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Purpose: To compare the efficacy of peribulbar bupivacaine with routine analgesics for pain management in patients undergoing scleral buckling., Methods: In total, 72 patients undergoing scleral buckling or combined with vitrectomy were enrolled in this study. Patients were randomized into two groups, each containing 36 patients. Patients of group A received 5 mL of bupivacaine (0.5%) injection at the end of surgery, whereas group B patients received routine analgesics. The postoperative pain score was assessed in the first 24 hours of the postoperative period with the visual pain analog score., Results: Maximum postoperative pain scores were lower in patients receiving bupivacaine block (median: 3; range: 3-7) than in the control group (median: 5; range: 3-9). Pain scores in group A were lower than in the control group both at 3 and 6 hours after surgery, which was statistically significant ( P < 0.001). Four patients in group A and 17 patients in group B needed additional analgesia in the first 24 hours of the postoperative period. In addition, two patients in group A and seven patients in group B experienced episodes of nausea and vomiting in the first 24 hours of surgery., Conclusion: The results of this study suggest that the postoperative experience of patients undergoing scleral buckling surgery can be made more comfortable with the use of bupivacaine block at the end of surgery., (Copyright © 2024 Copyright: © 2024 Indian Journal of Ophthalmology.)

The collapsible tubular mast (CTM) can be compactly folded for transport and deployed in orbit to serve as a key structural element. Once deployed, the CTM is vulnerable to buckling under axial load and bending moments, compromising its load-bearing capacity. The intricate relationship between the CTM's cross-section and its buckling behavior poses a significant challenge for designers. This is due to the ultra-thin nature of the CTM, which gives rise to highly localized buckling modes rather than global ones. To overcome this challenge, we developed surrogate models using a neural network (NN) trained with data from finite element analysis (FEA). These NN-based surrogate models provide high computational accuracy in predicting nonlinear buckling loads under axial force and bending moments around the two principal axes of the CTM's cross-section, achieving R 2 values of 0.9906 , 0.9987 , and 0.9628 , respectively. These models also significantly improve computational efficiency, reducing prediction time to a fraction of a second compared to several minutes with FEA. Furthermore, the NN-based surrogate models enable the usage of the non-dominated sorting genetic algorithm (NSGA-II) for multi-objective optimization (MOO) of the CTMs. These models can be integrated in the NSGA-II algorithm to evaluate the objective function of existing and new individuals until a set of 1000 non-dominated solutions, i.e., cross-sectional configurations optimizing buckling performance, is identified. The proposed approach enables the design of ultra-thin CTMs with optimized stability and structural integrity by promoting design decisions based on the quantitative information provided by the NN-based surrogate models. [ABSTRACT FROM AUTHOR]

The buckling curves, which enable the prediction of buckling resistance of steel structural elements, are physically connected with their type of cross-section, initial out-of-straightness, and the magnitude of residual stresses due to the different manufacturing technologies. It is known that hot-dip galvanisation changes and relives residual stresses, but so far the current design provisions do not take directly into account the impact of hot-dip galvanising on the reduction of residual stresses, and thus the reduction the generalised imperfection in the Ayrton-Perry model. The paper presents the difference between the relative buckling resistance of steel angles with residual stresses resulting from hot rolling and the same elements in which the magnitude of residual stresses was decreased by the hot-dip galvanising process. Carried out tests and geometrically and materially non-linear analyses with imperfections (GMNIA) have shown that angles with residual stresses reduced by heat treatment caused by hot-dip galvanising have higher buckling resistance compared to those with residual stresses after hot rolling. This increase ranges from 2 to 7%. The analyses carried out confirmed that the predicted reduction factors  exhibit values closer to the buckling curve ‘a’, but these values do not reach the ‘a0’ curve recommended by the EN 50341-1 standard.

