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Adaption of active boundary conditions in structural fire testing

Ramla Karim Qureshi (Department of Civil, Structural and Environmental Engineering, State University of New York, Buffalo, New York, USA)
Negar Elhami-Khorasani (Department of Civil, Structural and Environmental Engineering, State University of New York, Buffalo, New York, USA)
Thomas Gernay (Department of Civil Engineering, Johns Hopkins University, Baltimore, Maryland, USA)

Journal of Structural Fire Engineering

ISSN: 2040-2317

Article publication date: 1 August 2019

Issue publication date: 11 October 2019

134

Abstract

Purpose

This paper aims to investigate the need for active boundary conditions during fire testing of structural elements, review existing studies on hybrid fire testing (HFT), a technique that would ensure updating of boundary conditions during a fire test, and propose a compensation scheme to mitigate instabilities in the hybrid testing procedure.

Design/methodology/approach

The paper focuses on structural steel columns and starts with a detailed literature review of steel column fire tests in the past few decades with varying axial and rotational end restraints. The review is followed with new results from comparative numerical analyses of structural steel columns with various end constraints. HFT is then discussed as a potential solution to be adapted for fire testing of structural elements. Challenges in contemporary HFT procedures are discussed, and application of stiffness updating approaches is demonstrated.

Findings

The reviewed studies indicate that axial and rotational restraints at the boundaries considerably influence the fire response of steel columns. Equivalent static spring technique for simulating effect of surrounding frame on an isolated column behavior does not depict accurate buckling and post-buckling response. Additionally, numerical models that simulate fire performance of a column situated in a full-frame do follow the trends observed in actual test results up until failure occurs, but these simulations do not necessarily capture post-failure performance accurately. HFT can be used to capture proper boundary conditions during testing of isolated elements, as well as correct failure modes. However, existing studies showed cases with instabilities during HFT. This paper demonstrates that a different stiffness updates calculated from the force-displacement response history of test specimen at elevated temperature can be used to resolve stability issues.

Originality/value

The paper has two contributions: it suggests that the provision of active boundary conditions is needed in structural fire testing, as equivalent static spring does not necessarily capture the effect of surrounding frame on an isolated element during a fire test, and it shows that force-displacement response history of test specimen during HFT can be used in the form of a stiffness update to ensure test stability.

Keywords

Citation

Qureshi, R.K., Elhami-Khorasani, N. and Gernay, T. (2019), "Adaption of active boundary conditions in structural fire testing", Journal of Structural Fire Engineering, Vol. 10 No. 4, pp. 504-528. https://doi.org/10.1108/JSFE-12-2018-0042

Publisher

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Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited

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