Evaluation of the Warping Model for Analysis of Polystyrene Concrete Slabs with Profiled Steel Sheeting

In this article the possibility of applying the warping model offered by V. G. Piskunov, A. V. Goryk and V. N. Cherednikov for analyzing polystyrene concrete slabs with profiled steel sheeting is considered. The adequacy of the offered model was verified by comparing the experimental and calculated deflections of the slab. Test specimens of polystyrene concrete slabs with profiled steel sheeting (PCSPSS) were made for experimental studies and then mechanical properties of the slab components – the polystyrene concrete and the profiled steel sheeting – were determined. Then the behaviour of slabs under a load was studied. The calculation of the warping model of PCSPSS was done at the same time. The obtained results have proved the possibility of applying of the offered warping model for analysis of PCSPSS. It is proposed to use the considered model for further study of the stress-strained state of inhomogeneous slabs

Study of technological features of tubular compressed concrete members in concreting

The technological features of core concreting were analyzed as the main factor in ensuring of strength and reliability of compressed concrete-filled steel tubular (CFST) members. We have conducted the analysis of existing concreting methods of CFST members. In this respect, the most dangerous types of possible technological defects of concrete core of CFST members are inhomogeneity along the height, voids, caverns, and concrete “weak spots”. The authors considered the influence of such technological factors of concreting: placeability, time, concrete mixture compaction method, concreting height on the concrete core strength of CFST members. Based on the experimental studies conducted we suggested the regression correlations for determining the concrete strength of CFST members of different length depending on the movability of concrete mixture and a time for its compaction. The authors performed the correlation analysis of technological factors of concreting on the strength of the concrete core. We carried out the comparison of data on the concrete core strength of CFST members, that were determined by non-destructive methods (sclerometer test results, ultrasonic method) and direct compression strength tests. We experimentally proved that using movable mixtures with the slump of about 4 – 9 cm the overall variation coefficient of concrete core strength of CFST members along the height reaches nearly 13%. Based on the experimental studies conducted we suggested the guidelines on optimal regimes of concrete compaction during manufacturing CFST members at a construction site environment

ІМОВІРНІСНЕ ОЦІНЮВАННЯ НАДІЙНОСТІ ПАСИВНИХ

The introduction of probabilistic methods for assessing the reliability of building structures is governed by modern design standards. When constructing engineering facilities, the task is to construct the structural elements using passive anchors. This work is aimed at creating and testing an algorithm of probabilistic assessment of passive anchors, which determines its relevance. The work’s objective is to develop an algorithm of probabilistic assessment of the reliability of passive anchors by the criteria of loss of reliability, which are possible during the operation of the anchor– concrete system, taking into account the random nature of the material properties and load. In creating the algorithm of probabilistic assessment of the anchor reliability, the probabilities of reaching the following boundary conditions were considered: strength of the contact between concrete and anchor reinforcement; concrete bearing strength of the contact between concrete and anchor reinforcement; tensile and shear strength of the steel anchor.The input deterministic parameters of the algorithm were: basic anchorage length; a cross-sectional area of the anchor; Poisson’s ratio of concrete; concrete modulus of elasticity. Random inputs were: axial tensile strength and compression strength; tensile resistance of rebar; axial and shear forces. The calculation is performed by the method of statistical tests N times. The number of tests, in which the rod is considered unreliable, refers to the total number of tests and determines the risk for the steel anchor of reaching its boundary conditions for its entire service life, followed by calculation of the annual risk for the anchor of reaching its boundary conditions. According to the results of probabilistic calculations, the risk for the anchor of reaching its boundary conditions for the assigned service life is Р = 1.87 10-2 year-1, the annual risk for the anchor of reaching its boundary conditions is Рr = 3.77 10-4 year-1, which does not exceed its permissible value of Ріех = 5 10-4 year-1, provided for by the design standards for structures of CC2 consequences (responsibility) class for the estimated lifetime of Tef = 50 years.Запровадження імовірнісних методів оцінювання надійності будівельних конструкцій регламентовано сучасними нормами проектування. Під час зведення об’єктів будівництва постає завдання конструювання вузлів будівельних конструкцій із застосуванням пасивних анкерів. Дана робота націлена на побудову й апробацію алгоритму імовірнісного оцінювання пасивних анкерів, що обумовлює її актуальність. Завданням роботи є розроблення алгоритму імовірнісного оцінювання надійності пасивних анкерів за критеріями втрати надійності, які є можливими під час експлуатації системи анкер-бетон, з урахуванням випадкового характеру властивостей матеріалів і навантаження

Study of technological features of tubular compressed concrete members in concreting

The technological features of core concreting were analyzed as the main factor in ensuring of strength and reliability of compressed concrete-filled steel tubular (CFST) members. We have conducted the analysis of existing concreting methods of CFST members. In this respect, the most dangerous types of possible technological defects of concrete core of CFST members are inhomogeneity along the height, voids, caverns, and concrete “weak spots”. The authors considered the influence of such technological factors of concreting: placeability, time, concrete mixture compaction method, concreting height on the concrete core strength of CFST members. Based on the experimental studies conducted we suggested the regression correlations for determining the concrete strength of CFST members of different length depending on the movability of concrete mixture and a time for its compaction. The authors performed the correlation analysis of technological factors of concreting on the strength of the concrete core. We carried out the comparison of data on the concrete core strength of CFST members, that were determined by non-destructive methods (sclerometer test results, ultrasonic method) and direct compression strength tests. We experimentally proved that using movable mixtures with the slump of about 4 – 9 cm the overall variation coefficient of concrete core strength of CFST members along the height reaches nearly 13%. Based on the experimental studies conducted we suggested the guidelines on optimal regimes of concrete compaction during manufacturing CFST members at a construction site environment

