André Reis, Nuno Lopes and Paulo Vila Real
AKNOWLEDGMENTS
This research work was funded by the Portuguese Government through the FCT (Foundation
for Science and Technology) under the PhD grant SFRH BD 85563 2012 awarded to the fírst
author.
REFERENCES
[1] CEN - EN 1993-1-5, Eurocode 3: Design of Steel Structures - Part 1-5: Plated structural
elements, Brussels, 2006.
[2] Hõglund T. - Shear buckling resistance of steel and aluminium plate girders. Thin-Walled Structures; vol. 29, no 1-4, 1997, p. 13-30.
[3] CEN NP EN 199312, Eurocode 3: Design of Steel Structures Part 12: General rules -Structural fire design, Brussels, 2005.
[4] Reis A., Lopes N. & Vila Real P. - Modelação numérica da resistência de vigas metálicas
sujeitas a encun/adura por esforço transverso à temperatura normal e ao fogo, IX Congressode Construção Metálica e Mista e l congresso Luso-Brasileiro de Construção Metálica
Sustentável, 2013, p. 705-716.[5] Gomes C. M. M., Cruz P.J.S. e Simões da Silva L. - Avaliação experimental do
comportamento ao corte de vigas de aço esbeltas, Engineering Civil Magazine of University of
Minho, no. 7, 2000.
[6] Franssen J.M. - SAFIR A Thermal/structural program modelling structures under fire,
Engineeríng Journal, vol. 42, no. 3, 2005, p. 143-158.[7] Franssen J. M. - User's manual for SAFIR - A computer program for analysis of structures
subjected to fire: Department ArGEnCO. University of Liège, 2011 .
[8] CEN - EN 1090-2 - Execution of steel structures and aluminium structures - Part 2: Technical requirements for steel structures, Brussels, 2008.
[9] CAST3M - CAST3M is a research FEM environment; its development is sponsored by the
French Atomic Energy Commission, 2012. <http://www-cast3m.cea.fr/>
[10] Couto C., Vila Real P. & Lopes N. - RUBY an interface software for running a buckling
analysis ofSAFIR models using CAST3M, University of Aveiro, 2013.
[11] ECCS - Manual on stability of steel structures. Publication no. 22. ECCS - Technical
Committee 8 - Structural Stability, 1976.
[12] ECCS TC8 - Ultimate limit state calculation of sway frames with rigid Joints. Publication
no. 33, 1984.[13] Beg D., Kuhlmann U., Davaine L. & Braun B. Design of Plated Structures
Eurocode 3: Design of Steel Structures, Part 15: Design of Plated Structures, ECCS -Eurocode Design Manuais, 2010.14
IFireSS - International Fire Safety Symposium
Coimbra, Portugal, 20th-22nd Aprü 2015
PARTIALLY ENCASED SECTION: STRENGTH AND STIFFNESS UNDER
FIRE CONDITIONS
Paulo Piloto' Professor
IPB - Bragança Portugal
David Almeida Student
IPB - Bragança Portugal
A. B Ramos-Gavilán Professora
U. Salamanca
Spain
Luís M. R. Mesquita Professor
IPB - Bragança Portugal
Keywords: Partially Encased Sections; Fire Resistance; Simplified Calculation Methods;
Advanced Calculation Methods.
1. INTRODUCTION
Fire resistance of partially encased sections (HEB and IPE) depends on the temperature
evolution during fire exposure. Eurocode 4, part 1.2 [1], proposes the assessment of the cross
section using the method of the four components (flanges, web, reinforcement and concrete) to
determine the resistance and stiffness under fire. This study aims to assess the balanced summation model of Eurocode (informative annex G) with respect to the plastic resistance toaxial compression and the effective flexural stiffness of the cross section with respect to the
weak axis. New formulas will be proposed to evaluate fire resistance, based on new simple
formulas to determine the flange average temperature, the residual height and average temperature of the web, the residual cross section ana average temperature of concrete, the reduced stiffness and strength of reinforcement. The advance calculation method was used to validate new and safe formulae, based on the analysis of the cross section totally engulfed in tire (fire in four sides).'Corresponding author - Department of Applied Mechanics, Polytechnic Institute of Bragança. Campus Santa Apolónia, ap. 1134. 5301-857 Bragança.
