Numerical and Experimental Investigations on Static Behaviour of Composite Cold-Formed Steel and Timber Flooring System

Karki, Dheeraj

Numerical and Experimental Investigations on Static Behaviour of Composite Cold-Formed Steel and Timber Flooring System

Karki, Dheeraj

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Publication Type:: Thesis
Issue Date:: 2023

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Field	Value	Language
dc.contributor.author	Karki, Dheeraj
dc.date.accessioned	2023-11-26T23:11:35Z
dc.date.available	2023-11-26T23:11:35Z
dc.date.issued	2023
dc.identifier.uri	http://hdl.handle.net/10453/173571
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	Currently, the use of Cold-Formed Steel (CFS) joists with timber-based floorboards for constructing lightweight flooring systems in residential buildings is widespread. However, the potential benefits of composite action that arise due to the interaction of the top flange of cold-formed steel joist and the bottom surface of timber floorboard due to shear connection are not considered in the design of such a flooring system. As a result, it led to conservative designs of cold-formed steel joists. This thesis presents a comprehensive experimental and numerical investigation into the flexural behaviour of composite cold-formed steel and timber flooring systems considering the beneficial effect of composite action. As a part of an experimental program, thirteen full-scale composite beam tests were carried out. CFS C-sections with dimensions of 254mm depth and 2.4mm thickness were sheathed with structural plywood panels using four different types of mechanical fasteners as shear connections. For all the tested composite specimens, improvements in the ultimate loading capacity and stiffness were found as a result of the mobilisation of composite action. A three-dimensional (3D) finite element model was developed in ANSYS software and validated against the experimental results. The validated numerical model was used for parametric studies to investigate the influence of various factors that affect the structural behaviour of the composite CFS flooring system. Simplified analytical models are proposed to predict the elastic bending capacity and flexural stiffness of the composite CFS and timber beams. The proposed design methodology discussed herein enables to design for enhanced structural performance to be achieved in CFS flooring systems by utilising the potential benefits of composite action to establish the practical design rules to be used by practising engineers. Connecting timber floorboard sheathing to CFS joists using mechanical fasteners (e.g. screws and bolts) is a novel method for developing a hybrid and prefabricated eco-friendly floors. This study, through experimental and numerical investigations, has demonstrated the feasibility of composite action to be considered in designing the load-carrying capacity of such lightweight floors. The conducted research shows the substantial gains in structural performance and the influence of key parameters for the composite construction. The findings from the presented study highlights the enhanced structural performance of CFS-plywood composite beams floor system and is an excellent potential option to be utilised in sustainable modular building construction.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/173571/1/thesis.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2023 Dheeraj Karki
dc.rights	au.edu.uts.lib/cph
dc.title	Numerical and Experimental Investigations on Static Behaviour of Composite Cold-Formed Steel and Timber Flooring System	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Currently, the use of Cold-Formed Steel (CFS) joists with timber-based floorboards for constructing lightweight flooring systems in residential buildings is widespread. However, the potential benefits of composite action that arise due to the interaction of the top flange of cold-formed steel joist and the bottom surface of timber floorboard due to shear connection are not considered in the design of such a flooring system. As a result, it led to conservative designs of cold-formed steel joists. This thesis presents a comprehensive experimental and numerical investigation into the flexural behaviour of composite cold-formed steel and timber flooring systems considering the beneficial effect of composite action. As a part of an experimental program, thirteen full-scale composite beam tests were carried out. CFS C-sections with dimensions of 254mm depth and 2.4mm thickness were sheathed with structural plywood panels using four different types of mechanical fasteners as shear connections. For all the tested composite specimens, improvements in the ultimate loading capacity and stiffness were found as a result of the mobilisation of composite action. A three-dimensional (3D) finite element model was developed in ANSYS software and validated against the experimental results. The validated numerical model was used for parametric studies to investigate the influence of various factors that affect the structural behaviour of the composite CFS flooring system. Simplified analytical models are proposed to predict the elastic bending capacity and flexural stiffness of the composite CFS and timber beams. The proposed design methodology discussed herein enables to design for enhanced structural performance to be achieved in CFS flooring systems by utilising the potential benefits of composite action to establish the practical design rules to be used by practising engineers. Connecting timber floorboard sheathing to CFS joists using mechanical fasteners (e.g. screws and bolts) is a novel method for developing a hybrid and prefabricated eco-friendly floors. This study, through experimental and numerical investigations, has demonstrated the feasibility of composite action to be considered in designing the load-carrying capacity of such lightweight floors. The conducted research shows the substantial gains in structural performance and the influence of key parameters for the composite construction. The findings from the presented study highlights the enhanced structural performance of CFS-plywood composite beams floor system and is an excellent potential option to be utilised in sustainable modular building construction.

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