Abstract

This paper presents the numerical analysis of reinforced concrete beams with rectangular and T sections and of steel–concrete composite beams subjected to high temperatures. To obtain the numerical results, which refer to the moment x curvature relations for different temperatures, as well as the maximum values achieved for the bending moments, it was used the fibers method or fibers model, with the constitutive relations of materials (concrete and steel) defined by the considerations of the EUROCODE 2 part 1.2 and by the ABNT NBR 15200. From the results obtained, which are compared with the responses of analytical expressions defined by ABNT NBR 6118 and by ABNT NBR 8800, it is possible to identify the residual strength of the structure as the fire exposure time increases and also demonstrate the effective reduction of its rigidity.

Abstract

Although laminated materials have been used for decades, their employment has increased nowadays in the last years as a result of the gained confidence of the industry on these materials. This has provided the scientific community many reasons to dedicate considerable amount of time and efforts to address a better understanding of their mechanical behavior. With this objective both, experimental and numerical simulation have been working together to give response to a variety of problems related with these materials.

Regarding numerical simulation, a correct modeling of the kinematics of laminated materials is essential to capture the real behavior of the structure. Moreover, once the kinematics of the structure has been accurately predicted other non-linear phenomena such as damage and/or plasticity process could be also studied.

In consequence, in order to contribute to the constant development of simpler and more efficient numerical tools to model laminated materials, a numerical method for modeling mode II/III delamination in advanced composite materials using one-and two-dimensional finite elements is proposed inthis work. In addition, two finite elements base on a zigzag theory for simulating higly heterogeneous multilayered beams and plates structures are developed here.

The document is written based on results of four papers published in indexed journals. Copies of all these papers are included in Appendix. The main body of this thesis is constituted by Chapters 2 to 4. Chapter 2 deals with the numerical treatment of laminated beams and plates. Chapter 3 presents the formulation of the LRZ beam and the QLRZ plate finite elements based on the Refined Zigzag theory. Finally, the main contribution of this thesis, the LRZ/QLRZ delamination model, is developed in Chaptert 4.