Fire design of a steel hall without fire protection - HAMK 2011/Presentations/Day1/Horvath_121020… · Fire design of a steel hall without fire protection ... SHS 12010 3. SHS 1006

Patrik Takács – BSc student , BME / MSc student, TU Vienna László Horváth – BME Department of Structural Engenieering István Szontagh – Ruukki Hungary Ltd.

Fire design of a steel hall without fire protection

METNET Seminar Aarhus, 12-13. November 2011

Fire Design

Goal of the study

Structure and requirements

Temperatures and effects in fire situation

Comparison of fire design strategies

Results

Conclusions

Content


1

• Eurocodes for fire design of steel structures - EN 1991-1-1:2002 - EN 1993-1-2:2005 •Hungarian National Fire Regulations (2008)

•Hungarian Chamber of Engineers – series of design aids

Goal of the study Fire Design


2

•Studies at our Department : fire design for typical steel hall structures

•R15

•R30 ????

•Usually with fire protection (painting) •Additional material (strenghten the members) ??? •Change the steel grade ???

Goal of the study – ideas for R30 Fire Design


3

Fire Design

Characteristics of the building:

Area: ∼30×50 m

Steel hall with storage function

Portal frames

Hollow-sectioned truss beam

Steel columns: welded non-uniform cross-section

Steel grade: S355

The structure

4


Fire Design Requirements

Function: Storage

Number of storeys: 1

Specific fire load: < 250 MJ/m2 „E” fire risk class

Fire compartment area: < 1500 m2 IV. fire resistance category

Fire resistance requirements:

frame: 15 min – R15

bracing system: 15 min – R15

Extended application field :

frame: 30 min – R30

bracing system: 30 min – R30

National Fire Code H

5


Fire Design Fire models

If engineering methods used, then:

Fire scenario: only the standard ISO 834 fire curve is accepted

4 side fire exposure for all members

Uniform temperature distribution in all members

National Fire Code H

6


Fire Design Determination of Temperatures in case of Fire

7


Fire Design

Determination of Material Properties

8

Temperatures of the structural elements of the trusses

Modul of elasticity

Temperature [°C]

[1/°

C]

(*

10

-5)

[N/m

m2]

[N/m

m2]

Yield strength

Tem

per

atu

re

[°

C]

Time [min]

°C

[°C]

Coefficient of thermal expansion

ISO 834 curve

RHS 150*100*5

RHS 120*120*6

RHS 80*80*4

RHS 60*60*4


where:

▪ Ad: design value of an accidental action ( elevated temperatrure in fire)

▪ variable load: frequent value of the principal variable load

Additional effects of actions from thermal deformation can not be neglected!

The changes of the material properties have to be taken into account:

▪ modulus of elasticity -> modification of the internal force distribution

Fire Design Determination of the effect of actions

9

Effect of actions in case of fire - general method: for accidental design situations acc. EN 1990:


1i

1,11

,, ik,k,1djk, "+""+""""" QQAPGEj

tdfi i2,

Fire Design Determination of the effect of actions

where:

Ed : effect of actions from the structural analysis for normal temperature design

Fields of application according the National Fire Code in Hungary: :

▪ only with ISO-834 fire curve

▪ can be used for individual member analysis

▪ additional effects of actions from the restrained thermal expansion can be neglected

Effect of actions in case of fire – simplified method with ηfi reduction factor:

h fi =gGAGk +y1.1Qk.1

gGGk +gQ.1Qk.1

Efi,d,t =h fi *Ed

10


Fire Design Eurocode fire design methods

11

ConSteel 6.0 fire module

Individual finite

element model

with ηfi reduction factor

in accidental design situation

Determination of the effects of actions in case of fire

Determination of the critical temperature: on the basis of the degree of utilization: μ0

Verification of the fire resistance expressed

in terms of..

