Introduction. The robustness requirements should be fulfilled already at the stage of conceptual ... more Introduction. The robustness requirements should be fulfilled already at the stage of conceptual design of the structural system, taking into account the use of various strategies for its protection from progressive collapse. Compared to monolithic reinforced concrete structural systems, precast concrete systems are more susceptible to the effects of accidental actions. To ensure the integrity of the damaged system in the original prefabricated structural system, it is necessary to provide (reserve) a sufficient number of horizontal (internal and perimetric) and vertical ties with the required degree of continuity and plastic deformability. Materials and methods. Analytical models of the resistance of horizontal ties based on the equations of the energy balance of the system. Results. On a real example of a prefabricated floor, calculations of the required parameters of horizontal ties were performed according to the proposed dependencies, based on the model of the energy balance of the system and the design models included in the standards of various countries. Comparison of the results obtained showed that the calculation models of the norms in a number of cases can give an unsafe result, underestimating the required cross-sectional area of horizontal ties. This is due to the fact that all dependencies for calculating the tie forces are based on constant values of the ultimate deflection (usually from 1/6 to 1/10 of the span) without checking the limiting deformability of horizontal ties. Conclusions. Deformability of ties is one of the basic parameters that should be monitored when checking the robustness of structural systems made of precast concrete. The proposed method, based on the provisions of the energy balance, makes it possible to take into account the limiting deformability of horizontal ties when determining the membrane (chain) forces and calculate the maximum dynamic response of the damaged structural system.
This paper presents a mechanical model of the shear resistance based on Critical Shear Crack Theo... more This paper presents a mechanical model of the shear resistance based on Critical Shear Crack Theory (CSCT) and its application for the checking of the shear ultimate state of self-stressed elements reinforced with FRP bars. The shear force, which is transmitted through the inclined crack by aggregate interlock, residual tensile strength, dowel action and inclined chord of the compression concrete, is calculated depending on the value of the inclined crack opening, determined according to the modified law “bond-slip” for FRP bars. The reliability of the proposed approach is confirmed by comparison both with the results of our own experimental investigations and with numerous research results by various authors.
This paper proposes a design model (2D MSDM) for assessment the early-age stress-strain parameter... more This paper proposes a design model (2D MSDM) for assessment the early-age stress-strain parameters of two-axially restrained expansive concrete elements. The analytical model allows defining the restrained expansion strains and corresponding self-stresses in case of arbitrary restraint conditions in orthogonal directions by taking into consideration the elastic-plastic behavior of concrete during the expansion period. The results of solution according to the proposed model were compared with the experimental results of expansive concrete elements with orthogonal confinement carried out by authors and other researchers.
Fuzzy logic is the useful tool when assessing the existing reinforced concrete structures. The in... more Fuzzy logic is the useful tool when assessing the existing reinforced concrete structures. The introduction of expert system in assessing the technical condition of the existing structures built on the fuzzy logic represents a transition to a new and higher-quality level for survey of constructions sites. As a result, it is seen that the assessment of the existing building with usage of the proposed expert system is in compliance with the estimation of the qualified experts.
In accordance with the basic assumptions of the European design standards (Eurocodes), currently ... more In accordance with the basic assumptions of the European design standards (Eurocodes), currently in use in the territory of the Republic of Belarus, it is proposed to carry out the design of building structures, made of different materials, belonging to the same reliability class with the same target value of the reliability level (or with the same degree of reliability), expressed in the permissible values of the reliability index or equivalent to it the probability of failure. However, the practical implementation of this idea involves a very large number of problems. The study is devoted to the analysis of reliability levels and equivalent to them probabilities of failure provided by Eurocodes for models of resistance for bending of steel and reinforced concrete elements under rather abstract conditions: the action of self weight and snow load for the reference period of 1 year, however this analysis allows qualitatively highlight the problems, associated with existing approaches...
An analytical design model for estimation the shear resistance of plane self-stressing concrete e... more An analytical design model for estimation the shear resistance of plane self-stressing concrete elements with orthogonal reinforcement is presented. The design model is based on the strut-and-tie model concept and takes into consideration the restrained expansion strains and selfstresses as a result of self-stressing concrete expansion. The results of theoretical investigations were finally compared to the experimental ones showing the suitability of proposed design method.
This paper presents the results of testing beams reinforced with FRP in combination with expansiv... more This paper presents the results of testing beams reinforced with FRP in combination with expansive concrete. Failure modes under uniformly distributed loading and ultimate forces recorded in tests are described. The results of comparison of shear resistance models against the background of experimental data are presented.
The paper presents the implementation of the modified strains development model (MSDM) for the tw... more The paper presents the implementation of the modified strains development model (MSDM) for the two-way restrained self-stressed members such as expansive concrete-filled steel tubes and expansive concrete plane elements with arbitrary orthogonal reinforcement. The analytical approach allows defining the restrained strains and stresses in any 2D restraint conditions by following the iterative procedures and accounting for the elastic-plastic behaviour of expansive concrete at an early age. The consistency of the proposed method was confirmed by assessing the experimental results of the two series of the expansive concrete-filled steel tubes and three series of the expansive concrete plane members with mesh reinforcement in the centre of gravity.
