The local buckling of RHS members at elevated temperatures

Tiina Ala-Outinen, Jukka Myllymäki

Research output: Book/ReportReport

Abstract

In Eurocode 3, Part 1.2 (ENV 1993-1-2 1993) simple calculation models are given by which the load-bearing capacity can be determined for different structures at elevated temperatures. These simple models are restricted to steel sections where the first order theory in global plastic analysis may be used. Eurocode 3, Part 1.2 gives no simple calculation method for a class 4 cross-section but does mention that the steel temperature of a class 4 cross-section should be below 350 °C, otherwise a general calculation method should be used. If the temperature is limited to 350 °C the insulation thickness increases, making structures of class 4 cross-sections uneconomical. The aim of this study is to find a simple calculation method for calculating the fire resistance of certain structures that may fail by local buckling. A series of fire tests was carried out for cold-formed rectangular hollow sections (RHS 200 x 200 x 5 and RHS 150 x 100 x 3) of structural steel S355. Both concentric and eccentric compression tests were performed. The fire tests were transient-state tests (heating rate 10 *C per minute under constant load) on unprotected specimens. A proposition for a simple calculation method is submitted. According to the proposition the effective width at elevated temperatures may be determined with the same formulae as at normal temperature, but the yield strength and the modulus of elasticity must be reduced. The yield strength of steel is determined corresponding the 0.2% proof strain at elevated temperatures. The stress-strain relationship and the modulus of elasticity at elevated temperatures are determined according to Eurocode 3, Part 1.2. The effects of actions during fire exposure may be deduced from the properties determined at normal temperature, using the reduction factor. With the typical value of the reduction factor, the end temperature according to load-bearing capacity calculated with a proof strain of 0.2% is clearly above 350 °C for rectangular hollow sections RHS 200 x 200 x 5 and RHS 150 x 100 x 3. The fire tests were analysed with the finite element method (FEM). Both geometrical and material non-linearity were included and the used stress-strain relationship at elevated temperatures was as determined in Eurocode 3, Part 1.2.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages81
ISBN (Print)951-38-4827-2
Publication statusPublished - 1995
MoE publication typeNot Eligible

Publication series

SeriesVTT Tiedotteita - Meddelanden - Research Notes
Number1672
ISSN1235-0605

Fingerprint

Buckling
Fires
Temperature
Steel
Bearing capacity
Yield stress
Loads (forces)
Elastic moduli
Fire resistance
Heating rate
Insulation
Plastics
Finite element method

Keywords

  • buckling
  • construction materials
  • hollow sections
  • steels
  • steel structures
  • calculations
  • methods
  • fire resistance
  • compressing
  • tests
  • temperature

Cite this

Ala-Outinen, T., & Myllymäki, J. (1995). The local buckling of RHS members at elevated temperatures. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Meddelanden - Research Notes, No. 1672
Ala-Outinen, Tiina ; Myllymäki, Jukka. / The local buckling of RHS members at elevated temperatures. Espoo : VTT Technical Research Centre of Finland, 1995. 81 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1672).
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Ala-Outinen, T & Myllymäki, J 1995, The local buckling of RHS members at elevated temperatures. VTT Tiedotteita - Meddelanden - Research Notes, no. 1672, VTT Technical Research Centre of Finland, Espoo.

The local buckling of RHS members at elevated temperatures. / Ala-Outinen, Tiina; Myllymäki, Jukka.

Espoo : VTT Technical Research Centre of Finland, 1995. 81 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1672).

