FIRE SAFETY WITH CONCRETE — Experiences from real

FIRE SAFETY WITH CONCRETE - Experiences from real fires and full scale tests Tauno Hietanen standardization manager Finnish Concrete Industry Association

Contents of the presentation - examples and cases on: • Comprehensive fire protection with concrete – Case: Colindale London • Effects of thermal deformations – Case: Library fire in Sweden • Case: Windsor Tower fire in Madrid • Fire damage costs Tauno Hietanen Rakennusteollisuus RT ry 2

Essential requirements - Safety in case of fire Comprehensive fire protection Construction Product Directive: – the load bearing capacity 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 the fire to neighbouring construction works is limited; – occupants can leave the works or be rescued by other means; – the safety of rescue team is taken into consideration. Protection of people Protection of property Protection of environment Inside defined area Outside defined area Tauno Hietanen Rakennusteollisuus RT ry 3

Concrete does not burn • Best European Reaction to fire class A 1 • • does not ignite does not spread fire or smoke does not increase fire load does not generate toxic gases Tauno Hietanen Rakennusteollisuus RT ry 4

Temperature development in buildings Univ. Prof. Dr. techn. Dr. h. c. Ulrich Schneider Vienna University of Technology Effects of fire load on the fire scenario Temperature T [°C] Standard Temperature Curve Concrete/Brick Timber Construction Duration of fire t [min] Tauno Hietanen Rakennusteollisuus RT ry 5

Case: Timber construction site Colindale London 2006 Several 6 storey timber framed blocks were destroyed in fire • 15. 39 Fire was discovered in block A 2 of building complex A and Fire Service was alerted • 15. 42 The whole of building complex A is on fire • 15. 44 Fire Brigade arrives Tauno Hietanen Rakennusteollisuus RT ry 6

• • 15. 39 Fire was discovered 15. 44 Fire Brigade arrives 15. 48 Building complex A (blocks A 1, A 2 and A 3) begins to collapse. 16. 26 Fire spreads to the upper floors of block B 1 of building complex B Block A under construction where the fire starts Tauno Hietanen Rakennusteollisuus RT ry Block B partly finished 7

• 17. 10 The whole of block B 1 is on fire, with flames visible on the roof of block B 2 • 17. 31 Fire spreads from the roof of block B 2 to the lower storeys • 17. 58 80% of block B 2 is on fire • 17. 34 The London Fire Brigade brings the fire under control. • 21. 30 The fire is extinguished Tauno Hietanen Rakennusteollisuus RT ry 8

European resistance to fire classification REI is based on standard fire National fire regulations (required class or fire resistance time) Parametric fire Fire resistance time Nominal fire European REI classification CE marking based on harmonized product standard REI Fire parts of Eurocodes - Tabulated data - Simplified calculation - Advanced calculation EN 13501 -2 Classification standard EN 1363, EN 1365 Tauno Hietanen Rakennusteollisuus RT ry 9 Fire tests

Parametric fire curves Fire safety Engineering FSE Standard fire Tauno Hietanen Rakennusteollisuus RT ry 10 • Gas temperatures as function of fire load, oxygen supply (openings), surface materials etc. • Active fire protection methods may also be taken into account (fire brigade, sprinklers, …) • Fire safety level is not the same as by using standard fire curve • Later alterations are limited (use of the building, openings, surface materials, …)

Effects of thermal deformations Tauno Hietanen Rakennusteollisuus RT ry 11

The effects of thermal deformations need normally not be considered Tauno Hietanen Rakennusteollisuus RT ry 12

Thermal expansion and deflection of a simply supported hollow core slab in fire test Expansion loaded unloaded Deflection loaded unloaded Note: only a small part of the deflection is caused by external load, most of it is thermal curvature Tauno Hietanen Rakennusteollisuus RT ry 13

Thermal expansion and rotation of a simply supported hollow core slab in fire test Note: Expansion at mid height and bottom of the slab -restrained expansion creates additional ”prestressing” force - no risk that the slab would fall down from the supports due to curvature Tauno Hietanen Rakennusteollisuus RT ry 14

Influence of restraint Welded joint Friction bearing • The connections should be detailed in such a way that restraint force gives ”prestressing” in the lower part of the beam increasing fire resistance • Restraint in the upper part is negative for fire resistance Tauno Hietanen Rakennusteollisuus RT ry 15

Library collapse in Linköping in Sweden 1996 concrete structure designed for 60 minutes collapsed 47 minutes after fire alarm and 30 minutes after flash-over in heavy fire Tauno Hietanen Rakennusteollisuus RT ry 16

