بررسی تحلیلی توزیع دما و مقاومت باربری تیرهای سقف مرکب کم عمق تحت آتش

فخریان, شایان; بهبهانی, حمید; مشهدی, شایان

doi:10.30478/jcsm.2020.220758.1148

بررسی تحلیلی توزیع دما و مقاومت باربری تیرهای سقف مرکب کم عمق تحت آتش

نوع مقاله : مقاله پژوهشی

نویسندگان

¹ گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه مازیار، رویان، ایران

² گروه راه و ترابری، دانشکده مهندسی عمران، دانشگاه علم و صنعت ایران، تهران، ایران

³ گروه مهندسی نفت، دانشکده مهندسی شیمی، دانشگاه تربیت مدرس، تهران، ایران

10.30478/jcsm.2020.220758.1148

چکیده

در این نوشتار، یک روش تحلیلی نسبتا دقیق با استفاده از حل معادله یک بعدی حرارت برای تعیین توزیع دما در یک مقطع فولادی مدفون در دال بتنی با عنوان تیرهای سقف مرکب کم عمق (CoSFB) ارائه می شود. ابتدا مطالعات انجام شده در زمینه بررسی رفتار حرارتی-مکانیکی سقف های مرکب کم عمق در محدوده آزمایشگاهی و مدل سازی نرم افزاری مورد بررسی قرار می گیرد. سپس برای تعیین توزیع دما در مقطع SFB یک روش تحلیلی تابع زمان-مکان ارائه می شود. در این بررسی، بخش فولادی مدفون در دال بتنی، تحت یک شار حرارتی وابسته به زمان منطبق بر منحنی آتش استاندارد قرار داده می شود. روش ارائه شده، یک حل تحلیلی ساده شده از شکل عمومی معادله گرما برای انتقال حرارت رسانشی نامانا به منظور محاسبه مقاومت باربری SFB می باشد. بدین منظور، با توجه به نتایج حاصل از مطالعات عددی مختلف، روش ارائه شده را بر فرضیاتی استوار کردیم تا ضمن حفظ دقت عمل در محاسبات، از پیچیدگی های مطبوع در روش تحلیلی بکاهیم. این حل تحلیلی ساده شده از طریق مقایسه با نتایج حاصل از شبیه سازی عددی، اعتبارسنجی شده است. در پایان با ارائه مثال کاربردی نحوه طراحی سقف مرکب کم عمق تحت آتش مورد بررسی قرار گرفت.

کلیدواژه‌ها

موضوعات

تحلیل و طراحی سازه های بتنی

عنوان مقاله [English]

Analytical study on the distribution of temperature and bearing strength of slim-floor beams under fire

نویسندگان [English]

Shayan Fakhrian ¹
Hamid Behbahani ²
Shayan Mashhadi ³

¹ Department of Civil Engineering, Faculty of Engineering and Technology, Maziar University, Royan, Iran

² Department of Road and Transportation, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran

³ Department of Petroleum Engineering, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran, Iran

چکیده [English]

In this paper, a detailed analytic solution of the 1-D heat equation is presented to determine the distribution of temperature within a steel section integrated into a concrete slab, known as composite slim-floor beams (CoSFB). At first, the previous studies about the thermo-mechanical behavior of the slim-floor beams in the scale of experimental campaigns and numerical modeling have been investigated. Then, an analytical method, function of space and time, is suggested to determine the temperature distribution within the SFB section. Therefore, a steel section integrated into a concrete slab which is subjected to a time-dependent heat flux according to the standard fire curve will be examined. The proposed method is an analytical solution of the general form of the heat equation for transient conduction that simplified in order to calculate the load bearing resistance of SFB. This non-homogeneous differential equation is solved by applying the method of variation of parameters, setting up a homogenous problem and applying the separation of variables to get the homogeneous system. Hence, according to the results of FE modeling, the method has been based on assumptions to retain the accuracy of the calculations as well as to reduce the complications in the analytical method. At last, the results of the simplified analytical solution are compared with the numerical simulation, which confirms the logical process. Contrary to numerical methods, the newly proposed method can pragmatically be solved the heat equation with the moving boundary.

کلیدواژه‌ها [English]

Steel-concrete composite
Slim-floor beams
Fire resistance
Heat equation
Analytical method

مراجع

[1] Braun M, Hechler O, Birarda V 140 m2 Column Free Space due to Innovative Composite Slim Floor Design. In: 9th International Conference on Steel Concrete Composite and Hybrid Structures, Leeds, UK, 2009. pp 978-981.

[2] Braun M, Obiala R, Odenbreit C, Hechler O CoSFB–Design and application of a new generation of slim-floor construction. In: 7th European Conference on Steel and Composite Structures, Naples, Italy, 2014. Eurosteel.

[3] Braun M, Zaganelli D, Hanus F, Obiala R, Cajot LG, Peirce A (2017). Simplified analytical determination of the temperature distribution and the load bearing resistance of slim‐floor beams. ce/papers 1 (2-3):2780-2789.

