Sustainable building thanks to high strength steels
Sustainability is playing an increasingly important role in building. However, this concept is not just restricted to ecological issues, but also comprises economic and socio-cultural aspects. Only structures which fulfill all of this criteria are permanently successful and therefore sustainable.
In this regard, constructional steelwork certainly has an advantage over other constructive forms thanks to structural steel which spares resources when manufactured and is infinitely reusable. Moreover, the increasing usage of high strength steels enables the possibility to further optimise the sustainability of the steel or composite construction.
Modern steels such as HISTAR® 460, for example, demonstrate an outstanding weldability thanks to thermomechanical rolling and subsequent QST treatment in addition to high strength owing to carbon equivalent.
Principally, the use of high strength steels is worthwhile if tension problems are decisive when measuring structural components. This is often the case with composite girders, comprehensive roof supporting frameworks, trusses, or heavily burdened supports. The somewhat higher price per tonne is far and away exceeded through savings on material, processing, transport, and assembly.
HISTAR® for car park ceiling girders
One area in which high strength steels have been utilised is car park ceiling girders. A span of approximately 16 m is usually required. An example can be seen in Table 1. With the use of HISTAR® 460, the assessment usually results in an IPE 500 profile as opposed to an IPE 600 when using an S235JR+M. In this way, the component weight can be reduced by 24%. This leads to a cost saving of 17% for the pre-finished structural component.
Apart from the considerable economic advantage with use of the high strength steels, a contribution to environmental sustainability is made at the same time.
This can be calculated for a car park with a capacity for 1000 vehicles. 250 ceiling girders are used in such a building. If trusses are used according to variant 2, a total of 127 tonnes of steel will be saved. Consequently, in addition to the lower emissions in the manufacturing process, seven journeys to the construction site by lorry can be spared for the ceiling girders alone.
Along with this, there are still savings through shorter supports, shorter lift shafts and stairwells, more favourable arrangements for ramps, and a reduced facade area. Moreover, the reduced headroom leads to a lower overall height of the building – for example, a six-storey car park can be built 60 cm smaller.
Reducing surfaces & costs
High strength steels also have great advantages when used in industrial construction and multi-storey buildings. Reduced dimensions of roofs or roof girders, for example, result in decreased building heights.
For this reason, the exterior surface area of the building can be reduced. Apart from saving on construction costs for wall and facade areas, one can also save on regular costs for heating and air-conditioning respectively.
Finally, it can be determined that the use of high strength steels in the building industry is generally recommended for constructions in which use of tension is relevant to building specifications. With the use of HISTAR® 460 as opposed to the S235JR+M, approximately 25% of component weights and approximately 15 – 20% of component costs are saved in everyday applications.
In extreme cases – e.g. with comprehensive timber work construction – savings may even amount to 50%. Apart from economic advantages, a contribution to environmental sustainability is also made. In order to fully benefit from the advantages described, it is important that high strength steels are included early on in the planning phases for the components in question.
Text: Marc Blum & Falk Satzger, ArcelorMittal