Nonlinear Analysis of Reinforced Concrete Shear Walls Using Nonlinear Layered Shell Approach

This study discusses nonlinear modelling of a reinforced concrete wall utilizing the nonlinear layered shell approach. Rebar, unconfined and confined concrete behaviours are defined nonlinearly using proposed analytical models in the literature. Then, finite element model is validated using experimental results. It is shown that the nonlinear layered shell approach is capable of estimating wall response (i.e., stiffness, ultimate strength, and cracking pattern) with adequate accuracy and low computational effort. Modal analysis is conducted to evaluate the inherent characteristics of the wall to choose a logical loading pattern for the nonlinear static analysis. Moreover, pushover analysis’ outputs are interpreted comprehensibly from cracking of the concrete until reaching the rupture step by step.

Multi-Pass Welding Distortion Analysis Using Layered Shell Elements Based on Inherent Strain

In this article, a layered shell element-based, elastic finite element method for predicting welding distortion in multi-pass welding is developed. The welding distortion generated in each pass can be predicted by employing layer-by-layer equivalent plastic strains as thermal expansion coefficients and using the heat-affected zone (HAZ) width as the mesh size. The final distortion can be expressed as the sum of the distortions for each pass. This study focuses on extraction of the equivalent plastic strain and HAZ width through 3D thermal elastic plastic analysis (TEPA) for each pass. The input variables extracted from each pass can be converted and added to simulate the final distortion of the multi-pass welding. A 10 mm thick, multi-pass butt-welded joint, subjected to three passes, is simulated via the proposed method. The predicted welding distortion is compared with the 3D TEPA results and the measured experimental data. The outcome indicates that good agreement can be obtained.

Optimized Design for Illusion Device by Genetic Algorithm

The optimized design for the illusion device is studied based on the genetic algorithm. For an electrically small target, a core-shell illusion device by optimizing the material and geometrical parameters of the covering shell can achieve the equivalent scattering, in which the monopolar and dipolar modes are dominant. With the increase of the device size, more scattering terms become obvious, and the ability of the single-layered shell to manipulate the scattering is very limited. For a target with dimension compared with the wavelength, we construct a concentric multi-layered device made of isotropic and homogeneous materials. The full-wave simulations are carried out to demonstrate the illusion performance of the optimized multilayer. The physical explanation is given that all scattering modes of the multi-layered illusion device after optimization approach to that of the target.

The Manufacturer’s Deliberate Modification of the Shell Structure of the BellaGel® SmoothFine in Violation of the Regulatory Requirement

The BellaGel® SmoothFine (HansBiomed Co. Ltd., Seoul, Korea) is the only fifth-generation of a silicone gel-filled breast implant from a Korean manufacturer. The BellaGel® SmoothFine with a 5-layered shell structure was approved for clinical use, but the manufacturer deliberately modified the shell structure in violation of the regulatory requirement of the Korean Ministry of Food and Drug Safety. This was hidden by both plastic surgeons and the manufacturer. With the use of high-resolution ultrasound, however, we confirmed that both 4-layered and 5-layered devices were circulated in the Korean market. Further investigations are warranted to disclose a relationship between plastic surgeons and the manufacturer.

Numerical Simulation and Parametric Analysis of Precast Concrete Beam-Slab Assembly Based on Layered Shell Elements

Precast concrete (PC) plays an important role in the industrialization processes of buildings, so it is critical to study the seismic performance of such structures. Several experimental and numerical studies have been conducted to investigate the behavior of PC beam-to-column connections. However, most of the previous studies neglect the contribution of slabs. In light of this, this paper presents a numerical simulation method for dry connected beam-slab assemblies based on the layered shell element available in OpenSees. The beams were modeled with fiber elements, while the slabs were modeled with layered shell elements. The developed model was validated by simulating a typical beam-slab assembly test, with the characteristics of hysteretic performance found to be well reflected by the model. Moreover, a parametric study was performed to quantify the influence of slab parameters. The results showed that the thickness of the slab had a significant effect on the hysteretic performance of the specimen and that the influence of the slab width was obviously reduced after it exceeded a certain limit. Besides, the effect of the reinforcement ratio on stiffness and loadbearing capacity was not obvious and was accompanied by a slight positive correlation with the energy dissipation capacity.

Adaptive Powell’s Identification of Elastic Constants of Composite Glass Girder with Layered Shell Element Theory

For the composite glass box girder, the generalized Bayesian objective function of elastic constants of the structure was derived based on layered shell element theory. Mechanical performances of the composite glass box girder were solved by layered shell element method. Combined with quadratic parabolic interpolation search scheme of optimized step length, the adaptive Powell’s optimization theory was taken to complete the stochastic identification of elastic constants of composite glass box girder. Then the adaptive Powell’s identification steps of elastic constants of the structure were presented in detail and the adaptive Powell’s identification procedure was accomplished. From some classic examples, it is finally achieved that the adaptive Powell’s identification of elastic constants of composite glass box girder has perfect convergence and numerical stability, which testifies that the adaptive Powell’s identification theory of elastic constants of composite glass box girder is correct and reliable. The stochastic characteristics of systematic responses and elastic constants are well deliberated in generalized Bayesian objective function. And in iterative processes, the adaptive Powell’s identification is irrelevant with the complicated partial differentiation of the systematic responses from the layered shell element model to the elastic constants, which proves high computation efficiency.