Augusto Gomes

Nonlinear cyclic stress-strain relationship of reinforcing bars including buckling

Abstract A modification of the Monegotto-Pinto cyclic stress-strain steel relationship is presented. The modification was developed to take into account the effect of the inelastic buckling of the longitudinal reinforced concrete bars. The buckling stress-strain path is simulated by a simplified model based on the equilibrium of a plastic mechanism of the buckled bar. A comparison of the numerical model with experimental results is presented.

Compressive strength evaluation of structural lightweight concrete by non-destructive ultrasonic pulse velocity method.

In this paper the compressive strength of a wide range of structural lightweight aggregate concrete mixes is evaluated by the non-destructive ultrasonic pulse velocity method. This study involves about 84 different compositions tested between 3 and 180 days for compressive strengths ranging from about 30 to 80 MPa. The influence of several factors on the relation between the ultrasonic pulse velocity and compressive strength is examined. These factors include the cement type and content, amount of water, type of admixture, initial wetting conditions, type and volume of aggregate and the partial replacement of normal weight coarse and fine aggregates by lightweight aggregates. It is found that lightweight and normal weight concretes are affected differently by mix design parameters. In addition, the prediction of the concretes compressive strength by means of the non-destructive ultrasonic pulse velocity test is studied. Based on the dependence of the ultrasonic pulse velocity on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless the type of concrete and its composition. More than 200 results for different types of aggregates and concrete compositions were analyzed and high correlation coefficients were obtained.

Tuberculosis with malaria or HIV co-infection in a large hospital in Luanda, Angola

INTRODUCTION Three major public health problems, tuberculosis, malaria and HIV/AIDS, are widespread in Angola, often as co-infections in the same individual. In 2009, it was assumed that 44,151 new cases of TB occurred in Angola. Interestingly, interventions such as treatment/prevention of malaria appear to reduce mortality in HIV-infected and possibly TB co-infected patients. However, despite the seriousness of the situation, current data on TB and co-infection rates are scarce. This study aimed to characterize all TB cases seen at the Hospital Sanatório de Luanda, and to determine the co-infection rate with HIV and/or malaria. METHODOLOGY This retrospective study collected demographic, diagnostic and clinical data from all patients admitted during 2007. RESULTS A total of 4,666 patients were admitted, of whom 1,906 (40.8%) were diagnosed with TB. Overall, 1,111 patients (58.3%) were male and most patients (n=1302, 68.3%) were adults (≥ 14 years). The rate of HIV co-infection was 37.4% (n=712). Malaria was diagnosed during admission and hospital stay in 714 patients (37.5%), with Plasmodium falciparum the predominant species. Overall mortality was 15.2% (n=290). CONCLUSIONS Because Luanda does not have the infrastructure to perform culture-based diagnosis of TB, confirmation of TB is problematic. The HIV-co-infection rate is high, with 37.4% of patients requiring integrated approaches to address this problem. With more than 1/3 of the TB patients co-infected with malaria, even during the hospital stay, the prevention of malaria in TB patients appears to be an effective way to reduce overall mortality.

Zn-TiO2 and ZnNi-TiO2 Nanocomposite Coatings: Corrosion Behaviour

This work presents the corrosion behaviour of the as-prepared of Zn-TiO2 and ZnNi-TiO2 films in neutral Na2SO4 solution and a first attempt to correlate with their composition, morphology and structure. The films were prepared by galvanostatic pulse method onto steel electrodes, at room temperature. The X-ray diffraction study revealed that the ZnNi alloy consists of a homogenous Ni5Zn21 phase and that the preferred crystallographic orientation of Zn deposits changes in the presence of TiO2. The SEM results show that the morphology of the metallic coating is function of the metal phase composition and become more porous in the presence of 1.5 wt% TiO2.The corrosion parameters for the nanocomposite coatings were compared with those of pure Zn and ZnNi electrodeposits, and the ZnNi-TiO2 nanocomposite coating shows the less cathodic corrosion potential.

In Situ Techniques for the Characterisation of Rendering Mortars

Compressive strength, porosity and two “in situ” techniques (ultrasonic velocity and rebound hardness test) are used for the characterisation of several aerial, hydraulic lime-based and cement-based mortars. Prismatic specimens and mortars applied as a brick render are used for the characterisation. A comparative analysis of the “in situ” test results and compressive strength is performed and the relationship between porosity and ultrasound velocity is analysed. A satisfactory relationship between the porosity and ultrasound velocity values is found and this indicates the possibility of estimating porosity from ultrasound velocity. The relationship between ultrasound velocity, rebound values and compressive strength emphasizes the potential of the “in situ” test methods for characterisation of mechanical properties of mortars.

