Fire performance of affordable and high quality steel modular building systems

Perera, Kurugamage Dilini Nuwanthika (2022) Fire performance of affordable and high quality steel modular building systems. Doctoral thesis, Northumbria University.

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Abstract

Steel Modular Building Systems (MBSs) are an emerging technology in the construction industry where the applications of MBSs have widely spread across residential, commercial, health care and education streams. At the same time fire safety of built environments has become one of the fundamental design considerations in the industry when the fatal and catastrophic fire accidents in buildings have been reported. The recent developments in the building culture such as, compact and high-rise-built structures and lightweight building materials that are associated with reduced heat capacities and perhaps with combustibility characteristics have been identified as the driving forces for elevated fire risks in the buildings. Furthermore, thermal insulation material is widely applied in the wall/ floor designs with the intention of reducing energy costs hence to reduce the life-cycle costs of the buildings and improve sustainability features. However, the combustibility of such thermal insulation material has been given minimal consideration at many building designs, so that the insulation materials incorporated in some buildings are found to be highly combustible. Although heavier traditional constructions such as concrete and masonry are appreciable for their endurance in fire, other industry forces associated with lightweight and robust techniques of MBSs, make it inevitable for the industry to move for MBSs. Pre-fabrication and mass-scale production of MBSs have addressed several burning restraints in the construction industry such as cost, construction time, construction waste, skilled labor availability and elevated standards and quality controls. Despite of favorable qualities associated with MBSs over traditional methods in mentioned criteria, fire safety of MBSs cannot be undermined. Hence, in depth knowledge of steel MBS designs has been recognized as a research scope that needs to be immediately addressed.

While fire experiments on steel MBSs are extremely limited, several research studies implemented on Light-gauge Steel Frame (LSF) walls/ floors are available with full-scale fire experiment results. Since LSF methods had laid the foundation to steel MBSs, the two designs share many common attributes. Therefore, a thorough literature review on LSF and steel modular constructions was conducted to understand the scope and variables of the research project. Moreover, with the availability of reliable fire experimental results and computational facilities for the accurate Finite Element Modelling (FEM) of those fire tests, transient Heat Transfer Analyses (HTA) were extensively used to investigate fire performance of steel modular wall/ floor systems. The validity of the FEM methods was analyzed against the theoretical fundamentals and against the available experimental results. Simultaneously, studying through a series of experimental and numerical results of structural fire failures of channel section joist, channel section stud and Square Hollow Section (SHS) stud, asserting correlations between applied Load Ratio (LR) on the structural elements and critical steel temperatures could be established. These correlations can be referred to estimate the structural fire ratings of the wall/ floor systems.

The location of insulation material, wall/ floorboard thickness, insulation type, innovative concepts of Back Blocking (BB) panels and Discontinuous Insulation (DI) options and incorporation of cavity insulation at various ratios in the steel MBSs have been comprehensively investigated in this thesis. Among the key research findings, enhanced structural fire performance obtained with partial or full movement of insulation material towards the fire side, similar structural fire ratings achieved with conventional LSF and mapped steel modular walls, and the improvements in structural fire ratings of walls with BB and DI innovative concepts can be highlighted. Furthermore, partial cavity insulation in conventional LSF and steel MBS structures was identified as a cost effective, energy efficient, and lighter weight solution that also inherited appreciable structural and insulation fire ratings. The effect of each variable related to the study scope with respect to the structural/ insulation fire ratings and energy efficiency have been presented.

The research findings on methods of improving structural and insulation Fire Resistance Level (FRL) and the thermal transmittance for better energy performance will enhance the MBS applications confirming fire safety and energy efficiency. Moreover, further research investigations have been recommended for the optimization of MBSs maintaining fire and energy performances.

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