Thermal Defensiveness in Terms of Temperature Evolution of Hollow Clay Brick Masonry Walls Subjected to a Fire Curve

Performance-based fire safety design is becoming more common as it demonstrates how fire science can be utilised to resolve fire protection problems, with respect to building structures subjected to explicit environmental trends and identified risks. It provides a flexible and reliable way to attain aesthetic, functional and cost objectives, while maintaining safety levels to an acceptable degree. This goal can be reached by adopting a progressive feedback loop (PFL) to regulate the basic parameters, that otherwise would been erroneously restricted by stringent implementation of prescriptive-based requirements. Performance-based design of fire enclosures, as it covers a wide spectrum of engineering concerns, includes numerous provisions that the structure is meant to meet, such as the clear layer height, the smoke layer temperature and the extinction coefficient. Although this approach substantiates a tailored-made fire safety roadmap, special consideration should also be given on the thermal responsiveness and robustness of walls on fire plumes; this performance is meant to encompass the majority of occupancies and building configurations in a straightforward manner. This chapter aims to analyse the thermal behaviour of a hollow-brick masonry wall under a tenable fire action referring to the standard time–temperature curve, EN1991-1-2. The temperature evolution of the non-exposed wall surface delineates the thermal defensiveness (TD) that is intimately linked to the inherent thermal resistance, in terms of the well-known insulation criteria. After a brief description of the basic principles and concepts of transient thermal analysis, under elevated temperatures, this chapter presents the key aspects and pitfalls of TD, such as those encountered during the design process of fire-wall configurations. Special attention is given on the peculiar influence of the varying thermophysical properties of the clay material and the fundamental effect of the thermal emissivity of hollow-brick cavity surfaces, as well as on the role of a flammable thermal insulation layer. A holistic discussion on the expected future trends that might be beyond those normally required by code (long-term implications and future renovations), points out the challenges in this critical and sensitive research field.