BUCKLING AND POST-BUCKLING OF ISOTROPIC AND COMPOSITE STIFFENED PANELS: A REVIEW ON ANALYSIS AND EXPERIMENT (2000-2012)

Stiffened panels made out of isotropic or anisotropic materials are being extensively used as structural elements for aircraft, maritime, and other structures. In order to maintain stiffness and strength with light weight, new design techniques must be employed when utilising these materials. Their stability, ultimate strength and loading capacity are the key issues pertaining to these engineering structures which have attracted a number of investigators to undertake in- depth research, either in an academic or actual engineering context. This paper provides an extensive review of the research which has been conducted in recent years (2000-2012) on the buckling and post-buckling response of isotropic and composite stiffened plate and shell structures related to analysis and experiment. The key objective of this review article is to collate the research performed in the area of buckling and post-buckling behaviour of stiffened structures, thereby giving a broad perspective of the state-of-the-art in this field.

Study on Dynamic Snap-Through and Nonlinear Vibrations of an Energy Harvester Based on an Asymmetric Bistable Composite Laminated Shell

Bistable energy harvesters have been extensively studied. However, theoretical research on the dynamics of bistable energy harvesters based on asymmetric bistable composite laminated plate and shell structures has not been conducted. In this paper, a theoretical model on the dynamics of an energy harvester based on an asymmetric bistable composite laminated shell is established. The dynamic snap-through, the nonlinear vibrations and the voltage output with two potential wells of the bistable energy harvester are studied. The influence of the amplitude and the frequency for the base excitation on the bistable energy harvester is studied. When the frequency for the base excitation with a suitable amplitude in the frequency sweeping is located in a specific range or the amplitude for the base excitation with a suitable frequency in the amplitude sweeping is located in a specific range, the large-amplitude dynamic snap-through, nonlinear vibrations and voltage output with two potential wells can be found to occur. The amplitude and the frequency for the base excitation interact on each other for the specific amplitude or frequency range which migrates due to the softening nonlinearity. The vibration in the process of the dynamic snap-through behaves as the chaotic vibration. The nonlinear vibrations of the bistable system behave as the periodic vibration, the quasi-periodic vibration and the chaotic vibration. This study provides a theoretical reference for the design of energy harvesters based on asymmetric bistable composite laminated plate and shell structures.

Research on the Layout Optimization of Acoustic Radiation Power Flow Reinforcement Based on Weight-Guide method

In order to reduce the noise radiation of the plate and shell structure, the Weight-Guide method is used to optimize the layout of stiffeners for acoustic radiation power flow. Firstly, Rayleigh integral method and Helmholtz equation are used to derive the acoustic radiation power flow, and the sensitivity is calculated by using explicit approximation technique, which takes the acoustic power flow as the objective function. Secondly, the guide weight method is used to update the design variables to optimize the layout of stiffeners and change the shape of the vibration structure, so as to transform the structure into a weak radiator to reduce the radiated sound power. Finally, the optimized structure can optimize the frequency of the partial frequency band reduction by the analysis of numerical examples, and at the same time, the full band optimization of the sound power spectrum can be achieved by changing the number and position of the peaks.

Performance Based Analysis of Shear Wall with Flexible Soil Base

Shear wall is usually modeled with different types of elements with fixed base to tolerate lateral load. Membrane, plate and shell elements are chosen to model shear wall without reinforcement. In the present study an attempt is made on a 3D, 10 storey building with flexible soil base. The building is analyzed with and without shear wall. The shear wall is provided at all four corners throughout the height of the building. The building is resting on flexible soil base and analyzed for nonlinear analysis. The shear wall is modeled with different elements and different number of layer section (i.e., concrete and steel layers). Shear wall is modeled separately with membrane, plate and shell elements. In addition to this combination of elements is also tried to model shear wall. The combination to model shear wall chosen is plate and membrane element with variation in number of concrete and steel layers. This study is helpful to predict response of shear wall provided with various elements. It gives us idea as to model shear wall with elements separately or in combination. The behavior of shear wall modeled with variation in concrete and steel layers is also predicted.

Shape-Sensing of Beam Elements Undergoing Material Nonlinearities

The use of in situ strain measurements to reconstruct the deformed shape of structures is a key technology for real-time monitoring. A particularly promising, versatile and computationally efficient method is the inverse finite element method (iFEM), which can be used to reconstruct the displacement field of beam elements, plate and shell structures from some discrete strain measurements. The iFEM does not require the knowledge of the material properties. Nevertheless, it has always been applied to structures with linear material constitutive behavior. In the present work, advances are proposed to use the method also for concrete structures in civil engineering field such as bridges normally characterized by material nonlinearities due to the behavior of both steel and concrete. The effectiveness of iFEM, for simply supported reinforced concrete beam and continuous beams with load conditions that determine the yielding of reinforcing steel, is studied. In order to assess the influence on displacements and strains reconstructions, different measurement stations and mesh configurations are considered. Hybrid procedures employing iFEM analysis supported by bending moment-curvature relationship are proposed in case of lack of input data in plastic zones. The reliability of the results obtained is tested and commented on to highlight the effectiveness of the approach.