scholarly journals Prestress state evolution during thermal activation of memory effect in concrete beams strengthened with external SMA wires

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
A. Debska ◽  
Piotr Gwozdziewicz ◽  
A. Seruga ◽  
X. Balandraud ◽  
J. F. Destrebecq
Keyword(s):  
Ambient Temperature ◽  
Memory Effect ◽  
Concrete Beams ◽  
Macroscopic Model ◽  
Maximum Temperature ◽  
Joule Effect ◽  
Mechanical Coupling ◽  
State Evolution ◽  
Definition Of ◽  
Concrete Elements

Abstract The memory effect of shape-memory alloys (SMAs) has opened interesting perspectives to create prestress states in concrete elements. However, the procedure has not been yet fully resolved due to the complex thermomechanical behavior of these alloys, in addition to the practical difficulties of mechanical coupling between SMA and concrete elements. The present study deals with tests on the development of prestressing forces in concrete beams during the thermal cycle required in the procedure. Pre-stretched nickel–titanium wires were externally placed on concrete prismatic beams equipped with strain gauges. As concrete rupture may occur during the heating by the Joule effect, a compromise must be found between the SMA pre-stretch level and the maximum temperature to be applied before returning to ambient temperature. A macroscopic model was developed to analyze this compromise. The complex thermomechanical response of SMAs implies a particular attention in the definition of the ambient temperature and heating conditions for the creation of prestress states in concrete components.

scholarly journals Behavior of an asphalt mixture MDC-19 under the cycles of ambient temperature in the city of Tunja, Colombia

Respuestas ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 56-64
Author(s):  
Carol Rosabeth Sanabria Sanabria ◽  
Carlos Hernando Higuera Sandoval
Keyword(s):  
Ambient Temperature ◽  
Environmental Temperature ◽  
Asphalt Mixture ◽  
Early Morning ◽  
Maximum Temperature ◽  
Temperature Cycles ◽  
Weather Factor ◽  
Asphalt Mix ◽  
And Performance ◽  
Definition Of

The weather factor plays an important role in the behavior and performance of asphalt mixtures as a surface layer in a flexible pavement structure, not just from the moisture, but also from the environmental temperature. Asphalt layers of the flexible pavements in Tunja city exposes daily to environmental temperature variations, which usually occur when the highest temperatures are reached during the daytime, and the lowest temperatures appear at night and early morning time. Firstly, this research is based , on the definition of the environmental temperature cycles that occur daily in Tunja City, from the analysis of the temperature series. Subsequently, the analysis was done through laboratory tests on an asphalt mix MDC-19 INVIAS type, made and compacted in the laboratory, to determine the influence of the cycles of environmental temperature on its density, stability and flow properties, during 120 daily and continuous temperature cycles, which consist of 12 hours of maximum temperature and 12 hours of minimum temperature to simulate the environmental conditions. As a result of this investigation, the presentation density is presented, presenting a tendency to increase the measurement that increases the temperature cycles and then a decrease in the briquettes of the mixture that have sometimes been until the last cycles. Variations in the resistance to deformation of the analysis mixture were obtained as the ambient temperature cycles were sometimes made, which concludes that the ambient temperature cycles have an influence on the behavior of the asphalt mixture.

Flexure Behaviour the Concrete Beams Reinforcement with Polymer Materials

2013 ◽  
Vol 687 ◽  
pp. 472-479 ◽  
Author(s):  
Naser Kabashi ◽  
Cenë Krasniqi ◽  
Ali Muriqi
Keyword(s):  
Carbon Fibers ◽  
Concrete Beams ◽  
Point Load ◽  
Polymer Materials ◽  
Rc Beams ◽  
External Reinforcement ◽  
Frp Reinforcement ◽  
Beam Bending ◽  
Definition Of ◽  
Concrete Elements

Improvement of flexure behavior using the polymer materials is one of the very important factors in analyzing the concrete elements, especially concrete beams. In this case we analyze two different cases: • Improvement using the polypropylene microfibers in ready mix concrete • Improvement using the carbon fibers in external reinforcement In both case studies we used three-point-load experimental beam-bending tests for: three conventional RC beams (referent beams), three RC beams with polypropylene fibers and three RC beams with carbon fibers. All results concern comparing the effect of fibers on improvement of energy capacity of concrete elements, and increasing the bearing capacity of concrete beams. One of the most important values based on the behavior of the structure is ductility. The ductility is a structural design requirement in most design codes. The traditional definition of ductility cannot be applied in structures reinforced with FRP reinforcement. Several methods, such as the energy based method and the deformation based method have been suggested to calculate the ductility index for FRP reinforced structures. Furthermore the behavior of RC beams is analyzed with the help of cracks, their position and width under the loads.

