Some Information on Eurocode 4 part 1.2

Transcription

1 Brussels, February 2008 Dissemination of information workshop 1 Some Information on Eurocode 4 part 1.2 (mainly from DIFISEK project report) Joël KRUPPA CTICM Coordinator CEN TC 250 / Horizontal Group "FIRE"

2 Composite slabs & beams Options Brussels, February 2008 Dissemination of information workshop 2 Flat concrete slab or composite slab with profiled steel sheeting Shear connectors Profiles with or without Fire protection material slabs Reinforcing bar Shear connectors beams Optional slab Stirrups welded to web of profile Reinforcing bar

3 Composite columns Options Brussels, February 2008 Dissemination of information workshop 3 (a) (b) (c) a: steel embedded in concrete (traditional approach) b: concrete between flanges (f.r. dependent on reinforcement) c: concrete filled SHS - without reinforcement (f.r. ca. 30 minutes or less) - with reinforcement (f.r. dependent on reinforcement)

4 Calculation procedure thermal response Composite elements Brussels, February 2008 Dissemination of information workshop 4 Non-uniform temperature distribution Load bearing and (possibly) separating function Load bearing capacity Thermal insulation Integrity Options tabulated data simple calculation model advanced calculation model

5 Tabulated data (steel and concrete composite members) Brussels, February 2008 Dissemination of information workshop 5 Composite beams Composite columns Slab Concrete for insulation

6 Tabulated data and relevant parameters (composite columns pren ) Brussels, February 2008 Dissemination of information workshop 6 A c e w b e f As u s us h Standard Fire Resistance R30 R60 R90 R120 Minimum ratio of web to flange thickness e w /e f 0,5 1 Minimum cross-sectional dimensions for load level η fi,t 0,28 Standard fire rating Load level minimum dimensions h and b [mm] minimum axis distance of reinforcing bars us [mm] minimum ratio of reinforcement A s /(A c +A s ) in % 2 Minimum cross-sectional dimensions for load level ηfi,t 0, minimum dimensions h and b [mm] minimum axis distance of reinforcing bars us [mm] minimum ratio of reinforcement A s /(A c +A s ) in % 3 Minimum cross-sectional dimensions for load level ηfi,t 0, minimum dimensions h and b [mm] minimum axis distance of reinforcing bars us [mm] minimum ratio of reinforcement A s /(A c +A s ) in % Section dimension Reinforcing steel Concrete cover

7 Composite Beams Brussels, February 2008 Dissemination of information workshop 7

8 Totally encased steel sections Brussels, February 2008 Dissemination of information workshop 8

9 How to apply tabulated data in fire design (two different situations) Brussels, February 2008 Dissemination of information workshop 9 VERIFICATION R d of θ 20 C PRE-DESIGN E fi.d and E d E fi.d η fi,t = E fi.d / E d η fi,t = E fi.d / R d Section dimension reinforcing steel concrete cover Standard fire rating Section dimension reinforcing steel concrete cover Standard fire rating R d E d

10 Concrete with only insulation function Brussels, February 2008 Dissemination of information workshop 10

11 Composite elements Calculation rules thermal response Brussels, February 2008 Dissemination of information workshop 11 Similar to concrete elements Complications due to shape Simple calculation rules available

12 Thermal response composite elements Advanced model (illustration) Brussels, February 2008 Dissemination of information workshop 12 Temperatuur temperature [ 0 C] [ C] ==> G F E D C B A Tijd [min] ==> time [min] A B C D E F G computer simulation test vs. simulation

13 Composite elements Simple calculation models thermal response Brussels, February 2008 Dissemination of information workshop 13 Semi-empirical approach Parameter study based on systematic calculation with advanced calculation model Direct application of advanced calculation model

14 Simple calculation models Semi-empirical approach Brussels, February 2008 Dissemination of information workshop 14 b b c,fi u 1 Z e f Y h Components cross section: flanges steel section web steel section concrete re-bars h w,fi b c,fi u2 e w Reduced cross section For each component: reduced strength and/or reduced area

15 Simple calculation models Parameter study approach Brussels, February 2008 Dissemination of information workshop 15 Composite slabs with profiled steel sheet Decking type re-entrant (6x) trapezoidal (49x) Concrete depth H B [mm] 50, 60, 70, 80, 90, 100, 110, 120 Concrete type NCW and LWC ENV standard fire conditions - profiled shape deckings taken into account - thermal properties according to EC - average moisture content: 4% (NWC) and 5% (LWC) Note: total number of simulations: 880

16 Typical temperature distribution at the unexposed side of a composite slab Brussels, February 2008 Dissemination of information workshop 16 temperature [ C] average Insulation criterion: -ΔΘ av 140 ºC -ΔΘ max 180 ºC

