Rodrigo Barreto Caldas

Influence of Surface Area and Geometry of Specimens on Bond Strength in a Microtensile Test: An Analysis by the Three-Dimensional Finite Element Method

PURPOSE This study employed three-dimensional (3D) finite element analysis to investigate the stress distribution patterns in a microtensile test with the goal of evaluating the effects of the bond surface area and geometry on bond strength. MATERIALS AND METHODS Finite element models of six specimens were generated: three stick models and three hourglass models. All models simulated the bond strength between dentin and ceramic. The mechanical properties of the materials-the modulus of elasticity and Poissons coefficient-were defined according to a literature review. The base of each specimen was considered inserted (constrained area) and possessed nodes with displacements restricted in all directions. A traction load, which was calculated to generate a uniformly distributed stress of 20 N/mm(2) at the bond interface, was applied to the top of the specimen. The distribution pattern of the generated stress was qualitatively and quantitatively measured based on color scales ranging from blue to red, according to the von Mises equivalent stress. RESULTS Specimens with similar shapes demonstrated similar stress distributions. Ceramic specimens had a higher stress value (30.35 MPa) compared to specimens consisting of resinous cement (23.59 MPa) and dentin (19.77 MPa). At the bond interface, the specimens with square sections demonstrated stress values ranging from 22.00 to 24.20 MPa. For the circular section, the stress values ranged from 23.40 to 27.00 MPa. CONCLUSION The maximum stress values determined for the circular and square sections were similar among specimens with the same interface area. At the bond interface, the highest stress values were observed in hourglass-shaped specimens.

Finite element implementation for the analysis of 3D steel and composite frames subjected to fire

This paper presents a finite element formulation for the numerical analysis of three-dimensional framed steel, reinforced concrete or composite steel and concrete structures subjected to fire. Several specialized and commercial programs may be used for the analysis of structures in fire condition. Within this context, the purpose of this work is to present the steps taken to extend a previously developed static analysis procedure with beam elements in order to cope with the thermal and structural analysis of structures under fire action. Physical nonlinearity and material property degradation considering the temperature distribution are taken into account at the cross section level, which is divided into quadrilateral or triangular finite elements. Thermal strains are considered through the effective strain concept, and the resulting nonlinear system of equations is solved by the Newton-Raphson scheme. The accuracy and capability of the formulation to simulate the behavior of framed structures under fire action are assessed through comparison with various numerical and experimental results.

MÉTODO DE ENSAIO DE CISALHAMENTO UTILIZADO EM PILARES MISTOS TUBULARES DE AÇO PREENCHIDOS COM CONCRETO

The European Standard EN 1994-1-1:2004 introduces a standardized push test to characterize the behaviour of shear connectors applied in composite steel and concrete stuctures. However, when other types of structural composite elements are analyzed, this standard recommends that specific tests should be carried out. In the current literature are found different methodologies for push test performed in concrete-filled steel tube columns elements. In this paper, it is introduced an adapted push test methodology to characterize the behaviour of shear connectors applied in these columns. This methodology is based on the European standardized test and take into account different procedures found in the scientific literature. An exemple of application of this method is presented and the outputs shows its efficiency. Keywords: Push test, filled composite column, shear connector, load transfer.

Application of general method for design of concrete columns and encased composite steel and concrete columns

Resumo The purpose of this work is the development and implementation of a numerical procedure for the design of reinforced concrete columns (RC) and composite columns with fully concrete encased steel I-section (SC). For this purpose, a computer program was developed to determine the load capacity of these columns, applying the General Method adopted by ABNT NBR 6118:2014. The program is based on an iterative process from integration of the curvatures along the column, obtained by determining the moment-curvature relationship of the cross section by the Newton-Raphson method. Several experimental and numerical results are compared to the program’s to demonstrate the accuracy of the procedure.

Bases do dimensionamento de pilares mistos de aço e concreto segundo o projeto de revisão da NBR 8800

This paper presents the design methods for steel and concrete composite columns subjected to compression axial load and bending moments according to the Revision Project of the Brazilian Code ABNT NBR 8800:1986. Presented also is the theoretical basis of the methods, using the European Standard EN 1994-1-1:2004 as a main guideline and the American Standard ANSI/AISC 360-05. It is showed that the results issued from the Revision Project of the Brazilian Code are in good agreement with more accurate results obtained by the finite element method.