Concrete structures analysis under the time effects: an efficient and accurate approach qhich takes into account the viscoelasticity, the plasticity, the cracking, the prestressing and constructions by stages.

Author(s)

Hudson Chagas dos Santos

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2006-05-25

Examining board members

Paulo de Mattos Pimenta; Roberto Chust Carvalho; Guillermo Juan Creus; João Carlos Della Bella; Ricardo Leopoldo e Silva França

• Advisor: Paulo de Mattos Pimenta

Abstract

In this work, an efficient and accurate methodology to analyze the effects of time in concrete structures is presented. This methodology is based on the Finite Elements Method (FEM), and it is shown how to perform the finite element analysis on concrete framed structures taking into account the viscoelasticity phenomenon in the formulation of the constitutive equation. The solution for such problem, called quasi-static incremental analysis, may be resolved by establishing the stresses, displacements and deformations fields at specific time from their known values on the previous moment. In this work, the incremental analysis is performed by using an algorithm of stresses integration written into a computational procedure based on the FEM. The Creep Function used in this work, besides being very efficient according to the methodology based on the MEF, it may be, easily, adjusted to any real experiment data or to any creep function presented on codes. Another important characteristic is that such creep function does not demand the computational storage of all the history of stresses variables in a specified time, resulting in an effortless analysis and back-analysis of concrete framed structures. Needless to write that some discussions and judgments against the creep function presented on the NBR-6118:2003 will be performed in order to justify the efficiency of the creep function proposed. Another consistent methodology for the analysis of a fully nonlinear sliding cable element with friction is also presented. It is discussed an accurate geometrically nonlinear formulation and the computational implementation of cable elements based on FEM that incorporates sliding with friction in a simple manner. The cable element may furnish natural procedures to simulate the process of construction assembly, and the results of time-dependent loads on such structures. Furthermore, the presented methodology has promising fields of application in modeling pre-stressed concrete, tensioned cables structures, membranes, stayed and suspended bridges. Along the text, it is presented some examples analysis in order to verify the methodology efficiency. (AU)