Open this publication in new window or tab >>2019 (English)Report (Other academic)
Abstract [en]
The temperature in the lower chord of steel trusses subjected to localized fires is difficult to estimate as most thermal exposure correlation formulas presented in the literature focus on heating along the ceiling where the temperature is very different from that of the lower chord [1], [2]. At the same time as the upper chord is engulfed in a ceiling jet from a localized fire, the lower chord may be surrounded by air at ambient temperature.
Two existing methods by Zhang and Usmani [3] and Guowei et al. [4], [5] along with one new approach for calculating the thermal exposure of the lower chord are presented in this paper and compared to the results from experiments conducted in Trondheim 2015 [6].
A new approach presented in this paper is evaluated based on two separate assumptions of the thermal exposure. Outside the plume, the radiative contribution is assumed originating from the plume in the form of a cylinder and inside the plume, the temperature is assumed decreasing according to a Gaussian shape from the central axis temperature to the temperature down to the temperature from the first part of the model at the transition between inside and outside the plume.
All models provide good correlation to the experimental data outside the plume perimeter. Inside the plume perimeter, the thermal impact depends to a high degree to the relation between the flame height and the height of the horizontal surface of interest.
Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019. p. 18
Series
Research report / Luleå University of Technology, ISSN 1402-1528
Keywords
Performance-based design, heat transfer, localized fires
National Category
Building Technologies Infrastructure Engineering
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-73430 (URN)978-91-7790-663-6 (ISBN)
Funder
Brandforsk, 312-131
2019-04-042019-04-042020-09-30Bibliographically approved