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Influence of Concrete Resistance and Steel Reinforcement on Tenacity and Damper Coefficient on Reinforced Concrete Beams
Joaquim Carneiro, Said Jalali, F. Q. de Melo, Mário Vaz, Mário André, Miguel Tomás
Published in the 6º Congress of National Seismology and Seismic Engineering 2004, Guimarães, Portugal
This work describes an application of pseudo-dynamic techniques (PSD) to the study of the dynamic behavior of reinforced concrete beams under the action of forces that vary over time. The reinforced concrete elements tested, assimilable to systems with a degree of freedom, were subjected to free and forced vibration in order to extract the damping coefficients, an important parameter in the field of seismic action. On the other hand, a set of destructive static tests were carried out on the same elements in order to assess the contribution of the amount of reinforcement and strength of the concrete to the energy absorption capacity (toughness). The results obtained made it possible to carry out a comparative and quantitative analysis of the mechanical behavior of these structural elements as a function of the reinforcement rate and the strength class of the concrete.
The Effect of Concrete Strength and Reinforcement on Toughness of Reinforced Concrete Beams
J.O. Carneiro, S. Jalali, V. Teixeira, M. Tomás, Published in the Journal “Construction and Building Materials”, Volume 19, Issue 7, September 2005, Pages 493-499
The objective pursued with this work includes the evaluating of the strength and the total energy absorption capacity (toughness) of reinforced concrete beams using different amounts of steel-bar reinforcement. The experimental campaign deals with the evaluation of the threshold load prior collapse, ultimate load and deformation, as well as the beam total energy absorption capacity, using a three point bending test. The beam half span displacement was measured using a displacement transducer, and the applied force was monitored using a load cell. The tested samples consists on a set of ten reinforced concrete beams having three different levels of steel-bar-reinforcement percentages and four different concrete compositions (i.e., giving rise to a different values of concrete strength). It was observed that the most influential parameter in the beams energy absorption capacity is the amount of steel-bar reinforcement. The results have presented good agreement between themselves. In fact, for beams with a given concrete compressive strength, a decrease in beam’s deformation was measured for higher steel-bar-reinforcement percentages. Moreover, the results had shown that for a particular steel-bar-reinforcement percentage, the concrete compressive strength have also influence in the total energy absorption capacity of the beams.
The use of Pseudo-Dynamic Method in the evaluation of damping characteristics in reinforced concrete beams having variable bending stiffness
J.O. Carneiro, F J Q de Melo, S Jalali, V. Teixeira, M. Tomás, published in the journal “Mechanics Research Communications” Volume 33, September 2006, pages 601-613
The objective of this work is to determine experimentally the damping properties of concrete reinforced beams under mechanical vibrations. This is a very important property in earthquake engineering once damping provides structure energy dissipation during moderate or strong earthquake motions. The experimental campaign used the pseudo-dynamic (PsD) method to analyse the beam dynamic behaviour. Essentially the PsD test method is a hybrid computer-driven testing procedure where a numerical algorithm and experimental step are used and combined on-line in order to solve a dynamic problem. The implementation of the method is not expensive and has the leading advantage of offering the operator a total control of any intermediate structure state during the test still keeping the realism of a real dynamic testing. In this analysis the dynamic model was assumed as single degree-of-freedom system (SDOF). For the calculation of the structural damping factor, the structure stiffness was determined prior the set-up of the time integration algorithm; thereafter a pseudo-dynamic process dealing with a free and a forced vibration scheme, where this last was achieved with an external harmonic load, led to the definition of the structure response where the dissipative effect of the damping properties of reinforced concrete beams was evidenced.