17 Composite slabs Thermal insulation (illustration) Brussels, February 2008 Dissemination of information workshop 17 Issues: h 1 h 2 l 2 l 1 l 3 A L r t f = t f (l 1, l 2,, A/L r, φ) with: l 1, l 2,.. geometry slab A volume rib L r exposed surface rib φ configuration factor t f = a 0 + a 1 h 1 + a 2 φ + a 3 A/L r + a 4 1/L 3 + a 5 A/L r 1/l 3 [min] with: a i coefficients, depending on duration of s.f.c. exposure

18 Thermal insulation composite slabs Verification simple calculation rule Brussels, February 2008 Dissemination of information workshop Fire resistance (new rule). Fire resistance (adv. model) [-] ==> Unsafe Safe Fire resistance (adv. model) [min] ==> μ σ Unsafe Safe Fire resistance (adv. model) [min] ==> μ σ Fire resistance (Eurocode 4). Fire resistance (adv. model) [-] ==> (a) ENV rule (b) new rule

19 Composite slabs Thermal response positive reinforcement Brussels, February 2008 Dissemination of information workshop 19 z compression zone concrete (20 C) u 2 u 1 u 3 Temperature reinforcement has significant impact on M + p,θ Θ r = Θ r (u 1, A/O, l 3, z..) z = z(u 1, u 2,u 3 ) Note: steel sheet may significantly contribute to the load bearing capacity!

20 Thermal response positive reinforcement Simple calculation rule Brussels, February 2008 Dissemination of information workshop 20 Temperature (EC 4). Temperature (adv. model) [-] ==> safe unsafe Temperature (adv. model) [ 0 C] ==> O A μ σ u 1 (a) ENV rule 1 / 2 L 3 α H Temperature (new rule). Temperature (adv. model) [-] ==> safe unsafe Temperature (adv. model) [ 0 C] ==> O (b) new rule A μ σ u 1 1 / 2 L 3 α H

21 Composite slabs Brussels, February 2008 Dissemination of information workshop 21 h eff l 2 h3 3 h 1 h h h l 1 l 3 chape béton tôle d'acier l 1 l 3 l 2 Thermal Insulation (ISO fire) Equivalent thickness h eff [mm] I h 3 I h 3 I h 3 I h 3

22 Concrete filled SHS columns Resistance to fire (traditional approach) Brussels, February 2008 Dissemination of information workshop 22 Design charts available Unpractical Need for user friendly design tool e.g. POTFIRE no. concrete rebar quality % 1 C C C C C C C C C40 4.0

23 POTFIRE In- & output Brussels, February 2008 Dissemination of information workshop 23 input output

24 Validation POTFIRE Brussels, February 2008 Dissemination of information workshop 24 temperature test assumptions: - α conv = 25 W/m 2 k - ε res = 0.7 Concrete Filled Steel Hollow Section temperature (Potfire)

25 Logiciels de calcul Brussels, February 2008 Dissemination of information workshop 25 Logiciels «AFcolumn» et «AFbeam» Développés par ProfilARBED Peuvent être obtenus sur le site

26 Simple calculation model (steel and composite members) Brussels, February 2008 Dissemination of information workshop 26 Beams (steel or composite) Columns

27 Simple calculation model (composite beam) - plastic resistance theory Brussels, February 2008 Dissemination of information workshop 27 S 1 Concrete slab Connector Steel section S 1 Section S F c + F t + D + Section geometry Temperature distibution Stress distribution Moment resistance M fi,rd + = F + t D +

28 Composite beams Brussels, February 2008 Dissemination of information workshop 28 b eff b2 h c ew h w e 2 h bare b 1 e 1 température [ C] min min facteur de massiveté [m-1] insulated température de l'acier [ C] EC HA UFFEM EN T : 90 m in. 15 m m 20 mm 25 m m m facteur de massiveté (S/V en m-1)

29 Simple calculation model (composite column) - buckling curve Brussels, February 2008 Dissemination of information workshop 29 P A ai Z 1.0 χ(λ θ ) L fi A cj Y 0.5 Effective section A sk 0 Appropriate buckling curve λ θ Load capacity: N fi.rd = χ(λ θ ) N fi.pl.rd χ(λ θ ) strength and rigidity of effective section + column buckling length L fi

30 Construction details shall be respected in order to consistent with numerical models Brussels, February 2008 Dissemination of information workshop 30 Reinforcing bars between slab and edge columns φ12 in S500 Maximum gap of 15 mm between beam and column and between lower flange of the beam gap gap 15 mm

