Analysis and Design of Reinforced Concrete Thin Cylindrical Shell

The need to come up with economical and efficient structural design led the engineers and researchers to focus more on shell structures. It is more durable, economical as it requires a minimum amount of material provides larger interior space and is aesthetic. A shell dominantly behaves as a membrane, though, at the edges, bending stresses get accumulated. Albeit several theories have been put forward, Schorer’s theory is eminent in the analysis of the long span thin cylindrical shells. This study is focused on the analysis of the stresses by utilizing the Fourier series and Schorer’s theory. Further, the shell is designed for the steel reinforcement as per the Concrete Reinforcing Steel Institute (CRSI) Design Handbook after calculating the final stress resultants and the detailing is also depicted.

A research on the stress-strain behaviour of structures made of filled shells

Introduction. The study of the stress-strain state of structures, made of filled shells, remains relevant in terms of interaction between principal structural elements (the shell, the filler, the bed), identification of the optimal combination of shell/filler characteristics, and conditions of their contact. The article addresses the findings of the research on a structural model of a thin cylindrical shell with a filler. Materials and methods. The problem of determining an effective ratio of basic dimensions of a structure is solved in the context of the maximally uniform distribution of forces in a shell with regard for the accepted constraints concerning the conditions of loading, fixing, and describing interaction between the model elements. In addition, the ratio of indicators of mechanical properties of the filler material and the shell is taken into account. The efficiency criterion is determined as a result of evaluating the stress state of a structure, at which forces inside the shell are distributed most evenly and the values of the radial forces are close to the forces directed along the generatrix of a shell. Results. The range of the effective ratio of the main dimensions of a shell is identified with regard for the ratio of the values of the indicator of the stress-strain behaviour of the shell and the filler, which is identified for larger groups of the internal filler, distinguished by the value of indicators of deformation characteristics. The co-authors have identified the ranges of ratios of geometric, rigidity and mechanical parameters of the system, that allow the structure to be attributed to the category of filled shells whose analysis can be performed with the help of applicable provisions of computational modeling. Conclusions. The results of the study allow for the selection of structural parameters based on the pre-set conditions and the criterion of uniformity of distribution of forces in a shell. The study also enables to identify the ratios of the above geometric, rigidity and mechanical parameters at which the structure should be attributed to the category of filled shells or “shells that have a filler” under the pre-set design conditions.

Dynamic Behavior of a Cylindrical Shell with a Liquid under the Action of Nonstationary Pressure Wave

The problem of axisymmetric hydroelastic deformation of a thin cylindrical shell containing a liquid under the action of a moving load is approximately solved. It is reduced to the equation of bending of the shell and the condition of incompressibility of the liquid in the cylinder. The deflections of the shell and the level of lowering of the liquid are unknown. For solution, the Galerkin method is used and the problem is reduced to a system of nonlinear algebraic equations. A simpler solution is considered without taking into account the incompressibility condition. Here, in addition to the deformed state of the shell, the critical speeds of the moving load are determined analytically.

A Nondestructive Technique for the Evaluation of Thin Cylindrical Shells' Axial Buckling Capacity

The axial buckling capacity of a thin cylindrical shell depends on the shape and the size of the imperfections that are present in it. Therefore, the prediction of the shells buckling capacity is difficult, expensive, and time consuming, if not impossible, because the prediction requires a priori knowledge about the imperfections. As a result, thin cylindrical shells are designed conservatively using the knockdown factor approach that accommodates the uncertainties associated with the imperfections that are present in the shells; almost all the design codes follow this approach explicitly or implicitly. A novel procedure is proposed for the accurate prediction of the axial buckling capacity of thin cylindrical shells without measuring the imperfections and is based on the probing of the axially loaded shells. Computational and experimental implementation of the procedure yields accurate results when the probing is done in location of highest imperfection amplitude. However, the procedure overpredicts the capacity when the probing is done away from that point. This study demonstrates the crucial role played by the probing location and shows that the prediction of imperfect cylinders is possible if the probing is done at the proper location.

Structural model updating study in consideration of complex pre-stress distribution

In the present work, to improve the accuracy of the numerical model, the structural model updating problem is investigated in consideration of the influence of pre-stress. In order to eliminate the influence of complex pre-stress on the calculation scale and calculation precision for the continuous structures, the structural dynamic model updating is implemented by using the structural optimization strategy. The optimization function is established, in which the residual value of natural frequency parameter between the finite element model with/without complex pre-stress distribution is defined as objective function under certain constraints. Finally, the thin cylindrical shell structure with welding residual stress distribution, for example, the structural model updating is carried out, and the numerical results verify the feasibility and effectiveness of the proposed method.

An Interactive Method to Analysis of the Response of the Different Reinforcement Structures of a Door Opening of a Wind Tower

The aim of this work is to present a precise numerical calculus method capable to predict the behavior of a wind turbine mast, which is characterized by an open door in its lower part in order to facilitate the access to maintenance tasks. A parametric study had been conducted in this context. The structure studied of steel tower is considered a thin cylindrical shell with constant section and thickness along its studied height. The geometry of the tower had been modeled by non-linear shell type elements. Designers use interior reinforcements to avoid local buckling and minimize the disturbance of the distribution of stress in extreme conditions. The designs adopted in the models are proposed to achieve optimized results, the minimization of the mass, the maximization of the natural frequency and the rigidity at the end of the work. Many configuration had been considered in this study, the enhancement of the gap by using a panel with variable thickness value, by longitudinal stiffeners, by combined stiffeners and finally by a stiffened panel. A numerical model had been suggested to examine a cylindrical shell behavior in compression using the Abaqus software. The obtained results demonstrate the viability and performance of the proposed approach which perfectly meets the structural requirements of the wind tower. We have observed that the stiff plate model gives reliable results to stability under extreme load. On the other hand it is economically profitable is less material needed for manufacturing, which reduces the cost.

Application of Corrugated Core Sandwich Structures in Thin Cylindrical Pressure Vessels

the need for the high strength to weight structures is increasing day by day. The structures with high strength to weight ratio helps in reducing the costs in transport of materials. The sandwich structures are being developed to meet this criterion. A sandwich structure consists of two flat sheets with core between them. The material of core and outer flat surfaces may or may not be the same depending upon the application of the structure. In this project, the corrugated core sandwich structure will be used for the cylindrical shell of the pressure vessels. Pressure vessel with corrugated core sandwich structures will be designed and various analyses will be performed. The results will be compared with thin cylindrical shell pressure vessel under similar conditions. The pressure vessels will be designed in solidworks software and structural analysis will be performed in ansys workbench.