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Connections are critical structural elements of building frames, and in a fire are subject to forces very different from those at the ambient temperature for which they are designed. The fracture of a connection can cause the collapse of the connected beam, which may lead to a progressive collapse sequence affecting the entire building. This paper overviews the sequence of research on connection behaviour in a fire at the University of Sheffield. Early work focused on studying connections in terms of their moment-rotation behaviour alone. Concurrent full-scale building fire tests led to the realization that the tying capacity of connections is of prime importance for maintaining the structural stability in a fire. For wholestructure numerical modelling in performance-based fire engineering design, the development of the component-based approach, which was initially introduced for ambient temperature connection design, is an appropriate way to rationalize and model connection behaviour under these complex loadings. The effect of high co-existent rotation on the tying capacity of connections has been studied in furnace tests at various temperatures, which have provided data to assist in the characterization of the component-based model. A general component-based connection element, into which appropriate component models can be inserted, has been developed so that full connection performance, including fracture of components, can be integrated into global non-linear structural fire analysis. This will allow buildings to be modelled for a range of fire scenarios so that they can be designed to avoid progressive collapse in a fire. Fires in buildings may have enormous consequences on life safety and economy. Structural fire safety is therefore a key consideration in the design of buildings and is attracting worldwide attention. Significant advances in research have increased the knowledge on the structural behaviour in fire, and fire safety engineering has become a highly regarded discipline integrating all aspects of fire safety into the design of buildings.To exploit the innovations and advances gained recently, Structural Engineering International launched towards the end of 2011 a call for papers on the topic of Structural Fire Engineering and received a great response from around the world. In this issue, 10 Scientific Papers and one Technical Report are presented. The first papers deal with steel and composite structures with focus on the material and structural behaviour of connections in fire, which is important for the overall stability and safety of buildings. While some areas like the behaviour of steel structures in fire are becoming well understood, others like, for example, the fire behaviour of concrete structures need further studies-trends that are reflected by the contribution to this issue with two scientific papers, one of them presenting the state of art of concrete structures that incorporate FRP. Because of the combustibility of wood, most building codes have strictly limited the use of timber ...

<p>Polypropylene fibres (PPF) are used in concrete principally to reduce plastic shrinkage cracking, but also to prevent explosive spalling of concrete exposed to fire. In the EU alone, an estimated 75,000 tonnes of virgin PPF are used each year. At the same time an estimated 63,000 tonnes of polymer fibres are recovered from end-of-life tyres, which are agglomerated and too contaminated with rubber to find any alternative use; currently these are mainly disposed of by incineration. The authors have initiated a study on the feasibility of reusing tyre polymer fibres in fresh concrete to mitigate fire-induced spalling. If successful, this will permit replacement of the virgin PPF currently used with a reused product of equal or superior performance. A preliminary experimental investigation is presented in this paper. High-strength concrete cubes/slabs have been tested under thermo-mechanical loading. This study has shown promising results; the specimens with the tyre polymer fibres have shown lower vulnerability to spalling than those of plain concrete.</p>

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The paper investigates the use of notched strip tensile tests, originally proposed by R. Hill, to determine the yield characteristics of stainless steel. The original concept is thereby improved in two important ways. First of all, digital image correlation techniques are used to allow an accurate measurement of strain rates in a very localized area. Second, new theoretical developments are presented, which eliminate the need for measuring the applied load and which allow the yield surface of an anisotropic material to be determined starting from a parameterized equation. An experimental program is described where the method has been successfully applied to a ferritic grade as well as an austenitic grade stainless steel. As a disadvantage, a relatively large scatter in test results appears to be intrinsic to the method of notched strip tests.