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Prof. Dr.-Ing. Dietmar Hosser

Structural fire design according to the Eurocodes Lecture 1 Introduction to Eurocode 1 Part 1-2 Overview and General Rules Actions on Structures exposed to Fire. Prof. Dr.-Ing. Dietmar Hosser Institute of Building Materials, Concrete Construction and Fire Protection (iBMB)

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Prof. Dr.-Ing. Dietmar Hosser

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  1. Structural fire designaccording to the EurocodesLecture 1Introduction to Eurocode 1 Part 1-2Overview and General Rules Actions on Structures exposed to Fire Prof. Dr.-Ing. Dietmar Hosser Institute of Building Materials, Concrete Constructionand Fire Protection (iBMB) Braunschweig University of Technology

  2. Introduction Institute of Building Materials, Concrete Construction and Fire Protection (iBMB) Material Testing Station (MPA) 4 Divisions,  60 scientists + 20 others7 Division,  120 employees

  3. Introduction Division of Fire Protection Scientific staff

  4. Research Activities • Fire behaviour of structural members and systems • Reaction to fire of building materials • Development of advanced constructionand material concepts • Simulation of fire phenomena • Preventive measures for special fire risks • Structural health monitoring(Collaborative Research Center 477) • Multimedia- teaching and e-learning in civil engineering

  5. Experimental Research Highlights • Fire behaviour of tunnel shellsfire-resistant concrete(no spalling) • Intumescent coating for woodfire resistance of20 - 40 minutes

  6. Prof. Dr.-Ing. Dietmar Hosser 62 years old, married since 1968, 2 children Education and fields of specialisation Concrete construction Extreme-load design Reliability and risk Fire protection and fire safety Career Design engineer + consultant (since 1970) Professor TU Braunschweig (since 1986) Consulting engineer + checking engineer (since 1987) Chairman of DIN committee „Structural fire safety“ Chairman of GFPA working group „Fire safety engineering“ Chairman and general organizer of national and international symposia on fire protection

  7. Time Schedule

  8. Time Schedule

  9. Time Schedule

  10. Lecture 1 • Background of the Eurocodes • Eurocodes for structural fire design • Steps of evolution • General requirements for design • Eurocode 1: Actions on structures exposed to fire • Overview • General rules • Thermal actions • Mechanical actions • Discussion

  11. Council Directive 89/106/EEC • Construction Product Directive - CPD • Definition of 6 Essential Requirements • Essential Requirement No. 2: Safety in case of fireThe construction works must be designed and built in such a way, that in the event of an outbreak of fire • the load bearing resistance of the construction can be assumed for a specific period of time, • the generation and spread of fire and smoke within the works are limited, • the spread of fire to neighbouring construction works is limited, • the occupants can leave the works or can be rescued by other means, • the safety of rescue teams is taken into consideration.

  12. Interpretative Document No. 2 • Functional requirements • Minimum requirements for construction works and products • Various possibilities for fire safety strategies prevailing in the Member States, e.g. design for • nominal fires or • natural fires • Consideration of • passive fire protection measures and/or • active fire protection measures

  13. Interpretative Document No. 2 • Fire safety design • Specification of passive measures in terms of standard fire resistance rating (based on standard fire tests) or • Assessing passive and active measures by fire safety engineering • Parts 1-2 of the Eurocodes • Specific aspects of passive fire protection • Design of structures for adequate load bearing resistance and for limiting fire spread

  14. Evolution of the Eurocode Fire Parts 94/95 1999 1993 Revisionof ENVs Trans-lation ENV English version: ENV 1991-2-2 ENV 199x-1-2 x : 2 to 6 and 9 German version: DIN V ENV 1991-2-2 DIN V ENV 199x-1-2 x : 2 to 6 and 9 < 1990 1990 EG CEN EC National application documents

  15. Evolution of the Eurocode Fire Parts 02/03 03/04 02/06 07/09 (?) 2010 (?)  3 years Evaluation by the authorities National annex with NDP Acceptance by the nationalauthorities as EN-package actions + design „cold“ + design „hot“ Withdrawal of national standards prEN Draft Trans-lation EN Appr. Concrete structures: EN 1990 EN 1992-1-1 EN 1991-1-2 EN 1992-1-2 English version: prEN 199x-1-2 x : 1 to 6 and 9 English version: EN 199x-1-2 x : 1 to 6 and 9 cold hot

  16. Eurocode Programme 1-1 EC 3 Steel structures Teil 1-2 Fire 1-1 1-1 EC 2 Concrete structures EC 4 Composite structures 1... Part 1-2 Part 1-2 Fire Fire 1... 1... 1-1 1-1 EC 6 Masonrystructres EC 9 Aluminiumstructres Part 1-2 Part 1-2 1-1 EC 5 Timber structures Fire Fire Part1-2 1... 1... Fire 1... Prof. Hosser Prof. Schaumann Prof. Winter Prof. Jäger

