A History of Fire Testing: Past, Present, and Future

Adaption of active boundary conditions in structural fire testing

Journal of Structural Fire Engineering ◽

10.1108/jsfe-12-2018-0042 ◽

2019 ◽

Vol 10 (4) ◽

pp. 504-528

Author(s):

Ramla Karim Qureshi ◽

Negar Elhami-Khorasani ◽

Thomas Gernay

Keyword(s):

Boundary Conditions ◽

Structural Steel ◽

Test Specimen ◽

Fire Test ◽

Structural Elements ◽

Fire Testing ◽

Content Type ◽

Steel Columns ◽

History Of ◽

Force Displacement

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.

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Concrete Fire Testing - A Review of the Thermal Boundary Conditions

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.711.496 ◽

2016 ◽

Vol 711 ◽

pp. 496-503

Author(s):

Cristian Maluk

Keyword(s):

Boundary Conditions ◽

Experimental Studies ◽

Time History ◽

Concrete Specimen ◽

Radiant Heat ◽

Heat Fluxes ◽

Fire Testing ◽

Conservation Of Energy ◽

Thermal Boundary Conditions ◽

History Of

Experimental studies of concrete in fire or at elevated temperature have traditionally given relatively little scientific attention to quantifying the severity, and to some extent reproducibility, of the thermal boundary conditions imposed on specimens during testing. This paper examines the heat transfer fundamentals of fire testing when controlling the time-history of temperature inside a furnace (or oven), versus controlling the time-history of incident radiant heat flux at a specimen’s exposed surface. The thermal boundary conditions of a concrete specimen during fire testing are fundamentally based on conservation of energy, and thus typically formulated in terms of heat fluxes. While from the standpoint of concrete fire behaviour the aim is typically only to gauge the distribution of temperatures inside concrete; this is rarely explicitly acknowledged or quantified during concrete fire testing. This shows that continued unexamined use of varied heating techniques presents a serious threat to harmonization of the thermal boundary conditions imposed during concrete testing. The current work proposes adopting test control by in-depth temperature distributions or net heat fluxes for a rigorous comparison of the thermal boundary conditions imposed on test specimens when using different heating techniques.

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