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Fire damaged structures COST C26 Final Conference Naples 16-19 September 2010 Ime avtorja Y. C. Wang, F. Wald, J. Vcha, M. Hajpl University of Manchester Czech Technical University in Prague MI, Budapest Maribor, mesec 2004 Motivation

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Maribor, mesec 2004 Ime avtorja

Fire damaged structures

COST C26 Final Conference Naples 16-19 September 2010

Y. C. Wang, F. Wald, J. Vácha, M. Hajpál

University of Manchester Czech Technical University in Prague ÉMI, Budapest

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COST C26 Final Conference, Naples 16-19 September 2010

Motivation

 To present the achievements

 in WG 1 of Cost Action C26  in field of assessment and repair

f fire damaged structures

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COST C26 Final Conference, Naples 16-19 September 2010

Outline

 Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development

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COST C26 Final Conference, Naples 16-19 September 2010

Introduction

 In fire design

the structure should resist the required time of fire

 The structural behavior after fire is not determined

 After compartment fires all the interior is

substantially damaged

 Bearing structure only part of the cost of the building  Except of special cases, like tunnels, highrised

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COST C26 Final Conference, Naples 16-19 September 2010

Outline

 Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development

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COST C26 Final Conference, Naples 16-19 September 2010

Assessment Procedure

 Site visit  Desk study  Detailed collection of evidence  Damage assessment  Specification of repairs

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COST C26 Final Conference, Naples 16-19 September 2010

Site Visit

 To gain early scale of damage  To advise on safety of building and

to recommend protection measures

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COST C26 Final Conference, Naples 16-19 September 2010

Desk Study

 Collect relevant information

 Original design of building  Construction materials, usage before fire, cause of fire  Duration of fire  Fire spread  Contents left unburnt

 Establish a strategy for gathering

f more detailed information

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COST C26 Final Conference, Naples 16-19 September 2010

Detailed Assessment Strategy Demage classification

A. No damage
B. Repairable damages – detailed collection
f evidences
C. Major damage – replacement of structural member
D. Total damage – scrap

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COST C26 Final Conference, Naples 16-19 September 2010

Detailed Collection of Evidence

 Residual strength and stiffness of material  Temperature attained in structure  Fire development  Cooling  Result of firemen's intervention  Correlation of results

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COST C26 Final Conference, Naples 16-19 September 2010

Fire Developments

 Burnt combustible materials  Openings  Construction materials of enclosure  Correlation with physical evidence

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COST C26 Final Conference, Naples 16-19 September 2010

Temperatures Attained in Structural Members

 Fire development + thermal analysis

 Metallurgy analysis  Colour changes in concrete

 More detailed testing: thermoluminescence test  Physical evidence  Correlation of results

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COST C26 Final Conference, Naples 16-19 September 2010

Mechanical Properties

 Temperatures + residual properties relationships  Non-destructive testing

 Schmit Hammer Test  Ultrasonic Pulse Velocity Test

 Destructive testing  Correlation of results

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COST C26 Final Conference, Naples 16-19 September 2010

Destructive Tests

 Concrete core test  Steel coupone test Steel degradation after heating to 950°C see Outinen and Mäkeläinen, 2004

50 100 150 200 250 300 350 400 450 500 550 2 4 6 8 10 12 14 16 18 20

Strain, %

Stress, N/mm 2

Test pieces taken before high-temperaure tests Test pieces taken after high-temperature tests

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COST C26 Final Conference, Naples 16-19 September 2010

References to assesment procedure

Steel structures, Kirby et al, 1986 Concrete structures, Concrete Soc., 1990

Preliminary inspection and immediate measures for securing public safety Fire causing possible structural damage Demolish Structural repair Non structural remedial work Is building/structure essential Is building/structure safe Has structure adequate life expectancy Carry out damage classification survey Prop Consider scheme for repair and propping Consider method

f repair and

consult with specialist repair contractors Preliminary design for major re-building scheme Is structural repair required Client/Legislative Assembly Approval for repair scheme Is scheme still viable Detail design Is major new work required Can

riginal strength

be restored Re-analyse and re-appraise the loadings, safety factors, actual strengths and use Can and adequate repair now be done Client approval to demolish Agreement of Legislative Assembly Approval of client for remedial work Any defects

