Steel and metal building construction
Modern steel buildings are built using a portal frame structure with the frames co-ordinated into the form of bays. In use, the frame bears the weight of the building and walls. And for bigger buildings, more bays are used to spread the design to the available space. The beams that build up the frame allows the weight of the building to be held without needing supporting walls or interior columns. This frame structure provides for a huge amount of flexibility in design and allows for many types of walling or cladding and doors and windows..
The basic construction method involves firstly placing and fitting the frame. Normal groundworks start by preparing a concrete base to support the upper pillars. Once the base has been created the frame structure can be put together quickly using a crane/cherry picker.
Portal frames are most commonly built out of rolled-steel for strength. The beams and columns then fit together almost like giant-sized 'meccano'. The pillars are linked horizontally by purloin beams using the triangle of the sloping roof to provide rigidity to the structure - one of the keystones for the design is the strength of the joints that join the beams. These beams and joints determine what load the building can carry - both the weight of the walls and fixings, but also against wind and external forces.
A key feature of the steel beams is that it allows the building to span wide spaces without the need for intermediate supporting columns so providing the maximum effective space for the land available. For situations where you want to be able to get access for large machinery - like cranes, combines or aircraft, there is no real alternative to a steel-framed building.
In terms of design, the core loading factors to be taken into consideration are
- the dead loading (the self-weight of the building),
- the loading from added structures - for instance furniture etc. In many building designs this imposed loading can be carried by a separate internal structure.
- the wind loading - the large wall area available and relatively lightweight materials in use means the structure needs to have stiffness and strong links to solid foundations.
With the frame in place, the building can be clad and kitted out with a variety of materials. For cost and convenience, organic-coated steel panels are most often used as they have excellent weather-resistance and low maintenance requierments. However, this is not the only option. For specialist or aesthetic reasons, as the walls of the building do not hold the weight, the exterior walls of a steel buildings can wood, brick or glass.For instance for showrooms or office blocks glass might be the best choice, for use such as in a conservation area, or for say a riding arena, wood might be used.
This flexibiility and strength of the portal frame, also allows for the use of a wide variety of doors especially those that are extra high or wide - eg large roller doors high vehicles like crane or JCB access, or wide doors for things like planes. The frame also allows windows and skylights to be placed almost anywhere on the building.
With this flexibility, the building can be designed to the precise requirements of the customer. For instance walls can be double skinned, or include insulation so as to better retain heat, and may include internal floors or mezzanine levels. As there is no internal weight supporting structure, the interior can be fitted out in an variety of configurations - from stabling or offices with individual rooms, to large open warehouse structures with easy access for forklift trucks.
Designs of steel buildings can range from the simple to complex for more architecturally interesting shapes and the design will take care to consider loading weight, wind factors, usage and position.
