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Über dieses Buch

This Handbook is focused on structural resilience in the event of fire. It serves as a single point of reference for practicing structural and fire protection engineers on the topic of structural fire safety. It is also stands as a key point of reference for university students engaged with structural fire engineering.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Foreword and Introduction

Abstract
This chapter introduces structural fire engineering along with the specific contents of this handbook. The handbook has called upon the input of global experts to deliver a resource that brings together a significant volume of material on the topic of structural performance in the event of fire. The book is primarily written for practicing consulting engineers. However, it is foreseen that it can be a useful resource for students of structural engineering who wish to develop a deeper understanding of structural performance in the event of fire, as well as building authorities to assist with review of such alternative designs. Many would argue that whilst evidence exists which suggests that prescriptive methods for structural fire protection usually lead to adequate performance levels, few if any could quantify the level of safety that is provided within this framework. More likely, the actual level of structural fire safety is variable from building to building, subject to coincidental structural design decisions for other hazards (and then retrospectively protected/insulated). In contrast, structural fire engineering proactively designs the structure and applied fire protection to achieve targeted performance levels under fire conditions.
Danny Hopkin, Kevin LaMalva

Chapter 2. The Fire-Resistive Principle

Abstract
Evaluation of structural fire protection may be considered within two distinct domains: the time domain and the strength domain. Time is conventionally used for standard fire resistance requirements in building codes, in which a particular fire resistance assembly is shown to provide adequate resistance to a standard fire exposure under test conditions for a period of time. Strength compares applied gravity loads and fire effects (e.g., thermally induced forces) to the capacity (e.g., temperature-dependent strength) of the structural system.
In the context of structural engineering, the fundamental philosophy used to design structures can be simply expressed as capacity > demand. The demand refers to loads that are imposed on a structure including its self-weight. The capacity refers to the global and local ability of a structure to carry an imposed demand. The conventional design of a structural system evaluates demand and capacity with respect to specific performance objectives including strength, stability, and stiffness.
Evaluation of structural fire protection within the time domain primarily considers the demand on the structure due to heating, which can be reduced with the application of protective insulation. However, this type of evaluation does not necessarily credit nor discount the capacity of the structure itself to endure fire exposure nor does it properly evaluate all aspects of the demand (e.g., thermally induced forces; see Sect. 2.1.4). Also, the consideration of demand due to heating is not with respect to specific performance objectives, but rather superficial failure criteria enforced during standard fire testing.
Evaluation of structural fire protection within the strength domain accounts for all contributions of the demand on a structural system, as well as its capacity to endure these demands with respect to required performance objectives.
There is no practical method for a designer to quantitatively compare the level of safety provided by an analysis conducted within the time domain compared to one conducted with the strength domain. Hence, the designer should adopt one or the other exclusively for a given analysis.
Kevin LaMalva, John Gales, Anthony Abu, Luke Bisby

Chapter 3. Keys to Successful Design

Abstract
The primary keys to a successful structural fire engineering design include the following: effective conveyance of the method's benefits, setting realistic expectations, and proper execution of the design. As structural fire engineering design is relatively new to many jurisdictions (e.g., North America) the impact of these aspects can become amplified. Hence, the designer should be well prepared when embarking as such, and this section provides applicable guidance.
Martin Feeney, Kevin LaMalva, Spencer Quiel

Chapter 4. Design Fires and Actions

Abstract
This chapter addresses design fires in the context of structural fire safety. First, the design fuel load must be derived for the given space, which represents the potential energy that needs to be considered. Once the design fuel load is established, estimation of the fire exposure intensity on the structure is a key next step in the process. Specifically, thermal boundary conditions acting on structural and/or insulative exposed boundaries must be derived so that subsequent heat transfer analyses may be conducted to determine the temperature histories of the given structural system. Structural fire engineering designs typically only consider a subset of design fires, which are those that are uncontrolled (any cooling effects of active fire protection systems and/or manual intervention are neglected). Other design fires (e.g. those used for determining the available safe escape time) would not commonly be used for SFE applications. Accordingly, fire dynamics concepts pertaining to uncontrolled fire exposures are presented in this chapter.
Danny Hopkin, Ruben Van Coile, Charlie Hopkin, Kevin LaMalva, Michael Spearpoint, Colleen Wade

