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Urban Habitat Constructions under Catastrophic EventsFINAL CONFERENCE. Naples, 16th- 18th September 2010Chair of the Action: Federico Mazzolani, IT, fmm@unina.itCOST Science Officer: Thierry Goger, tgoger@cost.esf.org
COST Action C26
ASSESSMENT OF THE ROBUSTNESS OF STRUCTURES SUBJECTED TO FIRE FOLLOWING EARTHQUAKE THROUGH A PERFORMANCE-BASED APPROACH
B. Faggiano, D. De Gregorio & F. M. Mazzolani
University of Naples ‘Federico II’, Naples, ITALY
INTRODUCTION
The analysis of the behaviour of structures under the effect of fires following an earthquake is a significant research field, which is not yet fully explored. The high probability of occurrence of firesin civil and industrial buildings after being struck by a seismic shake justifies the need to investigate the response to high temperatures of the structural systems, they being already in a state ofirreversible deformed configuration due to earthquake. In order to preliminary take into account in the design phases the effect of the combination of the seism and fire accidental loads, thepaper presents a proposal for a methodology aimed at the robustness assessment under fire of structures already damaged to different extent by the earthquake, through a performance- basedapproach. The procedure should be valuable as a design tool in all seismic prone area, as it is envisaged for buildings of high strategic importance. In this paper the methodology will beexemplified with reference to steel structures.
THE FIRE FOLLOWING EARTHQUAKE (FFE) HAZARD
• STRUCTURE DAMAGED BY EARTHQUAKE
• COMBINATION OF HUMAN DENSITY, STRUCTURAL CHARACTERISTICS AND METEOROLOGICAL CONDITIONS
• LEAK AND/OR ELECTRIC SHORT-CIRCUIT PRODUCED BY FIRE
• WATER SUPPLY INCREASES DUE TO THE DIFFICULTIES FOR THE FIREMEN IN REACHING THE PLACE FOR CONCOMITANT SEISMIC COLLAPSES OF ROAD NETWORKS AND FAILURE OF THE WATER SYSTEMS
MAIN HISTORICAL RECORDS
Fire after 1923 Tokyo seism(Japan)
Fire after 1994 Northridge seism(USA)
Fire after 1995 Kobe seism(Japan)
Fire after 2009 Pandang seism(Indonesia)
RISK FACTORS
THE CURRENT CODIFICATION APPROACH
METHODOLOGY FOR THE ROBUSTNESS ASSESSMENT OF STRUCTURES UNDER FIRE AFTER EARTHQUAKE
• ABAQUS. 2004b. ABAQUS Standard User’s Manual, Ver.6.5.• CEN 2002. EN 1990, Eurocode. Basis of structural design.• Bianco L. 2006. Effects of the fire on structural material (in Italian). www.buildup.it.• Faggiano B., Esposto M., Mazzolani F.M. 2008a. Risk assessment of steel structures under fire following earthquake, 14th World Conference on Earthquake Engineering, Beijing, PRC, 12-17 October, No. S19-015.• Faggiano B., Esposto M., Mazzolani F.M., Landolfo R. 2007. Fire analysis on steel portal frames damaged after earthquake according to performance based design. Workshop in Prague Urban Habitat Constructions under catastrophic events,
COST-Action C26, Prague, Czech Republic, March 2007, F. Wald, F.M. Mazzolani, M. Byfield, D. Dubina, M. Faber (Eds.), Print Prazska technica, ISBN: 978-80-01-03583-2, pp. 35-40.• ISO/TR 13387. 1999. Fire safety engineering.• Purkiss J.A. 2007. Fire safety engineering. Design of structures. Butterworth-Heinemann, Elsevier. ISBN-13: 978-0-7506-6443-1.
REFERENCES
EARTHQUAKE
1971 California(USA)
1994 Kobe(Japan)
1995 Northridge(USA)
2009 L’Aquila(Italy)
FIRE
TRADITIONAL APPROACH of deterministic type(Eurocodes)
MODERN APPROACH of performance type(FSE: Fire Safety Engineering, ISO/TR 13387, 1999)
PERFORMANCE BASED DESIGN (FEMA 356, November 2000)
OPERATIONAL
(O)
IMMEDIATE OCCUPANCY(IO)
LIFE SAFE
(LS)
COLLAPSE PREVENTION
(CP)
Very Light overall damage: the post-earthquake damage state in which the structural and non-structural components are able to support the pre-earthquake functions present in the building.
