Steel structural framing systems

[edit] Introduction

Steel structures are formed from a skeleton frame that consist of vertical columns, horizontal beams and so on made from steel materials, riveted, welded or bolted together, often in a rectilinear grid. Steel structures are typically used for medium and high-rise, industrial, warehouse and residential buildings.

Advantages of steel structures include:

• Resilience to earthquakes and wind loading.
• Ease of construction and deconstruction.
• Short construction time.
• Resistance to fire when treated.
• Can be used in combination with other types of construction.
• Easy to join.
• High precision.
• Offsite fabrication.
• High ratios of strength to weight and strength to volume.
• Permit long clear spans.
• Narrow columns.
• Can be made to be exposed

[edit] Steel structural systems

The main steel buildings elements include walls, floors, roofs and bracing members can be arranged to have a certain type of system that aids in the structural stability of the building depending on the type or use of the building, the nature and intensity of the applied loads and the design life required

[edit] Wall bearing framing

Wall bearing framing involves the erection of masonry walls on the perimeter and interior of the building and the structural steel members are then anchored on the masonry walls using bearing and end steel plates and anchor bolts. The design and construction of the wall bearing framing depends on the load intensity and the span distance between successive supports.

While lower depth beams help to increase the clear headroom height of the building it also poses a requirement for the closer spacing of the columns and hence limits the clear floor space area. On the other hand, deep beam frames help to span long distance.

[edit] Skeleton framing

This is the column – beam structural framework system, in which all the lateral and gravity loads are transmitted to the steel framework and transferred down to the foundation. Walls are made as a curtain wall with no load bearing. Skeleton framing typically comprises of spandrel beams, main or primary beams, intermediate or secondary beams, wall columns and interior columns and reinforced concrete slab. For eccentric connections between column and beams there are a lot of techniques involved such as the use of metal brackets, gusset plates and haunches which help to distribute the induced stresses. Shims help in making line and elevation adjustments. Shelve angle brackets help in attaching the spandrel beam and column.

[edit] Long-span framing

A long span is a span that exceeds 12m. It helps to provide a flexible floor space, column free internal spaces, reduction in the on-site construction period, allows for installation of multiple services and mixed use of spaces. It is typically used for large industrial buildings, auditoriums, theatres, exhibition spaces and so on.

The following techniques are used; stub girders, hunched composite beams, composite trusses, cantilever suspensions spans, folded plates, curvilinear grids, thin shells domes, cable networks, space trusses, portal frames and so on.

[edit] Girders

These are deep steel beams which help to span long distances. The spanning length depending on the girder steel grade and the span depth ratio. Girders are installed in different ways, there are stub girders which span longitudinally across the structures being connected to the main girders and the hybrid girders, these are the manipulated girders stiffened to carry higher amount of loads by addition of the welded parts in the both top and bottom flanges.

[edit] Trusses

Trusses have the advantage of spanning long distances due to the greater depth they possess making them stiff against deflections. The types of trusses used for long span construction includes Pratt trusses, Warren Trusses, Fink Trusses, Scissors, Bow String and Vierendeel Trusses. For more information see: Truss.

These truss forms can be used as the main supporting structural members in floor and roof framing systems.

[edit] Rigid frames

The degree of rigidity in the beam-column connections must be carefully analysed. In rigid frames connections are designed to bear both bending moment and shear forces. They are designed as full continuous frames through the whole length and height in the absence of the hinges or pins in the crowns and in mid-span.

Large rigid foundations help to carry and distribute the moment and shear to the ground. For economical reasons the ground conditions should be checked as it could lead to higher foundations costs in poor subsoil conditions.

[edit] Arches

Arches can be made as solid arches or open web arches, three hinged, two hinged or fixed arches. These depend on the type of structural materials to be used, strength capacities, anchorage, building use, foundation type and the loading conditions.

The three hinged arch can help to span long distances even when there are adverse conditions such as poor climate, heavy loaded structures and so on. Two pinned arches are less strong compared to three hinged arch structures. Fixed arches are used in buildings with lighter loads and good ground conditions.

[edit] Related articles on Designing Buildings

• 8 reasons why structural steel frames are advantageous for any building project.
• Braced frame.
• Concept structural design of buildings.
• Concrete frame.
• Concrete-steel composite structures.
• Girder.
• Guidance for construction quality management professionals: Structural Steelwork.
• Gusset.
• Light gauge steel framing systems.
• Portal frame.
• Off-site prefabrication of buildings: A guide to connection choices.
• Skeleton frame.
• Steel frame.
• Structural steelwork.
• Timber frame.
• Types of frame.
• Types of steel.