11 research outputs found
Fire resistance of reinforced concrete and steel structures
No full textThe scientific bases of ensuring fire resistance of reinforced concrete and steel building structures in the conditions of modern extreme influences are laid.
The current state of fire safety of buildings and structures, as well as approaches, methods and tools for its assessment are analyzed. Analysis of emergencies and fires in the world has shown that the vast majority of them occur in buildings and structures. It is shown that the cause of catastrophic consequences and destruction is the non-compliance of the actual limit of fire resistance of building structures with regulatory requirements. This is due to the imperfection of methods and means of assessing the fire resistance of building structures, including fire-retardant.
To overcome the shortcomings identified during the analysis, the paper develops physical and mathematical models of thermal processes occurring in the fire-retardant reinforced concrete structure. Based on the proposed models, a computational-experimental method for estimating the fire resistance of such structures has been developed. The efficiency of the proposed method was tested by identifying the relationship between the parameters of the fire-retardant plaster coating “Neospray” and the fire resistance of fire-retardant multi-hollow reinforced concrete floor.
The study of fire resistance of steel structures is proposed to be carried out using reduced samples in the form of steel plates with dimensions of 500×500×5 mm. Based on the proposed models, a calculation and experimental method for estimating the fire resistance of steel structures, as well as an algorithm and procedures for its implementation have been developed. The verification of the efficiency of the proposed method was carried out in the ANSYS software package using the aged coating “Phoenix STS” and the coating “Amotherm Steel Wb” under heating conditions at the temperature of the hydrocarbon fire.
The reliability of the developed models and methods is checked. It is established that random errors in temperature measurement significantly affect the accuracy of determining the thermophysical characteristics and limits of fire resistance. In general, the efficiency of the proposed calculation and experimental methods with sufficient accuracy for engineering calculations is confirmed
Hot Torsion Tests of AA6082 Alloy
No full textMaterials characterization and the knowledge of their elastic-plastic behavior are of fundamental importance for the design of industrial manufacturing processes. Nowadays, FEM simulation is the main tool used to optimize product quality and minimize scraps, and the numerical codes have evolved over the years to obtain accurate solutions with reduced computational times. Nevertheless, in order to perform reliable simulations, it is necessary to include accurate modeling of the material flow stress. Hot torsion is a powerful method for the characterization of the material flow stress because, tests can be carried out at constant speeds and temperatures, reaching large strain values, and thus getting over the limits of compression and tensile tests. In this paper the hot torsion characterization applied to AA6082 alloy is presented: tests were performed with equivalent strain rates of 0.01, 0.1, 1, and 10 s-1, in the temperature range from 440 to 550 °C (from 713.15 to 823.15 K). The results are presented in terms of equivalent stress vs equivalent strain. Finally, the material flow stress curve was predicted by the Hyperbolic sine model and Hensel-Spittel law, and the material parameters A, m1-9 are provided for the temperature expressed in °C and K
Fire resistance evaluation of reinforced concrete floors with fire-retardant coating by calculation and experimental method
No full textWith the help of a previously developed technique based on the
solution of inverse and direct problems of heat conductivity, the fire
resistance of a hollow-core reinforced concrete floor with “Neosprei” fire-
retardant plaster coating was estimated. The thermal and physical
characteristics, as well as characteristics of the fire-proof ability of
“Neosprei” fire-retardant plaster coating, have been determined. The
conclusion has been made on the effectiveness of this coating and on the
boundaries of the fire-retardant coatings use to ensure the normed values of
the fire resistance degree of hollow-core reinforced concrete floors,
including in the mining industry
Development and implementation of environmentally safe biotechnologies for the utilization of aquatic organisms biomass
No full textHuman-induced water nutrient enrichment, termed "cultural eutrophication", spurs algae proliferation. This study proposes removing excess cyanobacterial biomass, or blue-green algae, for biofuel production. The resultant digestate serves as organic and mineral fertilizer. Investigating bio-methanogenesis, the study examines reactions for biogas production from BGA, analyzing its chemical and physical properties. This eco-friendly approach, utilizing excess organic matter from algal blooms, ensures sustainable resource utilization. The viability of utilizing cyanobacterial biomass underscores its ecological and economic importance. This paper establishes safe cyanobacterial biomass processing principles, offering a comprehensive technological framework for methane and fertilizer production from various substrates. © 2024 Trans Tech Publications Ltd, All Rights Reserved
