Working Stresses for Columns and Thin-Walled Structures

1933 ◽  
Vol 1 (4) ◽  
pp. 173-177
Author(s):  
S. Timoshenko
Keyword(s):  
Mechanical Properties ◽  
Elastic Stability ◽  
Structural Elements ◽  
Metallic Structures ◽  
Thin Walled Structures ◽  
Thin Walled

Abstract In metallic structures such as airplanes, airships, ships, bridges, etc. slender bars, thin webs, and thin-walled tubular members are very often used. In choosing working stresses for such structural elements, not only the mechanical properties of the material but also the elastic stability of these elements should be considered. The method of choosing working stresses for such structures is illustrated in this paper by several examples.

Modeling the Varying Dynamics of Thin-Walled Aerospace Structures for Fixture Design Using Genetic Algorithms

2011 ◽  
Vol 223 ◽  
pp. 652-661
Author(s):  
Mouhab Meshreki ◽  
Helmi Attia ◽  
József Kövecses
Keyword(s):  
Numerical Models ◽  
Research Work ◽  
Computational Effort ◽  
Computational Time ◽  
Fixture Design ◽  
Structural Elements ◽  
Thin Walled Structures ◽  
Thin Walled ◽  
High Flexibility ◽  
High Level

Fixture design for milling of aerospace thin-walled structures is a challenging process due to the high flexibility of the structure and the nonlinear interaction between the forces and the system dynamics. At the same time, the industry is aiming at achieving tight tolerances while maintaining a high level of productivity. Numerical models based on FEM have been developed to simulate the dynamics of thin-walled structures and the effect of the fixture layout. These models require an extensive computational effort, which makes their use for optimization very unpractical. In this research work, a new concept is introduced by using a multi-span plate with torsional and translational springs to simulate the varying dynamics of thin-walled structure during machining. A formulation, based on holonomic constraints, was developed and implemented to take into account the effect of rigid fixture supports. The developed model, which reduces the computational time by one to two orders of magnitude as compared to FE models, is used to predict the dynamic response of complex aerospace structural elements including pockets and ribs while taking into account different fixture layouts. The model predictions are validated numerically. The developed model meets the conflicting requirements of prediction accuracy and computational efficiency.

The FITNET Fracture Module: Developments and Content

2005 ◽  
Author(s):  
Stephen Webster
Keyword(s):  
European Commission ◽  
European Countries ◽  
Technical Development ◽  
Framework Programme ◽  
Metallic Structures ◽  
British Standard ◽  
Thin Walled Structures ◽  
The Usa ◽  
Thin Walled

FITNET is a four-year European thematic network with the objective of developing and extending the use of fitness-for-service (FFS) procedures for welded and non-welded metallic structures throughout Europe. It is partly funded by the European Commission within the fifth framework programme and commenced in February 2002. The network currently consists of about 50 organisations from 17 European countries but also includes contributions from organisations in the USA, Japan and Korea. Further information can be found in the FITNET TN website: http://www.eurofitnet.org. The FITNET FFS Procedure is built up in four major analysis modules namely; Fracture, Fatigue, Creep and Corrosion and the procedure is being developed for completion in early 2006 in the form of CEN Document. The aim of this paper is to present the features, main analysis routes and major areas of technical development pertinent to the Fracture Module of the FITNET FFS Procedure. The procedure is based on previous developments carried out within the SINTAP project as well as advances in other standards such as the British Energy R6 rev 4 and the current amendments to the British Standard BS7910. In addition the work from other EU projects has been used to extend the treatment of several problem areas, such as the effect of constraint and the treatment of thin walled structures.

scholarly journals CREEP OF REINFORCED CONCRETE THIN-WALLED STRUCTURES TAKING INTO ACCOUNT REVERSE DEFORMATIONS

2020 ◽  
Vol 6 (159) ◽  
pp. 113-117
Author(s):  
O. Chuprynin ◽  
N. Sereda ◽  
A. Garbuz
Keyword(s):  
Reinforced Concrete ◽  
Material Properties ◽  
Concrete Structures ◽  
Design Stage ◽  
Reinforced Concrete Structures ◽  
Nonlinear Creep ◽  
Structural Elements ◽  
Thin Walled Structures ◽  
Proposed Model ◽  
Thin Walled

One of the main tasks, which is solved at the design stage of the reinforced concrete element, is the analysis of the stress-strain state, as well as the determination of the service life. The article is devoted to modeling of nonlinear creep of reinforced concrete structural elements taking into account damages and return of the creep. The high priority of the research topic is substantiated, the purpose and objectives are formulated. A combination of a plastic model with fracture mechanics is proposed to simulate the behavior of concrete in accordance with its characteristics, including not only stress and deformation, but also the degradation of its stiffness. The resulting equations of state correspond to the law reverse deformations. The finite element method is used to solve the boundary value problem. For the sake of numerical modeling of thin-walled structures, the use of special shell elements is proposed. The mathematical formulation of the problem of creep of reinforced concrete structural elements taking into account anisotropy of material properties and creep deformations and return of the creep is presented. Creep problems of thin-walled structural elements were solved with the help of developed software. Analyzed the deformation of reinforced concrete panel of cylinder. The analysis of the results allows us to judge the effectiveness of the proposed model as a whole. The equation of state reflects the anisotropy of the material properties and takes into account the damage, which allows for a reliable assessment of the strength, stiffness and durability of reinforced concrete structures. Conclusions about the adequacy of the analysis of reliability and durability of reinforced concrete structures using the proposed model.

