scholarly journals Checking of the robustness of precast structural systems based on the energy balance method

Vestnik MGSU ◽  
2021 ◽  
pp. 1015-1033
Author(s):  
Viktor V. Tur ◽  
Andrei V. Tur ◽  
Aliaksandr A. Lizahub
Keyword(s):  
Energy Balance ◽  
Progressive Collapse ◽  
Precast Concrete ◽  
Analytical Models ◽  
Structural Systems ◽  
Structural System ◽  
Cross Sectional ◽  
Basic Parameters ◽  
Comparison Of The Results ◽  
Methods Analytical

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.

PROGRESSIVE COLLAPSE RESISTANCE OF FACILITIES EXPERIENCED TO LOCALIZED STRUCTURAL DAMAGE - AN ANALYTICAL REVIEW

2021 ◽  
Vol 95 (3) ◽  
pp. 76-108
Author(s):  
N.V. FEDOROVA ◽  
◽  
S.YU. SAVIN ◽  
Keyword(s):  
Bearing Capacity ◽  
Structural Damage ◽  
Scientific Literature ◽  
Progressive Collapse ◽  
Structural Systems ◽  
Structural System ◽  
Scientific Review ◽  
Collapse Resistance ◽  
The World ◽  
New Research

During the entire life cycle, the facilities are experienced to force and environmental actions of various nature and intensity. In some cases, such influences can lead to a loss of the bearing capacity of the structural elements of a building, which in turn can lead to a disproportionate failure of the entire structural system. Such phenomenon was called progressive collapse. Major accidents at facilities, such as the collapse of a section of the Ronan Point high-rise residential building (London, 1968), the Sampoong department store (Seoul, 1995), the Transvaal Park pavement (Moscow, 2004), the World Trade Center (New York, 2011) and others, clearly demonstrated the urgency of this problem. In this regard, the regulatory documents of the USA, Great Britain, EU, China, Australia, Russia and other countries established requirements for the need to calculate structural systems of buildings for resist to progressive collapse after sudden localized structural damage. However, the steady increase in the number of new publications on the problem of progressive collapse observed in the world scientific literature indicates that the results of such studies do not yet provide exhaustive answers to all questions related to this phenomenon. In this regard, the proposed review article is aimed at systematizing, generalizing and analyzing new research results on resistance to progressive collapse of facilities, identifying new trends and proposing new research directions and tasks to improve the level of structural safety of design solutions for buildings and structures. In order to achieve this goal, the following aspects were considered: the nature of the impacts leading to progressive collapse; features of modeling the progressive collapse of structural systems of buildings and structures; mechanisms of resistance to progressive collapse and criteria for evaluation of a progressive collapse resistance. Particular attention in the scientific review is paid to the analysis of works related to a new direction of research in the area under consideration, associated with the assessment of the bearing capacity of eccentrically compressed elements of structural systems, the effect on their resistance to progressive collapse of the parameters of the loading mode, degradation of material properties and the topology of the structural system. The significance of the proposed scientific review is that, along with the well-known and new results presented in the English-language scientific literature, it summarizes and analyzes the original approaches, methods and research results published in Russian-language scientific publications, primarily included in the RSCI Web of Science.

scholarly journals Simplified analytical method for the robustness assessment of precast reinforced concrete structural systems

2022 ◽  
Vol 20 (4) ◽  
pp. 093-114
Author(s):  
Viktar Tur ◽  
Andrei Tur ◽  
Aliaksandr Lizahub
Keyword(s):  
Energy Balance ◽  
Balance Method ◽  
Analytical Models ◽  
Dynamic Resistance ◽  
Structural System ◽  
Load Path ◽  
Energy Balance Method ◽  
Central Column ◽  
Simplified Calculation ◽  
Energy Balance Approach

The article presents the simplified implementation of alternative load path method based on the energy balance approach. This method should be used to check the global resistance of a damaged structural system after the occurrence of an accidental event. Basic assumptions of simplified analytical models for modelling resistance of horizontal ties in a damaged structural system, taking into account the membrane (chain) effects, were presented. An approach to modelling the dynamic resistance of a damaged structural system based on the energy balance method is described. Calculated dependencies for checking the robustness of a prefabricated multi-storey building with hollow-core slabs after the loss of the central column are proposed and considered using an example. On the considered example, a comparison of the required tie sections area with the dynamic resistance designed using the energy balance method (EBM) and according to the current standards, and a statistical assessment of the reliability of the load-bearing capacity models are carried out. In the end, a brief algorithm for the simplified calculation of the dynamic resistance of a damaged structural system is proposed.

scholarly journals Fire behavior of shallow prestressed hollow core slabs from computational modeling

2020 ◽  
Vol 13 (2) ◽  
pp. 398-432
Author(s):  
D. L. ARAÚJO ◽  
G. D. C. PINTO
Keyword(s):  
Fire Resistance ◽  
Numerical Models ◽  
Precast Concrete ◽  
Fire Behavior ◽  
Steel Structures ◽  
Analytical Models ◽  
Structural Systems ◽  
Hollow Core ◽  
Finite Element Software ◽  
Standard Fire

