August 31st, 2023
The recession of 1980 hit the UK's industry hard, particularly the manufacturing and engineering sectors. Businesses such as foundries and general fabrication companies saw a significant decline in demand, causing many to close down. Even bending companies were affected, leading to the search for alternative uses of steel rings and curved steel.
One challenge with using steel in construction was the need to protect it from fire. This involved encasing the steelwork in a fire-resistant material, which was both expensive and time-consuming. Although this process effectively protected the steelwork frame during a fire, it was a handicap for the steel industry.
However, it was known that structural steel retained 80% of its strength at 400 degrees Celsius, which was still strong enough to support a building even in a fire. This meant that people would have enough time to evacuate the building before the steelwork reached that temperature and the fire brigade would be able to do their job.
Not only was there an appreciation for the introduction of intumescent paint, which can expand up to 50 times its size when exposed to high heat, but there was also a significant benefit. This paint prevented structural elements from reaching temperatures above 600 degrees Celsius, which could cause structural failure.
Before this, concrete structures were the norm. However, the appreciation for the strength of steel frames, resulting from laboratory tests and the use of intumescent paint, led to a major change. The increased use of steel allowed for lighter frames, faster construction, longer spans, and more flexible designs.
At that time, there was a high demand for large structures to hold people. Airport terminals were constantly being built or renovated to keep up with the demand for air travel.
Steel was the logical choice for building structures such as airport terminals, sports stadiums, conference halls, and shopping malls.
In the past, bending beams and columns was only possible in colliery arches and shipbuilding. Arches were easier to bend as they were not as deep and had thicker webs. Compression was the main focus, so the cross-sectional area was more important than the section modulus.
The use of a 4th roll that pulled back on the flanges at the point of bending allowed tension to be put in the web and prevented the web from collapsing. Hydraulic cylinders were used to control the pulling back of the flanges. For instance, it was possible to pull with 40% of the total force and push the inner flange with 60% of the total force to curve the structural curve element.
The old ship frame bender from the early 20th century shares the same principle as modern machines used for curved steel bends in universal beams.
However, the older machines were more time-consuming due to their incremental pressing along the bar's length, unlike rolling machines.
This has allowed Barnshaw Section Benders Ltd, a leading section bending company, to confidently offer the ability to bend beams up to the maximum size of 1016 x 305 x 584Kg around their strong axis for structural fabricators.
