Fire damaged structures COST C26 Final Conference Naples 16-19 - PowerPoint PPT Presentation

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

Motivation  To present the achievements  in WG 1 of Cost Action C26  in field of assessment and repair of fire damaged structures COST C26 Final Conference, Naples 16-19 September 2010

Outline  Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development 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 COST C26 Final Conference, Naples 16-19 September 2010

Outline  Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development COST C26 Final Conference, Naples 16-19 September 2010

Assessment Procedure  Site visit  Desk study  Detailed collection of evidence  Damage assessment  Specification of repairs 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 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 of more detailed information COST C26 Final Conference, Naples 16-19 September 2010

Detailed Assessment Strategy Demage classification A. No damage B. Repairable damages – detailed collection of evidences C. Major damage – replacement of structural member D. Total damage – scrap 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 COST C26 Final Conference, Naples 16-19 September 2010

Fire Developments  Burnt combustible materials  Openings  Construction materials of enclosure  Correlation with physical evidence 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 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 COST C26 Final Conference, Naples 16-19 September 2010

Destructive Tests Stress, N/mm 2 550 Test pieces taken before high-temperaure tests 500  Concrete core test 450 Test pieces taken after high-temperature tests 400  Steel coupone test 350 300 250 200 150 100 50 0 Strain, % 0 2 4 6 8 10 12 14 16 18 20 Steel degradation after heating to 950°C see Outinen and Ma ̈ kela ̈ inen, 2004 COST C26 Final Conference, Naples 16-19 September 2010

References to assesment procedure Obtain information about the fire and build up a mental picture of its severity eg. Fire a) Type of contents causing b) Cause of fire possible c) Duration of fire Event structural d) Fire spread damage e) Contents left unburnt f) Structural collapse eg. roof falling in Preliminary inspection and immediate Categorise the building into different levels of measures for securing public safety Structural damage Measurement of damage No Is Is Yes EXTENSIVE DAMAGE SLIGHT DAMAGE Carry out damage building/structure building/structure NO DAMAGE Suctions of the steelwork may classification survey All the steelwork twisted and No evidence of heating eg. essential safe distorted beyond acceptable be distorted and others paintwork unblistered, paper not appear straight Paintwork levels No charred plastics not blackened car be either unaffected, deflections in the steelwork are blister or completely burnt Yes acceptable taking into account off Has Consider scheme SCRAP their loading structure adequate for repair and Prop life expectancy propping Carry out straightness measurements and determine the extend of distortion RE-USE STOP in the structural members No No Preliminary Is structural repair design for major re-building required scheme Are there any structural Yes Can the section be No Yes Are there any bolted SCRAP No members where the distortion connections of unheated repaired or reinforced Yes is unacceptable? Yes Is major STOP steel sections with Any defects new work heated sections? Yes outstanding required STOP Carry out or site tests to No Repair or Design Yes No determine if there has been reinforce Consider method any deterioration in Yes mechanical properties of repair and Can Check and if necessary consult with original strength replace the bolts. specialist repair be restored Choose the lightest contractors No sections, eg. angle, channel, Re-analyse and RSI end test areas which re-appraise the were subjected to the STOP No loadings, safety highest temperatures and Is scheme compare the results with factors, actual still viable strengths and use less affected areas No Yes No Has there been any Yes RE-USE Can and adequate STOP significant deterioration in Detail design but replace all bolts repair now be mechanical properties? done Yes No Do the strength levels fall Approval Client approval Client/Legislative Assembly RE-USE Agreement of Legislative Assembly well inside current to demolish Approval for Under reduced Approval of client specification? repair scheme load bearing for remedial work capacity or Yes reinforce and RE-USE replace all bolts Contract to full design load but Non Structural replace all bolts Demolish structural repair remedial STOP work STOP Steel structures , Kirby et al, 1986 Concrete structures , Concrete Soc., 1990 COST C26 Final Conference, Naples 16-19 September 2010

Outline  Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development 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 COST C26 Final Conference, Naples 16-19 September 2010

Outline  Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development 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 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 COST C26 Final Conference, Naples 16-19 September 2010

120 m of the steel transport bridges attact Steel partially demaged bridges Discarge Concrete tunels 37 m 30 m 30 m 30 m 50 m 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 COST C26 Final Conference, Naples 16-19 September 2010

Deformed upper stiffening truss COST C26 Final Conference, Naples 16-19 September 2010

Reconstruction Replacing of the end frame  Elements with excessive deformations were replaced  Maximum allowed out of straightness 10 mm  Operational test after reconstruction COST C26 Final Conference, Naples 16-19 September 2010

View into the reconstructed bridge 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 COST C26 Final Conference, Naples 16-19 September 2010

Straightening of riveted connections Straightening of frame geometry  Not visibly deformed  After detailed calculation  Assumed 15 % reduction of resistance  Unsatisfactory connection strengthened by welding COST C26 Final Conference, Naples 16-19 September 2010

Bridge after reconstruction Uncovered bridge Reconstruction in three weeks COST C26 Final Conference, Naples 16-19 September 2010

Outline  Intoduction  Assesment  Design procedure  Structural aspects  Case study  Further development COST C26 Final Conference, Naples 16-19 September 2010