Analysis of steel-framed open car parks under localized fire Authors: R. Zanon ArcelorMittal R&D, O. Vassart Luxembourg L.-G. Cajot M. Sommavilla R. Zandonini University of Trento, F. Gadotti Italy 16 September 2010, Naples
Open Steel – framed Car Parks in Europe Dorneind, Helmond (NL) Wölfsburg (DE) Erfurt (DE) Amershan (UK) Arnhem (NL) Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 1
Architectural layout of Open Car Parks To allow a better functionality of the building it is advised to avoid columns between the parking lots. This increases greatly the dynamic capacity of the car park. Such a layout requires rather considerable spans (about 16 m), which are most suited for steel – framed structures. Open = natural ventilation through permanent openings in the facades ~16 m Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 2
Common structural solutions - Steel beam + traditional composite slab (shallow steel decking, slab span 2.5 ... 3.3 m) Parking Centre Hospedalier, GD-Luxembourg Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 3
Common structural solutions - Steel beam + traditional composite slab (shallow steel decking, slab span 2.5 ... 3.3 m) - Steel beam + innovative composite slab (deep steel decking, slab span 5.0 m) Parking Bouillon, GD-Luxembourg Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 4
Common structural solutions - Steel beam + traditional composite slab (shallow steel decking, slab span 2.5 ... 3.3 m) - Steel beam + innovative composite slab (deep steel decking, slab span 5.0 m) - Steel beam + concrete slab (in-situ or precast concrete units, slab span 2.5 ... 5.0 m) Parking Auchan Kirchberg, GD-Luxembourg Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 5
Common structural solutions - Steel beam + traditional composite slab (shallow steel decking, slab span 2.5 ... 3.3 m) - Steel beam + innovative composite slab (deep steel decking, slab span 5.0 m) - Steel beam + concrete slab (in-situ or precast concrete units, slab span 2.5 ... 5.0 m) - Integrated floor beam solutions (Slim Floor) (Hollowcore slabs up to 16.0 m span) Parking City Esch, GD-Luxembourg Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 6
Fire Resistance requirement in Open Car Parks Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 7
Structural Fire design approaches Resistance Single element Whole structure Nominal fire Prescriptive approach Actions Natural fire Performance based approach Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 8
Steps of the performance – based approach 1 - Definition of fire actions according to the combustion of vehicles simplified model from experimental tests 2 - Definition of fire scenarios with flame development and propagation simplified model from experimental tests 3 - Thermal Analysis with localised fire model analytical model based on experimental results 4 - Mechanical Analysis of the structure numerical model validated by experimental results Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 10
1. Test on cars to determine the RHR - curve In the scope of various national and european projects, a total of 20 cars were burnt at CTICM laboratory in Maizieres-les-Metz in order to assess the combustion process of standard vehicles. 0 min. 5 min. 16 min. 34 min. 37 min. 49 min. The cars were ignited with 1.5 litres of petrol in an open tray under the gear lever. All doors and windows were closed. A hood was built to collect smokes, combustion products and pollutants emitted during the fire. At the same time, the car was placed on a weighting platform that recorded the mass loss during the test. Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 11
1. Results of the tests on single vehicles Experimental RHR curves Design RHR curves Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 12
2. Full scale test in Open Car Park In a recent European project a real steel-framed car park was built in Vernon (France) in the scope to validate experimentally natural fire scenarios to be applied and to determinate the way to calculate the heat flux which the structure is submitted. 8 min. 15 min. 30 min. 36 min. Three big full scale tests involving several cars were run. No structural damage could be observed, and the deflection occurred during the fire could be fully recovered after cooling. From this experience the fire scenarios of several cars was confirmed. A propagation time of 12 minutes between a burning car and the ignition of the adjacent one was found to be a reasonable conservative hypothesis for fire modeling. Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 13
2. Fire propagation to many vehicles RHR Cars 12 min. RHR of Special vehicles Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 14
2. Practical design: First fire scenario 1 vehicle burning below beam mid-span Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 15
2. Practical design: Second fire scenario 4 vehicles burning around a central column Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 16
2. Practical design: Third fire scenario Burning wave: 7 vehicles burning along the border Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 17
3. Thermal analysis Currently two models are available in the EN1991-1-2 Annex C to describe the effects of localised fire to the structure: D 3.91m 1 0.7 W f m 35 c m 2 K Heskestad model Hasemi model for fire not impacting the ceiling for fire impacting the ceiling Parameters for the thermal analysis Fire diameter: D 3.91m In the case of open Car Parks, the W experimental campaign has been used to 35 Convection factor: c m 2 K validate the Hasemi model as design tool 0.7 able to reproduce with sufficient safety Steel emissivity factor: m margin the temperature field in the structure 1 f Fire emissivity factor: caused by burning cars. W 5.6710 8 Stephan-Boltzmannconstant: m 2 K 4 Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 18
4. Mechanical analysis – FEM model Restraints Cold part of the structure Columns Heated part of the structure Slab Ribs Beams Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 19
Validation of the numerical model on tests The comparison between experiments and numerical simulations has been showed the need to use 3D models to describe properly the structural behaviour under fire exposure. Such models are able to reproduce in reliable way the complex load-paths (in particular the membrane action) which developes under severe fire conditions and which allows for the structural stability. Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 20
Calculation example – First fire scenario 2 levels car park IPE400 S355 IPE400 S355 5.0m IPE400 S355 IPE400 S355 5.0m 5.0m IPE400 S355 IPE400 5.0m S355 HEB200 S355 16.0m 16.0m Load: Slab: - 2.2 kN/m 2 selfweight - composite slab, total thickness 120 mm, C30/37 - 1.0 kN/m 2 permanent loading - open trapezoidal steel sheeting rib height 60 mm, S280GD - 2.5 kN/m 2 variable loading - reinforcing mesh Q257, B500C Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 21
Calculation example – Third fire scenario 1. Cold situation 4. Cooling phase 2. Heating phase 3. Temperature peak 1. Slab in 2. Slab in tension 3. Slab in tension with 4. Slab in compression in compression In central part compression ring cooling phase Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 22
Calculation example – Second fire scenario 2 levels car park IPE400 S355 IPE400 S355 5.0m IPE400 S355 IPE400 S355 5.0m 12 min 5.0m IPE400 S355 12 min 0 min IPE400 5.0m S355 HEB200 S355 16.0m 16.0m Load: Slab: - 2.2 kN/m 2 selfweight - composite slab, total thickness 120 mm, C30/37 - 1.0 kN/m 2 permanent loading - open trapezoidal steel sheeting rib height 60 mm, S280GD - 2.5 kN/m 2 variable loading - reinforcing mesh Q257, B500C Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 23
Calculation example – Second fire scenario 2 ° phase 1 ° phase 1 ° phase: due to thermal expansion of the column, the slab displaces upwards 3 ° phase 2 ° phase: column buckles and the slab displaces downwards 3 ° phase: collapse, the displacement grows indefinitely Column buckling about weak axis Naples - 16 September 2010 Analysis of steel-framed open car parks under localized fire 24
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