scholarly journals Application of artificial neural networks to predict the deflections of reinforced concrete beams

2016 ◽  
Vol 38 (2) ◽  
pp. 37-46 ◽  
Author(s):  
Mateusz Kaczmarek ◽  
Agnieszka Szymańska
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Artificial Neural Network ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
The Neural Network ◽  
Eurocode 2 ◽  
Artificial Neural ◽  
Concrete Elements

Abstract Nonlinear structural mechanics should be taken into account in the practical design of reinforced concrete structures. Cracking is one of the major sources of nonlinearity. Description of deflection of reinforced concrete elements is a computational problem, mainly because of the difficulties in modelling the nonlinear stress-strain relationship of concrete and steel. In design practise, in accordance with technical rules (e.g., Eurocode 2), a simplified approach for reinforced concrete is used, but the results of simplified calculations differ from the results of experimental studies. Artificial neural network is a versatile modelling tool capable of making predictions of values that are difficult to obtain in numerical analysis. This paper describes the creation and operation of a neural network for making predictions of deflections of reinforced concrete beams at different load levels. In order to obtain a database of results, that is necessary for training and testing the neural network, a research on measurement of deflections in reinforced concrete beams was conducted by the authors in the Certified Research Laboratory of the Building Engineering Institute at Wrocław University of Science and Technology. The use of artificial neural networks is an innovation and an alternative to traditional methods of solving the problem of calculating the deflections of reinforced concrete elements. The results show the effectiveness of using artificial neural network for predicting the deflection of reinforced concrete beams, compared with the results of calculations conducted in accordance with Eurocode 2. The neural network model presented in this paper can acquire new data and be used for further analysis, with availability of more research results.

Design and Fabrication of a Magnetocaloric Microcooler

2005 ◽  
Author(s):  
Sangchae Kim ◽  
Bharath Bethala ◽  
Simone Ghirlanda ◽  
Senthil N. Sambandam ◽  
Shekhar Bhansali
Keyword(s):  
Magnetic Field ◽  
Ambient Temperature ◽  
Temperature Change ◽  
Entropy Change ◽  
Temperature Sensors ◽  
Experimental Results ◽  
Maximum Temperature ◽  
Alternative Technology ◽  
Temperature Conditions ◽  
Si Wafer

Magnetocaloric refrigeration is increasingly being explored as an alternative technology for cooling. This paper presents the design and fabrication of a micromachined magnetocaloric cooler. The cooler consists of fluidic microchannels (in a Si wafer), diffused temperature sensors, and a Gd5(Si2Ge2) magnetocaloric refrigeration element. A magnetic field of 1.5 T is applied using an electromagnet to change the entropy of the magnetocaloric element for different ambient temperature conditions ranging from 258 K to 280 K, and the results are discussed. The tests show a maximum temperature change of 7 K on the magnetocaloric element at 258 K. The experimental results co-relate well with the entropy change of the material.

scholarly journals Influence of Cooling Methods on the Residual Mechanical Behavior of Fire-Exposed Concrete: An Experimental Study

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3512 ◽  
Author(s):  
Espedito Felipe Teixeira de Carvalho ◽  
João Trajano da Silva Neto ◽  
Paulo Roberto Ribeiro Soares Junior ◽  
Priscila de Souza Maciel ◽  
Helder Luis Fransozo ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Ambient Temperature ◽  
Mechanical Behavior ◽  
Residual Strength ◽  
Maximum Temperature ◽  
Experimental Program ◽  
Lower Strength ◽  
Cooling Method ◽  
Temperature Levels ◽  
Cooling Methods

This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 °C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.

scholarly journals Are Household Potato Frying Habits Suitable for Preventing Acrylamide Exposure?

Foods ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 799 ◽  
Author(s):  
Marta Mesias ◽  
Cristina Delgado-Andrade ◽  
Francisco J. Morales
Keyword(s):  
Mitigation Strategies ◽  
French Fries ◽  
Maximum Temperature ◽  
Replacement Rate ◽  
Frying Temperature ◽  
French Fry ◽  
Acrylamide Formation ◽  
Golden Color ◽  
Domestic Setting ◽  
Definition Of

