation abstract Buckling lengths in the digital age – a didactic‐technical toolThe critical load of a member in the case of stability failure is the basis for the design according to the equivalent member method of EN 1993‐1‐1. It has become established that the critical load is determined via the buckling length. In the simplest case, the buckling length corresponds to one of the Euler cases, which rarely occurs in typical steel structures. In more complex systems, the buckling length often depends on adjacent structures and their stiffnesses. Determining the buckling length is so important that it is usually taught in steel construction lessons, although it is a classic structural analysis problem. The same happens at the Innsbruck Chair of Steel Construction. A tool that is didactically and technically state‐of‐the‐art and intended to improve education has been developed as part of educational modernization. This tool can playfully convey access to the determination of buckling lengths on complex structures while modern numerical methods take over the actual calculation work in the background. The developed software buckL.ing (freeware) is available for download on the Unit of Steel Construction and Mixed Building Technology's homepage (www.uibk.ac.at/stahlbau/software). [ABSTRACT FROM AUTHOR]

Background: Enhanced depth imaging (EDI) optical coherence tomography (OCT) provides high-definition cross-sectional images of the choroid. Information on alterations in choroidal thickness (CT) after scleral buckling surgery (SBS) is rare., Patients and Methods: The medical charts of 122 patients (122 eyes) who underwent SBS for macula-off rhegmatogenous retinal detachment (RRD) were retrospectively analyzed. Patients with a follow-up ≥ 6 months were included. Postoperative EDI-OCT images concerning CT were evaluated 1 week, 1 month and 6 months postoperatively in 4 groups: group 1 cerclage + cryopexy (n = 39 eyes), group 2 cerclage + cryopexy + sponge (n = 28 eyes), group 3 SBS + subretinal fluid drainage (SRD) (n = 25 eyes) and group 4 SBS + sponge + SRD (n = 30 eyes). Subfoveal CT was compared between the groups and with the non-operated fellow eye., Results: Subfoveal CT in groups 1, 2, 3 and 4 was thicker 1 week postoperatively. There were no significant differences between the groups or when comparing the operated eye with the fellow eye 1 and 6 months postoperatively., Conclusion: There were no differences in subfoveal CT 1 and 6 months after SBS between the eye with macula-off RRD and the fellow eye. The use of a sponge or SRD induced no differences concerning subfoveal CT.

Better and simpler possibilities of structural optimization due to increasing computational power but also for reasons of environmental sustainability, the use of materials and their reusability lead to greater acceptance towards more advanced numerically intensive, so‐called 'design by analysis' methods like geometrically and materially non‐linear analyses with imperfections (GMNIA). The general choice of imperfections and their combination in such models, especially for slender cross sections of intermediate length prone to an interaction between a global and local plate buckling, is crucial in terms of the reached load‐bearing capacity. Annex C of EN 1993‐1‐5:2010 makes use of the '70 %‐rule' for the combination of imperfection modes and amplitudes. This rule postulates that two GMNIA calculations should be conducted when local and global interactive buckling may be dominant; one with 100 % + 70 % of the maximum specified amplitude in either case. In addition, extended information is provided on the choice and combination of imperfections in the newly introduced and currently available draft of the prEN 1993‐1‐14:2020 (design assisted by finite element analysis). Although information is provided on how the local and global imperfections should be combined, it is not stated when it is relevant to consider those. Based on conducted GMNIA simulations on SHS/RHS (square and rectangular hollow sections) and I‐shaped sections, this article presents general decision support on the choice of equivalent imperfections. On the basis of numerical analysis, the developed flow chart and design routine allow for the decision whether the consideration of the interaction of local and global imperfections is required or not. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate results of optical coherence tomography (OCT) with regard to anatomic and functional outcome after scleral buckling surgery (SBS) in macula-off rhegmatogenous retinal detachment (RRD)., Methods: Medical charts of 87 patients (87 eyes), who underwent SBS for macula off RRD were analysed retrospectively. Patients with follow-up ≥ 6 months were included. Exclusion criteria were giant retinal tears, retinal dialysis, chorioretinal dystrophies, proliferative vitreoretinopathy ≥ grade-C1, schisis detachment and vitreous opacities. Reattachment success rate, pre- and postoperative visual acuity (VA) were examined. Postoperative spectral-domain (SD) OCT images were evaluated. The status of photoreceptor inner segment/outer segment (IS/OS) and external limiting memrane (ELM) junction were analysed. Potential risk factors influencing postoperative VA were evaluated by using linear multivariate logistic regression., Results: The primary anatomic success rate was 93.8 % (81 eyes), final success rate was 98.7 % (86 eyes). Preserved ELM (OR 0.58, p = 0.004) and IS/OS integrity (OR 0.84, p = 0.031), drainage of subretinal fluid (OR 0.42, p < 0.0001) were detected as significant independent factors for influencing postoperative VA favourably. Duration of detachment > 6 days (OR 1.46, p = 0.04), two/three retinal breaks (OR 1.30, OR 1.36, 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 (β 0.724, OR 2.06, p < 0.0001)., Conclusion: Severe IS/OS disruption may be the most important predictor of postoperative VA after successful surgery in macula-off rhegmatogenous retinal detachment., (Georg Thieme Verlag KG Stuttgart · New York.)

