Robustness of Steel Joints in Fire: Temperature Development and Structural Fire Behaviour

Transcription

1 Robustness of Steel Joints in Fire: Temperature Development and Structural Fire Behaviour Y C Wang, C G Bailey and X H Dai School of Mechanical, Aerospace and Civil Engineering The University of Manchester, UK 1 1

2 Main contents Part-1: Joint temperature development Effects of partial fire protection on temperature development in steel joints protected using intumescent coating Part-2: Structural fire behaviour Failure modes and joint tying forces of typical steel beam-column joint assemblies under elevated temperature 2 2

3 Part-1: Joint Temperature Development joint types Column: UC254x254x89 Length 1000mm. (a) Flush endplate joint (b) Flexible endplate joint Beam: UB305x165x40 Length 605mm, 485mm. Slab: 1000x1000mm Overall depth 130mm. (c) Fin plate joint (d) Web cleat joint 3 3

4 Part-1: Joint Temperature Development fire protection options (a) No protection (a) Completely unprotected joint assembly. (b) Partial protection in joint zone: Leaving the bolts unprotected in a protected joint. (c) Partially protected beams. (d) Fully protected joint zone. (b) unprotected bolts (c) protected bolts 4 4

5 Part-1: Joint Temperature Development conclusions by tests Whether or not protecting bolts had little influence on temperatures in other connection components in a protected joint. In a protected joint with unprotected bolts, the unprotected bolt temperatures were higher than those with full bolt protection, but still much lower than bolt temperatures in a completely unprotected joint. Protecting the beam for 400mm is sufficient to achieve full protection to the joint. 5 5

6 Q F A + (1 F ) Q A up e e p Part-1: Joint Temperature Development Simple prediction method Temperatures in protected components may be calculated by assuming the joint is fully protected Temperatures in unprotected bolts may be approximately calculated by the following method: T = T + ( T T ) F pp fp up fp e Tup and Tfp Calculated using the simple calculation method F e Exposure factor may be calculated using the approximate calculation method as described following: Which is the ratio of the unprotected surface area of a bolt connection to the total surface area of the bolt connection 6 6

7 Test arrangement 7 7

8 Specimen and test set-up Loads: 40kN (a) Fin plate (b) Web cleat (c) Flexible end plate (d) Flush end plate (e) Extended end plate 8 8

9 Details of specimen member dimensions Fire test ID Connection component dimension (mm) Test-1: fin plate 150x130x10 Test-2: flexible endplate 150x130x8 Test-3: flush endplate 150x200x8 Test-4: web cleat 90x150x10 (depth: 130) Test-5: extended endplate 150x250x8 Test-6: fin plate 150x130x10 Test-7: flexible endplate 150x130x8 Test-8: flush endplate 150x200x8 Test-9: web cleat 90x150x10 (depth: 130) Test-10: extended endplate 150x250x8 Column section UC 254x254x73 Uc152x152x23 Beam section UB 178x102x19 9 9

10 Fail modes of specimens with fin plate joint (a) Test-1, colum: UC254x254x73; beam: UB178x102x19 (b) Test-6, column: UC152x152x23; beam: UB178x102x

11 Tying force development in fin plate joint Tying force (kn) Test-1 Test-6 Max temperature at beam bottom flange (C) max beam temp when 0 tying force developed 748C and 733C max beam temps when max catenary force developed: 760C and 757C max catenary forces developed 47.3kN and 25.6kN 11 11

12 Fail modes of specimens with flexible end plate joint (a) Test-2, column: UC254x254x73; beam: UB178x102x19 (b) Test-7, column: UC152x152x23; beam: UB178x102x

13 Tying force development in flexible end plate joint Tying force (kn) Test-2 Test-7 Max temperature at beam bottom flange (C) max beam temp when 0 tying force developed 728C and 700C max beam temps when max catenary force developed: 739C and 714C max catenary forces developed 34.5kN and 32.6kN 13 13

14 Temperatures in two joints Applied load (kn) Right jack Left jack Temperature (C) Left connection Right connection Fire time (min) Fire time (minutes) Temperature measured in right joint was much higher than that in left joint 14 14

15 Fail modes of specimens with flush end plate joint (a) Test-3, column: UC254x254x73; beam: UB178x102x19 (b) Test-8, column: UC152x152x23; beam: UB178x102x

16 Tying force in flush end plate joint Tying force (kn) Test-3 Test-8 Max tem perature at beam bottom flange (C) max beam temps when 0 tying force developed 728C and 706C max beam temps when max catenary force developed: 729C and 719C max catenary forces developed 29.4kN and 17.7kN 16 16

17 Temperatures in two joints Applied loads (KN) Right jack Left jack Fire time (minutes) Temperature (C) Lef t connection Right connection Temperature measured in right joint was much lower than that in left joint Fire time (min) 17 17

18 Fail modes of Specimens with web cleat joint (a) Test-4, column: UC254x254x73; beam: UB178x102x19 (a) Test-9, column: UC152x152x23; beam: UB178x102x

19 Tying force development in web cleat joint Tying force (kn) Test-4 Test-9 Max temperature at beam bottom flange (C) max beam temp when 0 tying force developed 743C and 721C max beam temps when max catenary force developed: 767C and 733C max catenary forces developed 41.3kN and 16.9kN 19 19

20 Fail modes of specimens with extended end plate joint (a) Test-5, column: UC254x254x73; beam: UB178x102x19 (b) Test-10, column: UC152x152x23; beam: UB178x102x

21 Tying force in extended end plate joint Tying force (kn) Test-5 Test-10 Max temperature at beam bottom flange (C) max beam temp when 0 tying force developed 755C and 742C max beam temps when max catenary force developed: 818C and 754C max catenary forces developed 54.6kN and 21.4kN 21 21

22 Tying force in joint against beam max temperature Tying force (kn) Tying force (kn) Test-1: fin plate Test-2: flexible endplate Test-3: flush endplate Test-4: web cleat Test-5: extended endplate Max temperature at beam bottom flange (C) Test-6: fin plate Test-7: flexible endplate Test-8: flush endplate Test-9: web cleat Test-10: extended endplate Max beam temperature when 0 tying force developed: 748 (fin), 728(flexible), 728(flush), 743(cleat), 755(extended plate) Max beam temperature when max tying force developed: 733 (fin), 700(flexible), 706(flush), 721(cleat), 744(extended plate) Max temperature at beam bottom flange (C) 22 22

23 General conclusions c Various possible joint failure modes observed Beam deflections were very large (span/8~span/6), even though no failure (fracture) was observed in some tests. Specimens with stronger connections such as extended endplate, survived higher temperatures. But the difference is small (less ( than 50 C) if the beam limiting temperature is based on bending (axial force=0). The difference of limiting temperatures (based on axial force=0) between specimens with two column sizes is very small (less than 30 C) C).. However some joints connected to the large column failed due to higher catenary forces. It would be interesting to conduct further tests using protected joints (which will be necessary anyway) and follow the tests until failure

24 Acknowledgements EPSRC funding (collaborator: University of Sheffield, UK) 24 24

25 Thank you for your attention Questions? 25 25