A survey was conducted of 730 Spanish households to identify culinary practices which might influence acrylamide formation during the domestic preparation of french fries and their compliance with the acrylamide mitigation strategies described in the 2017/2158 Regulation. Spanish household practices conformed with the majority of recommendations for the selection, storing and handling of potatoes, with the exception of soaking potato strips. Olive oil was the preferred frying oil (78.7%) and frying pans were the most common kitchen utensils used for frying (79.0%), leading to a higher oil replacement rate than with a deep-fryer. Although frying temperature was usually controlled (81.0%), participants were unaware of the maximum temperature recommended for preventing acrylamide formation. For french fries, color was the main criteria when deciding the end-point of frying (85.3%). Although a golden color was preferred by respondents (87.3%), color guidelines are recommended in order to unify the definition of “golden.” The results conclude that habits of the Spanish population are in line with recommendations to mitigate acrylamide during french fry preparation. Furthermore, these habits do not include practices that risk increasing acrylamide formation. Nevertheless, educational initiatives tailored towards consumers would reduce the formation of this contaminant and, consequently, exposure to it in a domestic setting.

P1943Ambient temperature and seasonal effects on blood pressure in 2.6 million Australians

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
E Atkins ◽  
Q Pilard ◽  
K Rogers ◽  
A Salam ◽  
A Rodgers
Keyword(s):  
Blood Pressure ◽  
Seasonal Variation ◽  
Ambient Temperature ◽  
Medication Use ◽  
South Australia ◽  
Seasonal Effects ◽  
Lipid Lowering ◽  
Maximum Temperature ◽  
History Of ◽  
The Mean

Abstract Background There is evidence that blood pressure (BP) levels vary considerably from season to season, due principally to variation in ambient temperature. This gives the potential for both under- and over-treatment if BP lowering medications are not varied seasonally, but is not acknowledged in clinical guidelines. We will describe the seasonal variation in BP and assess the association between systolic blood pressure (SBP) and outdoor maximum ambient temperature in Australia. Methods The primary care data is an extract from MedicineInsight, a national general practice data program developed and managed by NPS MedicineWise, which extracts deidentified data from almost 10% of all Australian general practices. We included patients aged 30–90 years with at least one BP measure recorded from 1 Jan 2010 to 1 Aug 2017. Australian Bureau of Meteorology daily max temperature is linked by matching observation dates and location to nearest weather station. Decomposition of the mean will determine seasonal variation. Multiple linear regression was used to estimate the associations between max temperature and SBP with adjustment for age, sex, socioeconomic index, current smoking, comorbidities, BP lowering medication use, lipid lowering medication use and year of BP measurement. Results The study population includes 2.6 million people, mean age 55 years (standard deviation [SD] 16.3). Fifty-five percent are female, over a third of the cohort reside in New South Wales, and 62.4% reside in major Australian cities. The mean (SD) temperature was 23°C (6.6). There was a mean (SD) of 7 (11.4) BP measurements per person over the study period, median 3 measures (interquartile range 1–8). A quarter had a history of hypertension, 8% had a history of cardiovascular disease, and 8% had a history of diabetes. Twenty-six percent had at least one prescription for BP lowering therapy. The average monthly SBP for the cohort demonstrated strong seasonal variation with higher values in winter. The population mean varies by 3mmHg SBP between seasons across Australia, ranging from 1.7mmHg in the Northern Territory to 3.5mmHg in South Australia (range of mean maximum temperature 3°C [30–33] and 14°C [15–29] for the capital cities respectively). Each 10°C increase in max outdoor temperature was associated with a 1.8mmHg [95% CI 1.80–1.83] lower mean SBP. The proportion of people with SBP>140mmHg varied by season, irrespective of age, sex and use of BP lowering treatment. For example, among those treated control rates varied between 70 and 81%, and among those not treated between 78 and 85% (Figure). Blood pressure seasonality in Australia Conclusions BP control rates vary considerably by season. These findings have implications for the reliable diagnosis of hypertension, and suggest seasonal adjustments in treatment should be considered for some patients. The clinical and public health relevance of this phenomenon is expected to increase with increasing climate variability. Acknowledgement/Funding National Health and Medical Research Council Australia, National Heart Foundation Australia

scholarly journals Laser System for Testing Early Shrinkage of Concrete Elements in Conjuction with the Deterioration of the Setting Time

2016 ◽  
Vol 16 (2) ◽  
pp. 25-34
Author(s):  
Jacek Gołaszewski ◽  
Tomasz Ponikiewski ◽  
Grzegorz Cygan ◽  
Małgorzata Gołaszewska
Keyword(s):  
Concrete Beams ◽  
Setting Time ◽  
Laser System ◽  
Scratch Resistance ◽  
Sound Waves ◽  
Concrete Elements ◽  
Speed Propagation

Abstract The paper presents a method for testing the shrinkage of concrete beams with dimensions of 10x10x50cm. Measurements followed from setting into the form until 24 hours after setting. It was used modified TLS system, which originally was meant for the determination of changes in the length of thin-mortar. Simultanously measured were the changes of speed propagation of sound waves by Vikasonic, what allows to specify the setting time of binders. It could be a base for determining the scratch resistance of the concrete in the first 24 hours after casting.

