PRELIMINARY PROPOSAL FOR PERFORMANCE-BASED STRUCTURAL ENGINEERING FOR FIRE FOLLOWING EARTHQUAKE (original) (raw)

An application of the PEER performance based earthquake engineering framework to structures in fire

Engineering Structures, 2014

The Pacific Earthquake Engineering Research (PEER) Center's Performance Based Earthquake Engineering (PBEE) framework is well documented. The framework is a linear methodology which is based upon obtaining in turn output from each of the following analyses: hazard analysis; structural analysis; loss analysis, and finally decision making based on variables of interest, such as downtime or cost to repair. The strength of the framework is in its linearity, its clear flexibility and in the consideration of uncertainty at every stage of the analysis. The framework has potential applications to other forms of extreme loading; however in order for this to be achieved the 'mapping' of the framework to the analysis of structures for other loading situations must be successful. This paper illustrates one such 'mapping' of the framework for Performance Based Fire Engineering (PBFE) of structures. Using a combination of simple analytical techniques and codified methods as well as random sampling techniques to develop a range of response records, the PEER framework is followed to illustrate its application to structural fire engineering. The end result is a successful application of the earthquake framework to fire which highlights both the assumptions which are inherent in the performance based design framework as well as subjects of future research which will allow more confidence in the design of structures for fire using performance based techniques. This article describes the PEER framework applied to structural earthquake design then follows the framework from start to completion applying suitable alternative tools to perform each stage of the analysis for structures in fire.

Severity Measures and Stripe Analysis for Probabilistic Structural Fire Engineering

Fire Technology, 2018

This paper presents modifications to the adoption of a Performance-Based Earthquake Engineering (PBEE) framework in Probabilistic Structural Fire Engineering. Potential Fire Severity Measures, which capture significant characteristics of fire scenarios, are investigated. A suitable Fire Severity Measure (FSM), which best relates fire hazard intensity with structural response, is identified by satisfying efficiency and sufficiency criteria as described by the PBEE framework. The study also implements a new analysis method called Fire Stripe Analysis (FSA) to obtain the relationship between FSM and the structural response. In order to obtain the annual rate of exceedance of damage and repair cost/time for an office building, an occurrence model and an attenuation model for office structure fires are generated for both Christchurch city and New Zealand. The process is demonstrated with the help of a case study performed for a steel-concrete composite beam. Structural response is recorded for the beam exposed to several fire profiles which are generated by varying fuel loads from 200 MJ/m 2 to 1000 MJ/m 2 and ventilation factors from 0.02 m 1/2 to 0.08 m 1/2. FSA and dispersion curves of structural response are plotted for every fire severity measure. Cumulative incident radiation is found to be the most efficient and sufficient FSM. The mean annual rate of exceedance of given levels of fire severity and structural response are evaluated for both New Zealand and Christchurch city. It is found that Christchurch city has a 15% less probability of exceedance of the given fire severity level in comparison to the whole of New Zealand. The extension of this work would facilitate designers/insurers to evaluate the probability of damage or failure of a structure due to a probable fire hazard.

Performance based investigations of structural systems under fire

Prescriptive measures and procedures developed over the past here are mostly aimed at preventing structural failures of single elements for the time required for the evacuation (Giuliani&Budny, 2010). The response to fire and fire effects of the structural system as a whole remains often unknown and the survival of the construction after this time cannot always be granted. This is even more true in case of unaccounted events like human errors or rare but severe occurrence like a fire after explosion, which cannot be contemplated in the usual design. Even if a structure could be hardly designed to resist fully integer all these kinds of events, the mitigation of possible collapse induced by fire should be achieved. In this respect, a performance-based investigation of the structure aimed at highlight fire effects and fire-induced collapse mechanisms becomes of interest. In the paper collapse mechanisms of some simple structures are presented and discussed, with particular attention to methodological aspects. The effects of different assumptions in the modeling and in the definition of the collapse are highlighted, as critical aspects of a performance-based investigation.

Risk-based structural fire design

2014

To date, structural fire design has been largely based on extreme fire scenarios. Now, the University of Canterbury is investigating the use of probabilistic assessment to improve building performance during fires.

