Barbara Lane

Behavior of Structures in Fire and Real Design - A Case Study

A great deal of work on the behavior of composite steel-concrete structures in fire has been developed since the Cardington frame fire tests (UK) conducted in the 1990s. This has now been broadened so that the design of structures to resist fire has a real engineering basis and is not reliant on results from single element testing in the standard furnace. Several projects involving office buildings in the UK and abroad have highlighted the need for developing the understanding of whole frame behavior in fire. Since the collapse of the World Trade Center in New York City in 2001 (9/11), robust engineering solutions incorporating the response of a building to fire are in great demand. The basics of structural mechanics at high temperatures can be used in such designs to understand the fire response of many structures with the aid of computer modeling. This article provides a direct comparison between the structural response of an eleven-story office building in the city of London, when designed in a prescriptive manner with applied fire protection on all load bearing steelwork, and the response of the same structure designed using a performance-based approach leaving the majority of secondary steelwork unprotected. The intent is to demonstrate that structural stability during a fire can be maintained in specific cases without relying on passive fire protection. This study contributes to the field of structural fire engineering by extending the research work previously conducted by the author to a real design case and addresses the issues raised by approving authorities, insurers, and the client when a fire engineered approach is used to calculate structural response to fire. It also demonstrates the use of advanced analysis to understand beam-core connection

Fire Resistance Design of Unprotected Concrete Filled Steel Hollow Sections: Meta-Analysis of Available Furnace Test Data

Concrete filled steel hollow structural sections are an efficient, sustainable, and attractive option for both ambient temperature and fire resistance design of columns in multi-storey buildings and are increasingly common in modern construction practice around the world. Whilst the design of these sections at ambient temperatures is reasonably well understood, and models to predict the strength and failure modes of these elements correlate well with observations from tests, this appears not to be true in the case of fire resistant design. This paper assesses the statistical confidence in available fire resistance design models/approaches that are used in North America and Europe by performing a meta-analysis which compares the available experimental data from large-scale standard fire tests performed around the world against fire resistance predictions from design codes. It is shown that available design approaches carry a large uncertainty of prediction, suggesting that they fail to properly account for fundamental aspects of the underlying mechanics during fire. Current North American design approaches for CFS columns are shown to be considerably less conservative, on average, than those used in Europe.

Modelling of the collapse of large multi-storey steel frame structures in fire

Publisher Summary The chapter presents results from a number of non-linear finite element analyses of simple two-dimensional (2D) models of multi-storey structural frames subjected to fire. One of the analyses was carried out for a large range of fire scenarios. The chapter advances that work to include a number of different structural configurations and presents a few more collapse mechanisms. The results of this work are based on very simple 2D analyses, and further computational and experimental research should be carried out to confirm these initial findings, which nonetheless show a clear failure mechanism in multiple floor fires. The chapter presents a selection of results obtained from the simpler 2D models and describes the most interesting failure mechanism. The understanding developed in this manner is of enormous benefit to designers and consulting engineers to understand the true effect of fire in their structures and to ensure that the mechanisms discovered are prevented from occurring with appropriate design and detailing.