02 November EN : Structural fire design EC2 Workshop Eurocodes Moscow 2010 J.C. Walraven Vermelding onderdeel organisatie

02 November Information on structural fire design - Eurocode 1: EN , : Loads on structures, Part 1-2: General loads – Loads due to fire - Eurocode 2: EN : : Design and calculation of concrete structures: General rules and rules for buildings - Eurocode 2: EN :

02 November Control of structures subject to fire Eurocode distinghuises analysis of elements, partial systems and structures as a whole Analysis of structural member Analysis of structural system For the design of standard fire requirements in general the analysis of structural members is sufficient.

02 November Alternative design procedures EC2 Prescriptive Rules Member analysis Analysis of part of structure Analysis of entire structure Calculation of mechanical actions at boundaries Tabulated data Simple calculation models Advanced calculation models Simple calculation models Advanced calculation models Advanced calculation models Calculation of mechanical actions at boundaries Selection of mechanical models

02 November Alternative design procedures Performance based design; physically based thermal actions Selection of simple or more advanced fire development models Member analysis Analysis of part of the structure Analysis of entire structure Calculation of mechanical actions at boundaries Calculation of mechanical actions at boundaries Selection of mechanical models Simple calculation models Advanced calculation models Advanced calculation models Advanced calculation models

02 November Summary table for alternative methods Tabulated dataSimplified calculation methodsAdvanced calcu- lation methods Member analysis Member considered to be isolated. Indirect fire actions are not considered, except those resulting from thermal gradients Yes - Data given for standard fire only, 5.1(1). - In principle data could be developed for other curves Yes -Standard fire and parametric fire, 4.2.1(1) - Temperature profiles given for standard fire only, 4.2.2(1) - material models apply only to heating rates similar to standard fire (2) Yes 4.3.1(1) Only principles are given Analysis of parts of the structure Analysis of the entire structure. Indirect fire actions within the subassembly are considered, but no time dependant interaction with other parts of the structure NoYes -Standard fire and parametric fire 4.2.1(1) -temperature profiles given for standard fire only 4.2.2(1) - material models only for heating rates similar to standard fire (2) Yes 4.3.1(1)P Only the principles are given Global structural analysis Analysis of entire structure. Indirect fire actions considered throughout structure No Yes 4.3.1(1)P Only principles are given

02 November Alternative design procedures Prescriptive rules (traditional): Rules for minimum cross sections, minimum cover, reinforcement geometry, mostly based on ISO 834 curve Performance based design (modern/future))  Bearing capacity should be maintained during fire (Criterion R)  In case of subdivision of building in compartments: separating elements (including joints) should keep their separating function during the fire, so: - no loss of integrity due to cracks, wholes which would allow transmission of gas or flames (Criterion E) - no loss of isolating function which would lead to rise of temperature at opposite side resulting in fire (Criterion I). Mostly assumed to be satisfied if max.  T < 180 K.

02 November Modeling the fire load For general (standard cases) ISO 834 curve is appropriate

02 November More advanced heating curves (for performance based design) Parameters Burning capacity of materials in room Opening-factor Wall-, floor and ceiling properties Risk factors (presence of sprinklers or alarm system) Ventilating conditions Parametric temperature – time curves

02 November Load on the structure during fire Accidental loading situation applies: for buildings: 0,5   x,1  0,9 and 0,3   x,2  0,8 Accidental action A d due to imposed deformations as a result of thermal actions in statically indeteminate structures

02 November Special case of imposed deformations Accidental load due to restrained temperature deformations Dotted lines: shifted moment lines due to temperature restraint!

02 November Basis for control of fire resistancce R d bearing resistance (no fire) E d design load (no fire) R fi,d (t) bearing resistance (fire) E d =  fi R d governing load for fire situation t fi,req required fire resistance in minutes (criterion R) R fi,d (t) can be calculated on the basis of material laws which reflect material deterioration under increasing temperature for t fi,req

02 November Control with tables -Based on ISO temperature – time curve -Provides design solutions for standard fire exposure up to 4 hours -Valid for normal weight concrete with siliceous aggregate -For calcareous or lightweight aggregates the minimum dimension may be reduced by 10% -No further checks required for shear, torsion or anchorage -No further checks required for spalling up to an axis distance of 70mm -For HSC (> C50/60) the minimum cross section dimension should be increased -Axis distance a according to figure (nominal values -The tables have been derived for a critical rein- forcing steel temperature of C and a loading degree of  fi = E d,fi /E d a Axis Distance

