In recent years several high-profile building fires have highlighted shortcomings in the way we design for the complex interaction of structures and fire. These weaknesses appear to arise from a combination of gaps in knowledge of some of the more intricate aspects of compartment fire dynamics and from limitations in the engineering applications developed to date from hitherto established fundamentals. In particular the One Meridian Plaza Fire (1991), the Madrid Windsor Tower Fire (2005) and the Lakanal House Fire (2009) have emphasised the need for further study in the field of post-flashover compartment fires and the often consequent external fires that emerge from the compartment openings. External fire plumes impinge upon the structural façade, causing added structural stress, and often result in external fire spread and secondary ignition in upper level compartments. Hence a better understanding of the effect had by the internal compartment fire on the development of external flaming and the insult of the plume to its surroundings is beneficial for Structural Engineers, Fire Protection Engineers and Emergency Response Personnel alike. This research explores existing correlations, identifies their limitations and proposes a simplified methodology that links key parameters found to govern the internal post-flashover compartment fire to the heat flux potentially imposed on the exterior façade. Existing correlations addressing the effect of compartment fires on the insult to the external structure have largely been compiled by Law and are summarised in the form of a design manual for bare external structural steel [1]. Formulated in the 1970s, these correlations are based on the combined findings of several different experimental tests devised to investigate component phenomena of compartment fires and external flaming, forming an analytical model which is mostly empirical in nature. The methodology is convoluted and has several inherent assumptions which give rise to various limits of applicability however it is currently still used in structural-fire design, but best known as Annex B of both Eurocodes 1 and 3 [2,3]. As part of the present research, full-scale fire tests are conducted in situ, in a highly instrumented high-rise building, to provide high-resolution measurements of several internal compartment fire characteristics during a post-flashover fire in a modern, realistically-furnished compartment. External high resolution instrumentation in the main test also provides detailed measurements of the external flaming and distribution of heat flux incident on the façade. The tests provide realistic benchmark scenario data for comparing physical measurements against the analytical Law Model, the difference in which allows for an evaluation of the assumptions used in the model, which are often defined as ‘conservative’ in nature from the perspective of structural design. A detailed sensitivity study of the main input parameters in the Law Model allows for the identification of parameters of pivotal influence on the resultant heat flux incident on the plane of the external façade. Analysis of the Law Model and its underlying experimental basis also enables the identification of several limits of applicability of the model. Combined, these assessments show the analytical model can be stripped of unnecessary complexity and a Simplified Model is proposed with clear bounds of applicability. The proposed model describes the distribution of heat flux to the façade above a compartment opening and features only parameters of key importance, where low-dependency parameters are grouped into associated error bars. This results in a model that can be applied in the design of several building components that fall in the plane of the façade, such as structural elements, façade cladding and window arrangements. Its ease of implementation renders the model more widely accessible to different factions of the Fire Engineering Community. Furthermore, analysis of the Law Model identifies further parameters of potential importance that have, as of yet, not been addressed. A preliminary investigation conducted using Computational Fluid Dynamics (CFD) tools shows that variation in some parameters – that are not individually accounted for in the Law Model – may influence the compartment fire conditions, the consequent external flaming and the resultant external heat exposure. Therefore, it is recommended that further comprehensive experimental research be conducted into the potential influence of the identified parameters.

External flaming from buildings occurs as a result of a large amount of fuel being available in the room of fire origin in comparison to the amount of ventilation provided. The size of the openings in a compartment affects the amount of oxygen available within the fire room, and hence the amount of combustion that can take place inside. Excess fuel that is not burnt within the room flows out of the opening and combusts upon reaching the oxygen in the air outside. It is in this situation that flames are seen projecting out of the window. Flames projecting from openings pose the threat of fire spread from the room of fire origin. This threat increases with the size of the flames. Thus a dependable method for predicting the size of flames projecting from openings is required. This research addresses the issue of predicting flame heights projecting from openings, based on the heat release rate of a fire. The results are based on laboratory experiments and are presented in non-dimensional form, allowing application to scenarios that have not been specifically tested. This work supports the findings of other researchers, with appropriate adjustments made to compensate for differing experimental approaches. This indicates that the relationships established between the non-dimensional heat release rate and flame height are formed from a sound underlying principle. An empirical relationship between the non-dimensional flame height and heat release rate of a fire is presented in a simplified format to enable ease of use. The temperatures attained, and other observations from the compartment fire experiments are also presented and discussed. These were found to have dependence on a number of factors, with relationships varying between the individual experiments. The widely-used computational fluid dynamics model Fire Dynamics Simulator, Version 4 (FDS), was found to currently be unreliable in modelling the experimental scenarios. The results obtained were unrealistic and bore minimal resemblance to the experimental results, with extensive computational simulation time. The ability of the programme to model the compartment fire scenario requires further investigation to determine whether a finer grid resolution may improve results, or whether it is simply not able to model combustion processes involved at this stage.