PORTUGAL. Telef. : +351 273 303157 Fax: +351 273 313051. e-mail: ppilotofajipb. pt
Paulo Piloto, David Almeida, A. B Ramos-Gavilán and Luís M. R. Mesquita
2. MATERIAL AND METHODS
A new simple calculation method is proposed alternatively to the existing formulae ofthe annex
G of Eurocode EN1994-1-2 [1], based on the thermal results of an advance calculation method(ANSYS). Current empirical coefficients leads to unsafe strength and stiffness of partially
encased sections for certain fire resistance periods. This method of analysis considers thegeometry and parameters represented in figure 1. A set of 24 partially encased section (section
factors) were used to validate the results and grouped into two section series (HEB and IPE). Todetermine the average temperature and the reduction of strength and stiffness in flanges and
reinforcement, the criterion of the arithmetic mean value was used over the corresponding nades. To determine the residual resistant section of the concrete, the criterion of 500 °Cisothermal was considered [5]. To determine the reduction ofthe web height, the criterion of 400
°C isothermal was used [6].h bc. fi^
bc,' hw, fi'
6f,t
9s,t -|
hw.fi
hbc. fi ew,t
A.
ec,t
i-bc. fi
a)
b)
c)
Figure 1: Partially encased section with concrete: a) section parameters; b) residual cross section in fire design; c) average temperature of each component.
3. RESULTS
Based on the numerical temperature fíeld determined for each standard fire rating (R30, 60, 90,
120), each criteria was applied to the corresponding component to compare the results of
different formulae. Figure 2 presents the average flange temperature for different sections
factors using: the actual linear approximation of Eurocode, the numerical results and the new
bilinear approximation. Figure 3 presents the results of the web height reduction for each standard fire rating. New simple formulae is proposed, using the parametric approximation based on the values of section factors and fire rating periods. Figure 4 demonstrates that the externai layer of concrete to be neglected is not uniform in both directions for HEB sections.Paulo Piloto, David Almeida, A. B Ramos-Gavüán and Luís M. R. Mesquita
Similar results were determined to IPE sections. New simple quadratic formulas are proposed to each cross section type, direction of reduction layer and fire rating. Figure 5 presents the results for a new proposal, based on parametric expressions, using the section factor, fire rating and
concreto cover thickness as parameters.
TTipcr»turf|aC| -ANSYS -ü-EN!994-l-2 - - New proposal
FR120
-*-ANSyS -e-)S:VlW4-l.2 --Nw pruposal
ll.j. ln""] au ^ -i- i
,
«o N
IM ,/
] 40
Figure 2 -Average flange temperature. Left (HEB), right (IPE).
'S -B-FNI994.1-2 --Nnspropw^l h^a Emm] -A-ANSYS -si-l-^iÍWA. ^l --Newproptisal
rTi
^^ ^^
ü ---. 10 11
btAli^l«wial Í m"!
80
-,-.----.-18 19 20 21 22 23 24 25
Arnrt' lm']
Figure 3 -Web height reduction. Left (HEB), right (IPE).
.ANSYS -B-ENIW. I.S --N«»-pro|«>nl b,^. ^.^ |mm| -«-ANSYS -e-EN19ft»-l-2 --Nc«-prop«i«l
SSXSSS i-j
Ü -- .-1Ü l! 12 13
Paulo Piloto, David Almeida, A. B Ramos-Gavilán and Luís M. R. Mesquita
2. MATERIAL AND METHODS
A new simple calculation method is proposed alternatively to the existing formulae ofthe annex
G of Eurocode EN1994-1-2 [1], based on the thermal results of an advance calculation method(ANSYS). Current empirical coefficients leads to unsafe strength and stiffness of partially
encased sections for certain fire resistance periods. This method of analysis considers thegeometry and parameters represented in figure 1. A set of 24 partially encased section (section
factors) were used to validate the results and grouped into two section series (HEB and IPE). Todetermine the average temperature and the reduction of strength and stiffness in flanges and
reinforcement, the criterion of the arithmetic mean value was used over the corresponding nades. To determine the residual resistant section of the concrete, the criterion of 500 °Cisothermal was considered [5]. To determine the reduction ofthe web height, the criterion of 400
°C isothermal was used [6].h bc. fi^
bc,' hw, fi'
6f,t
9s,t -|
hw.fi
hbc. fi ew,t
A.
ec,t
i-bc. fi
a)
b)
c)
Figure 1: Partially encased section with concrete: a) section parameters; b) residual cross section in fire design; c) average temperature of each component.
3. RESULTS
Based on the numerical temperature fíeld determined for each standard fire rating (R30, 60, 90,
120), each criteria was applied to the corresponding component to compare the results of
different formulae. Figure 2 presents the average flange temperature for different sections
factors using: the actual linear approximation of Eurocode, the numerical results and the new
bilinear approximation. Figure 3 presents the results of the web height reduction for each standard fire rating. New simple formulae is proposed, using the parametric approximation based on the values of section factors and fire rating periods. Figure 4 demonstrates that the externai layer of concrete to be neglected is not uniform in both directions for HEB sections.16
Paulo Piloto, David Almeida, A. B Ramos-Gavüán and Luís M. R. Mesquita
Similar results were determined to IPE sections. New simple quadratic formulas are proposed to each cross section type, direction of reduction layer and fire rating. Figure 5 presents the results for a new proposal, based on parametric expressions, using the section factor, fire rating and
concreto cover thickness as parameters.