[4] Ellobody E (2011). Nonlinear behaviour of unprotected composite slim floor steel beams exposed to different fire conditions. Thin-Walled Structures 49 (6):762-771.

[5] Ma Z, Mäkeläinen P (2000). Behavior of composite slim floor structures in fire. Journal of Structural Engineering 126 (7):830-837.

[6] CEN European Committee for Standardization (2002) EN 1991-1-2, Eurocode 1: Actions on structures. Part 1-2: General actions – Actions on structures exposed to fire. BSI British Standards, Brussels.

[7] CEN European Committee for Standardization (2004) EN 1992-1-2, Eurocode 1: Design of concrete structures. Part 1-2: General rules - Structural fire. BSI British Standards, Brussels.

[8] CEN European Committee for Standardization (2005) EN 1993-1-2, Eurocode 3: Design of steel structures. Part 1-2: General rules – Structural fire Design. BSI British Standards, Brussels.

[9] CEN European Committee for Standardization (2005) EN 1994-1-2, Eurocode 4: Design of composite steel and concrete structures. Part 1-2: General rules – Structural fire Design. BSI British Standards, Brussels.

[10] Kim HJ, Kim HY, Park SY (2011). An experimental study on fire resistance of Slim Floor beam. Applied Mechanics and Materials 82:752-757.

[11] Kang H, Lee DH, Hwang J-H, Oh J-Y, Kim KS, Kim H-Y (2016). Structural performance of prestressed composite members with corrugated webs exposed to fire. Fire Technology 52 (6):1957-1981.

[12] Baldassino N, Roverso G, Ranzi G, Zandonini R Service and Ultimate Behaviour of Slim Floor Beams: An Experimental Study. In: Structures, 2019. Elsevier, pp 74-86.

[13] Albero V, Espinós A, Serra E, Romero M, Hospitaler A (2019). Numerical study on the flexural behaviour of slim-floor beams with hollow core slabs at elevated temperature. Engineering Structures 180:561-573.

[14] Albero V, Serra E, Espinós A, Romero M, Hospitaler A (2020). Innovative solutions for enhancing the fire resistance of slim-floor beams: Thermal experiments. Journal of Constructional Steel Research 165:105897.

[15] Zaharia R, Duma DM, Vassart O, Gernay T, Franssen J-M Simplified method for the temperature distribution in slim floor beams. In: International Conference Applications of Structural Fire Engineering, 2011. Print Prazska technika, pp 11-22.

[16] Zaharia R, Franssen J-M (2012). Simple equations for the calculation of the temperature within the cross-section of slim floor beams under ISO Fire. Steel and Composite Structures 13 (2):171-185.

[17] Cajot L-G, Gallois L, Debruyckere R, Franssen J-M Simplified design method for slim floor beams exposed to fire. In: Nordic Steel Construction Conference, Oslo, Norway, 2012.

[18] Espinos A, Romero ML, Hospitaler A, Pascual AM, Albero V (2015). Advanced materials for concrete-filled tubular columns and connections. Structures 4:105-113.

[19] Hanus F, Zaganelli D, Cajot LG, Braun M (2017). Analytical methods for the prediction of fire resistance of “reinforced” slim floor beams. ce/papers 1 (2-3):2508-2517.

[20] Fellinger JH, Twilt L Fire resistance of slim floor beams. In: Composite Construction in Steel and Concrete III, Irsee, Germany, 1996. ASCE.

[21] Newman G (1995). Fire resistance of slim floor beams. Journal of Constructional Steel Research 33 (1-2):87-100.

[22] Lawson RM, Mullett DL, Rackham J (1997) Design of asymmetric slimflor beams using deep composite decking. Steel Construction Institute, Berkshire, U.K.

[23] Alam N, Nadjai A, Vassart O, Hanus F (2019). A detailed investigation on thermal behaviour of slim floor beams with web openings at elevated temperatures. Journal of Structural Fire Engineering.

[24] Both K, Fellinger J, Twilt L (1997). Shallow floor construction with deep composite deck: from fire tests to simple calculation rules. Heron 42 (3):145-158.

[25] Wang Y, Burgess I, Wald F, Gillie M (2012) Performance-based fire engineering of structures. CRC press.

[26] Franssen J-M, Gernay T (2017). Modeling structures in fire with SAFIR®: theoretical background and capabilities. Journal of Structural Fire Engineering 8 (3):300-323.

[27] Franssen J-M (2005). SAFIR: A thermal/structural program for modeling structures under fire. Engineering Journal 42 (3):143-158.

[28] CEN European Committee for Standardization (2004) EN 1994-1-1, Eurocode 4: Design of composite steel and concrete structures. Part 1-1: General rules and Rules for Buildings. BSI British Standards, Brussels.

[29] Alam N, Nadjai A, Ali F, Nadjai W (2018). Structural response of unprotected and protected slim floors in fire. Journal of Constructional Steel Research 142:44-54.