The present study develops a new finite element (FE) formulation for the lateral torsional buckling (LTB) analyses of steel beams exteriorly bonded with orthotropic fiber-reinforced polymer (FRP) layers. The formulation considers shear deformations, partial material interaction, local and global warping deformations, and orthotropic FRP properties. The buckling responses of multispan FRP-bonded steel beams predicted by the present solutions are excellently validated against experiment and numerical solutions. As observed, the FRP strengthening is highly effective for the LTB resistance of steel beams. However, the LTB responses are strongly dependent on the orthotropic properties and strengthening lengths of FRP layers. The effects of shear deformations, span ratios, and loading conditions on the LTB responses are also quantified in the present study.

Abstract Automated fiber placement (AFP) enables the efficient and precise fabrication of complex-shaped aerospace composite structures with lightweight and high-performance properties. However, due to the excessive compression on the inner edge of the tow placed along the curved trajectory, the resulting defects represented by buckling and wrinkles in spatial tow steering can induce poor manufacturing accuracy and quality degradation of products. In this paper, a theoretical model of tow buckling based on the first-order shear deformation laminate theory, linear elastic adhesion interface and Hertz compaction contact theory is proposed to analyze the formation mechanism of the wrinkles and predict the formation of defects by solving the critical radius of the trajectory, and finite element analysis involving the cohesive zone modeling (CZM) is innovated to simulate the local buckling state of the steered tow in AFP. Additionally, numerical parametric studies and experimental results indicate that mechanical properties and geometric parameters of the prepreg, the curvature of the placement trajectory and critical process parameters have a significant impact on buckling formation, and optimization of process parameters can achieve effective suppression of placement defects. This research proposes a theoretical modeling method for tow buckling, and conducts in-depth research on defect formation and suppression methods based on finite element simulation and placement experiments.

Abstract To improve the energy dissipation and self-resetting ability of bridge structures under strong earthquakes, a new buckling-restrained SMA bar-based friction damper (SFD) is proposed. The damper is composed of buckling-restrained super-elastic SMA bars, friction pads, and a steel frame. The buckling-restrained SMA bars provide self-reset capability, while the friction pads provide additional energy dissipation capacity. Firstly, the configuration, working mechanism, and restoring force model of the SMA bar-based friction damper are introduced. Secondly, a specimen of the damper is made, and the pseudo-static test is carried out. Finally, the experimental results are analyzed based on the Abaqus finite element model. The results indicate that the damper has better self-resetting ability and energy dissipation capacity.

This research studies the first part of the failure of a compression member structure due to buckling. This unstable equilibrium collapse, exposes brittle failure which occurs suddenly and therefore should be avoided wherever possible. Unavoidable geometric imperfections due to structural fabrication, will weaken the structure against buckling. The behavior of bar under compression will be closely examined by taking a set of geometric imperfection data synthesized from previously available from the measurement of conical shells. Therefore, the two-dimensional surface imperfection is converted into several one-dimensional imperfection with some probability properties. In order to obtain a comparison tool for different type of imperfections, Fourier analysis is used to convert the imperfection into coefficients of trigonometric function. By examining the coefficients, geometric imperfection patterns introduced by a certain fabrication process are able to be identified. The study successfully demonstrates the applicability of Fourier analysis in representing inherent geometric imperfections as an initial step for conducting probabilistic buckling analysis. Fourier analysis has shown its capability to simultaneously characterize imperfections in two crucial parameters - the magnitude and configuration of the imperfection.

The research focuses on examining the impact of technological defects, specifically "dry-spot" and "wrinkles," on the mechanical behavior and buckling resistance of structural composites. The investigation of the buckling phenomenon was carried out through a compression test on a thin plate fabricated from carbon-fiber-reinforced polymer (CFRP) laminate. This test was performed using a specialized fixture designed in accordance with ASTM 3410 standard. For the analysis, the study employed a three-dimensional digital optical system, Vic-3D, in conjunction with the AMSY-6 acoustic emission system. The research showcases findings from acoustic emission signals that verify the shear-based mechanism of buckling in plates constructed from CFRP featuring "dry-spot" type defects. In the case of "wrinkles" defects, it was observed that transverse shear transpires at the stress concentration points created by the "excess" layers.