RELIABILITY RISK ASSESSMENT IN HIGH RISE BUILDINGS IN CASE OF FIRE

The practice of structural fire safety engineering remains to be case-specific and the estimation of fire resistance of structures is mostly deterministic. Many researchers in structural fire engineering utilize the performance- based design method but these studies do not include the inherent uncertainties in both the demand and capacity. This paper investigates the structural fire reliability of tall buildings based on the framework used for earthquake hazard by the Pacific Earthquake Engineering Research (PEER) and Eurocode. The financial district of Istanbul in Turkey is taken as a case study for this research. Parameters such as building type and height, structural system, number of floors, floor area, number of elevators and stairs, the use of fire suppression systems, evacuation routes are provided by the municipalities in order to develop a probabilistic methodology to estimate the fire safety of these structures. The analysis is conducted by estimating the intensity or the hazard curve as described by PEER framework. The hazard domain includes random variables such as the fire load, the opening factor, the fire duration and the maximum fire temperature. The findings of this research will provide essential information on the fire safety risk of each tall building in a densely populated financial district. It will allow the municipalities and fire brigades to have a probabilistic risk assessment of these structures and develop evacuation and human rescue plans accordingly in case of a fire hazard. Further, this research will provide useful data to insurance companies to estimate fire hazard insurance premiums.

Fire Following Earthquake Modelling, Probabilistic Ignition Model For Building Stock

Fire following earthquake (FFE), as an indirect seismic hazard involves three main phases: ignition, spread and suppression. Records of historical FFE's shows higher significance for ignitions taken place inside buildings. This paper therefore, focuses on ignition following earthquake (IFE) and introduces a probabilistic algorithm for intra-structure ignition modelling. The occurrence of intra-structure ignitions depends on several parameters such as structural damages, non-structural damages, ground and structural PGA, overturning critical acceleration for building components and equipments, buildings occupancy, building height, building area and earthquake time. A GIS-based computer program has been designed and developed in this work which models probability of ignitions for each building using synthetic earthquake scenarios. Logic tree and Monte Carlo simulation processes are used for combining uncertainties associated with different components controlling intra-structure ignition such as earthquake parameters and building behaviour. The proposed model is based on an analytical methodology which takes into account many effective parameters controlling IFE. The main objective of this study is to develop a methodology to probabilistically convolute different uncertainties associated with factors controlling intra-structure IFE. The approach is introduced as an alternative solution to the statistical ignition model currently being used in many FFE hazard models. However, detailed studies towards quantification and calibration of probability functions used in this study are beyond the scope of this paper and require further statistical data and investigations. The proposed model and the developed computer tool are used to model IFE for a city district in northern Tehran. Ignition probabilities obtained from this model are compared against those estimated by the HAZUS ignition model.

Practical case studies in performance-based structural fire engineering design

The specialist field of structural fire engineering is developing rapidly, along with the more general discipline of fire safety engineering. The results of international research and large-scale tests such as those conducted at Cardington in England during the 1990s are now starting to be used in practical fire-resistance design. Performance-based structural fire engineering guidance documents and standards have now been published in the United Kingdom and these are being used to realise more cost effective buildings. Furthermore, sophisticated finite element analysis software programs are being adopted by consulting engineers to predict the actual performance of structural frames in fire scenarios, and thus to enable robust yet cost-effective design solutions which optimise the extent and placement of fire protection. Such techniques are suitable for use as part of an integrated structural design process, treating the fire case as one of a series of limit states which contribute to both the conceptual and detailed design phases, rather than simply as a means of retrospectively calculating thicknesses of fire protection materials. This paper uses the recently completed Leeds Nuffield Hospital in England, as an example of how such structural fire engineering techniques can be used by designers to optimise the inherent fire resistance of structures and the fire protection strategies which have been used to produce safe but economic solutions. It describes the use of Vulcan, a finite element program developed at the University of Sheffield, together with other levels of design calculation, and also outlines the rigorous sensitivity studies and checking procedures that were imposed to ensure flexible, robust solutions.

Probabilistic Performance Analysis of Existing Buildings under Earthquake Loading

Journal of Earthquake Engineering, 2014

A probabilistic methodology is proposed for the seismic performance analysis of existing buildings using global metrics to determine if the behavior conforms to a given limit state. The referred performance metrics are the mean annual frequency of the limit state, the corresponding expected loss associated to the repair of the building, and the corresponding number and type of mechanisms that occur. The consideration of these assessment parameters to control building performance widens the scope of the limit state definitions proposed in current codes. Therefore, current limit state descriptions were updated to establish adequate risk-and cost-related limit state definitions using the Eurocode 8 Part 3 proposals as a basis for discussion. The description of the proposed procedure is detailed and addresses its applicability for different limit states and its ability to include the uncertainty in the limit state capacities. An application involving the performance analysis of a reinforced concrete structure for several limit states is also presented and discussed.