ВИЗНАЧЕННЯ ПАРАМЕТРІВ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ ЛЕГКОБЕТОННИХ КОМБІНОВАНИХ ПЛИТ ЗА НЕКЛАСИЧНОЮ ЗСУВНОЮ МОДЕЛЛЮ

The non-classical shear model for determination of the parameters of stress-strained state (SSS) of slabs with a non-uniform cross-section was improved. The improvement concerned the expressions for determination of the stresses functions of trough-thickness distribution of the cross-section and the physical and mechanical characteristics of the cross-sections. The holes into the cross-section were account for these obtained mathematical expressions. For this purpose, with the help of the apparatus of generalized functions, a discrete function is introduced which allows determining the width of the cross-section at the appropriate trough-length coordinate. After inputting the width function, the subintegral expressions of the stress distribution functions at the trough-length of the cross were converted and the corresponding integrals were found. The executed transformations allowed to correct the error that arose in the calculation of slabs in a non-classical shear model with holes in the cross-section. The refined model is used for calculation of light concrete combined slabs with profiled steel sheeting. The performed calculations allowed to defined new features in the distribution of the parameters of the stress-strained state, such as the change of the trough-length distribution of stresses of the cross-section and the length distribution of stresses of the slab. They also confirmed the possibility of applying a refined non-classical shear model to calculate light concrete combined slabs, and studying the parameters of the stress-strained state at any point and under different loading and fixing conditions.Доработана некласическая сдвиговая модель определения физико-механических характеристик поперечных сечений неоднородной структуры и применена для расчета легкобетонных комбинированных плит с профилированным настилом. Расчет по универсальной сдвиговой модели позволяет определить параметры напряженно-деформированного состояния в любой точке образца плиты и исследовать их изменение при различных условиях нагрузки.Доопрацьовано некласичну зсувну модель визначення фізико-механічних характеристик поперечних перерізів неоднорідної структури і застосовано її для розрахунку легкобетонних комбінованих плит із профільованим настилом. Розрахунок за універсальною зсувною моделлю дає змогу визначити параметри напружено-деформованого стану у будь-якій точці зразка плити та дослідити їх зміну при різних умовах навантаження

Probabilistic analysis of deformed mode of engineering constructions’ soil-cement grounds

The results of the analysis of probabilistic methods that are used to assess the deformed state of the foundations of engineering structures are presented. A finite element analysis of the stress-strain state of the “man made soil ground – foundation – structure” system was carried out. A method for probabilistic calculation using the finite element method is proposed. On a real example, the level of reliability of a design decision based on a deterministic calculation is estimated by probabilistic calculation. On the basis of the statistic data obtained by imitational modeling, the probability of failure and no-failure operation of the structure regarding the absolute value of settlement and regarding the value of tilt against the reinforcement ratio of soft soil grounds settlements was determined. The probability of failure regarding the value of tilt against the reinforcement ratio was taken (15 to 25%), which is 0.03 – 0.05

Development and implementation of algorithms of building structure engineering calculations for shear fraction under pressing-through.

Development of calculating algorithms for designed and patented constructive solutions for beamless monolithic slab and concrete reinforced column connection in the form of software program is presented in this article. Also a mathematical model for the constructive solutions was created using finite elements method. A theoretical part of the research includes engineering technique for the connection nodes between monolithic concrete slab and reinforced concrete column in stress strain state. A technical goal is simplifying and reliability increasing of loading capacity of the junction and assembly work facilitation along with reducing building frame costs. To perform testing of connection nodes between monolithic reinforced concrete beamless non-bearing slab and reinforced concrete column for shear existing calculating algorithm was improved using the designed formula. A connection node for a shear along the column body calculation according to the technique was also implemented as a software program. A technique for calculating a connection node between monolithic beamless non-capital concrete reinforced slab and concrete reinforced columns was developed. Visual Basic for Applications was used to automate calculating of the connection nodes for shear. The research results have been implemented into practical design and calculation during extension of manufacturing building of Skvira confectionary shop in Skvira settlement

Development and implementation of algorithms of building structure engineering calculations for shear fraction under pressing-through.

Development of calculating algorithms for designed and patented constructive solutions for beamless monolithic slab and concrete reinforced column connection in the form of software program is presented in this article. Also a mathematical model for the constructive solutions was created using finite elements method. A theoretical part of the research includes engineering technique for the connection nodes between monolithic concrete slab and reinforced concrete column in stress strain state. A technical goal is simplifying and reliability increasing of loading capacity of the junction and assembly work facilitation along with reducing building frame costs. To perform testing of connection nodes between monolithic reinforced concrete beamless non-bearing slab and reinforced concrete column for shear existing calculating algorithm was improved using the designed formula. A connection node for a shear along the column body calculation according to the technique was also implemented as a software program. A technique for calculating a connection node between monolithic beamless non-capital concrete reinforced slab and concrete reinforced columns was developed. Visual Basic for Applications was used to automate calculating of the connection nodes for shear. The research results have been implemented into practical design and calculation during extension of manufacturing building of Skvira confectionary shop in Skvira settlement