02 November a Axis Distance Example of a table: Minimum thickness and axis distance for flat slabs Control with tables Standard fire resistance Minimum slab thick- ness (mm) Minimum axis dis- tance (mm) R R R R R R

02 November Control with tables Combination with diagrams In combination with the tables diagrams can be used, which give the reduction of the steel strength as a function of the increasing temperature. These relations can be used to convert the results of the tables to degrees of loading different from 0,7 and critical temperatures other than C Prestressing strands and wires Reinforcing steel Prestressing bars

02 November Control with tables The tables have been derived for a critical steel temperature  cr = 500 0, a loading degree  fi = 0,7, and  s = 1,15. The corresponding steel stress is for E d,fi /E d = 0,7;  s = 1,15 and A s,req /A s,prov = 1 a stress  s =300 MPa is found, so  s /f yk =0,6. This is confirmed by the diagram Temp.

02 November Control with tables Procedure for combined use of tables and diagrams Example: Q k =G k and  fi = 0,7. With  G =1,35 and  Q =1,5 it is found that  fi = E fi,d /E d = (1/1,35 + 0,7/1,5)/(1+1)=0,6 If A s,req /A sprov = 0,9, then the stress in the rein- forcing steel under fire conditions is:  s =  fi  {f yk (20 0 )/  s }  (A s,req /A s,req ) = 0,6  (500/1,15)  0,9 = 235 MPa. So = 235/500 = 0,47. From the diagram (and corresponding mathematical relations) it is read that the critical temperature is  cr = 556 MPa. So the axis distance (Tabulated value) can be reduced by:  a = 0,1( ) = - 5,6 mm Temp.

02 November Control with tables N Rd = A s f yd + A c f cd = A s f yk +A c  cc f ck /  c Example of table: dimensions for columns

02 November Design with tables Standard fire resistance Slab thickness (mm)One direction 2 directions l y /l x  1,5 2 directions 1,5 < l y /l x  2 R3060a = 10 mma= 10 R6080a = 20mma= 10a= 15 R90100a= 30 mma= 15a= 20 R120120a= 40 mma= 20a= 25 R180150a= 55 mma= 30a= 40 R240175a= 65 mma= 40a= 50 Minimum slab thickness and axis distance a for slabs spanning in one and 2 directions

02 November °C isotherm method (Annex B1) (Anderberg) Determine the position of the 500  C isotherm for the specific fire exposure. Determine the values of d fi and b fi. Determine the temperature and reduced strength of reinforcing bars in the tension and compression zones. Use conventional calculation method to determine ultimate load capacity.

02 November Zone method (Annex B2) (Hertz) Section is divided into zones. The mean temperature and mean compressive strength, f cd (  ) of each zone is determined The fire situation is represented by a reduced cross section ignoring a damaged zone of thickness a z. The value of a z is determined by assessing the mean properties of the concrete at point M The example shows the combination of two sets of calculations. One for the flange and one for the web. The point M is an arbitrary point selected on the centre-line of the section

02 November Divide cross-section into zones with mean temperature of 20  C, 100  C, 200  C, 300  C... up to 1100  C. Buckling effects on columns (Annex B3) (Isquierdo) Determine temperature of each reinforcing bar. Determine ultimate moment capacity, M Rd,fi for N Ed,fi and nominal second order moment, M 2,fi for corresponding curvature. Integrate to determine moment-curvature diagram for each zone and reinforcing bar for N Ed,fi Determine ultimate first order moment capacity, M 0Rd,fi and compare with M 0Ed,fi

02 November Fire in praxis Fire in Faculty of Architecture, Delft University of Technology 13 May 2008, 10h30

02 November TU Delft, Faculty of Architecture, May 13th 2008, 13h00 Fire in praxis

02 November TU Delft, Faculty of Architecture, May 13 th h00 Fire in praxis

02 November TU Delft, Faculty of Architecture, May 13 th h00 Fire in praxis

02 November TU Delft, Faculty of Architecture, May 13 th h00 Fire in praxis