..critical temperature:

Θd ≤ Θcr,d

..load-bearing resistance : Efi,d,t ≤ Rfi,d,t

Only for tension members (truss, bracing)


For all members

Fire Design

Individual finite element model

Re-defined material

properties (temperature)

Load: mechanical + temperature

Combinations of actions for accidental design situations

Second order effect of actions

Uniform temperature distribution

Determination of the effect of actions

12 / 20 12 / 20 12


Fire Design

ConSteel 6.0 fire module

Load case: fire

Can be defined:

fire curve: ISO-834

duration of fire load: 15 and 30 minutes

fire protection yes/not: unprotected steel „I” and hollow sections

3 or 4 side fire exposure: 4 side, with uniform temperature distribution

Second order effect of actions

Determination of the Effect of Actions

13 / 20 13


Simplified method with ηfi reduction factor : significant differences in truss members method not suitable for trusses !!!

Earlier studies: method is suitable for framed structures made from rolled or welded profiles, because there the normal forces from thermal expansion are not high (reduction of the modulus of elasticity)

FEM analysis: only slight differences between the individual and ConSteel fire-module results (temperatures and internal forces)

both model and method acceptable

we calculated with FEM models (2D and 3D version; individual and firemodule; normal and elevated temperatures = 12 models)

Fire Design Comparison of the internal force results

14


Fire Design Truss profiles for R15

15 / 20

Bracing system

2. 3. 4.

5.

6.

7. 8.

1.

3. 2.

1.

4.

1.

RHS 150*100*5

2.

SHS 120*6

3.

SHS 80*4

4.

SHS 60*4

5.

SHS 80*4

6.

RS30

7.

RS24

8.

RS20

15

Truss


S 355

Fire Design Truss profiles for R30

16 / 20

Bracing system

2. 3. 4.

5.

6.

7. 8.

1.

3. 2.

1.

4.

1.

RHS 150*100*6

2.

SHS 120*10

3.

SHS 100*6

4.

SHS 60*4

5.

SHS 90*5

6.

RS40

7.

RS30

8.

RS20

16

Truss


S 460

Simplified method – critical time method for tension members

Member check with load-bearing resistances in fire situation

both method acceptable !

Fire Design Member verification in fire situation

17


250*12

900*10

250*10

250*12

900*10

250*10

250*12

589*8

250*10

250*12

842*8

250*10

250*12

657*8

250*10

250*12

200*6

250*10

250*12

365*6

250*10

Fire Design Column cross-sections for R15

3. D.

1.

2.

B.

A.

C.

3.

1.

2.

Real column member

C.

B.

A.

D.

Replacing column member

18


S 355

250*20

900*16

250*16

250*20

900*16

250*16

250*20

589*16

250*16

250*20

842*16

250*16

250*20

657*16

250*16

250*20

200*12

250*16

250*20

365*12

250*16

Fire Design Column cross-sections for R 30

3.

1.

2.

Real column member

C.

B.

A.

D.

Replacing column member

19 /

D.

C.

B.

A. 1.

3.

2.


S 460

Paper: related to overall constructional weight (load bearing structure + secondary + …)

only load-bearing: columns +58% truss +39% together +49%

Fire Design Increase of weight

20


Conclusions

Section factor plays a major role in the temperature development:

→ practical to use stockier and thicker cross-sections

Steel frames may be used for R30 with higher steel grade + some changes in the profiles.

In case of statically indeterminate structures - like a trussed

framework, which supports the bending moment as a

couple of tensile and compressive forces - the additional

effects of actions from thermal deformation are significant

and can not be neglected.

FEM softwares may help effectively at the fire desing also.

21

Fire Design


Thank you for your kind Attention!


Fire design of a steel hall without fire protection - HAMK 2011/Presentations/Day1/Horvath_121020… · Fire design of a steel hall without fire protection ... SHS 120*10 3. SHS 100*6

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Fire design of a steel hall without fire protection - HAMK 2011/Presentations/Day1/Horvath_121020… · Fire design of a steel hall without fire protection ... SHS 12010 3. SHS 1006