Disparity as an evolutionary index: a comparison of Cambrian and Recent arthropods

Paleobiology ◽  
1994 ◽  
Vol 20 (2) ◽  
pp. 93-130 ◽  
Author(s):  
Matthew A. Wills ◽  
Derek E. G. Briggs ◽  
Richard A. Fortey
Keyword(s):  
First Generation ◽  
Character State ◽  
Early Cambrian ◽  
State Evolution ◽  
Cambrian Radiation ◽  
Taxonomic Framework ◽  
Definition Of ◽  
Morphological Attribute ◽  
Attribute Space ◽  
Agreed Definition

Disparity is a measure of the range or significance of morphology in a given sample of organisms, as opposed to diversity, which is expressed in terms of the number (and sometimes ranking) of taxa. At present there is no agreed definition of disparity, much less any consensus on how to measure it. Two possible categories of metric are considered here, one independent of any hypothesis of relationship (phenetics), the other constrained within an evolutionary framework (cladistics).The Early Cambrian radiation was clearly a period of significant morphologic and taxonomic diversification. However, we question the interpretation of its first generation products as numerous body plans at the highest level. Four phenetic and two cladistic measures have been used to compare disparity among Cambrian arthropods with that in the living fauna. Phenetic methods assessing character-state variability and the amount of morphological attribute space occupied yield similar results for Cambrian and Recent arthropods. Assessments of disparity within a taxonomic framework rely on the identification of particular characters that delineate higher level body plans. This requires a phylogenetic interpretation, a cladistic investigation of hierarchical structure in the data. Both sets of arthropods fall within the same major clades, and within this cladistic framework the amount of character-state evolution in the two groups is comparable. None of these methods identifies markedly greater disparity among the Cambrian compared with the Recent taxa.Although measures of disparity are applied here to a consideration of the Cambrian radiation, the metrics clearly have a much wider potential for estimating macroevolutionary trends independently from existing taxonomic frameworks. Geometric morphometry is ideal for measuring morphological variety at lower taxonomic levels, but it requires the recognition of homologous landmarks in all the forms under comparison, or the identification of entire homologous structures. Conventional phenetics has much wider application as it can operate on data coded as discrete homologous character states (this facility is also a requirement of cladistics), which are a more appropriate basis for comparing disparity in markedly dissimilar forms.

Biogeographical effects on body mass of native Australian and introduced mice, Pseudomys hermannsburgensis and Mus domesticus: an inquiry into Bergmann's Rule

2008 ◽  
Vol 56 (6) ◽  
pp. 423 ◽  
Author(s):  
Sean Tomlinson ◽  
Philip C. Withers
Keyword(s):  
Ambient Temperature ◽  
Body Mass ◽  
Rainfall Variability ◽  
Negative Influence ◽  
Bergmann’S Rule ◽  
Annual Rainfall ◽  
Maximum Temperature ◽  
Mus Domesticus ◽  
Arid Areas ◽  
Bergmann's Rule

We investigated interactions of body mass with geographical location, and five climatic measures for two Australian rodents, the native Australian sandy inland mouse (Pseudomys hermannsburgensis) and the introduced house mouse (Mus domesticus). Correlation and regression analyses identified interactions of body mass with latitude, longitude, average highest maximum and lowest minimum temperatures, average annual rainfall, rainfall variability, and aridity. There was a significant correlation of body mass with latitude and longitude for Mus domesticus and P. hermannsburgensis. House mice were heavier in the south and east, and sandy inland mice were heavier in the north and east. M. domesticus conforms to Bergmann’s Rule, while P. hermannsburgensis does not. Maximum temperature, aridity and rainfall variability significantly influenced body mass of M. domesticus, which was heavier at cooler maxima, in less arid areas, and in areas of greater rainfall variability. Only aridity significantly influenced body mass of P. hermannsburgensis, which was heavier in more arid areas. Temperature did not interact significantly with body mass. After accounting for climatic variables, there was still a significant relationship between the residuals of body mass with locality for both species, with a negative influence of latitude and a positive influence of longitude in both; the latitudinal interaction for both species was converse to Bergmann’s Rule. We suggest that latitude, ambient temperature and other selection pressures (such as aridity or productivity) can act in opposing directions, and speculate that the influence of other factors, such as food availability or sociality, may be more important than latitude or ambient temperature.

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