Abstract Prestressed hollow core slabs are one of the structural systems whose use has increased the most in recent years in Brazil due to its efficiency and versatility. They can be used in many types of structural systems, such as masonry, precast concrete, cast-in-place concrete and steel structures. However, there are few analytical models to evaluate the fire behavior of hollow core slabs. In a simplified way, the fire resistance is evaluated indirectly through the minimum distance of the surface in contact with fire to the reinforcement axis. In this paper, some numerical models in finite element software were developed to analyze the variation of temperature with fire exposure time of shallow hollow core slabs, focusing on the presence of voids in the transversal section of the slab. The 500 °C isotherm method applied to 20 cm high slabs confirmed the Standard Fire Resistance obtained from the tabular method. However, when applied to shallow prestressed hollow core slabs that are 16 cm high, the 500 °C isotherm method indicated that the Standard Fire Resistance of these slabs is lower than values obtained from tabular methods.

scholarly journals Modeling damaged precast structural system when its robustness check

2021 ◽  
pp. 63-81
Author(s):  
Viktar TUR ◽  
Andrei TUR ◽  
Aliaksandr LIZAHUB
Keyword(s):  
Progressive Collapse ◽  
Precast Concrete ◽  
Experimental Studies ◽  
Resistance Mechanisms ◽  
Calculation Model ◽  
Dynamic Resistance ◽  
Building Structures ◽  
Structural System ◽  
Non Linear ◽  
Central Column

Within the framework of traditional approaches to checking for resistance of reinforced concrete buildings and structures to the progressive collapse development, membrane (chain) forces in a damaged structural system are calculated separately, without considering its non-linear bending behavior during the formation of the plastic hinges and without checking the possibility of achieving large deflections.The authors propose an approach to modelling a nonlinear quasi-static reaction of a damaged structural system in an accidental design situation. This approach considers non-linear bending and the resistance of reserved horizontal ties, considering their ultimate ductility. The authors verified the proposed approach based on the results of experimental studies by others researchers.An example of the application of the proposed approach in assessing the robustness of a structural system made of precast concrete with a sudden removal of the central column is considered. In accordance with the provisions of the energy approach, an analysis is made of the contribution of individual resistance mechanisms to the total quasi-static and dynamic resistance of the damaged structural system.We show that the proposed calculation model adequately describes the behavior of a damaged structural system in an accidental design situation, and therefore to carry out parametric studies and check the robustness of building structures.

COMPREHENSIVE REFORMING OF TECHNOLOGICAL, FUNCTIONAL AND STRUCTURAL SYSTEMS OF SKIN UNITS OF HOSPITALS

2020 ◽  
pp. 211-218
Author(s):  
Владимир Григорьевич Донцов ◽  
Елена Владимировна Донцова ◽  
Любовь Анатольевна Новикова ◽  
Лариса Николаевна Борзунова
Keyword(s):  
Service System ◽  
Medical Examination ◽  
Structural Systems ◽  
Structural System ◽  
Structural Units

В статье доказана порочность переустройства только одной структурной системы (реструктуризации), так как это чревато поломками элементов, звеньев и блоков, сомой системы кожной службы. Допустимо лишь незначительная адаптация к конкретным условиям больниц, где это будет внедряться. Сформулированы понятия конечного результата работы врачей и структурных подразделений медицинских стационаров в современных условиях общественно-политической формации. Описаны преимущества реконструкции комплекса систем судебно-медицинской экспертизы как экспериментальной службы для кожного отделения городской многопрофильной больницы и работы самого кожного отделения. Описана форма структурного построения судебно-медицинской и кожной служб. По аналоги с экспертным учреждением ожидаются аналогичные изменение конечного результата в кожном подразделении многопрофильного стационара The article proves the viciousness of the reorganization of only one structural system (restructuring), since this is fraught with breakdowns of elements, links and blocks, the soma of the skin service system. Only slight adaptation to the specific conditions of the hospitals where it will be implemented is acceptable. The concepts of the final result of the work of doctors and structural units of medical hospitals in the modern conditions of the socio-political formation are formulated. The advantages of reconstruction of a complex of forensic medical examination systems as an experimental service for the skin department of a city multidisciplinary hospital and the work of the skin department itself are described. The form of structural structure of forensic and skin services is described. By analogy with an expert institution, a similar change in the final result is expected in the skin department of a multidisciplinary hospital

scholarly journals Parametric Analysis of the Shear Lag Effect in Tube Structural Systems of Tall Buildings