utstanding

No Yes Yes Yes No No No No No No No Yes Yes Yes Yes Yes No Contract Approval Design Measurement of damage Event Obtain information about the fire and build up a mental picture of its severity eg. a) Type of contents b) Cause of fire c) Duration of fire d) Fire spread e) Contents left unburnt f) Structural collapse eg. roof falling in EXTENSIVE DAMAGE All the steelwork twisted and distorted beyond acceptable levels NO DAMAGE No evidence of heating eg. paintwork unblistered, paper not charred plastics not blackened deflections in the steelwork are acceptable taking into account their loading Check and if necessary replace the bolts. Carry out straightness measurements and determine the extend of distortion in the structural members RE-USE Under reduced load bearing capacity or reinforce and replace all bolts Can the section be repaired or reinforced RE-USE Has there been any significant deterioration in mechanical properties? Choose the lightest sections, eg. angle, channel, RSI end test areas which were subjected to the highest temperatures and compare the results with less affected areas RE-USE but replace all bolts Repair or reinforce STOP STOP STOP Categorise the building into different levels of Structural damage SCRAP SCRAP SLIGHT DAMAGE Suctions of the steelwork may be distorted and others appear straight Paintwork car be either unaffected, blister or completely burnt

STOP Are there any bolted connections of unheated steel sections with heated sections? Are there any structural members where the distortion is unacceptable? STOP Carry out or site tests to determine if there has been any deterioration in mechanical properties STOP RE-USE to full design load but replace all bolts Do the strength levels fall well inside current specification? STOP Yes Yes Yes Yes Yes No No No No

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COST C26 Final Conference, Naples 16-19 September 2010

Outline

 Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development

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COST C26 Final Conference, Naples 16-19 September 2010

Design Calculations for Repair

Load

 Include extra weight of repair materials  Temporary support loads  Reduced material factors

Model

 Treat structure as simply supported  Complex modelling at elevated temperature

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COST C26 Final Conference, Naples 16-19 September 2010

Outline

 Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development

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COST C26 Final Conference, Naples 16-19 September 2010

Repair Methods

Reconstruction

 Sprayed concrete  Resin repair  Overcladding

Others

 FRP strengthening  Change of use  Additional supports

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COST C26 Final Conference, Naples 16-19 September 2010

Case study Steel coal feeding bridge

 Fire - September 2005, Opatovice power station, Czech Republic  Coal belt transport infrastructure completely burned  Bearing structure noticeably damaged

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COST C26 Final Conference, Naples 16-19 September 2010

120 m

f the steel transport bridges attact

30 m 30 m 30 m 50 m 37 m Discarge Concrete tunels Steel partially demaged bridges

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COST C26 Final Conference, Naples 16-19 September 2010

Observations

 Geodetic measurements of major positions of the structure,

joints of the trusses and the rail of the conveyor

 Geometric measurements of straightness of compressed

elements

 Mechanical property by 54 coupon tests - reduction 10 %  Microstructure of steel – changes acceptable

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COST C26 Final Conference, Naples 16-19 September 2010

Deformed upper stiffening truss

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COST C26 Final Conference, Naples 16-19 September 2010

Reconstruction

 Elements with excessive deformations were replaced

 Maximum allowed out of straightness 10 mm

 Operational test after reconstruction

Replacing of the end frame

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COST C26 Final Conference, Naples 16-19 September 2010

Replacement

 Horizontal bridges

 Upper truss stiffeners  Upper crossbeams  Upper parts of the props of the end stiffeners

 Inclined bridge

 Also lower cross beams  Also lower stiffening trusses

View into the reconstructed bridge

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COST C26 Final Conference, Naples 16-19 September 2010

Straightening

f riveted

connections

 Not visibly deformed  After detailed calculation

 Assumed 15 % reduction of resistance  Unsatisfactory connection

strengthened by welding

Straightening of frame geometry

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COST C26 Final Conference, Naples 16-19 September 2010

Bridge after reconstruction

Reconstruction in three weeks Uncovered bridge

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COST C26 Final Conference, Naples 16-19 September 2010

Outline

 Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development

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COST C26 Final Conference, Naples 16-19 September 2010

Further Development

 Consideration of actual fire

fire generate non-uniform temperature

 Fire advanced modeling  Thermal deformation measurements  Destructive + non-destructive testing  Advanced models of damaged structure

 Assessment differs

from fire resistant design of the structure

 Fire damaged structures can be mostly repaired

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Maribor, mesec 2004 Ime avtorja

Thank you for your attention

František Wald Czech Technical University in Prague