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High Grade Steel Residential development Solihull steel. Fittings material is normally standard grade, span portal frames, in multi-storey structures being easier to source for items such as flats and for the columns, and in composite construction angles. There is a danger however, that the use for the beams as well. The photographs show of high grade steel will result in more complex examples of the use of high grade steel by the connections, particularly if inappropriately author’s company, Barrett Steel Buildings. These small beams size are selected. The experienced building types are the mainstream of the industry designer will avoid this problem by carefully and represent the areas where most steel is used considering the practicality of the joint when — hence the rapidly rising use of high grade steel. selecting the steel size, to ensure it is possible to Designs for this type of structure incorporating form a connection without the need for excessive high grade steel will give very economical welding or stiffening. solutions. Owing to classification of sections for design Commercial factors purposes, certain sizes are not suitable for plastic One of the major changes over recent years has action. In standard grade there are just five such been the increasing availability of high grade sizes (all are UCs). With high grade there are steels. Medium and large sizes of universal more, seven beams and nine columns. This only beams and columns are now widely available affects a few serial sizes, normally the lightest through steel stockholders, as are the Corus section in the size (such as 356x171x45UB or Hybox range of hollow sections. As these 406x178x54UB). Consequently these sections sizes have become more popular, stocks have are somewhat restricted in suitability for high increased, creating a virtuous circle of usage and grade use. Additionally high grade will probably availability. Additionally, the premium charged by not benefit designs where fatigue loading is steelmakers for high grade over standard grade present, or when buckling action is the critical has been progressively reduced, for some sizes case. disappearing altogether. High grade now offers It is normal to use standard grade material a very attractive cost-to-strength ratio when for connections. Therefore connection design, compared with standard grade. including weld strength, will be governed by the Availability is still an issue for small sections, strength of the connection material rather than the and is likely to stay that way. This is because there strength of the high grade main members. is little or nothing to be gained by using high grade steel for beam sizes below 406mm, and Future trends and conclusions therefore usage is small. Specifying high grade Increasing availability of high grade steel, coupled in these small sizes is wholly uneconomical and with diminishing premium costs, means that it should be avoided if possible. The same applies offers a very attractive cost-to-strength ratio. with flats, angles and channels. Consequently use is increasing rapidly, and this is improving the overall competitiveness of steel Design issues framed solutions. In the long term I believe it is In modern designs, high grade steel is essential likely that Grade 355 will become the standard to optimise the economy of the steel frame. Many grade for most beam, column and hollow section types of buildings will benefit from the use of high sizes, with Grade 275 only being retained for small grade steel — in single storey structures for large beams and fittings materials. NSC April 2005 29


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