Assessment of the technical state and the possibility of its control for the further safe operation of building structures of mining facilities
No full textThere are about 200 operating mines in Ukraine, most of which have not been reconstructed for more than 20 years. Modern anthropogenic and ecological impacts are caused by local technogenic catastrophes and the global ecological crisis. The statistical data on the safety of Ukrainian mines were considered. A literary analysis has been made of advanced expertise in the technical state assessment of the building structures. The purpose of the study is to make optimal decisions when constructing, operating and maintaining the buildings. The procedure for assessing the building state is the result of research, the purpose of which is to develop a technique for reliable and operational assessment of the building structures technical state. In this paper, a technique is proposed for inspecting the constructions and assessing their technical state. The maximum efforts in elements of the adapted frame were used for checking calculations and constructional design. The obtained calculation results were used in determining the sufficiency of existing cross section value of the structure elements. According to the calculation results, a conclusion has been made that hardness, stability and rigidity of the frame elements as a whole are ensured; further operation of the building structures is possible providing for the project development to strengthen building structures and to implement the design solutions at the construction site. In order to ensure the continued normal operation, it is necessary to develop a project for strengthening the structures, as well as a project for fire protection of building structures
Determination of the Composite Panel Moulding Pressure Value
No full textCurrently, prefabricated panel structures are typical products made of polymeric composite materials. The integrity of the composite panels, their structure and accuracy of making a contour are largely associated with the manifestation of residual technological stresses. The above phenomena and associated stress-strain behaviour inevitably occur in the process of moulding of the composite products. However, their value, nature, time of occurrence and dynamics of growth can be fully controlled and regulated. The paper deals with the study of the effect of moulding pressure on the quality of a composite product. A dependence is presented that allows us to determine the time for the degassing of the polymeric composite material package at the given temperature and pressure to obtain a monolithic and nonporous structure. It is shown that the peak of the maximum volatile-matter yield for the considered binder types lies in the temperature range where the degree of curing does not exceed 10%; that is, the viscosity values do not prevent the removal of volatile fractions. The effect of moulding pressure on the values of the volume content of the reinforcing material has been studied, and the dependence of the required thickness of the absorbent layer on the parameters of the package of polymer composite material and pressure has been obtained. The dependence of the required thickness of absorbent layer on the parameters of the package of polymeric composite material and pressure has been obtained. The mathematical model developed by us provides an opportunity to predict the stress-strain behaviour of a composite structure at any time during the moulding process. The model is closely related to chemo-viscous and thermal models. It allowed us to synthetize a method for choosing the rational parameters of the moulding process (temperature, pressure, and time), materials of additional layers and equipment. The experiments proved the presence of several defects, such as de-lamination of edges, waviness, swelling and poor adhesion of upper layers in the specimen of the composite panel cooled stepwise in the absence of the vacuum pressure. The surface quality of the specimen of the panel cooled stepwise under vacuum pressure was significantly better, and no visible defects were observed. The obtained theoretical values of deflections, considering the change in physic-mechanical characteristics that depend on the temperature and rheonomic properties of the material, showed an error that did not exceed 7%, compared to the experimental data. Our results can be applied at the enterprises engaged in designing and manufacturing panel structures of polymeric composite materials
Оцінювання вогнестійкості вогнезахищених залізобетонних конструкцій
No full textA finite-element model for the heat engineering calculation of fireproof reinforced concrete slab has been built, which is designed to assess the fire resistance of unprotected reinforced concrete structures. A feature of the model is the correct choice of types of heat transfer in the cavities of reinforced concrete ceilings. An algorithm that includes experimental and calculation procedures in determining the fire resistance of unprotected reinforced concrete structures has been applied. The initial, boundary conditions for the construction of the model were formulated; the thermophysical properties of materials were substantiated. Thermal calculation of fireproof multi-hollow reinforced concrete ceiling under conditions of fire was carried out. The adequacy of the developed finite-element model was checked. A satisfactory convergence of experimental and calculated temperatures with an accuracy of 10 % was established, which would suffice for the engineering calculations.