Research output: Book/ReportReport

TY - BOOK

T1 - The local buckling of RHS members at elevated temperatures

AU - Ala-Outinen, Tiina

AU - Myllymäki, Jukka

PY - 1995

Y1 - 1995

N2 - In Eurocode 3, Part 1.2 (ENV 1993-1-2 1993) simple calculation models are given by which the load-bearing capacity can be determined for different structures at elevated temperatures. These simple models are restricted to steel sections where the first order theory in global plastic analysis may be used. Eurocode 3, Part 1.2 gives no simple calculation method for a class 4 cross-section but does mention that the steel temperature of a class 4 cross-section should be below 350 °C, otherwise a general calculation method should be used. If the temperature is limited to 350 °C the insulation thickness increases, making structures of class 4 cross-sections uneconomical. The aim of this study is to find a simple calculation method for calculating the fire resistance of certain structures that may fail by local buckling. A series of fire tests was carried out for cold-formed rectangular hollow sections (RHS 200 x 200 x 5 and RHS 150 x 100 x 3) of structural steel S355. Both concentric and eccentric compression tests were performed. The fire tests were transient-state tests (heating rate 10 *C per minute under constant load) on unprotected specimens. A proposition for a simple calculation method is submitted. According to the proposition the effective width at elevated temperatures may be determined with the same formulae as at normal temperature, but the yield strength and the modulus of elasticity must be reduced. The yield strength of steel is determined corresponding the 0.2% proof strain at elevated temperatures. The stress-strain relationship and the modulus of elasticity at elevated temperatures are determined according to Eurocode 3, Part 1.2. The effects of actions during fire exposure may be deduced from the properties determined at normal temperature, using the reduction factor. With the typical value of the reduction factor, the end temperature according to load-bearing capacity calculated with a proof strain of 0.2% is clearly above 350 °C for rectangular hollow sections RHS 200 x 200 x 5 and RHS 150 x 100 x 3. The fire tests were analysed with the finite element method (FEM). Both geometrical and material non-linearity were included and the used stress-strain relationship at elevated temperatures was as determined in Eurocode 3, Part 1.2.

AB - In Eurocode 3, Part 1.2 (ENV 1993-1-2 1993) simple calculation models are given by which the load-bearing capacity can be determined for different structures at elevated temperatures. These simple models are restricted to steel sections where the first order theory in global plastic analysis may be used. Eurocode 3, Part 1.2 gives no simple calculation method for a class 4 cross-section but does mention that the steel temperature of a class 4 cross-section should be below 350 °C, otherwise a general calculation method should be used. If the temperature is limited to 350 °C the insulation thickness increases, making structures of class 4 cross-sections uneconomical. The aim of this study is to find a simple calculation method for calculating the fire resistance of certain structures that may fail by local buckling. A series of fire tests was carried out for cold-formed rectangular hollow sections (RHS 200 x 200 x 5 and RHS 150 x 100 x 3) of structural steel S355. Both concentric and eccentric compression tests were performed. The fire tests were transient-state tests (heating rate 10 *C per minute under constant load) on unprotected specimens. A proposition for a simple calculation method is submitted. According to the proposition the effective width at elevated temperatures may be determined with the same formulae as at normal temperature, but the yield strength and the modulus of elasticity must be reduced. The yield strength of steel is determined corresponding the 0.2% proof strain at elevated temperatures. The stress-strain relationship and the modulus of elasticity at elevated temperatures are determined according to Eurocode 3, Part 1.2. The effects of actions during fire exposure may be deduced from the properties determined at normal temperature, using the reduction factor. With the typical value of the reduction factor, the end temperature according to load-bearing capacity calculated with a proof strain of 0.2% is clearly above 350 °C for rectangular hollow sections RHS 200 x 200 x 5 and RHS 150 x 100 x 3. The fire tests were analysed with the finite element method (FEM). Both geometrical and material non-linearity were included and the used stress-strain relationship at elevated temperatures was as determined in Eurocode 3, Part 1.2.

KW - buckling

KW - construction materials

KW - hollow sections

KW - steels

KW - steel structures

KW - calculations

KW - methods

KW - fire resistance

KW - compressing

KW - tests

KW - temperature

M3 - Report

SN - 951-38-4827-2

T3 - VTT Tiedotteita - Meddelanden - Research Notes

BT - The local buckling of RHS members at elevated temperatures

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Ala-Outinen T, Myllymäki J. The local buckling of RHS members at elevated temperatures. Espoo: VTT Technical Research Centre of Finland, 1995. 81 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1672).