It all begins with an idea.
Bypassing traditional fabrication methods, Portal Frame Steel Ltd brings an innovative steel structure solution for your steel construction projects.
Bringing an innovative new portal frame system to the United Kingdom
The Nested Tapered Box Beam
The Nested Tapered Box Beam Portal Frame system was developed by Steltech Structural Ltd in New Zealand to fill out it’s product range. The company is a three plate welded beam business producing wide span portal frames and welded beams for high rise structures and bridges.
The three plate welded beam option is not efficent (cost-effective) for span ranges below 35 metres clear span.
The tapered box beam was born to address this gap in the product offer.
The following images are New Zealand examples taken from the thesis of Amir Shahmohamidi as part of his Doctoral Studies at the University of Auckland.
Fig. to right - The sections in plate form after profile cutting and prior to folding to form the G sections which will then be “nested” together to form the finished section.
To support this feature purlins are often fitted between frames attached to the portal web plates. This then allows roof cladding to be installed flush with the frame top flanges. This then furthuer eliminates roosting possibilities for birds.
Additionally, the section type provides the same features when used as canopy framing over loading bays etc.
The section profile has a surface area less than a similar capacity I section profile. This, as there are no exposed flanges, the “inside” flange surface is not exposed. This results in less surface area therefore significant surface coating savings.
Furthermore, the tapered section further reduces material cost along with a fuurther reduction in surface area and coating costs.
Fly bracing required for Hot Rolled sections is not necessary with the tapered box section members due to the inherent tortional stability of the box profile.
The figures show the full-scale experimental tests and finite element analysis verification. University of Auckland 2017
The Nested Tapered Box Section developed to bridge that gap in the product offer.
The solution has additional benefits.
As the box section has no exposed flanges, there is no possibility of dust build up, nor is there any oportunity for birds or vermin to roost or nest.
This feature is valued where clean conditions are important. Food and agriculural applications and in New Zealand within the dairy industry.
Vertical and lateral loading on the specimen 1 (top picture) and Vertical loading on the specimen 2 (bottom picture)
58m-span VERTEBEAM ® frame in Auckland designed by the author
