Edgar Vladimiro Mantilla Carrasco

Experimental and numerical analysis of large ferrocement water tanks

Abstract In the current work the ferrocement construction technique is revisited with the purpose of applying the material in civil engineering structures, particularly in large water tanks for water treatment stations. Although it is not a new technology, ferrocement continues to be an attractive alternative. The plastic potential, the unsophisticated construction techniques and the low cost justify its use, especially suitable for developing countries. However, modelling studies of this material are rare in the literature; this is what justifies the studies currently being conducted to improve current practices of design, as well as to further advance the understanding of the material. This work describes experimental and numerical tests for large ferrocement tanks, part of the water treatment facility in Divinopolis, Brazil. Different finite element models have been used in the analyses in order to evaluate the effect of some adopted simplifications. Some comparisons of the investigated approaches with the experimental data are also included, as well as remarks on the use of different constitutive models, homogenisation techniques and accuracy of the modelling data.

Methodology for inspection of wood pathologie using ultrasonic pulses

Awareness has been on the rise on the part of society about the importance of wooden structures, in particular historic buildings. This concern is reflected in continued maintenance of historic heritage and has been increasingly leading professionals working in the field of wooden structures to seek improved techniques for inspection of such structures. Methods involving nondestructive testing (NDT) are the most recommended for inspection, as they do not affect the relevant architecture and thus help maintain the integrity and originality of the building. Among the various existing NDT methods, a widespread and promising option is the ultrasound technique. This work introduces a methodology for inspection of wooden structural elements using ultrasonic pulses. The methodology was applied to a glued laminated timber beam with signs of decay on its interior. Ultrasound results helped map the damaged areas of the beam on a plane by using isochromatic patterns. The contribution of this work is a methodology to help investigate wood pathologies which, in combination with other complementary techniques, will allow more accurate and reliable evaluations of wooden structures, avoiding unnecessary replacement of sound structural elements mistakenly presumed to be damaged, or else ensuring maintenance of extremely deteriorated elements that would otherwise compromise the overall stability of the structure.

INFLUÊNCIA DA INCLINAÇÃO DAS FIBRAS DA MADEIRA NA SUA RESISTÊNCIA AO CISALHAMENTO

The shear stress as a function of the inclination of the wood fibers were determined through experimental tests. The test specimens were obtained from a sample of wood beams 12 Eucalyptus saligna , following the requirements of NBR 7190. They were made with variable slope fiber (0 o, 15 o, 30 o, 45 o, 60 o, 75 o, 90 o). Through statistical analysis it was possible to estimate the parameters of variability of shear stress with the slope of the wood fibers. The shear stresses were corrected to standard moisture of 12%. With robust statistical analysis of the data set, it was possible to define the empirical equations that best define this phenomenon. Equations proposed in the literature by Hankinson, Karlsen, DIN 1052 and Keylwerth, the formulation prescribed by DIN 1052, with necessary modifications, has a better fit to the experimental results.

The Influence of the Water/Cement Ratio in the Open Porosity and in the Carbonation Front Advancing in Cementitious Matrix Composites

In this study involving cementitious matrix composites, the influence of the water/cement (w/c) ratio variation (0.48, 0.60, 0.70 and 0.75) was analyzed in its open pore structure and in the carbonation front advancing. Test specimens were molded in cylindrical dimensions of (5x10) cm and (2x4) cm for each mix proportions, and subjected into accelerated carbonation tests, at controlled exposure conditions. The open porosity of the material was obtained by using a helium pycnometer. A model based on Ficks second law was used to fit an equation to the curve of progress of the carbonation front over time. The results show that the water/cement ratio can highly influence the analyzed properties; the mathematical model used provided an excellent approximation of the advancing carbonation front trend, allowing a good evaluation of the carbonation coefficient (K) associated to each mixture proportioning.

Cross Laminated Timber in the International Context and in Brazil: Most Relevant Aspects

Timber is still being rediscovered as building material of excellence in Brazil, and especially as one of the most environmentally friendly one. In the scenario of the production of sustainable buildings, the construction system that uses wood panels - widely used in Europe, USA and Canada - called Glued Laminated Timber (GLULAM) and Cross Laminated Timber (CLT), occupies a prominent place, especially by the possibility of using wood from planted forests. This work aims to provide an overview of what is being produced in Europe and in Brazil.

