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Article
Publication date: 12 September 2016

Negar Elhami Khorasani, Maria Garlock and Paolo Gardoni

This paper aims to develop a framework to assess the reliability of structures subject to a fire following an earthquake (FFE) event. The proposed framework is implemented…

Abstract

Purpose

This paper aims to develop a framework to assess the reliability of structures subject to a fire following an earthquake (FFE) event. The proposed framework is implemented in one seamless programming environment and is used to analyze an example nine-story steel moment-resisting frame (MRF) under an FFE. The framework includes uncertainties in load and material properties at elevated temperatures and evaluates the MRF performance based on various limit states.

Design/methodology/approach

Specifically, this work models the uncertainties in fire load density, yield strength and modulus of elasticity of steel. The location of fire compartment is also varied to investigate the effect of story level (lower vs higher) and bay location (interior vs exterior) of the fire on the post-earthquake performance of the frame. The frame is modeled in OpenSees to perform non-linear dynamic, thermal and reliability analyses of the structure.

Findings

Results show that interior bays are more susceptible than exterior bays to connection failure because of the development of larger tension forces during the cooling phase of the fire. Also, upper floors in general are more probable to reach specified damage states than lower floors because of the smaller beam sizes. Overall, results suggest that modern MRFs with a design that is governed by inter-story drifts have enough residual strength after an earthquake so that a subsequent fire typically does not lead to results significantly different compared to those of an event where the fire occurs without previous seismic damage. However, the seismic damage could lead to larger fire spread, increased danger to the building as a whole and larger associated economic losses.

Originality/value

Although the paper focuses on FFE, the proposed framework is general and can be extended to other multi-hazard scenarios.

Details

Journal of Structural Fire Engineering, vol. 7 no. 3
Type: Research Article
ISSN: 2040-2317

Keywords

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Article
Publication date: 10 April 2017

Negar Elhami Khorasani and Maria E.M. Garlock

This paper aims to present a literature review on the problem of fire following earthquake (FFE) as a potential hazard to communities in seismically active regions. The…

Abstract

Purpose

This paper aims to present a literature review on the problem of fire following earthquake (FFE) as a potential hazard to communities in seismically active regions. The paper is important to work toward resilient communities that are subject to extreme hazards.

Design/methodology/approach

The paper lists and reviews the historical FFE events (20 earthquakes from 7 countries), studies the available analytical tools to evaluate fire ignition and spread in communities after an earthquake, discusses the available studies on performance of individual buildings under post-earthquake fires and summarizes the current literature on mitigation techniques for post-earthquake fires.

Findings

FFE can be considered a potential hazard for urban communities that are especially not prepared for such conditions. The available analytical models are not yet fully up to the standards that can be used by city authorities for decision-making, and therefore, should be further validated. Limited structural analyses of individual buildings under FFE scenarios have been completed. Results show that the drift demand on the building frame increases during post-earthquake fires. Despite the mitigation actions, there are still urban cities that are not prepared for such an event, such as certain areas of California in the USA.

Originality/value

The paper is a complete and an exhaustive collection of literature on different aspects of FFE. Research in earthquake engineering is well advanced, while structural analyses under fire load and performance of communities under FFE can be further advanced.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 8 no. 02
Type: Research Article
ISSN: 1759-5908

Keywords

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Article
Publication date: 9 December 2019

Ramla Karim Qureshi, Negar Elhami-Khorasani and Thomas Gernay

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…

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.

Details

Journal of Structural Fire Engineering, vol. 10 no. 4
Type: Research Article
ISSN: 2040-2317

Keywords

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