scholarly journals Numerical study of nonlinear problems in the dynamics of thin-walled structural elements

2021 ◽  
Vol 264 ◽  
pp. 05056
Author(s):  
Olim Kucharov ◽  
Fozil Turaev ◽  
Sergey Leonov ◽  
Kholida Komilova
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Nonlinear Problems ◽  
Rheological Parameters ◽  
Structural Elements ◽  
Critical Rate ◽  
Thin Walled Structures ◽  
Weakly Singular ◽  
Singular Kernels ◽  
Thin Walled

Mathematical model of the problem of vibration of thin-walled structural elements has been constructed based on Kirchhoff-Love theory. The problem is reduced, using the Bubnov-Galerkin method, to the solution of a set of nonlinear integro-differential Volterra type equations with weakly-singular kernels of relaxation. A numerical method based on the use of quadrature formulae being used for their solution. The influence of rheological parameters of the material on the values of critical velocity and amplitude-frequency characteristics of viscoelastic thin-walled structural elements is analyzed. It is shown that tacking account viscoelastic properties of the material of thin-walled structures lead to a decrease in the critical rate of gas flow.

Application of Prestressed CFRP Textiles for the Development of Thin- Walled Concrete Structural Elements

2019 ◽  
Author(s):  
Juan Pablo Osman Letelier ◽  
Alex Hückler ◽  
Mike Schlaich
Keyword(s):  
Prestressed Concrete ◽  
High Strength ◽  
Experimental Tests ◽  
Sustainable Construction ◽  
Structural Elements ◽  
Prestressing Steel ◽  
Thin Walled Structures ◽  
Reinforced Polymer ◽  
Thin Walled ◽  
Doubly Curved

<p>The success story of prestressed concrete is based on the utilization of high‐strength prestressing steel which enables large compressive forces to be introduced into the concrete. However, thin‐walled concrete structures often require considerable thicknesses for the sole purpose of preventing corrosion of the steel elements. In this paper the use of prestressed Carbon Fiber Reinforced Polymer (CFRP) for the development of thin‐walled concrete structural elements is briefly presented. The transition of material to stronger, lighter and corrosion‐resistant CFRP represents a significant improvement in concrete construction. Prestressing with CFRP elements leads to more slender and thereby more economical and durable structural elements. Through the additional prestressing of a reinforcement mesh, very light and highly rigid surface structures can be constructed. Prestressing technologies have been developed and adapted for specific applications i.e. slabs and doubly curved structural elements and validated by experimental tests. This paper shows that prestressed carbon reinforced concrete can be used for more durable and efficient thin‐walled structures, allowing for more sustainable construction.</p>

Dynamic Post-Buckling Behavior of Thin-Walled Structures With Flexible Knife-Edge Supports

1993 ◽  
Vol 46 (11S) ◽  
pp. S148-S155 ◽  
Author(s):  
M. A. Souza
Keyword(s):  
Boundary Condition ◽  
Lateral Displacement ◽  
Compressive Load ◽  
Elastic Stability ◽  
Knife Edge ◽  
Loading Process ◽  
Thin Walled Structures ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Thin Walled

The paper discusses the influence that changes of the simply supported boundary condition during the loading process have on the dynamic post-buckling behavior of elastic thin-walled structures. Of special interest is the knife-edge type of support which is associated to the free-to-rotate boundary condition. The results presented show how changes of the free-to-rotate condition during the loading process can dramatically alter the response of thin-walled structures. This fact is highlighted by the equilibrium paths and the characteristic curves presented. The former relate the applied compressive load and the lateral displacement, whereas, the latter relate the compressive load and the square of the corresponding natural frequency of vibration. The importance of an adquate design of the supports is stressed in view of the observed dramatic changes. The work is done in the scope of the elastic stability and damping is not included in the analysis.

Frame-Monolithic Technology of Construction of Low-Rise Buildings Made of Foam Gypsum and Steel Thin-Walled Structures

2018 ◽  
Vol 762 (8) ◽  
pp. 36-39 ◽  
Author(s):  
B.G. BULATOV ◽  
◽  
R.I. SHIGAPOV ◽  
M.A. IVLEV ◽  
I.V. NEDOSEKO ◽  
...  
Keyword(s):  
Thin Walled Structures ◽  
Thin Walled
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