Restoration of the Masonry Arch Bridge Over Jamor River in the National Palace of Queluz

The National Palace of Queluz is a reference of Portuguese Heritage and is listed as National Monument since 1910. Its Gardens extend to around 16 acres and have become a reference in European historical gardens due to their complex and harmonious landscaping. However, over the years, the Palace and the Gardens have been severely damaged by a great fire and various floods. In 2012 the management of the Palace and the Gardens was awarded to Parques de Sintra – Monte da Lua and a global restoration project was started. This paper focus on part of that project: the restoration of a masonry arch bridge over the Jamor River that accesses to the Botanical Garden. This bridge was probably constructed between 1752 and 1790 when a lot of construction work took place in the south part of the Gardens. However due to the cyclic floods and other causes, some repair works were made throughout the years, which included the use of concrete in 1967. In this project it was identified a range of pathologies and some severe structural problems, such as the loss of material in the left abutment as well as a crack that crosses the bridge vertically and horizontally. The intervention strategy, based on the minimal intervention philosophy, was defined by a multidisciplinary team and combines structural operations, that include the strengthening of the left abutment through micro piles and the repair and retrofitting of the arch using carbon fibers, with conservation works on originals mortars, bricklaying and pictorial finishing.

Flexural Behavior of Pultruded GFRP Deck Panels with Snap-Fit Connections

This paper presents experimental, analytical and numerical investigations about the flexural behavior of glass fiber reinforced polymer (GFRP) pultruded panels for footbridge decks. The analyzed panels, made of isophthalic polyester and E-glass fibers, comprise a multicellular thin-walled cross-section with panel-to-panel vertical snap-fit connections at their lateral edges. As part of a comprehensive study about the mechanical and structural behavior of this type of footbridge decks, the experimental study presented here addresses: (i) the mechanical characterization of the laminated material, and (ii) the quasi-static flexural behavior of the panels for both service and failure conditions. The experimental data obtained is used to validate and assess the accuracy of three-dimensional shell finite element (FE) models and analytical formulae. Particular focus is given to the serviceability and failure performance of the panels, in terms of their deformability and susceptibility to buckling phenomena, respectively. Regarding the serviceability behavior, the results obtained in this study demonstrate the importance of duly specifying the shear coefficient of the multicellular cross-section on Timoshenko beam theory, in order to obtain accurate deflection predictions. In terms of failure performance, both the flexural tests and the analytical formulae indicate that the local buckling of the compressive flanges seems to have triggered the collapse of the tested panels, thus limiting their load carrying capacity. The geometrically nonlinear FE analyses allowed understanding in further depth the ultimate behavior of the panels, providing further insights about their failure mechanisms.

Maintenance of building components supported in interactive environments

The main objective of the research was to develop a technological tool to support the maintenance activity of buildings. There were analyzed three main components of the building: roofs, facades and interior walls. A buildings roof covering of ceramic tiles constitutes a component of its surrounding and possesses an important function in its protection against the permeation of moisture and rain water; Facade coatings play a significant role in the durability of buildings, since they constitute the exterior layer that ensures the protection of the wall against the aggressive actions of physical, chemical or biological nature; The paint coating applied to interior walls conveys their aesthetic character, performs an important function of protection, and is exposed to agents of deterioration related to the building use. A survey of the main anomalies that occur in these components, the respective causes and the adequate interventions, in order to plan maintenance strategies was conducted. The information collected serves as a basis in the implementation of applications using interactive visualization technologies, to support the planning of building maintenance. This research work brings an innovative contribution to the field of maintenance supported by emergent technology.

Interactive Model Used in Maintenance Planning of Facades Based on Virtual Reality Technology

A virtual reality model was created in order to help in the maintenance of exterior closures and interior finishes of walls in a building. It allows the visual and interactive transmission of information related to the physical behavior of the elements, defined as a function of the time variable. To this end, the basic knowledge of material most often used in walls, anomaly surveillance, techniques of rehabilitation, and inspection planning were studied. This information was included in a database that supports the periodic inspection needed in a program of preventive maintenance. The results are obtained interactively and visualized in the virtual environment itself. This work brings an innovative contribution to the field of maintenance supported by emergent technology.

Chemical Shrinkage of Pastes Made with Shrinkage Reducing Admixtures

Shrinkage Reducing Admixtures (SRA) are being used more often in concrete structures in order to better control shrinkage cracks. High-performance concrete, nowadays with large application, has more proneness to crack at very early age due to the lower W/C. In this type of concrete, autogenous shrinkage is usually more important than drying shrinkage. Autogenous shrinkage is due to the volume decrease inherent to binder hydration reactions. The rate of these reactions is influenced not only by the type of binder but also by the presence of chemical admixtures. It is recognized that SRA delay the hydration, being a secondary effect of this type of admixtures. In this work changes on the degree of hydration of cement pastes with SRA and different binders are presented, using the chemical shrinkage test.