Chapter 5. Heat Transfer to Structural Elements

Abstract
In conventional prescriptive design, the fire performance of load-bearing structural elements is regularly defined in the temperature domain. When a more comprehensive structural behavior analysis is performed in the strength domain, the analysis of the temperature domain remains as a first step of the process. As described in Chap. 4 of the current handbook, fire is a combination of complex physical phenomena. The thermal boundary conditions, and to some extent heat transfer within structural elements (i.e., solid phase), require some level of understanding and perhaps careful simplification. Understanding the complex coupling between gas and solid phase is commonly avoided and the fire is treated as a thermal boundary condition.
Kevin LaMalva, Cristian Maluk, Ann Jeffers, Allan Jowsey

Chapter 6. Concrete Structures

Abstract
This chapter examines structural fire engineering considerations that are specific to concrete, which is a common construction material. First, thermal and mechanical properties of concrete at elevated temperatures are discussed. Second, failure modes specific to concrete structures (e.g., explosive spalling) are examined. Lastly, pertinent analysis techniques for structural fire engineering applications involving concrete structures are presented. Overall, analyzing the effects of fire on concrete material and concrete structures is a complex task. Concrete is, by itself, a complex composite material, composed of aggregates and a cementitious matrix that hardens over time. There exists a large variety of concrete compositions, which differ by the types of aggregates and cementitious matrix, as well as the presence of fibers and other adjuvants. These different compositions result in a variety of concretes that are generally grouped under categories based on weight, strength, presence of fibers, and performance level. This chapter examines each of these different aspects with respect to structural fire engineering designs.
Thomas Gernay, Venkatesh Kodur, Mohannad Z. Naser, Reza Imani, Luke Bisby

Chapter 7. Steel and Composite Structures

Abstract
This chapter examines structural fire engineering considerations that are specific to steel, which is a common construction material. First, thermal and mechanical properties of steel at elevated temperatures are discussed. Second, failure modes specific to steel structures (e.g. connection brittleness) are examined. Lastly, pertinent analysis techniques for structural fire engineering applications involving steel structures are presented. Notably, tensile membrane action theory is covered in depth, which is a mechanism that provides thin slabs with large load-bearing capacity, resulting from large vertical displacements, where induced radial tension in the centre of the slab (due to the large deflection) is resisted by a peripheral compression ring. Also, the performance of structural steel connections under fire conditions is closely examined. In the event of a fire, the global frame response is closely linked to the behaviour of such connections. When excessive axial and rotational deformations occur at high temperature, the connections need to be robust enough to provide structural integrity.
Anthony Abu, Ruoxi Shi, Mostafa Jafarian, Kevin LaMalva, Danny Hopkin

Chapter 8. Timber Structures

Abstract
This chapter examines structural fire engineering considerations that are specific to timber, which is a relatively emerging construction material for large engineered buildings. First, thermal and mechanical properties of timber at elevated temperatures are discussed. Second, failure modes specific to timber structures (e.g., adhesive debonding) are examined. Lastly, pertinent analysis techniques for structural fire engineering applications involving timber structures are presented. The renaissance of timber as a construction material, allied to its application in less common building forms, has led researchers to map many challenges that should be considered and addressed when seeking to demonstrate that an adequate level of structural fire safety has been achieved when adopting timber. In parallel, new research studies have emerged which fundamentally seek to understand the timber pyrolysis process and its translation to the enclosure fire context. These challenges and the recent prevalence of timber-associated fire research shape the content of this chapter.
Daniel Brandon, Danny Hopkin, Richard Emberley, Colleen Wade

