Analysis of perforated beams in fire using a virtual hybrid simulation approach

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThis thesis is concerned with the behaviour of composite perforated beams in fire conditions, and a new virtual hybrid simulation approach is proposed to facilitate the investigation. Composite perforated beams are an increasingly popular choice in the construction of long-span floor systems as they provide a structurally and materially efficient design solution and allow space for building services. Most of the relevant research conducted to date has been focussed on isolated beam elements, assuming simply-supported boundary conditions. These simplifying assumptions are largely due to the complexity of modelling the whole structure in high definition, as well as the significant associated computational expense. However, testing and analysing isolated components inherently ignores any load redistributions which take place in the structure and does not provide an insight into the thermomechanical interactions which develop during a fire. In this context, the two primary objectives of this work are to (i) develop a usable virtual hybrid simulation framework which assesses the response of individual structural elements subjected to fire, taking account of the surrounding structure and (ii) utilise this framework to investigate the behaviour of perforated beams exposed to fire including the effects from the surrounding structure in the form of axial and rotational restraint. In the virtual hybrid simulation method, the part of the structure which is exposed to fire is modelled in fine detail using shell and solid elements and the remaining surrounding structure is represented using simpler beam-column elements. The simulation is developed using a combination of the OpenSees, OpenFresco and Abaqus softwares and enables the user to investigate the behaviour of fire-exposed components while including the effect of the remaining structure without modelling the whole system in fine detail. The accuracy of the model is validated using available fire test data. The behaviour of composite perforated beams in fire is analysed using the developed framework and then compared with the predicted response obtained by modelling isolated simply-supported beams. The results highlight the importance of including the effects from the surrounding structure in the analysis. The virtual hybrid simulation framework is then utilised to investigate the influence of the most salient parameters including the type of fire, opening layout, restraint conditions as well as the material and geometric details. In the final part of the thesis, the current ambient temperature design standards for perforated beams are modified to account for the effects of fire. A series of analytical expressions are developed to estimate the fire resistance of composite perforated beams with different opening layouts, and these predictions are compared with the fire resistance obtained from the numerical simulations. It is shown that the proposed analytical approach provides a good estimation of the fire resistance for the majority of cases

An open-source software framework for the integrated simulation of structures in fire

The traditional methods to understand the development of elevated temperature in a structure, and also the associated structural response, are not representative of realistic fire scenarios. To provide a more accurate and realistic reflection of the fire development, the current paper develops a generic middleware which interfaces between the computational fluid dynamics (CFD) software Fire Dynamics Simulator (FDS) and the finite element (FE) analysis software OpenSees. This framework enables a fully integrated simulation of a realistic fire scenario including the heat transfer through the structure and the resulting thermo-mechanical response. The proposed framework is open-source and freely available and therefore can be used and further developed by researchers and practicing engineers and customised to their requirements. This paper shows validation against two sets of experimental results and one real fire incident. A number of different types of thermal boundary conditions such as gas temperatures and heat fluxes, are obtained from the CFD analysis and are then used in the subsequent heat transfer and thermo-mechanical analysis. The primary advantage of this computational tool is that it provides consultants and designers with the means to undertake large-scale projects requiring performance-based fire engineering solutions

Long-term sustainability and resilience enhancement of building portfolios

The role of community building portfolios in socioeconomic development and the growth of the built environment cannot be overstated. Damage to these structures can have far-reaching consequences on socioeconomic and environmental aspects, requiring a long-term perspective for recovery. As communities aim to enhance their resilience and sustainability, there is a cost burden that needs to be considered. To address this issue, this paper proposes a community-level performance enhancement approach that focuses on optimizing the long-term resilience and sustainability of community building portfolios, taking into account recurrent seismic hazards. A Gaussian process surrogate-based multi-objective optimization framework is utilized to optimize the cost objective while considering performance indicators for resilience and sustainability. The proposed framework involves using performance-based assessment methods to evaluate the socioeconomic and environmental consequences under stochastic and recurrent seismic hazard scenarios. These evaluated indicators are then used to efficiently optimize the community resilience and sustainability, taking into account the retrofit costs. Finally, approximate Pareto-optimal solutions are extracted and utilized for decision-making. In summary, this paper presents a novel approach for optimizing the long-term resilience and sustainability of community building portfolios by considering recurrent seismic hazards. The proposed framework incorporates performance-based assessment methods and multi-objective optimization techniques to achieve an optimal balance between cost, resilience, and sustainability, with the ultimate goal of enhancing community well-being and decision-making in the face of seismic hazards

Fire modelling framework for investigating tall building fire: A case study of the Plasco Building

Fire can damage structures severely and even cause the building collapse. Structural and fire engineers must carry out a comprehensive forensic investigation of major structural failures in the same rigorous and meticulous manner the airline industry investigates air crashes. The forensic assessment should identify the cause, fire spread scenario, fire behaviour patterns from its growth to decay, de-compartmentation, the performance of fire protection systems, and firefighting management. Using the available tools and data, the current paper proposes a methodology to reconstruct the fire for the forensic assessment of tall buildings. This is done by first organising observed data into a coherent timeline and presenting the actual fire spread obtained from the visual evidence. The total fire spread within the building is estimated based on fire dynamics principles and observed fire scenes that can be verified with a calibrated CFD model. The collapse of the Plasco Building is assessed by employing the proposed framework. The rise in construction of the tall buildings increases the risk of the occupants’ safety from the fire induced structural failure or collapse. The framework presented in this paper can guide engineers to improve the building resilience designs and reduce the fire accidents related risks