The model built makes it possible to assess the fire resistance of unprotected reinforced concrete structures. Thus, there is reason to argue that the model constructed can partially or completely replace the experimental assessment of fire resistance, provided that the construction and setting of the model parameters are correctРозроблено скінчено-елементну модель для теплотехнічного розрахунку вогнезахищеного залізобетонного перекриття, яка призначена для оцінювання вогнестійкості вогнезахищених залізобетонних конструкцій. Особливістю моделі є правильний вибір типів теплообміну в порожнинах залізобетонного перекриття. Застосовано алгоритм, що включає експериментальні та розрахункові процедури при визначенні вогнестійкості вогнезахищених залізобетонних конструкцій. Сформульовані початкові, граничні умови при побудові моделі, обґрунтовані теплофізичні властивості матеріалів. Проведено теплотехнічний розрахунок вогнезахищеного багатопустотного залізобетонного перекриття в умовах впливу пожежі. Проведено перевірку адекватності розробленої скінчено-елементної моделі. Встановлено задовільну збіжність експериментальних та розрахункових температур з точністю до 10 %, що задовольняє інженерні розрахунки.
Розроблена модель дозволяє проводити оцінювання вогнестійкості вогнезахищених залізобетонних конструкцій. Таким чином, є підстави стверджувати, що розроблена модель може частково або повністю замінити експериментальне оцінювання вогнестійкості при умові правильності побудови та задавання параметрів модел
Розробка методу оперативного виявлення загорянь на основі сумісних поточних вибіркових середніх та дисперсій контрольованого небезпечного параметру середовища
No full textThe object of research is the process of detecting the ignition of materials in a premise based on the joint use of current sample means and variances of the controlled hazardous gas environment parameter. The problem is to develop a method for detecting the ignition of materials based on the joint use of current sample means and variances of the controlled hazardous gas environment parameter in a premise. The synthesis of the optimal method for detecting fires was achieved by moving from the space of controlled hazardous gas environment parameters to the spaces of sample means, sample variances, and also the space of joint sample means and variances. Under conditions of large samples, the distribution of sample means, sample variances and its joint values asymptotically tends to a Gaussian distribution. This allows to use the likelihood ratio criterion, which is optimal, in the synthesis. Unlike the traditional approach, the likelihood ratio is current and is determined for a fixed Gaussian distribution in the case of a reliable absence of ignition. It is established that the optimal method of fire detection based on the joint use of sample means and variances with the same quality indicators outperforms the optimal methods of fire detection based only on the sample mean or sample variance of the controlled hazardous parameter of the gas environment. This is explained by the fact that the optimal method of fire detection based on the joint use of sample means and variances uses a larger amount of information contained in the controlled parameters of the gas environment. The results obtained are useful from a theoretical point of view for the proposed optimal methods of fire detection. The practical significance of the work lies in the further improvement of existing fire protection systems of facilities in order to prevent fires.Об’єктом дослідження є процес виявлення загоряння матеріалів у приміщенні на основі спільного використання поточних вибіркових середніх та дисперсій контрольованого небезпечного параметра газового середовища. Проблема полягає в розробці методу виявлення загоряння матеріалів на основі спільного використання поточних вибіркових середніх та дисперсій контрольованого небезпечного параметра газового середовища в приміщенні. Синтез оптимального методу виявлення загорянь вдалося виконати завдяки переходу з простору контрольованих небезпечних параметрів газового середовища у простори вибіркових середніх, вибіркових дисперсій, а також простору спільних вибіркових середніх та дисперсій. За умов великих вибірок розподіл вибіркових середніх, вибіркових дисперсій та його спільних значень асимптотичне прагне до розподілу Гауса. Це дозволяє при синтезі скористатися критерієм відношення правдоподібності, який є оптимальним. На відміну від традиційного