behaviour of a cold-formed steel portal frame in fire: full scale testing

Behaviour of a cold-formed steel

portal frame in fire: full scale

testing and finite element analysis

Ross Johnston

Project Advisors:

Dr. M. Sonebi

Dr. J.B.P Lim

Prof. C.G. Armstrong

Centre for Built Environment Research

START: Simple Problem

Determine the collapse behaviour of cold-formed steel portal frame structures at elevated temperatures (fire). Provide guidance to prevent undesirable outwards collapse mechanism.

Image courtesy of BBC, http://www.bbc.co.uk/news/uk-england-london-19234182. Accessed 13/08/2012,

START: Simple Problem

FINISH: Simple Solution

Funding

Literature Review

Constraints

Time

Collaboration

Current Practice

Benchmarking

Ambient validation prior to fire

Coupled instabilities

Lab testing

C

O

M

P

L

E

X

Image courtesy of CSB.

What is a cold-formed steel portal frame?

Viable alternative Sustainable Popular in Australia/NZ

Joints possess reduced capacity Limited research + guidance

Image courtesy of SCI P313 Publication, Simms and Newman.

Current guidance Only available for hot rolled steel portal frames. Based on SCI P313 Guidance

Document. No such guidance for cold-formed steel portal frames.

WHERE TO START?

DEVELOP RESEARCH AT AMBIENT TEMPERATURE FIRST

Funding

Literature Review

Constraints

Time

Collaboration

Current Practice

Benchmarking

Ambient validation prior to fire

Coupled instabilities

Lab testing

Ambient temperature (i)

OUTPUT:- BOLT STIFFNESS

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9

Load

(k

N)

Displacement (mm)

LAB test avg

ABAQUS FE

Zad./ Bryan

Ambient temperature (ii)

OUTPUT:- JOINT RIGIDITY

Ambient temperature (iii)

0

5

10

15

20

25

0 20 40 60 80 100

Load

(kN

)

Apex Displacement (mm)

OUTPUT:- VALIDATED AT AMBIENT TEMP

Elevated Temperature Study

Funding

Literature Review

Constraints

Time

Collaboration

Current Practice

Benchmarking

Ambient validation prior to fire

Coupled instabilities

Lab testing

CARRY OUT FULL SCALE SITE TEST AND VALIDATE NUMERICAL MODELS

Site test – planning

Site test – planning

Site test – construction

Site test – loading & instrumentation (i)

Site test – setup

Site test – images of building on fire

Site Fire Test Video

Site Test Results - temperature

Site Test Results – lateral eaves displacement

Site Test Results – frame displacement

Site Test Results – finite element

Firstly…What

happens to

steel in fire?

STRESS STRAIN CURVES

YOUNG’S MODULUS

EXPANSION

CONNECTION STIFFNESS

CONDUCTIVITY

SPECIFIC HEAT

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 200 400 600 800

Stif

fne

ss (

kN/m

m)

Temperature

Site Test Results – finite element

Site Test Results – finite element validation

-300

-200

-100

0

100

200

300

400

500

600

700

800

900

1000

1100

0 100 200 300 400 500 600 700 800 900 1000

La

tera

l E

av

es D

isp

lace

men

t (m

m)

Temperature (°C)

EXP Column H EXP Column B FE Column H FE Column B

Variance in FE and EXP due to beneficial effect of purlins, side-rails and

cladding?

Single portal frame model not able to accurately model this, need a multi-bay

portal frame arrangement.

Site Test Results – finite element

Parametric Study

-150

-130

-110

-90

-70

-50

-30

-10

10

30

50

0 100 200 300 400 500 600 700 800

Ve

rtic

al A

pe

x D

isp

lace

me

nt

(mm

)

Temperature (°C)

Shell Idealisation (nlgeom)

Beam Idealisation (nlgeom)

Potential for Application of Results

• Practical design guidance for engineers • Base for further research into the behaviour of such structures at elevated temperatures. •Design Procedure

•Critical Temperature

•Influence of purlins/side rails

•Effect of fire scenario

•Base fixity and Overturning moment

Acknowledgements Funding body Department for Employment and Learning (DEL). (For funding of full-scale site fire test: IStructE, ICE and EcoSteel Sdn. Bhd.) Acknowledgements My project advisors, Dr. M. Sonebi, Dr. J. Lim and Prof. C.G. Armstrong. Thanks to Mr Mei of EcoSteel Sdn. Bhd., Dr. H.H. Lau of Curtin University, Sarawak, Malaysia and Dr. Y. Xu, Strathclyde University for their expertise and continued collaboration within this research area. Dr. G. Abdelal, Dr. A. Hu and Mr A. Wrzesien for their assistance in composition of models. Further details Ross Johnston (E: rjohnston29@qub.ac.uk) Dr M Sonebi (E: m.sonebi@qub.ac.uk) Dr J Lim (E: james.lim@auckland.nz) Prof C. G. Armstrong (E: c.armstrong@qub.ac.uk)

Site test – planning (iii) Thank you for your

attention