On May 13, 2008, the Faculty of Architecture Building, or ‘Bouwkunde’, at the Delft University of Technology, Netherlands suffered a fire that resulted in the collapse of the northwest wing of the 13 story building. No one was injured but the building was a complete loss. Collapse of concrete buildings in fire is rare; this report aims to provide a preliminary evaluation of the structure and point to key areas that may be of interest to future analyses and investigations. To this end, a large database of information was collected, including original and renovation construction documents, original structural calculations, and over 3000 photographs of the structure during and after the fire. This data has been organized and reviewed to provide a clearer understanding of the building and fire. Preliminary models of the fire are developed and applied to selected structural elements in the FOA to the temperature distributions within the members. Also provided is an overview of available methods for calculating the ultimate strength of reinforced concrete members at elevated temperatures and a computer application, UT Fire: Reinforced Concrete Analysis, which can be used to estimate member capacities through a given fire event, based on their internal temperature distributions. / text

Timber is an inherently sustainable material which is important for future construction in the UK. In recent years many developments have been made in relation to timber technology and construction products. As the industry continues to look to construct more efficient, cost effective and sustainable buildings a number of new engineered timber products have emerged which are principally manufactured off-site. In terms of light timber frame, products such as structural insulated panels (SIPs) and engineered floor joists have emerged. For heavy timber construction, systems such as glulam and cross laminated timber (CLT) are now increasingly common. Despite many of the obvious benefits of using wood as a construction material a number of concerns still exist relating to behaviour in fire. Current fire design procedures are still reliant upon fire resistance testing and 'deemed to satisfy' rules of thumb. Understanding of 'true' fire performance and thus rational design for fire resistance requires experience of real fires. Such experience, either gathered from real fire events or large fire tests, is increasingly used to provide the knowledge required to undertake 'performance based designs' which consider both fire behaviour and holistic structural response. At present performance based structural fire design is largely limited to steel structures and less frequently concrete buildings. Many of the designs undertaken are in accordance with relevant Eurocodes which give guidance on the structural fire design for different materials. For the same approaches to be adopted for timber buildings a number of barriers need to be overcome. Engineered timber products, such as SIPs and engineered joists, are innovative technologies. However, their uptake in the UK construction market is increasing year on year. Little is known about how such systems behave in real fires. As a result the development of design rules for fire is a difficult task as failure modes are not well understood. To overcome this barrier the author has undertaken a number of laboratory and natural fire tests on SIPs and engineered floor joists to establish how such products behave and fail in real fires. The data gathered can be used to develop design approaches for engineered timber products in fire, thus negating the need to rely upon fire resistance testing. The development of design rules from the data gathered would be a progressive step towards performance based design. Realising performance based fire design for timber structures at present has three obvious barriers. Firstly, thermo-physical properties for timber exposed to natural fires are not well defined. Current guidance in standards such as EN 1995-1-2 provides data for standard fire exposure only. Movement towards design for parametric fires requires a better understanding of timber thermo-physical behaviour under different rates of heating and durations of fire exposure. Secondly, particularly in the UK, the fire performance of timber buildings is heavily influenced by the behaviour of gypsum plasterboard which is commonly used as passive fire protection. The thermal behaviour of gypsum under both standard and natural fire conditions is still not well understood. The majority of research available relating to gypsum in fire is dated, whilst board products continually evolve. Finally, the whole building behaviour aspects utilised in the fire design of steel and other structures have arisen as a result of complex numerical simulations. At present most commercial finite element codes are not appropriate for modelling entire timber buildings exposed to fire due to complexities relating to the constitutive behaviour of timber. Timber degrades differently depending upon stress state (i.e. tension or compression), temperature and importantly temperature history. In recognition of the above barriers, the author has made a number of developments. Firstly, a modified conductivity model for softwood is proposed which is shown to give acceptable depth of char and temperature predictions in timber members exposed to the heating phase of parametric fires. This model is suitable for adoption in any computational heat transfer model. Secondly, the finite element software TNO DIANA has been modified, via user supplied subroutines, to simulate large timber buildings exposed to fire by considering stress state, temperature and state history. The developments made in this engineering doctorate are intended to facilitate the progression of performance based design for timber structures. The numerical approaches adopted herein have been supported using multi-scale experimental approaches. As a result a number of novel tools for implementation in FEA models are proposed which should ultimately lead to a more rational approach to the fire design of timber buildings.

Recently in the United States, there has been increasing interest in developing engineered approaches to structural fire safety of buildings as an alternative to conventional code-based prescriptive approaches. With an engineered approach, the response of a structure to fire is computed and appropriate design measures are taken to assure acceptable response. In the case of steel buildings, one of the key elements of this engineered approach is the ability to predict the elevated-temperature properties of structural steel. Although several past research studies have examined elevated-temperature properties of structural steel, there are still major gaps in the experimental database and in the available constitutive models, particularly for ASTM A992 structural steel, a commonly used grade. Accordingly, the overall objective of this dissertation is to significantly enlarge the experimental database of the elevated-temperature properties for ASTM A992 structural steel and developing improved constitutive models for application in structural-fire engineering analysis. Specific issues examined in this dissertation include the following: tensile properties at elevated temperatures; room-temperature mechanical properties after heating and cooling; and creep and relaxation properties at elevated temperatures. For the elevated-temperature studies of tension, creep and relaxation, constitutive models were developed to describe the measured experimental data. These models were compared to existing theoretical and empirical models from the literature. / text

The essence of performance-based structural fire safety design of steel building structures is the ability to predict thermal and structural response to fire. An important aspect of such predictions is the ability to evaluate strength of columns at elevated temperatures. Columns are critical structural elements, and failure of columns can lead to collapse of a structure. The ability of steel columns to carry their design loads is greatly affected by timeand temperature-dependent mechanical properties of steel at high temperatures due to fire. It is well known that structural steel loses strength and stiffness with temperature, especially at temperatures above 400 °C. Further, the reductions in strength and stiffness of steel are also dependent on the duration of exposure to elevated temperatures. The time-dependent response or creep of steel plays a particularly important role in predicting the collapse load of steel columns subjected to fire temperatures. Specifically, creep of steel leads to the creep buckling phenomenon, where the critical buckling load for a steel column depends not only on slenderness and temperature, but also on duration of exposure to fire temperatures. The main focus of the research summarized in this dissertation is on a testing program to investigate the effects of time-dependent material behavior or creep on buckling of steel columns subjected to fire. Material characterization tests were conducted at temperatures up to 1000 °C to evaluate tensile and creep properties of ASTM A992 steel at elevated temperatures. In addition, buckling tests on W4×13 wide flange columns under pin-end conditions were conducted to characterize short-time and vii creep buckling phenomena at elevated temperatures. The column test results are further used to verify analytical and computational tools developed to model the time-dependent buckling of steel columns at elevated temperatures. Test results are also compared against code-based predictions such as those from Eurocode 3 and the AISC Specification. Results of the research study presented in this dissertation clearly indicate that thermal creep of steel has a very large effect on strength of steel columns at high temperatures due to fire. The effect of creep on column capacity at high temperatures can be predicted using analytical and computational approaches presented in this dissertation. / text