Development of a Novel Cold-Formed Steel Truss System

In recent years, cold-formed (CFS) trusses have gained popularity due to many advantages such as being lightweight, non-combustible, termite and rot resistant, flexible in design, and ease of handling and fabrication. Often CFS trusses are designed and assembled at a plant and then transported to the site, which reduces overall construction times. This research describes the development of a novel cold-formed steel truss system. It includes a novel cold-formed steel connection and a channel section, which are combined into a truss system that is used as medium to long-span (15 to over 20 m) light steel framed trusses for industrial and commercial buildings. Experimental and numerical programmes were designed to investigate the behaviour of the Howick Rivet Connector (HRC), which is hollow and creates a concentric type of connection, and the Howick Channel section (HCs), which is U-shaped (short web with long flanges) that is specially manufactured to accommodate HRC through flanges. Different sizes of HRC joints (Tee-stubs) were tested under tension load. It was then compared to bolted Tee-stubs. It was found the HRC and bolted Tee-stubs have similar behaviour, but the use of the HRC demonstrated an improved capacity and ductility. It was also found the main failure modes of the HRC are bearing of ply and shear of HRC. Therefore, design equations to quantify the bearing and shear strength of the HRC have been recommended. The Howick Truss System (HTS) is a Warren-style parallel chord truss. Due to the joint arrangement in a truss system, different lip configurations exist within a single concentric joint (cut, folded and intact). Subsequently, the HCs with different lip configurations were tested under compression load. Moreover, the initial geometric imperfections (GI) of the struts were measured and used as input for the finite element models (ABAQUS) for more accurate results. It was concluded that the cold-formed steel standard AS/NZS 4600 and NAS S100 fairly estimates the capacity for lipped and unlipped channel sections, however, for cut and folded lips channel sections there was no design guideline and therefore, new design equations were proposed. An analytical investigation was carried out to determine the maximum possible span of the HTS. The experimental results of HRC and HCs strength were compared to design actions which were based on the real-life loading used by engineering practices. The design actions were calculated. Comparing the design actions to the capacities of the HTS components, it was found the HTS does not span as long as desired (< 15 m). The limiting parameter of the HTS was determined and subsequently, recommendations have been given for enhancing the strength of the HRC, the HCs and the HTS configuration in order to increase the HTS span.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Structural Engineering

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2023

Author dc:creator

• Ahmadi, Amin

Advisors dc:contributor.advisor

• Clifton, George Charles
• Lim, James

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/63442

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/63442