Torsional and flexural-torsional buckling of compressed steel members in fire

Possidente, Luca; Tondini, Nicola; Battini, Jean‐Marc

doi:10.1016/j.jcsr.2020.106130

Cited by 7 publications

(11 citation statements)

References 31 publications

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“…Investigated sections JSFE particular, the 3D beam element was specifically conceived to properly consider torsion and warping in thin-walled elements with open cross-section at elevated temperature. In addition, the ability of these elements to capture flexural-torsional buckling was numerically validated in Possidente et al (2020a), since no experimental tests were available in literature. The beam and shell elements gave comparable results for the buckling mode identification and the associated buckling load evaluation of members prone to flexural-torsional buckling.…”

Section: Jsfementioning

confidence: 99%

“…In Figure 3 the results are presented for the T sections consisting of half H or half I only since a comparison with the EN 1993-1-2 for the remaining sections was already proposed in Possidente et al (2020a). Instead, the numerical results are shown for all the cross-sections in Figure 4, in which the outcomes of the analyses are compared with the AISC 360-16 curve.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…Instead, the numerical results are shown for all the cross-sections in Figure 4, in which the outcomes of the analyses are compared with the AISC 360-16 curve. The buckling curves are expressed with respect to the pure flexural buckling slenderness, allowing for a better representation of the length of the member and improved predictions (Popovic et al , 2001; Possidente et al , 2020a; Taras and Greiner, 2007). From the figures, it can be observed that the design buckling curves from the European and American norms give inaccurate results and over- or underestimate the N/Nyield ratio in most of the cases, providing unsafe or too conservative predictions.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…The proposed buckling curves were compared with the numerical results and the EN 1993-1-2 buckling curve for T sections consisting of half hot-rolled H or I profiles in Figure 3. The results for the other section types can be found in Possidente et al (2020a). Predictions from the proposal are safer and the introduction of a plateau (λ‾0) together with the change of the shape of the curve (β and γ), allow for a better representation of the numerical outcomes.…”

Section: New Buckling Curve Proposalsmentioning

confidence: 99%

“…In order to provide safe predictions, additional checks on the η and n factors were performed. For this purpose, the data relative to the envelope of the minimum values of the numerical results NFEA/Nyield in Figure 3 and from Possidente et al (2020a) and in Figure 4 were selected. Equivalent numerical factors ηFEA and n FEA associated to these data were compared with ηEN1993−1−2 and ηPROP (Table 4), and nAISC 360−16 and nPROP (Table 6), respectively.…”

Section: New Buckling Curve Proposalsmentioning

confidence: 99%

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Fire buckling curves for torsionally sensitive steel members subjected to axial compression

Possidente

Tondini

Battini

2021

JSFE

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PurposeBuckling should be carefully considered in steel assemblies with members subjected to compressive stresses, such as bracing systems and truss structures, in which angles and built-up steel sections are widely employed. These type of steel members are affected by torsional and flexural-torsional buckling, but the European (EN 1993-1-2) and the American (AISC 360-16) design norms do not explicitly treat these phenomena in fire situation. In this work, improved buckling curves based on the EN 1993-1-2 were extended by exploiting a previous work of the authors. Moreover, new buckling curves of AISC 360-16 were proposed.Design/methodology/approachThe buckling curves provided in the norms and the proposed ones were compared with the results of numerical investigation. Compressed angles, tee and cruciform steel members at elevated temperature were studied. More than 41,000 GMNIA analyses were performed on profiles with different lengths with sections of class 1 to 3, and they were subjected to five uniform temperature distributions (400–800 C) and with three steel grades (S235, S275, S355).FindingsIt was observed that the actual buckling curves provide unconservative or overconservative predictions for various range of slenderness of practical interest. The proposed curves allow for safer and more accurate predictions, as confirmed by statistical investigation.Originality/valueThis paper provides new design buckling curves for torsional and flexural-torsional buckling at elevated temperature since there is a lack of studies in the field and the design standards do not appropriately consider these phenomena.

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Section: Jsfementioning

confidence: 99%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Numerical Simulationmentioning

confidence: 99%

Section: New Buckling Curve Proposalsmentioning

confidence: 99%

Section: New Buckling Curve Proposalsmentioning

confidence: 99%

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Fire buckling curves for torsionally sensitive steel members subjected to axial compression

Possidente

Tondini

Battini

2021

JSFE

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Fire Fragility Curves for Industrial Steel Pipe-Racks Integrating Demand and Capacity Uncertainties

Possidente

Randaxhe²,

Tondini

2023

Fire Technol

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This paper aims at deriving fire fragility curves for a prototype steel pipe-rack in an industrial plant subjected to localised fires. In particular, starting from a reference case study, uncertainties related to the structural capacity and the size of the localised fires caused by a hole in a tank or a hole in a pipe are included in the analyses. Thus, the influence of uncertainties in the derivation of the fragility functions was highlighted by comparing four sets of analyses in which both demand and capacity uncertainties were progressively introduced. Moreover, alongside the cloud analysis (CA), the suitability of the Multiple Stripe Analysis (MSA) to build relevant probabilistic fire demand models was assessed. Fire fragility curves were derived by considering the interstorey drift ratio (ISDR) as engineering demand parameter (EDP) and by assessing different relevant intensity measures (IMs) that represent the severity of localised fires. It was found that by introducing uncertainties in the steel yield strength, lower probabilities to exceed the life safety and the near collapse limit states with respect to the reference case study were observed. Moreover, the inclusion of further uncertainties, described with continuous physically-based probability functions of the size of the fire diameter, affected the probabilistic models by lowering the probability of exceedance. These functions provide a more realistic description of the fire scenario, enabling a better representation of the structural vulnerability. For this case study, the CA exhibited better suitability for the derivation of fire fragility curves than the MSA. All the analysis results are thoroughly discussed in the paper.

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Validation of a New Analytical Formula to Predict the Steel Temperature of Heavily Insulated Cross-Sections

Possidente,

Tondini

2023

Fire Technol

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Fire protection is a popular solution to slow down the temperature increase in steel elements subjected to fire, and simple equations, such as the mass lumped formula proposed in EN1993-1-2, may be employed to estimate the steel temperature in the cross-section. The EN1993-1-2 formula assumes that the temperature of the exposed insulation surface and the surrounding gas are equal. This simplification may provide inaccurate results for heavily insulated steel sections. Therefore, a new mass lumped formula was derived, accounting for more accurate boundary conditions considering the heat flux impinging the insulation. On these premises, this work evaluates how the new simple formula fares with respect to the EN1993-1-2 formula. In this respect, a comprehensive comparison with the results of 1-D and 2-D analyses considering several insulation materials and thicknesses of insulation and steel is thoroughly presented. The proposal results in being always safe and better estimates steel temperatures relevant in the structural fire engineering context. Its use is particularly recommended for heavily insulated sections, where the ratio between the insulation and the steel heat capacities is higher than 14, and the EN1993-1-2 formula gives unsafe predictions.

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Torsional and flexural-torsional buckling of compressed steel members in fire

Cited by 7 publications

References 31 publications

Fire buckling curves for torsionally sensitive steel members subjected to axial compression

Fire buckling curves for torsionally sensitive steel members subjected to axial compression

Fire Fragility Curves for Industrial Steel Pipe-Racks Integrating Demand and Capacity Uncertainties

Validation of a New Analytical Formula to Predict the Steel Temperature of Heavily Insulated Cross-Sections

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