Light overall damage: the post-earthquake damage state guaranteeing the structure to remain safe to be occupied and to essentially retain the pre-earthquake design strength and stiffness.
Moderate overall damage: the post-earthquake damage state related to structural components, guaranteeing the structure to retain a safety margin against onset of partial or total collapse.
Severe overall damage: the post-earthquake damage state related to structural components, guaranteeing that the structure continues to support gravity loads but retains no safety margin against collapse.
• Unified approach for all the buildings categories
• Fire action modelled through the nominal curves• Simulations able to define different functions of
state for the fire phenomenon
• Finite Element structural analyses
• Possibility to investigate and to reduce the lossof life and damage to property,
• Possibility to quantify the risks and the hazardsinvolved and provide an optimal solution to theapplication of preventive or protective measures(Purkiss, 2007)
• IDENTIFICATION OF THE SEISMIC DAMAGE STATE, ACCORDING TO THEPRE-FIXED SEISMIC PERFORMANCE LEVELS, IN RELATION TO THEINTENSITY OF THE EVENT
• DETERMINATION OF THE RESIDUAL BEARING CAPABILITIES OF THESEISMIC DAMAGED STRUCTURES SUBJECTED TO FIRE, ACCORDING TOPRE-FIXED FIRE PERFORMANCE LEVELS, IN RELATION TO THE FIREEVENT.
OPERATIONAL Fire(Of)
IMMEDIATE OCCUPANCY fire(IOf)
LIFE SAFE Fire(LSf)
COLLAPSE PREVENTION fire(CPf)
Very Light overall damage. It shall be defined as the fire damage state in which the structural and non-structural components are able to support the pre-event functions present in the building.
Light overall damage. It shall be defined as the fire damage state that preserves equipments and contents and guarantees the structure to remain safe to be occupied.
Moderate overall damage. It shall be defined as the fire damage state that guarantees the structure to retain a safety margin against onset of partial or total collapse, while architectural, mechanical and electrical systems are damaged.
Severe overall damage. It shall be defined as the fire damage state that allows the structure to support gravity loads, without retaining a safety margin against collapse; while extensive damage to the non structural components are present.
METHODOLOGY
The methodology is the application of a performance-based approachinspired from the FEMA 356 Guidelines and the philosophy of the FSE
FIRE PERFORMACE LEVELS
SEISMIC PERFORMANCE LEVELS
CASE STUDY
FIRE LOCATION
SEISMIC PERFORMANCE LEVELS (FEMA 356, 2000)
FFE PERFORMANCE
IO LS CP1 CP2
Of 387 0 0 0
LSf 1382 0 0 0
CSf 1451 1446 1418 938
CLf 1587 1574 1544 1168
CGf 3076 2788 2340 1892
Operational fire(Of)
Life Safe fire(LSf)
Section Collapse fire(CSf)
Local Collapse fire(CLf)
Global Collapse fire(CGf)
S
Attainment of the yield stress in the most stressed section
Formation of the first plastic hinge
Failure of the cross-section
Beam mechanism
Global mechanism
NS
Negligible damage
Equipments,contents are secure
Architectural, mechanical electrical systems damaged
Extensive damage
(S= Structural components; NS= Non structural components)
RESISTANCE [s]
FIRE PERFORMACE LEVELS
STEEL FRAME GEOMETRY [m]
0
200
400
600
800
0,0% 1,0% 2,0% 3,0% 4,0% 5,0% 6,0% 7,0% 8,0% 9,0%
V [kN]
d/h [%]
IO
LS
CP1 CP2
PG
A=
0.99
PG
A=
1.18
PG
A=
1.26
PG
A=
1.25
O
MAIN PHASES
OfCL
f
CG
f 0
500
1000
1500
2000
2500
3000
3500
IO2
CP
1_
2
Performance Fire Levels
Resistance [s]
Performance Seismic Levels
IO2 LS2 CP1_2 CP2_2
Of 387 0 0 0
LSf 1382 0 0 0
CLf 1451 1446 1418 938
CSf 1587 1574 1544 1168
CGf 3076 2788 2340 1892
PERFORMANCE LEVELS (case d)
LS CP1IO SEISMIC PERFORMANCE
LEVEL
FIRE PERFORMANCE LEVEL
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