15 EN 1993-1-2 Simplified calculation method for ...people.fsv.cvut.cz/~wald/fire/ifer/2014-Meeting/PDF/15_.pdf · António Moura Correia, João Paulo Rodrigues, Valdir Pignatta e

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SIMPLIFIED CALCULATION METHOD FOR TEMPERATURE EVALU ATION OF STEEL COLUMNS EMBEDDED ON WALLSAntónio Moura Correia, João Paulo Rodrigues, Valdir Pignatta e Silva

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Institute for Sustainability and Innovation in Structural Engineering

FCTUCFaculdade de Ciências e TecnologiaUniversidade de Coimbra

The EN 1993-1-2 for fire design, does not take into account the case of steel elements

embedded in walls, presenting only a formulation considering uniform temperature. Thus

the thermal gradients observed within the cross-section are neglected.

Proposed changes

Eurocode EN 1993-1-2 Clause 4.2.5

The proposal consists of a new simplified calculation method to evaluate the

temperature distribution on steel columns embedded in walls. The method is based on Finite

Element Analysis and Fire Resistance Tests. Steel columns totally or partially embedded in

walls, with the web perpendicular or parallel to the wall surface, were studied.

Reasons for improvement

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1. 3D restraining steel frame;

2. Hydraulic jack of 1MN;

3. 2D reaction frame;

4. LVDT’s;

5. Furnace;

6. Safety structure;


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Walls on both sides of the columns were

built. The furnace applies the thermal

action, following the standard ISO curve.

The columns in test were placed on the centre

of a 3D restraining frame. The column was instrumented with

thermocouples and LVDT’s.

Preparation of the tests on steel columns embedded on walls


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Experimental tests on steel columns embedded on walls

400ºC400ºC400ºC

400ºC

400ºC400ºC 400ºC 400ºC

400ºC

400ºC

400ºC

400ºC

400ºC 400ºC

400ºC400ºC

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Thermal Gradients Web perpendicular to the walls Web parallel to the wallsEA

t(min)Exposed flange Web

Unexposed flange

0.0 20 20 20

1.8 100 49 20

3.2 200 87 20

4.5 300 127 20

5.9 400 170 21

7.6 500 220 23

10 600 280 28

14.6 700 362 42

t(min)Exposed

half-flange WebUnexposed half-flange

0 20 20 20

2.25 100 80 37

4.16 200 159 72

6.1 300 244 119

8.3 400 329 174

11.1 500 417 245

15.5 600 513 333

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25 30

T (

ºC)

t (min)

Exposed

flange

web

Unexposed

flange

Mean Steel

Temperature 0

100

200

300

400

500

600

700

800

0 5 10 15 20

T (

ºC)

t (min)

Exposed half-

flange

web

Unexposed

Half-flange

Mean Steel

Temperature


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Reduction factors

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Temperature evolution in unevenly heated columns, embedded on walls

Model 1 Model 2 Model 3

Analytical Proposals

Model 4 Model 5


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Model 2 – HEA 160 Model 5 – HEA 160

Analytical Proposals


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Conclusion

Concerning the assessment of the temperature evolution in the steel

profiles embedded on walls

The EN 1993-1.2 (2005) formulation using the section factor can be used, although

it was proven to be valid only for the exposed flange engulfed in fire (cases of wall

thickness smaller than web height). In all other cases, the temperature in each zone of the

cross-section can be calculated in function of the temperature of the exposed area.

Several reduction factors were defined in such a way that multiplying the temperature of

the exposed area of the steel profile by them, the temperature in the corresponding zone

is obtained.

Another aproach was proposed considering different formulae for the different

cases.


Documents

15 EN 1993-1-2 Simplified calculation method for ...people.fsv.cvut.cz/~wald/fire/ifer/2014-Meeting/PDF/15_.pdf · António Moura Correia, João Paulo Rodrigues, Valdir Pignatta e