Introduction. The robustness requirements should be fulfilled already at the stage of conceptual ... more Introduction. The robustness requirements should be fulfilled already at the stage of conceptual design of the structural system, taking into account the use of various strategies for its protection from progressive collapse. Compared to monolithic reinforced concrete structural systems, precast concrete systems are more susceptible to the effects of accidental actions. To ensure the integrity of the damaged system in the original prefabricated structural system, it is necessary to provide (reserve) a sufficient number of horizontal (internal and perimetric) and vertical ties with the required degree of continuity and plastic deformability. Materials and methods. Analytical models of the resistance of horizontal ties based on the equations of the energy balance of the system. Results. On a real example of a prefabricated floor, calculations of the required parameters of horizontal ties were performed according to the proposed dependencies, based on the model of the energy balance of the system and the design models included in the standards of various countries. Comparison of the results obtained showed that the calculation models of the norms in a number of cases can give an unsafe result, underestimating the required cross-sectional area of horizontal ties. This is due to the fact that all dependencies for calculating the tie forces are based on constant values of the ultimate deflection (usually from 1/6 to 1/10 of the span) without checking the limiting deformability of horizontal ties. Conclusions. Deformability of ties is one of the basic parameters that should be monitored when checking the robustness of structural systems made of precast concrete. The proposed method, based on the provisions of the energy balance, makes it possible to take into account the limiting deformability of horizontal ties when determining the membrane (chain) forces and calculate the maximum dynamic response of the damaged structural system.
This paper presents a mechanical model of the shear resistance based on Critical Shear Crack Theo... more This paper presents a mechanical model of the shear resistance based on Critical Shear Crack Theory (CSCT) and its application for the checking of the shear ultimate state of self-stressed elements reinforced with FRP bars. The shear force, which is transmitted through the inclined crack by aggregate interlock, residual tensile strength, dowel action and inclined chord of the compression concrete, is calculated depending on the value of the inclined crack opening, determined according to the modified law “bond-slip” for FRP bars. The reliability of the proposed approach is confirmed by comparison both with the results of our own experimental investigations and with numerous research results by various authors.
This paper proposes a design model (2D MSDM) for assessment the early-age stress-strain parameter... more This paper proposes a design model (2D MSDM) for assessment the early-age stress-strain parameters of two-axially restrained expansive concrete elements. The analytical model allows defining the restrained expansion strains and corresponding self-stresses in case of arbitrary restraint conditions in orthogonal directions by taking into consideration the elastic-plastic behavior of concrete during the expansion period. The results of solution according to the proposed model were compared with the experimental results of expansive concrete elements with orthogonal confinement carried out by authors and other researchers.
Fuzzy logic is the useful tool when assessing the existing reinforced concrete structures. The in... more Fuzzy logic is the useful tool when assessing the existing reinforced concrete structures. The introduction of expert system in assessing the technical condition of the existing structures built on the fuzzy logic represents a transition to a new and higher-quality level for survey of constructions sites. As a result, it is seen that the assessment of the existing building with usage of the proposed expert system is in compliance with the estimation of the qualified experts.
In accordance with the basic assumptions of the European design standards (Eurocodes), currently ... more In accordance with the basic assumptions of the European design standards (Eurocodes), currently in use in the territory of the Republic of Belarus, it is proposed to carry out the design of building structures, made of different materials, belonging to the same reliability class with the same target value of the reliability level (or with the same degree of reliability), expressed in the permissible values of the reliability index or equivalent to it the probability of failure. However, the practical implementation of this idea involves a very large number of problems. The study is devoted to the analysis of reliability levels and equivalent to them probabilities of failure provided by Eurocodes for models of resistance for bending of steel and reinforced concrete elements under rather abstract conditions: the action of self weight and snow load for the reference period of 1 year, however this analysis allows qualitatively highlight the problems, associated with existing approaches...
An analytical design model for estimation the shear resistance of plane self-stressing concrete e... more An analytical design model for estimation the shear resistance of plane self-stressing concrete elements with orthogonal reinforcement is presented. The design model is based on the strut-and-tie model concept and takes into consideration the restrained expansion strains and selfstresses as a result of self-stressing concrete expansion. The results of theoretical investigations were finally compared to the experimental ones showing the suitability of proposed design method.
This paper presents the results of testing beams reinforced with FRP in combination with expansiv... more This paper presents the results of testing beams reinforced with FRP in combination with expansive concrete. Failure modes under uniformly distributed loading and ultimate forces recorded in tests are described. The results of comparison of shear resistance models against the background of experimental data are presented.
The paper presents the implementation of the modified strains development model (MSDM) for the tw... more The paper presents the implementation of the modified strains development model (MSDM) for the two-way restrained self-stressed members such as expansive concrete-filled steel tubes and expansive concrete plane elements with arbitrary orthogonal reinforcement. The analytical approach allows defining the restrained strains and stresses in any 2D restraint conditions by following the iterative procedures and accounting for the elastic-plastic behaviour of expansive concrete at an early age. The consistency of the proposed method was confirmed by assessing the experimental results of the two series of the expansive concrete-filled steel tubes and three series of the expansive concrete plane members with mesh reinforcement in the centre of gravity.
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