Fragility Analysis of a Steel Building in Fire

2016

This work provides a framework to evaluate the resp on e of buildings in a community to fire following earthquake. As part of the framework, the paper discusses two methodologies: (1) how to develop fire fragilit y functions; (2) how the fire fragility functions can be used in conjunction with an original fire ignition model to estimate the potential losses in a community from f ire following earthquake. The paper focuses in particular on the development of f ire fragility functions for an entire building to measure the probability of reaching a damage sta t given a fire scenario. Next, the paper proposes an ignition model to evalu ate the probability of fire ignition after an earthquake. The ignition model together wi th fragility functions measure the probability of damage from fire following earthquak e given an earthquake scenario.

IABSE Symposium Report, 2015

The paper provides a framework to evaluate the response of buildings in a community subject to fire following earthquake. First, a model is developed to determine the probability of ignition in buildings of a community due to an earthquake. Second, fragility functions are developed for buildings subject to fire, to quantify the structural damage and the expected losses. The ignition model, combined with the fragility functions, can be implemented in a GIS based risk management platform to evaluate economical losses in a region from fire following an earthquake.

2017

Recent efforts aim at assessing the fire performance of structures in a probabilistic framework. But there is still no well-established method to quantify the reliability of entire buildings. Previous works focused on isolated structural members, therefore not allowing for a determination of the global safety level of buildings. Here, a new methodology is developed to quantify the reliability of buildings in fire. The methodology uses Monte Carlo simulations for constructing fragility functions associated with different fire breakout locations in a building, then combines the functions to characterize the overall building conditional probability of failure, and finally incorporates the probabilistic models for intensity measure and fire occurrence likelihood. The methodology is applied to multi-story steel buildings. This work addresses fire reliability at the building scale, and therefore is useful for standardizing safety level as well as for evaluating community resilience.

Steel Construction, 2011

2018

Reliability methods are at the core of ambient Eurocode design. Realising exceptional / complex buildings necessitates that an adequate level of safety be demonstrated. Rationally demonstrating adequate safety can only be achieved through the application of probabilistic risk assessment (PRA). This paper presents a novel application of PRA in a structural fire engineering context. It first proposes a generalised limit state for protected steel members undergoing failure modes dictated by yielding. Subsequently, fragility curves describing failure likelihood in function of protection specification and mean fire load are presented for a 1,000 m2 compartment, subject to fully developed fires (parametric and travelling fires). The presented fragility curves have subsequently proven to be of value for further life-time-cost-optimisation applications, with the intent of arriving at explicit safety targets.

Fire Safety Journal, 2003

Fires following earthquakes are considered one major threat in seismic regions. In fact, according to modern seismic codes, ordinary structures are designed to suffer damage to some extent during strong earthquakes, exploiting the structure own ductility to avoid collapse and safeguard human lives. Then, a fire coming soon after an earthquake will find a different, more vulnerable, structure with respect to the initial, undamaged, one. Depending on the extent of damage, the fire resistance rating of the structure could be significantly reduced. This paper is devoted to obtaining some quantitative information about this topic, with reference to steel moment-resisting frames, even if the adopted methodology could also be extended to either different structural types or structural materials. As a first step, a simplified modelling of earthquake-induced structural damage, based on the superposition of geometrical and mechanical effects, is proposed. Then, a wide numerical analysis is performed with reference to a single-bay single-storey frame structure, allowing the main parameters affecting the problem to be identified. Finally, two multi-storey plane frames, designed in accordance with methods specified by Eurocodes, are analysed as a case study. r

2016

Fire fragility functions can be used to characteriz e the probabilistic vulnerability of buildings to fire in the context of urban resilienc assessment. A methodology has been proposed to develop such functions for multi-s tory steel buildings. However, a large number of parameters with uncertainties play a role in the process of constructing the fragility functions. The goal of t his research is to identify the critical parameters that most affect the global fire safety by investigating the sensitivity of the fragility functions to different input parameters. Sensitivity in parameters affecting the fire model, the heat transfer process and the therm o-mechanical response is examined. The effects of different design assumptions at the system level are also studied. The presented approach is useful for selecting the prev ailing parameters in a fire reliability analysis and it provides important information for modeling tools that can be used to evaluate resilience for fire scenarios.

Reliability Engineering & System Safety, 2017

2012

Abstract Due to the significant vertical elevation and complexity of the structural system, high rise buildings may suffer from the effects of fire more than other structures. For this reason, in addition to evacuation strategies and active fire protection, a careful consideration of structural response to fire is also very important. In this context, it is of interest to investigate the characteristics of the structural system that could possibly reduce local damages or mitigate the progression of failures in case of fire.

Post-Earthquake Fire (PEF) is an important factor causing damage to buildings and life-line structures. While PEF events are not uncommon, current design codes do not consider it explicitly in the structural design. It is important to note that when all efforts to contain the fire fail, the structure provides the last line of defense. Therefore, in a multi hazard scenario such as PEF, the individual and the probable combination of events must be considered in the context of performance-based design. This paper presents a review of PEF hazard and performance of steel-frame building structures under PEF conditions. Unprotected steel is particularly vulnerable to fire hazard. The mechanical strength of steel reduces drastically at high temperature. In a post-earthquake scenario, the building frame and its fire protection system may be significantly damaged and consequently resistance to subsequent fire is reduced. An analytical study of two-dimensional steel frames under the effects of seismic lateral loads and subsequent fire has been presented. The study reveals that the PEF performance of steel frames is affected by the lateral deformation caused by the seismic ground motion.