Background: The purpose of this study is to report the long-term results of a refined scleral buckling technique for the treatment of retinal detachments., Patients/materials and Methods: We retrospectively reviewed the charts of 152 consecutive cases (129 patients), operated in our clinic by one surgeon. Indirect ophthalmoscopy was used for the identification and treatment of retinal breaks. All other steps of the operation were performed under the operating microscope. The main outcome measures were the retinal redetachment rate, intraoperative and postoperative complication rates as well as the functional outcome., Results: Reattachment was achieved in 130 eyes (85.5 %) after the first procedure and in 151 eyes (99.3 %) after reoperation. No intraoperative complications occurred in our series. Eighty-one eyes (53.3 %) showed a significant improvement in visual acuity after surgery, whereas 16 eyes (10.5 %) showed a significant deterioration in visual acuity. At the last follow-up visit, 101 cases (66.4 %) showed a visual acuity of 0.5 or better, 68 cases (44.7 %) had a visual acuity of 0.8 or better and in 7 cases (4.6 %) the visual acuity was lower than 0.1., Conclusions: Adding microsurgical techniques to scleral buckle surgery may help to minimise the incidence of intraoperative and postoperative complications resulting in a favourable functional outcome.

Abstract: General design concept for buckling structures – Suggestion for a new part F of EN 1993‐1‐5. A revised version of EN 1993‐1‐5 should soon be published. The reduced stress method will be reworked in section 10. The complementary regulations published recently in this journal, in particular to the biaxial pressed stiffened steel plate, are partly time‐consuming. In addition to these announced rules a concept with „gradual exactness” with which a low limit value of buckling resistance can be fast determined is applied in the code proposal. A new reduction factor is defined for stiffeners, based on an already published proposal for the geometrical imperfection amplitude. Because of the compatibility to the MNA/LBA concept in EN 1993‐1‐6, the suggestion for a new part F of EN 1993‐1‐5 can be used generally for compound steel structures in future. Examples are given for application of the code proposal. [ABSTRACT FROM AUTHOR]

Background: To present the long-term anatomical and functional results and the dynamics of proliferative vitreoretinopathy (PVR) after precise segmental scleral buckling without drainage, known as extraocular minimal surgery., Patients and Methods: In a prospective study 172 consecutive rhegmatogenous PVR detachments were included which were operated on between January 1994 and February 1996 at the Department of Ophthalmology, Higher Medical Institute, Plovdiv, Bulgaria, with cryopexy and segmental scleral buckling without drainage. The follow-up ranged between 54 and 79 months (xmacr; 5S years). In 43 eyes was a PVR stage A, in 50 stage B, in 60 stage CP, and in 19 a PVR stage CA. All detachments were studied precisely for retinal breaks pre- and intraoperatively and the breaks tamponaded by a precise buckle., Results: 1. Anatomical results: Complete retinal reattachment in 145 eyes (84 %) after 1 operation and in 148 eyes (86 %) after reoperation, residual tractional detachment with reattached macula in 12 eyes (7 %) and detachment due to progression of PVR in 12 eyes (7 %). 2. Functional results: Postoperative visual acuity ranged between 0.3 and 1.0 in 111 eyes after xmacr; 5S years. 3. Dynamics of PVR: In 113 detachments (65,7 %) PVR regressed completely and in 12 (7 %) it progressed; among these were 8 eyes with preoperative PVR-CA and 4 eyes with PVR-CP., Conclusions: Treatment of PVR detachments with nondrainage and minimal buckling provides good anatomical results with macular reattachment in 93 %, resulting in good long-term visual function. Results were best in detachments with PVR stage A, B and CP.

We report a survey among German-speaking vitreo-retinal surgeons, considering their decisive factors and preferred surgical techniques in simple and complicated rhegmatogenous situations. In cases of simple retinal detachment conventional buckling surgery is the favoured surgical approach. Minimal-invasive techniques like the balloon operation or pneumatic retinopexy are chosen by less than 5% of the surgeons. For more complicated retinal detachments a strong trend towards primary vitrectomy becomes apparent. In difficult rhegmatogenous situations which are still treatable with conventional buckling procedures, 45% of surgeons prefer a primary vitrectomy and only 55% chose scleral buckel or encircling band procedures.

Background: Scleral buckling surgery for retinal detachment alters the shape of the globe resulting in changes of the refractive state of the eye., Materials and Methods: In a prospective study of 52 eyes with retinal detachment we examined changes of corneal astigmatism and axial length induced by encircling buckling or segmental buckling spanning two quadrants. We compared our results with those found in literature., Results: In most patients we found a shortening of the globe, rather in cases with encircling buckles than in the cases with segmental buckles (parallelly to the limbus). We also saw changes in astigmatism postoperatively in all patients. There was no statistically significant difference between patients with encircling and segmental buckles fixed parallelly to the limbus, neither in the change of axial length nor in the change of astigmatism., Conclusions: In all cases of scleral buckling procedures changes of corneal astigmatism and axial length are to be expected. So our results differ from those of other authors who did not always find a change of astigmatism. We suppose that the authors of the publications which differ from our results did not consider the change of the corneal axis by using the vector method.