підходу, відношення правдоподібності є поточним та визначається для фіксованого розподілу Гауса у разі достовірної відсутності загоряння. Встановлено, що оптимальний метод виявлення загорянь на основі спільного використання вибіркових середніх та дисперсій при однакових показниках якості перевершує оптимальні методи виявлення загорянь на основі лише вибіркової середньої або вибіркової дисперсії контрольованого небезпечного параметра газового середовища. Пояснюється це тим, що оптимальний метод виявлення загорянь на основі спільного використання вибіркових середніх та дисперсій використовує більшу кількість інформації, яка міститься в контрольованих параметрах газового середовища. Отримані результати є корисними з теоретичної точки зору запропонованими оптимальними методами виявлення загорянь. Практичне значення роботи полягає в подальшому вдосконаленні існуючих систем протипожежного захисту об’єктів з метою запобіганню виникненню пожеж
Development of a method for rapid detection of fires based on combined current sampling and dispersions of a controlled hazardous environmental parameter
No full textThe object of research is the process of detecting the ignition of materials in a premise based on the joint use of current sample means
and variances of the controlled hazardous gas environment parameter. The problem is to develop a method for detecting the ignition
of materials based on the joint use of current sample means and variances of the controlled hazardous gas environment parameter in
a premise. The synthesis of the optimal method for detecting fires was achieved by moving from the space of controlled hazardous gas
environment parameters to the spaces of sample means, sample variances, and also the space of joint sample means and variances. Under
conditions of large samples, the distribution of sample means, sample variances and its joint values asymptotically tends to a Gaussian
distribution. This allows to use the likelihood ratio criterion, which is optimal, in the synthesis. Unlike the traditional approach, the
likelihood ratio is current and is determined for a fixed Gaussian distribution in the case of a reliable absence of ignition. It is established
that the optimal method of fire detection based on the joint use of sample means and variances with the same quality indicators outper -
forms the optimal methods of fire detection based only on the sample mean or sample variance of the controlled hazardous parameter
of the gas environment. This is explained by the fact that the optimal method of fire detection based on the joint use of sample means
and variances uses a larger amount of information contained in the controlled parameters of the gas environment. The results obtained
are useful from a theoretical point of view for the proposed optimal methods of fire detection. The practical significance of the work lies
in the further improvement of existing fire protection systems of facilities in order to prevent fires.
Keywords: fire detection, premises, hazardous parameters of the gas environment, sample means, sample variance
Assessment of Fire Resistance of Fireproof Reinforced Concrete Structures
No full textA finite-element model for the heat engineering calculation of fireproof reinforced concrete slab has been built, which is designed to assess the fire resistance of unprotected reinforced concrete structures. A feature of the model is the correct choice of types of heat transfer in the cavities of reinforced concrete ceilings. An algorithm that includes experimental and calculation procedures in determining the fire resistance of unprotected reinforced concrete structures has been applied. The initial, boundary conditions for the construction of the model were formulated; the thermophysical properties of materials were substantiated. Thermal calculation of fireproof multi-hollow reinforced concrete ceiling under conditions of fire was carried out. The adequacy of the developed finite-element model was checked. A satisfactory convergence of experimental and calculated temperatures with an accuracy of 10 % was established, which would suffice for the engineering calculations.
The model built makes it possible to assess the fire resistance of unprotected reinforced concrete structures. Thus, there is reason to argue that the model constructed can partially or completely replace the experimental assessment of fire resistance, provided that the construction and setting of the model parameters are correc