  17. Eurocode Programme EC 1 : Actions on structures 1-1 EC 3 Steel structures Part 1-2 Actions on structures exposed to fire 1-1 ... 1-3 ... 1 .... 1-4 ... Teil 1-2 Fire 1-1 EC 2 Concrete structures 1-1 EC 4 Composite structures 1... Part 1-2 Part 1-2 Fire Fire 1... 1... 1-1 1-1 EC 6 Masonrystructres EC 9 Aluminiumstructres Part 1-2 Part 1-2 1-1 EC 5 Timber structures Fire Fire Part1-2 1... 1... Fire 1... Prof. Hosser

  18. Alternative Design Procedures • Level 1: Tabulated Data • Single structural members • Minimum dimensions derived from standard fire tests • Level 2: Simplified Calculation Models • Single structural members(eventually parts of structural systems) • Engineering design methods appropriate for practice • Level 3: Advanced Calculation Models • Single members, parts of structures, structural systems • Numerical simulation of the load bearing and deformation behaviour under fire attack (FE analysis)

  19. Alternative Design Procedures Level 2 Level 3 Prescriptive Rules Nominal Fire Level 1 Mechanical Actions Part of the Structure Member Entire Structure Level 1 Level 3 Level 2 Level 3

  20. Alternative Design Procedures Level 2 Level 3 Performance-based Code Simple or Advanced Fire Development Model Level 2 or 3 Mechanical Actions Part of the Structure Entire Structure Member Level 3 Level 3

  21. Eurocode 1 Part 1-2 General Structural fire design procedures Thermal actions for temperature analysis Mechanical actions for structural analysis Annex A bis G (informative)  Lecture 2

  22. General • Design fire scenario • Fire as an accidental situation and action • Generally no combination with other accidental actions • Design fire • Generally fire assumed in one fire compartment • For members with specified fire resistance standard fire is used in most cases • Temperature analysis • Position of the fire in relation to the member is considered • Separating members exposed only from one side • External members the exposed through windows

  23. Fire Design Procedures • Selection of the design fire scenario • Determination of the design fire • Calculation of the temperature evolution in the structural members • Thermal analysis • Calculation of the mechanical behaviour of the structure • Mechanical analysis

  24. Fire Design Procedures Alternative limit states tfi,d  tfi,requ time domain Rfi,d,t Efi ,d,t strength domain d  cr,d temperature domain • Alternative thermal actions • Nominal temperature-time curve for a specified period of time • Fire model describing the full duration of the natural fire including the cooling phase

  25. Nominal Temperature-Time Curves Standard temperature-time curve External fire curve Hydrocarbon curve

  26. Nominal Temperature-Time Curves

  27. Thermal Action Convection c = coefficient of heat transfer [W/m2K] g = gas temperature [°C] m = surface temperature [°C] Radiation  = configuration factor (1.0, s. Annex G) m = surface emissivity (0.8) f = emissivity of the fire (1.0) • r = eff. radiation temperature [°C] • = Stephan Boltzmann constant (5.6710-8 [W/m2K4]) Net heat flux [W/m2]

  28. Nominal Temperature-Time Curves c = 25 W/m2K c = 25 W/m2K c = 50 W/m2K Standard temperature-time curve External fire curve Hydrocarbon curve

  29. Natural Fire temperature reaction to fire fire resistance flash-over fully developed fire cooling phase inflammation fire spread time flame spread fire spread to other compartments inflammability heat release smoke, toxicity, corrosivity inflammability

  30. Natural Fire Models • Simplified fire models • Based on physical parameters (e.g. fire load density and ventilation conditions) • Compartment fire: uniform temperature distribution • Localised fire: nonuniform temperature distribution • c = 35 W/m2K • Advanced fire models • One-zone-model • Two-zone-model • Computational fluid dynamic model • c = 35 W/m2K

  31. Mechanical Actions • Actions from normal temperature design • if they are likely to act in case of a fire • no decrease of imposed loads due to combustion • generally no decrease of snow loads due to melting • no actions from industrial operation • Actions due to constrained expansion or deformation caused by temperature change • neglected if recognised as favourable • accounted for by conservatively chosen support models • assessed in case of constrained thermal expansion of single structural members • Displacement of adjacent members due to thermal expansion of floor slabs

  32. Constrained Expansion

  33. Combination of Actions Accidental design situationEfi,d,t = gGA Gk + 1,1 Qk,1 + 2,i Qk,i Simplified combination rulesEfi,d,t = hfi. Ed withhfi = (gGA + 1,1)/(gG + gQ) = Qk/ Gk Reference load level for tabulated dataEfi,d,t = hfi. Rd

  34. Combination Values  values may be set in the National Annex

  35. Combination Values  values set in the National Annex for Germany

  36. Simplified Combination 1,1 = 0,8 Concrete structures steel structures hfi = (gGA + 1,1) / (gG + gQ) with = Qk,1 / Gk

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