Ignition and fire spread Joint 30 mm Opening between floors, 52 m long Staircase and stabilizing walls Tauno Hietanen Rakennusteollisuus RT ry 17

Collapsed part Slab exposed to fire on both sides – large thermal expansion Tauno Hietanen Rakennusteollisuus RT ry 18

Cast in situ flat slab 250 mm with columns Ø 350 mm Tauno Hietanen Rakennusteollisuus RT ry 19

This collapse was result of several reasons: • The slab was exposed to fire on both sides – higher temperature and only small thermal deflection • Too few expansion joints – 54 m long slab • Too few stabilizing walls • High fire load: library, wooden suspended ceiling • Sensitive structural systems Reference (in Swedish ): Yngve Anderberg, K. G. Bernander, Biblioteksbranden I Linköping den 21 september 1996, Studium av orsaken till tidig ras Tauno Hietanen Rakennusteollisuus RT ry 20

Fire in Windsor Tower in Madrid 2005. Concrete structures performed extraordinary well in severe fire Tauno Hietanen Rakennusteollisuus RT ry 21

Madrid Windsor Tower fire in February 2005 • fire started on 21 st storey of 29 -storey office building in Madrid’s financial district • the building was being refurbished, including fireproofing steel perimeter columns and new external escape stairs • 22 office floors were in use Tauno Hietanen Rakennusteollisuus RT ry 22

STRUCTURAL SYSTEM • Technical floors above 3 rd and 16 th floors • normal strength concrete central core, columns and waffle slab floors • steel perimeter columns • when fire broke out steel columns above technical storey 2 had not yet been fireproofed Tauno Hietanen Rakennusteollisuus RT ry 23

storeys 4 to 16 storeys 17 to 27 concrete columns instead of walls steel columns technical storey high beams through the building Tauno Hietanen Rakennusteollisuus RT ry 24

• 23: 05 Fire alarm on 21 st storey (other sources say at 23: 16) • 23: 25 Fire brigade arrives • 23: 35 21 st storey was completely in flames • 0: 20 Fire had reached storey 28 • 1: 00 Large portions of the façade began to fall off • 1: 15 Northeast corner of the building above technical floor collapsed Tauno Hietanen Rakennusteollisuus RT ry 25

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• The fire spread downwards and reached 5 th storey at 7: 00 • The fire was considered to be under control at 15: 00 Tauno Hietanen Rakennusteollisuus RT ry 28

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The spread of the fire to neighbouring construction works was avoided because the concrete frame resisted the whole fire without collapse. It was decided to demolish the building Technical investigation was made and published by INTEMAC, NIT 2 – 05, in Spanish and English Tauno Hietanen Rakennusteollisuus RT ry 30

Costs of fire damages Tauno Hietanen Rakennusteollisuus RT ry 31

”Fire in multi family houses” “Brand i flerbodstadshus” A Report on the cost of fire damages in relation to the building material of which the houses are constructed. Author Olle Lundberg Sweden Tauno Hietanen Rakennusteollisuus RT ry 32

Regardless of the building material fires will occur, but the building material is heavily influencing the severity of the fire! – Statistics from Insurance Association in Sweden who's members are covering/paying 90% of the fires in Sweden. – Limited to Big Fires where the total insurance coverage is more than € 150 000 excl house content. – 90% of fires in the fire statistics analysed for the period 1995 to 2004, hence is representative. (Totals 125 fires). Tauno Hietanen Rakennusteollisuus RT ry 33

Wooden multi family houses in Sweden • Represent 10% of the number of multi family houses, but 56% of the Big Fires! • Average cost per fire and per apartment in wooden houses is 5 times that of cement based houses. • Cost – Wooden houses: € 50 000 – Cement based houses: € 10 000 Tauno Hietanen Rakennusteollisuus RT ry 34

• The likelihood of developing a fire to a Big Fire is 11, 5 times as high in wooden houses than in cement based houses • Of the burned houses : – 9% of the cement constructed houses and – 50% of the wooden constructed houses have to be demolished Tauno Hietanen Rakennusteollisuus RT ry 35

Does not burn or increase fire load Prevents spread of fire and smoke Loadbearing Separating CONCRETE STEEL TIMBER Tauno Hietanen Rakennusteollisuus RT ry 36

Concrete offers built-in fire resistance Thank you for your attention Tauno Hietanen Rakennusteollisuus RT ry 37