2020 ◽  
Vol 11 (1) ◽  
pp. 278
Author(s):  
Ivan Hafner ◽  
Anđelko Vlašić ◽  
Tomislav Kišiček ◽  
Tvrtko Renić
Keyword(s):  
Parametric Analysis ◽  
Numerical Models ◽  
Tall Buildings ◽  
Structural Systems ◽  
Structural Elements ◽  
Structural System ◽  
Shear Lag ◽  
Shear Lag Effect ◽  
Lag Effect ◽  
Secondary Structural Elements

Horizontal loads such as earthquake and wind are considered dominant loads for the design of tall buildings. One of the most efficient structural systems in this regard is the tube structural system. Even though such systems have a high resistance when it comes to horizontal loads, the shear lag effect that is characterized by an incomplete and uneven activation of vertical elements may cause a series of problems such as the deformation of internal panels and secondary structural elements, which cumulatively grow with the height of the building. In this paper, the shear lag effect in a typical tube structure will be observed and analyzed on a series of different numerical models. A parametric analysis will be conducted with a great number of variations in the structural elements and building layout, for the purpose of giving recommendations for an optimal design of a tube structural system.

scholarly journals Reliability Estimation of Reinforced Slopes to Prioritize Maintenance Actions

2021 ◽  
Vol 18 (2) ◽  
pp. 373
Author(s):  
Farshad BahooToroody ◽  
Saeed Khalaj ◽  
Leonardo Leoni ◽  
Filippo De Carlo ◽  
Gianpaolo Di Bona ◽  
...  
Keyword(s):  
Urban Areas ◽  
Evaluation Method ◽  
Likelihood Function ◽  
Reliability Estimation ◽  
Analytical Models ◽  
Geotechnical Structures ◽  
Reinforced Slopes ◽  
The Stability ◽  
Methods Analytical ◽  
Asset Managers

Geosynthetics are extensively utilized to improve the stability of geotechnical structures and slopes in urban areas. Among all existing geosynthetics, geotextiles are widely used to reinforce unstable slopes due to their capabilities in facilitating reinforcement and drainage. To reduce settlement and increase the bearing capacity and slope stability, the classical use of geotextiles in embankments has been suggested. However, several catastrophic events have been reported, including failures in slopes in the absence of geotextiles. Many researchers have studied the stability of geotextile-reinforced slopes (GRSs) by employing different methods (analytical models, numerical simulation, etc.). The presence of source-to-source uncertainty in the gathered data increases the complexity of evaluating the failure risk in GRSs since the uncertainty varies among them. Consequently, developing a sound methodology is necessary to alleviate the risk complexity. Our study sought to develop an advanced risk-based maintenance (RBM) methodology for prioritizing maintenance operations by addressing fluctuations that accompany event data. For this purpose, a hierarchical Bayesian approach (HBA) was applied to estimate the failure probabilities of GRSs. Using Markov chain Monte Carlo simulations of likelihood function and prior distribution, the HBA can incorporate the aforementioned uncertainties. The proposed method can be exploited by urban designers, asset managers, and policymakers to predict the mean time to failures, thus directly avoiding unnecessary maintenance and safety consequences. To demonstrate the application of the proposed methodology, the performance of nine reinforced slopes was considered. The results indicate that the average failure probability of the system in an hour is 2.8×10−5 during its lifespan, which shows that the proposed evaluation method is more realistic than the traditional methods.

scholarly journals The effect of breakfast on appetite regulation, energy balance and exercise performance

2015 ◽  
Vol 75 (3) ◽  
pp. 319-327 ◽  
Author(s):  
David J. Clayton ◽  
Lewis J. James
Keyword(s):  
Energy Balance ◽  
Energy Expenditure ◽  
Energy Intake ◽  
Exercise Performance ◽  
Intervention Studies ◽  
Precise Determination ◽  
Positive Energy ◽  
Cross Sectional ◽  
Positive Energy Balance ◽  
The Impact

The belief that breakfast is the most important meal of day has been derived from cross-sectional studies that have associated breakfast consumption with a lower BMI. This suggests that breakfast omission either leads to an increase in energy intake or a reduction in energy expenditure over the remainder of the day, resulting in a state of positive energy balance. However, observational studies do not imply causality. A number of intervention studies have been conducted, enabling more precise determination of breakfast manipulation on indices of energy balance. This review will examine the results from these studies in adults, attempting to identify causal links between breakfast and energy balance, as well as determining whether consumption of breakfast influences exercise performance. Despite the associations in the literature, intervention studies have generally found a reduction in total daily energy intake when breakfast is omitted from the daily meal pattern. Moreover, whilst consumption of breakfast supresses appetite during the morning, this effect appears to be transient as the first meal consumed after breakfast seems to offset appetite to a similar extent, independent of breakfast. Whether breakfast affects energy expenditure is less clear. Whilst breakfast does not seem to affect basal metabolism, breakfast omission may reduce free-living physical activity and endurance exercise performance throughout the day. In conclusion, the available research suggests breakfast omission may influence energy expenditure more strongly than energy intake. Longer term intervention studies are required to confirm this relationship, and determine the impact of these variables on weight management.

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