Chapter 9. Uncertainty in Structural Fire Design

Abstract
Structural fire safety requirements implicitly balance up-front investments in materials (protection or element sizing) with improved performance (loss reductions) in the unlikely event of a fire. For traditional prescriptive fire safety recommendations, the underlying target safety levels are not clear to the designer, nor is the associated balancing of risk and investment costs. While easy to apply, guidance / code-based approaches to the specification of fire protection / resistance have the severe disadvantage that the level of safety investment is not tailored to the specifics of the case, resulting in large overinvestments in some cases, and possibly insufficient structural fire safety in others. This observation is a major driver for the use of performance-based design (PBD) methodologies, where the fire safety design is tailored to the needs of the building. However, it is posited in this chapter that traditional PBD in a structural fire context is deterministic, with the safety foundation premised upon the collective experience of the profession. It is separately noted that building forms are increasingly uncommon in nature, due to material choice, height, failure consequences, etc., and, as such, collective experience is increasingly a weak safety foundation. This is where probabilistic methods add value and provide a quantified / explicit basis for demonstrating the adequacy of a design. This chapter, thus, focusses on uncertainties and uncertainty quantification in the context of structural performance in the event of fire, introducing reliability and risk concepts, with supporting data and applications.
Ruben Van Coile, Negar Elhami Khorasani, David Lange, Danny Hopkin

Chapter 10. Advanced Analysis

Abstract
This chapter discusses the advanced analysis of structures in fire. It is aimed at practitioners and researchers in the field of structural fire engineering who aim at explicitly predicting the response of a structure in the fire situation, as opposed to following a prescriptive design method. The first section presents the basics of advanced analysis, including the purpose and scope of advanced analysis, the discretization of the structure for numerical modeling, the role of nonlinearity, and the main computational strategies to solve the problem. The second section discusses the modeling process, including the definition of the conceptual model, analysis procedure, representation of structural members and materials, representation of connections, mechanical boundary conditions, and imperfections. Section 10.3 discusses the capabilities and limitations of advanced analysis methods for structures in fire, with emphasis on the material and structural behavior, failure modes, and representation of fire as thermal boundary conditions. Section 10.4 discusses the assessment of failure. Section 10.5 presents the verification, validation, and review process. Finally, Sect. 10.6 briefly describes the different types of software used for advanced analysis of structures in fire.
Thomas Gernay, Panos Kotsovinos

Chapter 11. Reinstatement of Fire-Damaged Structures

Abstract
Although the title of this chapter is Reinstatement of Fire-Damaged Structures it really covers the three main stages involved in making detailed recommendations of how to deal with structural damage arising from a fire. These stages are initial inspection, assessment and finally reinstatement where it is feasible and desirable. The target audience is those structural engineers or other building professionals involved in the assessment of damage and in making recommendations relating to repair and reinstatement and in determining the nature and extent of any repairs required.
All structural materials suffer damage as a result of exposure to severe fires. In assessing the nature and extent of fire damage to a structure there are certain basic principles that apply although the precise nature of the methodology employed will be dependent on a number of parameters not least of which is the nature of the structural framing material itself. Aside from the direct costs of demolishing, repairing, reinstating or rebuilding following damage by a fire there are often consequential losses through disruption of business that may outweigh the initial capital costs associated with dealing with the initial incident. For this reason there is often a need for the initial assessment and subsequent report to be completed within as short a timescale as possible to maintain business continuity and minimize the economic loss. Although guidance is available (and referenced to in this chapter) to the professionals involved in the assessment of fire-damaged structures, it is often material specific. This chapter considers both the general principles of structural fire investigation and brings together guidance covering the most commonly used structural materials (steel, concrete, timber and masonry). The chapter deals only with damage to the load-bearing structure of the building and does not directly consider other issues such as damage to services, the impact of smoke damage to the building or the difficulties of eradicating unpleasant odours following a serious fire incident.
The assessment and inspection of fire-damaged structures is a specialist discipline. The information presented in this chapter is intended to provide background information, general guidance and references for structural engineers. In many cases the best approach is to seek specialist advice. Nonetheless, many of the basic concepts of structural fire engineering covered in this book lend themselves to this specialist discipline (e.g. understanding of fire effects due to restrained thermal expansion/contraction).
Tom Lennon, Octavian Lalu

Backmatter

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