31 Construction details to get hogging moment resistance in fire situation Brussels, February 2008 Dissemination of information workshop 31 Join detail - Example Continuous reinforcing bar studs Sections with infilled concrete gap A limited gap allowing to develop a hogging moment in the fire situation

32 Construction details for connection between concrete and steel Brussels, February 2008 Dissemination of information workshop 32 Connection between steel profile and encased concrete φ r 8 mm φ s 6 mm welding a w 0,5 φ s l w 4 φ s h ν studs d 10 mm h ν 0,3b φ r 8 mm Welding of stirrups to the web b Welding of studs to the web

33 Fire design by global structural analysis Brussels, February 2008 Dissemination of information workshop 33 Application requirement of advanced calculation models requirement on material models strain composition kinematical material model strength during cooling phase step by step iterative solution procedure check of possible failure untreated in direct analysis rupture due to excessive steel elongation cracking and crushing of concrete

34 Global analysis of steel and concrete composite floor under localised fire Brussels, February 2008 Dissemination of information workshop 34 Standard part of the floor system Composite slab Steel deck: 0.75 mm 3.2 m 4.2 m 15 m 10 m 10 m 10 m 15 m 15 m

35 Choice of structural model Brussels, February 2008 Dissemination of information workshop 35 Two different structural models may be adopted 2D composite frame model (beam elements) membrane effect is limited to one direction due to 1D effect slab model load redistribution is not possible between parallel beams 3D composite floor model (multi-type element) membrane effect over whole floor area load redistribution becoming possible with help of shell elements More realistic to apply 3D composite floor model

36 Validity of 3D composite floor model Brussels, February 2008 Dissemination of information workshop 36 Test 3D calculation model Vert. Disp. (mm) Hori. Disp. (mm) Time (min) Test Cal. 3D Cal. 2D Time (min)

37 Strategy of 3D composite floor modelling Brussels, February 2008 Dissemination of information workshop 37 Fire area Global structure without composite slab Detail of numerical modelling

38 Mechanical loading and boundary conditions Brussels, February 2008 Dissemination of information workshop 38 Uniformly distributed load: G + Ψ 1,1 Q θ = 0 Continuity condition of concrete slab θ = 0 Continuity condition of columns

39 Mechanical response of the structure Brussels, February 2008 Dissemination of information workshop 39 Total deflection of the floor and check of the corresponding failure criteria 140 mm 310 mm 20 min 40 min

40 Mechanical response of the structure Brussels, February 2008 Dissemination of information workshop 40 Total deflection of the floor and check of the corresponding failure criteria 60 min 230 mm Deflection (mm) mm L/20 = 500 mm Secondary beam Main beam Time (min) 280 mm L/20 = 750 mm

41 Mechanical response of the structure Brussels, February 2008 Dissemination of information workshop 41 Check of failure criteria: elongation of reinforcing steel 1.4 % 5 % 1.3 % 5 % Strain of reinforcing steel // slab span Strain of reinforcing steel slab span

42 Brussels, February 2008 Dissemination of information workshop 42 Unbraced frame R + 3

43 Design Brussels, February 2008 Dissemination of information workshop W 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q 0.5 W 1.0 G Q 1.0 G Q 0.5 W Unbraced frame

44 Edge column temperature Time : 90 minutes Brussels, February 2008 Dissemination of information workshop 44 Y X Temperature ( C) A B C External Column A B C Time (min)

45 Central column temperature Brussels, February 2008 Dissemination of information workshop Y X Temperature ( C) A B D C Central Column A C B D Time (min)

46 Bean-slab temperature Brussels, February 2008 Dissemination of information workshop Y X Temperature Beam ( C) A D B C B C D Time (min) A

47 Deformations of the frame Brussels, February 2008 Dissemination of information workshop Horizontal displacement HD (mm) Y X Time (min) HD

48 Braced frame Brussels, February 2008 Dissemination of information workshop G Q 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q 1.0 G Q Braced frame

49 Deformation of frame Brussels, February 2008 Dissemination of information workshop 49 0 Time (min) VD Vertical displacement VD (mm) Y X

50 Comparison Brussels, February 2008 Dissemination of information workshop 50 N of c ase R e s t r a i n t c o n d i t i o n d i m e n s i o n o f external colum n d i m e n s i o n o f c e n tr a l c o lu m n d i m e n s i o n o f b e a m F ire resistan of the fram ase 1 unbraced φ φ m in u t e s ase 2 unbraced φ φ m in u t e s ase 3 unbraced m in u t e s 200 φ φ20 ase 4 unbraced φ φ m in u t e s ase 5 braced φ φ m in u t e s ase 6 braced 200 φ φ m in u t e s