TTipcr»turf|aC| -ANSYS -ü-EN!994-l-2 - - New proposal
FR120
-*-ANSyS -e-)S:VlW4-l.2 --Nw pruposal
ll.j. ln""] au ^ -i- i
,
«o N
IM ,/
] 40
Figure 2 -Average flange temperature. Left (HEB), right (IPE).
'S -B-FNI994.1-2 --Nnspropw^l h^a Emm] -A-ANSYS -si-l-^iÍWA. ^l --Newproptisal
rTi
^^ ^^
ü ---. 10 11
btAli^l«wial Í m"!
80
-,-.----.-18 19 20 21 22 23 24 25
Arnrt' lm']
Figure 3 -Web height reduction. Left (HEB), right (IPE).
.ANSYS -B-ENIW. I.S --N«»-pro|«>nl b,^. ^.^ |mm| -«-ANSYS -e-EN19ft»-l-2 --Nc«-prop«i«l
SSXSSS i-j
Ü -- .-1Ü l! 12 13
Paulo Piloto. David Almeida, A. B Ramos-Gavilán and Luís M. R. Mesqtdta
15 17 19 21 23 25 37 2» 31
Am^jm-ii
Figure 5 -Average temperature of reinforcement. Left (HEB), right (IPE).
4. CONCLUSIONS
The current simple calculation method of Eurocode (EN1994-1-2) highlights unsafe results and
conservative results in comparison to the numerical results. The new proposals were define with
a certain levei of safety with respect to numerical results.5. REFERENCES
[1] CEN - EN 1994-1-2; "Eurocode 4 - Design of composite steel and concrete
structures-Part 1-2: General rules - Structural fire design"; Brussels, August 2005.
[2] ISO 834-1. "Fire-resistance tests - Elements of building construction - Part 1: general
requirements". 1999.[3] CEN EN 199112; "Eurocode 1: Actions on structures Part 12: General actions
-Actions on structures exposed to fire"; Brussels, November 2002.
[4] CEN EN 199312. Eurocode 3: Design of steel structures Part 12: General rules
-Structural fire design. Brussels, April 2005.[5] CEN EN 199212. Eurocode 2: Design of concrete structures Part 12: General rules
-Structural fire design. Brussels, December 2004.[6] Cajot louis-Guy, Gallois Louis, Debruyckere Rik, Franssen Jean-Marc, Simplified design
method for slim floor beams exposed to fire, Nordic Steel Construction Conference 2012, Oslo,
Norway, 5-7 September2012.IFireSS - International Fire Safety Symposium
Coimbra, Portugal, 20th-22nd April 2015
RECENT APPLICATION OF EN1993-1-2 IN GERMANY
Martin Mensinger Professor Dr-lng Technische Universitãt München, Germany
Florian M. Block Christian
Dipl.-lng. PhD BuroHappold Engineering, Frankfurta. M., Germany Maiershofer M. Eng. Ingenieurbüro Rudolf Otto Reisch Dipl.-lng. Univ. Ingenieurbüro Walter Borgogno
Dr. sc. tech.
Borgogno Eggenberger + Reisch, Augsburg, Reisch, Augsburg, PartnerAG,
Germany Germany St. Gallen
Switzerland
Keywords: EN 1993-1-2, fire design, levei 3 methods. 1. INTRODUCTION
The paper presents a levei 3 application of EN 1993-1-2 [1] in case of an industrial building in Germany. Caused by national fire regulation the fire design of the steel structure of a large hall
(8. 000 m área, 19, 0 m height and heavy load cranes with service loads up to 200 to) had to be
designed for 30 minutes ISO-fire. The design was performed by the consultants using the software package VULCAN [2]. For independent check engineering the software SAFIR [3] was used. The connections were designed by hand calculation according to EN 1993-1-2. Both designs show, that 30 minutes fire resistance could be reached. During the fire design it became obvious, that, caused by the ISO-fire scenario, a high number of nonlinearities
occurred, which made the calculation complicated. The paper describes the process of design
and check engineering, the concept of sub-modeling, which was used for the design, and the
design of main connections. A major experience of the project was, that the application of levei 3 calculation methods in combination with ISO-fire is suboptimal. The application of natural tire is preferable and will lead to a more detailed knowledge about the behavior of the structure inf i re.
Contact - Technische Universitât München, Chair of Metal Structures, Arcisstrasse 21, 80333 München, Germanv Tel. : +49 i
mensinger@tum.de