Life cycle assessment of steel and reinforced concrete structures: A new analysis tool
Alexandre Peyroteo, Miguel Silva, Said Jalali, published in the conference "Portugal SB07 - Sustainable Construction, Materials and Practices – Theme 1 - Building sustainability assessment tools" 2007, Lisboa, Portugal
In this paper is discussed the life cycle of steel and reinforced concrete structures using a sim-plified life cycle analysis. The developed methodology consisted in quantification of a series of parameters both economic and environmental that characterize both reinforced concrete and metallic structures. Based in the life cycle analysis, five parameters were selected in order to make the assessment, in witch: energy consumption, water, CO2, SO2, NOx. A database was developed into a software program that can perform life cycle analysis of these types of struc-tures giving their physical properties. As a result the software outputs the total amount of emis-sions caused by the production of a given structural element as well as determines the structur-al costs giving in the end a global project analysis.
Evaluation of concrete degradation models of reinforced concrete structures in a maritime environment
Miguel Tomás Silva, Rui Miguel Ferreira,
National Meeting of Structural Concrete 2008 – Theme 5 – Life Cycle Project page 321 Guimarães, Portugal
After the end of the Second World War, there was an exponential growth in reinforced concrete structures, which corresponded to one of the most expensive investments in our society. In general, the programming of the maintenance tasks of the structures was not carried out, since in their design, fulfilling the design requirements, it was underlying that this would last the corresponding useful life for which it would have been designed. However, it has been found that the performance of many buildings decreases significantly, affecting their safety and usage conditions and, ultimately, ruin, which leads to huge reconstruction costs. Nowadays, one of the main areas of study in which the scientific community is debating is the durability of reinforced concrete structures, especially those that are subject to maritime environmental exposure conditions. The growing interest in gauging durability, as well as the service conditions of reinforced concrete structures, allows its useful life to be maximized, leading to savings not only in terms of costs but also in environmental terms. Currently, there are several models of deterioration of reinforced concrete that simulate the degradation and transport mechanisms of a given structure. This article intends to carry out a comparative study of the applicability to the Portuguese reality of two models already developed and to analyze the durability performances for the useful lives considered (50 and 100 years).
Piezoresistivity in Micro Carbon Fiber Silicone Composites for Electrical Resistance to Strain Sensing
M. Tomás, Said Jalali, published in the journal “Advanced Engineering Forum” Volume 23, July 2017, pages 45-55
In order to develop a cost-effective carbon fiber reinforced polymer sensor for compressive strain monitoring, a study was carried out to assess electrical and piezoelectric properties of samples containing five different carbon fiber weight percentages. Testing focused on sensing ability throughout measurement of resistivity: (1) when submitted to uniaxial variable compressive strain; (2) to time prolonged relaxation at constant strain; (3) and influence of environment temperature on measurements. Results enabled the possibility of usage for live monitoring of samples by determining sensitivity values of each sample being tested. Electrical resistance measurements assessment test results, show real time resistivity change in respect to experienced strain. Further piezoelectric properties where determined. An exponential decay function was found in fractional resistance in respect to relaxation due to constant strain testing. The total amount of time needed for measurements to present an error less than 1% at the probes was determined and found to vary up to seven days. Strain reversibility of resistivity measurements varied according weight percentages of carbon fibers used in composite sample being tested. Samples were tested in situ for monitoring of displacement on foundations of a dwelling to be built, placed on foundation’s soil. The main objective here was to assess practical questions such as handling and how measurements could be made safely. Results demonstrated successful monitoring during construction phase with easy deployment on site, sensing each construction phase loading.
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M. Tomás, J.O.Carneiro
Weibull statistical probability determination of of cracks in a rectangular specimen
M. Tomás, J.O. Carneiro
Weibull statistical probability determination of of cracks in a rectangular specimen.
M. Tomás, Alexandre Peyroteo, Said Jalali
Life cycle assessment of steel and reinforced concrete structures: A new analysis tool.
Miguel Ferreira, M. Tomás
Duracon (2007 version beta).
Expert Automation Files
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Aires Camoes, M. Tomás
Fast study of concrete compositions using Faury method.
Granulometric Analysis of Aggregates .
Granulometric Analysis of Aggregates .
Quantification of materials for making mortars.
Concrete compression testing.
Mix analysis of materials for making Geopolymers.
Analysis of compacity in sand aggregates.