Variation of the Modulus of Elasticity and Anisotropic Factor over the Thickness of the Bamboo Wall

The objective of this study is to experimentally determine the physical and elastic properties of bamboo and set the anisotropic factor along the wall thickness of the bamboo. The physical properties were determined following the requirements of the Brazilian standard. The elastic modulus was determined by non-destructive testing using the impulse excitation method. The density in the shell region is 40% larger than the inner portion. The density variation in the wall thickness of the bamboo is not linear, having a more pronounced nonlinearity in the shell region. The results of the ANOVA table indicate that shrinkage factors in bamboo wall thickness can be considered statistically the same, i.e., they do not vary with the wall thickness of the bamboo. The anisotropic factor in the intermediate and inner region can be considered statistically equal, 1.8. As for the factor measured in the region close to the bark, 2.03, it cannot be considered equal to the other regions. There is a variation of the modulus of elasticity, between the interior and the bamboo bark, of 279%.

Propriedades Físicas da Madeira de Eucalyptus cloeziana F. Muell

We analyzed the wood physical properties of 70 Eucalyptus cloeziana trees, approximately 10 years old, from forests located in the Midwestern region of Minas Gerais. Moisture, basic and apparent density and shrinkage were determined. The samples showed mean values of 703 kg/m3, 843 kg/m3 and 916 kg/m3 for basic density, dry bulk density and apparent density at 12% moisture, respectively. Concerning the radial, tangential and axial shrinkage were found with average values of 7.08; 11.16 and 0.26%, respectively. The average volume shrinkage was 19.68%, and the anisotropic ratio of 1.60, thus the timber is considered stable dimensionally.

A Study of Adobes Made with No Usual Soils Concerning Grain Size Distribution Test

This article presents and discusses an adobe production with shows a clay/silt/sand proportion that is completely different from that recommended by most authors and construction associations. The main objective was to improve comprehension of earth behaviors as building material by studying these two atypical cases of adobe production. The soil was analyzed by different tests as the grain size distribution test and Atterberg limits. Adobe resistance was tested using a methodology proposed by Proterra network which was created by a group of researchers from different Iberian American laboratories. This methodology was used in Ph.D. thesis, too. The results show a soil with 1% clay and 65.1 silte and an average of resistance of 2.11 MPa for the adobes. These results show the importance of the clay mineral structure and the complexity of the soil behavior, indicating the need for additional studies.

Bond Strength between Old and New Concretes with Focus on the Strengthening of Reinforced Concrete Columns - Slant Shear Test versus Double Sleeve Test

The purpose of this paper is to present the main aspects and results of an experimental study to determine the bond strength between the concrete of a column of an existing structure (old concrete) and the concrete that will be used in its strengthening project (new concrete). For the bond strength tests, a specimen was conceived, called Double Sleeve specimen. The bond strength results obtained from the tests using Double Sleeve specimens, called Double Sleeve Tests, were compared to the results obtained from using the Slant Shear Test. The values for the bond strength between the two concretes, obtained from the Double Sleeve Tests, were either below or above the values obtained from linear regression of the Slant Shear Test results, depending on the sleeve diameter and the ratio of transverse reinforcement used. This fact, enabled concludes that the Double Sleeve Test is the most appropriate test to evaluate the bond strength between concretes of columns strengthened.

Influences of Scarf-Joint of the Laminae in the Strength and Elasticity of Glued Laminated Timber Beams

The objective of this work is to determinate the influence of the scarf-jointed in the strength and the modulus of elasticity of the glued laminated timber beam. To determine this influence, several tests with the outer laminae with scarf-joint and the bevel with different inclinations has been made. The models were made of Parana Pine, Araucaria angustifolia. For the tests were performed three points bending. With the load values and the deflection at mid-span and by linear regression were determined the effective elastic modulus. The results indicate that the performance is reduced considerably in the presence of a scarf-joint in the external laminae and also the reduction is greater when the scarf angle increases.