A Unified Approach to the Timoshenko Geometric Stiffness Matrix Considering Higher-Order Terms in the Strain Tensor

• Published in: Latin American Journal of Solids and Structures Vol. 16; no. 4
• Main Authors: Rodrigues, Marcos Antonio Campos, Burgos, Rodrigo Bird, Martha, Luiz Fernando
• Format: Journal Article
• Language: English
• Published: Latin American Journal of Solids and Structures 01.01.2019; Associação Brasileira de Ciências Mecânicas
• Subjects: Analysis; Differential equations; ENGINEERING, CIVIL; ENGINEERING, MECHANICAL; MECHANICS; Iran; Brazil; Shape Functions; Geometric Matrix; Higher-Order Terms in Strain Tensor; Timoshenko Beam Theory
• ISSN: 1679-7817; 1679-7825; 1679-7825
• DOI: 10.1590/1679-78255273

Nonlinear analyses using an updated Lagrangian formulation considering the Euler-Bernoulli beam theory have been developed with consistency in the literature, with different geometric matrices depending on the nonlinear displacement parts considered in the strain tensor. When performing this type of analysis using the Timoshenko beam theory, in general, the stiffness and the geometric matrices present additional degrees of freedom. This work presents a unified approach for the development of a geometric matrix employing the Timoshenko beam theory and considering higher-order terms in the strain tensor. This matrix is obtained using shape functions calculated directly from the solution of the differential equation of the problem. The matrix is implemented in the Ftool software, and its results are compared against several matrices found in the literature, with or without higher-order terms in the strain tensor, as well as the Euler-Bernoulli or Timoshenko beam theories. Examples show that the use of the Timoshenko beam theory has a strong influence, especially when the structure has small slenderness (short members). For high axial load values, the consideration of higher-order terms in the strain tensor results in larger displacements as expected.