Concrete Slab•Followed ASTM E119 for 2 hours•Gradually reduced air-temperature until 600C

Furnace Specifications

Elin Jensen, Jacob Van Horn, Nabil Grace, and Mena BebawyCollege of Engineering, Civil Engineering Department

New Large-Scale Structural Fire Chamber: Initial Experimental Considerations

Objective: •Define design fires for assessing structural fire performance.•Verify the performance characteristics of the new test facility.

Experimental Considerations:•Furnace specifications•Design fires & furnace response

•Standard air temperature-time curve – ASTM E119•High intensity short duration - Fire A•Progressive burning – Fire B

•Specimen shadow effect •Test repeatability

•Slab•T-beam

Left: Small slab subjected to air temperature – time curve (ASTM).Right: Deflected slab after test

View on left: right front corner of slab & environmental thermocouple in rod

New facility located in the Center for Innovative Materials Research (CIMR) at Lawrence Tech, Southfield, MI

•The internal workload dimensions are 6.0 m x 1.5 m x 1.5 m.

•Max workload equivalent to 5.5 m3 of concrete subjected to ASTM E119 standard temperature-time curve

•Heating capabilities • Nine burners - 555,00 MJ/hour – natural gas• Three control zones • Variable air-gas mixture• Forced air ejector stack

•Mechanical loading of Pmax = 490 kN (compression)

•Controller & Data Acquisition•Closed loop temperature control system•70 set-points available in each temperature-time curve•100 thermo-couple channels

Temperature uniformity in workload area

CharacteristicsMean: 1004CMax: 1016CMin: 983CSt. dev: 6.3CVariation: 0.6 %

Furnace meets the requirements

Standard Fire - ASTM E119: •Standard air temperature-time curve•Allowable deviation from standard curve•Test repeatability

Concrete Test Slab Information:Dimensions: Length (1.82 m)

Width (1.82 m) Thickness (12.5 cm)

Concrete grade: 32 MPaAge: 4 yearsHumidity levels at core: RH 74% - 77% at Tair = 25C

Standard Fire – ASTM E119

Temperature-Time Curve - ASTM E119

0

500

1000

1500

0 2 4 6 8

Test Duration (h)

Air

Tem

pera

ture

(C)

Investigation range for slab testing

Radiation Effect

Shadow Effect During Slab TestingThe furnace roof is covered with white ceramic blanket and the furnace floor is covered with fire brick.

•The fire bricks heat up slower showing an offset between temperature below and above slab.

•Temperature offset decreases from 100C after 6 minutes to 25C after 1 hour.

•Furnace capable of producing Standard Fire - ASTM E119.

•Repeated tests fall within allowable deviation from standard.

Real Fires

Motivation

Design Fires: •A short duration high intensity fire is a result of burning highly combustible materials.•Progressive burning is a result of temporary oxygen depletion in a deep room.

•Capability of Fire Furnace in producing a fire with 1.0 m3 of concrete •Fire A – fire bricks cover the floor•Modified Fire A – ceramic blanket added over fire bricks•Fire B – fire bricks cover the floor

Below and Above Slab Environmental Thermocouples

0

250

500

750

1000

0.0 0.2 0.4 0.6 0.8 1.0

Test Duration (h)

Air-

Tem

pera

ture

(C

)

6 minT(average, below) = 446 CT(average, above) = 555 C

T(average, below) = 800 CT(average, above) = 840 C30 min

60 minT(average, below) = 900 CT(average, above) = 925 C

Design Fires

0

500

1000

1500

0.0 0.5 1.0 1.5 2.0

Duration (h)

Te

mp

era

ture

(C

)

Progressive Burning - Fire B ASTM E119

High Intensity Fire A Modified High Intensity Fire A

Temperature Uniformity

940

960

980

1000

1020

1040

6 min 19 min 34 min 60 min

Tem

pera

ture

(C)

Internal Temperature Profiles

Temperature Development in Slab

0

400

800

1200

0.0 1.0 2.0 3.0 4.0

Duration (h)

Tem

pera

ture

(C

)

Surface TemperatureTemperature at depth: h/4 = 31 mm

Temperature at depth: h/2 = 62.5 mm

•Good agreement between predicted and measuredtemperature development in concrete slab. Variable radiation effect not modeled.

Predicted versus Measured Temperature Development in Slab Subjected to Standard Fire

0

300

600

900

0.0 0.5 1.0 1.5 2.0

Duration (h)

Te

mp

era

ture

(C

)

Depth h/2

Bold line: Predicted - FEAThin line: Measured

Depth h/4

Est thermal conductivity: 0.8 W/mKEst specific heat: 1000 J/kgC

{

Temperature Development at h/2

0

300

600

900

0.0 1.0 2.0 3.0 4.0

Duration (h)

Tem

pera

ture

(C

)

Sensor located over brick support area

Sensor away from brick support

CFRP Prestressed Concrete Beam:Concrete Beam Information:Dimensions: Length (3.99 m)

Cross Section Shown in sketch

Concrete grade: 48 MPaAge: 9 monthsHumidity levels at core: RH 84% - 87% at Tair =

25C

Temperature Development in T-Beam:Development of internal beam temperature in agreement with

expected trends. Post-construction installation of thermocouples is successful.

Acknowledgement:• Center for Innovative Materials Research (CIMR) College of Engineering, Lawrence Tech University, Southfield, MI• National Science Foundation, Award 0747775

• Assistance from: Charles ElderCody TelghederDaniel Ziemba

735°C after 1 hr 20 min

Effect after 5 h

1020°C after 2 hr 19 min

Large Scale Structural Fire-Load Furnace

Thermocouples steel columns

Effect of brick support on temperature development

K-type thermocouples