Background: The following questions should be addressed: (1) Is minimal detachment surgery justified in treating detachments with preoperative PVR stage B or C? (2) Can this reattach the retina with stabilization or regression of PVR?, Materials and Methods: 72 PVR detachments stage B or C (38 C1, 11 C2, 1 C3) were treated by cryopexy, segmental buckling (n = 68) or balloon (n = 4) without drainage or vitrectomy. Reoperation (n = 10) was done without cerclage or vitrectomy. The follow-up of patients alive is 11 to 13 1/2 years and of all patients (31 died) x 7 1/2 years., Results: After the primary operation the retina was reattached in 79%, partially in 15% and detached in 6%. An "early" redetachment (< or = 6 months postoperatively) occurred in 8.3%, no redetachment > 6 months to < 9 years and "late" redetachment (9-13 1/2 years postoperatively) in 2.8%. After reoperation (n = 10) the retina was reattached in 85%, partially in 3%, and detached in 12%. 34 eyes had delayed resorption (2 weeks to 18 months) with a residual concave detachment in area of starfolds and tractions, resulting in dry starfolds or their disappearance after months. Postoperatively there were no rubeosis iridis, no secondary glaucoma and no phthisis bulbi. Subsequent macular pucker developed in 12 eyes, which were not treated by vitreoretinal surgery. Six months postoperatively visual acuity was: 26x 20/60-20/25; 16x 20/200-20/100; 30x < or = 20/400 which was not statistically significant different (p = 0.549) after x 7 1/2 years., Conclusion: Primary treatment of a PVR detachment stage B or C1/C2 with cryopexy and segmental buckling and nondrainage seems justified to test for the chance of PVR-regression. The retina was reattached in 8 of 10 patients x 7 1/2 years postoperatively after primary operation without reoperation or vitrectomy and visual acuity was 20/60-20/25 in every third patient, thus implying a lack of late serious complications.

After a brief survey on the indications of the Lincoff buckling technique, the limits of this method are demonstrated by means of varions cases. Then the application of the intraocular gas tamponade with sulfur hexafluoride (SF6) as an additional measure is recommended and described. The combination with vitrectomies in cases of advanced vitreous complications (MPP, proliferations, haemorrhages) is indicated.

The importance of the scleral buckling technique without vitrectomy is discussed with reference to a patient with aphakia, myopia and morning-glory redetachment. In this almost hopeless situation, scleral buckling surgery was performed. The culyx of the periretinal membranes was opened without vitrectomy and in spite of massive vitreous body shrinkage. After surgery the retina attached almost completely and the patient's visual acuity improved from light perception to 0.06. His present condition is illustrated by sketches and photographs of the fundus. The value of the method is emphasized by reference to similar cases. The patient, who also underwent retinal detachment surgery on the fellow eye and had been pensioned, is now following his occupation again.

Experimental investigations on high‐strength CHS for crane‐ and scaffolding construction So far, only a limited amount of experimental results is available for the derivation and verification of design principles for cold‐formed, high‐strength crane and scaffolding tubes up to S960. In this article, the authors present the conduction and results of buckling tests on centrally loaded scaffolding and crane tubes of steel grades up to S960. Measurements of residual stresses as structural imperfections using the sectioning method are discussed on ungalvanized and galvanized CHS in S960. Additionally, the geometric imperfections of the test specimens, which were captured by 3D scanning, are discussed and compared with the approaches of the European buckling curves. The deformations of the test specimens in the buckling tests were recorded using digital image correlation (DIC). The effects of galvanization and the buckling direction on the load‐bearing capacity are highlighted and elucidated. [ABSTRACT FROM AUTHOR]

From January 1963 to December 1989, 1585 consecutive cases of retinal detachment were operated with homologous skin as buckling material, the rate of operative success being 91.6%. Human skin is easy to obtain, sterilize and preserve; because of its appropriate thickness and firm but elastic consistency it satisfactorily meets the need to produce sufficient height and to maintain necessary duration of the scleral buckling; in addition to a high rate of reattachment, homologous skin implantation was well tolerated, very rarely rejected (0.06%) and infected (0.25%), and no late complications occurred. Therefore, the authors prefer using human skin as buckling agent rather than conventional synthetic material, e.g., silicon sponge etc.

In this retrospective study about failures of epiretinal buckling procedures performed over 12 years the causes of failure are analysed. The main ones are: new retinal holes, PVR, wrong localization, and inadequate buckling effect. The aim of this investigation was to find indications of the best technique, with a view to improving the success rate, currently, 80-90%, even further.