DESIGNING AND DETAILING OF BUILDING SYSTEMS. MECHANICS IN CIVIL ENGINEERING

Influence of dynamic excitation on the bearing capacity of reinforced concrete columns exposedto fire effects

Вестник МГСУ 10/2013
  • Avetisyan Levon Avetisovich - Moscow State University of Civil Engineering (MGSU) postgraduate student, Department of Reinforced Concrete and Masonry Structures, Moscow State University of Civil Engineering (MGSU), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation; Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript .
  • Tamrazyan Ashot Georgievich - Moscow State University of Civil Engineering (National Research University) (MGSU) Doctor of Technical Sciences, Professor, full member, Russian Engineering Academy, head of the directorate, Moscow State University of Civil Engineering (National Research University) (MGSU), 26 Yaroslavskoe Shosse, Moscow, 129337, Russian Federation; Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript .

Страницы 14-23

This article provides an example of the calculation of eccentrically compressed reinforced concrete elements exposed to dynamic loads and fire effects. The dynamic factor for the concrete under regular conditions is available, and it exceeds one in any case. However, in case of a fire exposure, the value of this factor varies from 0,4 to 0,8, depending on the loading rate and temperature. The value of the dynamic factor was identified in the course of an experiment; thereafter, the pattern of influence of the dynamic effect caused by the progressive collapse of buildings and produced onto the bearing capacity and fire resistance of compressed elements of the pylon and the column was identified. ANSYS 12.1 software package was employed to perform the fire resistance analysis of the pylon on the 1st floor of a 59-storey building. The problem was modeled in the 3D formulation. It represented a pylon exposed to static loading and standard fire conditions. For comparison purposes, bearing capacity values were calculated for different values of the thermal load.The calculation of temperature fields was based on the resolution of boundary value problems of transient heat conduction in capillary-porous bodies.The solution to the problem of the four-sided fire exposure at standard fire temperature values was obtained in characteristic points of the support structure to assess the change in its load-bearing capacity.It is proven that dynamic effects of a fire reduce the bearing capacity of columns by 40 %. Therefore, the analysis of the bearing capacity of structures in terms of their fire resistance should take account of the possibility of progressive collapse of buildings.

DOI: 10.22227/1997-0935.2013.10.14-23

Библиографический список
  1. Tamrazyan A.G. Ogneudarostoykost’ nesushchikh zhelezobetonnykh konstruktsiy vysotnykh zdaniy [Fire Stability and Shock Resistance of Bearing Reinforced Concrete Structures of High-rise Buildings]. Zhilishchnoe stroitel’stvo [Residential Housing Construction]. 2005, no. 1, pp. 7—8.
  2. Lu D.G., Cui S.S., Song P.Y., and Chen Z.H. Robustness Assessment for Progressive Collapse of Framed Structures Using Pushdown Analysis Method. Proceeding of the 4th International Workshop on Reliable Engineering Computing. REC 2010, University of Harbin, vol. 1, pp. 268—281.
  3. Rastorguev B.S. Metody rascheta zdaniy na ustoychivost’ protiv progressiruyushchego razrusheniya [Methods for Stability Analysis of Buildings in Case of Progressive Collapse]. Vestnik otdeleniya stroitel’nykh nauk RAASN [Bulletin of Section for Civil Engineering Sciences of the Russian Academy of Architecture and Civil Engineering]. 2009, vol. 1, no. 13, pp. 15—20.
  4. Jinkoo Kim, Taewan Kim. Assessment of Progressive Collapse-resisting Capacity of Steel Moment Frames. Journal of Constructional Steel Research. 2009, no. 65, pp. 169—179.
  5. Bernhart D., Buchanan A., Dhakal R., Moss P. Effect of Top Reinforcing on the Fire Performance of Continuous Reinforced Concrete Beams. Fire safety science-proceedings of the eighth international symposium. Karslsruhe, Germany, 21—26 September 2008, pp. 259—270.
  6. Phan L.T., Lawson J.R. and Davis F.L. Effects of Elevated Temperature Exposure on Heating Characteristics, Spalling, and Residual Properties of High Performance Concrete. Materials and Structures. March 2001, vol. 34, pp. 83—91.
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  8. Bazhenov Yu.M. Beton pri dinamicheskom nagruzhenii [Concrete Exposed to Dynamic Loading]. Moscow, Stroyizdat Publ., 1970, 270 p.
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  13. Tamrazyan A.G., Mekhralizadekh B.A. Osobennosti proyavleniya ognevykh vozdeystviy pri raschete konstruktsiy na progressiruyushchee razrushenie zdaniy s perekhodnymi etazhami [Features of Fire Effects as Part of Analysis of Structures of Buildings Having Half Floors, If Exposed to Progressive Collapse]. Pozharovzryvobezopasnost’ [Fire and Explosion Safety]. 2012, no. 12, pp. 41—44.

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ANALYSIS OF EXPOSURE OF REINFORCED CONCRETE BUILDINGS TO TEMPERATURE LOADS

Вестник МГСУ 5/2012
  • Mkrtychev Oleg Vartanovich - Moscow State University of Civil Engineering (MSUCE) Doctor of Technical Sciences, Professor, Department of Strength of Materials, Moscow State University of Civil Engineering (MSUCE), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation; Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript .
  • Sidorov Dmitriy Sergeevich - Moscow State University of Civil Engineering (MSUCE) postgraduate student, Moscow State University of Civil Engineering (MSUCE), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation; Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript .

Страницы 50 - 55

The co-authors consider the problem of analysis of building structures in respect of combined effects of forces and temperatures. Results of fire tests of reinforced concrete walls and slabs are presented. Overview of the analysis of the fire resistance of reinforced-concrete buildings is also provided.
As a result of the research, numerical solutions were obtained in respect of deflections, stresses, deformations and internal forces arising in a reinforced concrete bearing wall and plate exposed to a combination of forces and thermal loads. Comparative analysis of the experimental data and the results of the numerical solution was performed. The conclusion is that the experimental data are in good fit to the results of the numerical solution.
Overall limit state of the monolithic building under consideration in terms of its fire resistance means its failure as a result of collapse. The limit state value is equal to 60; therefore, it is equal to 60 minutes. This value, if considered in respect of separate bearing elements, fits the fire resistance limit of buildings of Grade III (Fire Resistance) that is equal to 45. Evidently, assurance of higher fire resistance limits of the building under consideration requires special fire safety actions to be applied.

DOI: 10.22227/1997-0935.2012.5.50 - 55

Библиографический список
  1. GOST 30247.1-94. Konstruktsii stroitel’nye. Metody ispytaniy na ognestoykost’. Nesushchie i ograzhdayushchie konstruktsii [State Standard 30247.1-94. Building structures. Methods of Testing for Fire Resistance. Bearing and Envelope Structures]. Moscow, IPK Izdatel’stvo standartov [IPK Publishing House of Standards], 1995.
  2. Federal Law of 22.07.2008 N 123-FZ. Tekhnicheskiy reglament o trebovaniyakh pozharnoy bezopasnosti [Technical Regulations Governing Fire Safety Requirements]. Parlamentskaya gazeta [The Parliamentary Newspaper]. July 31, 2008.
  3. GOST 30247.0-94. Konstruktsii stroitel’nye. Metody ispytaniy na ognestoykost’. Obshchie trebovaniya [State Standard 30247.0-94. Building Structures. Methods of Testing for Fire Resistance. General Requirements]. Moscow, IPK Izdatel’stvo standartov [IPK Publishing House of Standards], 1996.
  4. Milovanov A.F. Stoykost’ zhelezobetonnykh konstruktsiy pri pozhare. M. [Durability of Reinforced Concrete Structures in Case of Fire]. Moscow, Stroyizdat Publ., 1998, 304 p.
  5. Bushev V.P. Issledovanie ognestoykosti odnosloynykh nesushchikh zhelezobetonnykh sten [Research of the Fire Resistance of Single-Layer Bearing Reinforced Concrete Walls]. Moscow, 1972.
  6. Mkrtychev O.V, Mkrtychev A.E. Raschet bol’sheproletnykh i vysotnykh sooruzheniy na ustoychivost’ k progressiruyushchemu obrusheniyu pri seysmicheskikh i avariynykh vozdeystviyakh v nelineynoy dinamicheskoy postanovke [Analysis of Resistance of Long-Span and High-Rise Buildings to Progressive Collapse under Seismic and Accidental Impacts in the event of Nonlinear Dynamic Formulation]. Stroitel’naya mekhanika i raschet sooruzheniy [Structural Mechanics and Analysis of Structures]. 2009, no. 4, p. 43—49.
  7. STO 36554501-006—2006. Pravila po obespecheniyu ognestoykosti i ognesokhrannosti zhelezobetonnykh konstruktsiy [Standards of Organizations 36554501-006—2006. Fire Resistance and Fire Endurance Rules for Reinforced Concrete Structures]. Moscow, FGUP «Stroitel’stvo» [Federal State Unitary Enterprise “Construction”], 2006.

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Increase of strength of partially destroyed wood of monuments of wooden architecture

Вестник МГСУ 11/2018 Том 13
  • Pokrovskaya Elena N. - Moscow State University of Civil Engineering (National Research University) (MGSU) Doctor of Technical Sciences, Professor, Moscow State University of Civil Engineering (National Research University) (MGSU), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation.

Страницы 1305-1314

Introduction. Monuments of wooden architecture - an invaluable part of the national culture, they reflect the originality and independence of the national architecture. The problem of preservation of monuments of wooden architecture with the passage of time is becoming increasingly important. Many monuments were burned; some were destroyed due to the loss of structural strength under the influence of humidity, biodestruction, etc. Materials and methods. The samples of partially destroyed wood of the Anglican Church of the city of Arkhangelsk, built in 1833, were studied. The samples were subjected to surface modification with the formation of a two-layer sandwich coating, the first layer of which was various phosphorus-containing flame retardants, and the second layer - polymer composites. As polymer composites, glue based on epoxy resin and polyurethane composition “Akvidur TT” were used. The reactive organophosphorus compounds, capable of forming covalent bonds with wood polymers in the surface layer of partially destroyed wood, were chosen as flame retardants. Modified samples were subjected to physicochemical studies to determine the strength, fire resistance, hydrophobicity. The strength of the modified samples was compared with the strength of the untreated samples of partially destroyed wood of the Anglican Church of Arkhangelsk. The appearance of covalent bonds between the wood and the modifier was determined by Fourier-transform spectroscopy. Results. Surface modification of the samples of the monument increased the strength of wood by 2-2.5 times, reduced water absorption by 3 times, reduced the loss of mass during combustion according to GOST 27484-87 to 5.0-6.4 %. Conclusions. The study solves the urgent problem of preservation of monuments of wooden architecture by increasing the strength of partially destroyed wood, as well as giving it fire resistance, hydrophobicity and biostability in carrying out restoration work.

DOI: 10.22227/1997-0935.2018.11.1305-1314

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