Long term observations of concrete structures analysis of temperature gradient effects

1985 ◽  
Vol 18 (4) ◽  
pp. 309-316 ◽  
Author(s):  
M. J. N. Priestley
Keyword(s):  
Temperature Gradient ◽  
Concrete Structures ◽  
Gradient Effects

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

Influence of Alkalinity and Ambient Temperature on Long-Term Properties of GFRP Reinforcement

2018 ◽  
Vol 760 ◽  
pp. 213-218
Author(s):  
František Girgle ◽  
Lenka Bodnárová ◽  
Ondřej Januš ◽  
Vojtěch Kostiha
Keyword(s):  
Tensile Strength ◽  
Ambient Temperature ◽  
Mechanical Characteristics ◽  
Current Problem ◽  
Concrete Structures ◽  
Experimental Program ◽  
Glass Fibres ◽  
Metallic Reinforcement ◽  
Gfrp Reinforcement

The article deals with the current problem of determining long-term reliability of non-metallic reinforcement in concrete structures. The alkaline environment of concrete with a pH higher than 12.0 affects the glass fibres degradative, whereas this degradation presents by reduction of their mechanical characteristics, resulting in a decrease in the tensile strength of the whole composite. The article summarizes the results of the ongoing experimental program so far, which aims to quantify this influence.

scholarly journals Residual Capability of Alkali Binding by Hydrated Pozzolanic Cements in Long-Service Concrete Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Mario Berra ◽  
Teresa Mangialardi ◽  
Antonio Evangelista Paolini
Keyword(s):  
Concrete Structures ◽  
Test Results ◽  
Cement Pastes ◽  
Experimental Procedure ◽  
Accelerated Curing ◽  
Alkali Aggregate Reaction ◽  
Simple Mass ◽  
Pore Liquid ◽  
Pozzolanic Cement

An experimental procedure was developed and applied to cement pastes made with two different pozzolanic cements (CEM IV/B (P) and CEM IV/B (V)) in order to ascertain the existence of a residual capability of alkali binding by long-term hydrated pozzolanic cements and, at the same time, to evaluate the alkali retention capability and the concentration of OH− ions in the pore solution of such cementitious matrices. The developed procedure consisted of accelerated curing of cement paste specimens (150 days at 60°C and 100% RH), subsequent leaching tests at 60°C for 30 days by using deionized water or basic solutions (NaOH or KOH at different concentrations) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions. The developed procedure was found to be appropriate for evaluating both the pore liquid alkalinity and the alkali retention capability by long-term hydrated pozzolanic cement pastes. A residual capability of alkali binding was also identified for both tested pozzolanic cements, thus indicating their potential ability to prevent (CEM IV/B (V)) or minimize (CEM IV/B (P)) the risk of deleterious expansion associated with alkali-aggregate reaction in long-service concrete structures, like concrete dams.

scholarly journals Different Growth and Sporulation Responses to Temperature Gradient among Obligate Apomictic Strains of Ulva prolifera

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2256
Author(s):  
Yoichi Sato ◽  
Yutaro Kinoshita ◽  
Miho Mogamiya ◽  
Eri Inomata ◽  
Masakazu Hoshino ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Carbon Content ◽  
Nitrogen Content ◽  
Environmental Conditions ◽  
Genetic Stability ◽  
Ulva Prolifera ◽  
Market Demand ◽  
Gene Sequences ◽  
Site Specific

The green macroalga Ulva prolifera has a number of variants, some of which are asexual (independent from sexual variants). Although it has been harvested for food, the yield is decreasing. To meet market demand, developing elite cultivars is required. The present study investigated the genetic stability of asexual variants, genotype (hsp90 gene sequences) and phenotype variations across a temperature gradient (10–30 °C) in an apomictic population. Asexual variants were collected from six localities in Japan and were isolated as an unialgal strain. The hsp90 gene sequences of six strains were different and each strain included multiple distinct alleles, suggesting that the strains were diploid and heterozygous. The responses of growth and sporulation versus temperature differed among strains. Differences in thermosensitivity among strains could be interpreted as the result of evolution and processes of adaptation to site-specific environmental conditions. Although carbon content did not differ among strains and cultivation temperatures, nitrogen content tended to increase at higher temperatures and there were differences among strains. A wide variety of asexual variants stably reproducing clonally would be advantageous in selecting elite cultivars for long-term cultivation. Using asexual variants as available resources for elite cultivars provides potential support for increasing the productivity of U. prolifera.

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