multiconsult.no The 4th Forum Wood Building Nordic in Växjö, September 24­-25 – 2015 Fire resistance – are we done now? Recent development in Norway Nils E. Forsén

multiconsult.no 2 Themes System of requirements ­ Regulations ­ Guidance ­ Standards Uncontrolled fire – levels/consequences - risks ­ Any reason at all to distinguish between combustible and non- combustible materials? ­ System of safety: Sprinklers/Reaction to fire/Fire brigade – access/Fire resistance Impact of –universal design requirements View back to the nineties …

multiconsult.no 3 Think tanks History, empericalRd>Ed, reliabilitySystem of requirements New interpretationsNew experiencesMain structural systems Modeled fireDesign procedure Fire engineering – structural engineering The road ahead

multiconsult.no 4 Urban Development – Timber! How tall? How dense? How large? Which use?

multiconsult.no 5 System of safety for protection of lives and values Sprinklers? Fire compartments with limited sizes (redundancy)? Access for fire brigade Structural fire resistance - and other fire safety requirements

multiconsult.no Functional requirement: Basic function for all buildings Structural resistance in fire sufficient for safe evacuation and rescue: Fire class 1 and 2

multiconsult.no Special structural considerations on survival Fire class 3 and 4 Tall buildings 10

multiconsult.no Universal design: Elevator required, when 3 storeys or more (dwellings) Sprinkler 8 Elevator Fire class 1 Fire class 2 Fire class 2 Fire class 3, GD: Non- combustible

multiconsult.no Essential height limits - dwellings – RKL 4 9

multiconsult.no 10 R d,fi > E d,fi

multiconsult.no Structural response – in principle Capacity Time Actions in fire, E d,fi Collapse – or… Fire resistance in minutes Capacity development during fire (E d )R d (E d,fi )R d,fi

multiconsult.no System of requirements

multiconsult.no System of requirements

multiconsult.no 14 The distinction between function, performance and verification should be noted: Function: The overall function of the main structural system, i.e. avoid collapse Performance: Measured or calculated fire resistance and material performance according to standard Verification: Use of methods according to standards to verify the performance, or function

multiconsult.no 15 Norwegian regulation TEK 10 § 11.3 (4) For the two higher building classes (3 and 4) the requirement is that the that the main structural system of the building shall be designed to maintain a sufficient structural resistance throughout a complete fire development, appropriately modeled..

multiconsult.no 16 Pre-accepted levels of performance E.g. R90, non-combustible Experienced and intended safety level: Resistance against collapse of tall buildings due to fire alone

multiconsult.no 17 Interpretations in the new age of timber

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multiconsult.no 20 Challenge Model a complete fire development, including the cooling phase Verify survival of the timber structure Tool: Eurocode 1 part 1-2 parametric fire ­ + probabilistic down-scaling? Effect of sprinklers? Tool thermal analysis FEM – e.g. ANSYS

multiconsult.no Modeled fire

multiconsult.no 22 Source: SP

multiconsult.no In comparison: Timber frame/parametric fire (Nordic Wood 1995) From ”Wood construction behaviour in natural/parametric fires J.König, J. Norén, N.Forsén 1995

multiconsult.no 24 Conclusion 3 layers required – an uneconomical and impractical design to withstand a total fire

multiconsult.no More robust: CLT -?

multiconsult.no 26 Structural engineering vs fire engineering

multiconsult.no 27 Important tasks to clarify between disciplines: Structural engineer: Define main structural system Structural fire design– Tools: Eurocodes 1, 5 Fire engineer: Define combustible structure as a deviation from Guidance Document and give input to a parametric fire model Assess the fire safety strategy in regard to a possible probabilistic down-scaling of the fire energy, refer Eurocode 1 (not pre- accepted in Norway)

multiconsult.no 28 Possible development in pre-acceptance for tall timber buildings in a future Norwegian GD? For apartment buildings up to 8 storeys (23m to highest floor)provided: Fire compartments moderate in size Sprinklers with high reliability Standard fire resistance R90.

multiconsult.no 29 Conclusions A significant market potential for 3-4 storey timber buildings has been there for the past 15 years, the fire regulations represent no obstacle For apartment buildings of 5-8 storeys, an opening in the GD for increased use of timber is possible, given that automatic extinguishing systems are required and that limitations in fire compartment sizes will be defined Beyond this, more spectacular concepts can always be put into life, provided that a comprehensive risk analysis is performed and controlled/approved

multiconsult.no Thank you for your attention!