Structural Steelwork and Price Influencing Factors

Introduction
Despite the overall cost competitiveness of steel in construction, many steel framed buildings remain more costly to manufacture and build than they need to be. Details and components often become unnecessarily complicated and expensive because the factors that govern production costs are not always appreciated.

The difference in construction techniques between in situ concrete and steel construction are fundamental to the basic nature of the two materials. Unlike concrete, which is essentially a wet process conducted on site, steel is produced and prefabricated within a controlled environment. This demands prior commitment and close cooperation between members of the design team to ensure that areas of joint responsibility are fully resolved and planned in advance.

Steel fabrication employs production engineering techniques and its success depends on good standardization. Time, and therefore labour , costs can be cut significantly by the repetition of dimensions, geometry, member sizes and shapes, centres and diameters of bolts, etc., all of which are accountable to rationalisation. Further economy is derived by reducing the number of detailed components which tends to be labour intensive even when this results in heavier parent material.

Commercial factors
There is a wide range of factors that influence prices of steelwork apart from the obvious. In general, they can be differentiated between ‘commercial’ and ‘technical’. Some of these include ‘lead times, erection times and typical prices.

Specialist works requires significant confidence and trust between parties involves in the construction (client, engineer, main contractor and steelwork contractor). Normally, with a tried and tested specialist contractor a lower price for the work can be expected as the expectations of mutual parties can often be predicted.

Expertise of the Engineer
A limited amount of consulting engineers are used to designing steel construction projects than others, with resulting simplicity and economy in their designs that will reduce total cost. Specialist steelwork contractors which offer design capabilities can be more economical as their vast experience and exposure to steel can be an added advantage in their designs.

Contract Conditions
Comparatively aggressive terms and conditions will result in higher prices from specialist contractor such as steelwork, which requires significant investment in materials and fabrication processes before any completed works arrives on site. Interim payments such as ‘materials off/on site’ will often lower the overall steelwork cost and improve contingency planning.

Market Conditions
When negotiating with or inviting potential steelworks contractors for a particular project, ascertain how busy they are in terms of their total design, detailing, fabrication and erection capacity when the work is to be placed as this will affect price levels.

Complete Package
Many steelwork contractors offer additional services such as concrete works, fire protection, decking, roofing and cladding. As usual, the larger the project and scope, the greater the economies of scale for price competitiveness.

Site Organisation
A well coordinated site ensures smooth running projects. ‘Congested’ sites in town centre and also remote site necessitate premiums due to transport and logistics. Ensure that the site has adequate access for steel transportation, unloading and erection at the site and adjacent access roads. Ensure that the ground is well prepared and level and is adequate to take the necessary wheel loads. Ensure that pre-site co-ordination is defined and where crane is provided by others it will always be available and in accordance to erection schedule. Ensure that all foundation works are completed within the schedule and anchor bolts set in place within the specified tolerances, free from damage and contamination. All works dependent or associated upon the steelworks needs to be properly identified as to whose responsibilities belies in the supplying and/or installing it.

Technical Factors
These are some ‘technical factors’ which are applicable to most general projects.

Specification
Use Standard Specifications such as those produced by BCSA or SCI to reduce uncertainty or demanding tolerances or testing other than that specified will increase costs.

Frame Grids
Structural steelwork prices are influenced by the number of pieces per tonne, which indirectly relates to the structural scheme or frame grids. Larger grid sizes, increases steel weight due to longer spans may be offset by the reduced price per tonne and also reduced the number of columns and related workmanship. Fewer columns with free column-space generally add value to a project. Lateral stability of frame by stiff core or frame bracing is usually less expensive than rigid or moment frames.

Complexity
Modern CNC fabrication equipment can cope with complex design but in general, the higher the complexity the greater the cost. Fabrication is more economic with:

· Single square cuts
· One hole diameter on any one piece avoids drill bit change
· Holes in flanges and web aligned where possible
· Web holes having adequate flange clearance
· Standardized range of connections
· Most connections are drilled then welded or bolted to the main member.

Where possible, allows the specialist steelwork contractor for alternative steel member selection and also leave the choice of the connections detail to them as the type, range of sections and design of connections directly influences the total frame cost. Design rationalisation of range and tonnages of section sized used is better off left to the steelwork contactor as they have first hand information on stocks, supply, fabrications and erection capability.

Complex individualistic designs are going to cost more per tonne even with modern CNC equipment. KEEP IT SIMPLE – if you wish to keep cost down.

Materials
Steel grades should not be mixed and where possible, rationalise the range of sections sizes/tonnages used in order to minimize cost, lead times and shop handling. In general steel grades S275 are adequate unless the strength requirements of S355 are paramount

Ensure that sections used are appropriate for its particular functions. ‘I’ sections are economical for conventional framing while tubes are good for trusses and to a certain extent for columns. Tubes have a lower gross weight required to perform the same function and also more aesthecally pleasing. Plate is usually used for Built-Up sections and in connections, stiffeners and base plate.

Architectural Requirements
Unnecessary finishing should be avoided and ensure that corrosion paints specifications is appropriate for the environmental conditions to be encountered. Grinding of welds is usually only required for exposed structure in close proximity to the human eye.

Quality of Drawings and Documentation
Accuracy, completeness, legibility and clarity of information are vital for a steelwork contractor to be able to examine the work involved. Where the steelworks are pre-designed, ensure that all member sizes are shown and that the connections forces are shown or are available.

Lead Times
The information that specifiers really need to understand is the elapse time from placing an order to the time of start of delivery of steelwork to site and commencement of erection. This data will varies depending on the complexity of the project but for a relatively straightforward project the period from receipt of order with full information to start of delivery can be typically around 6 to 8 weeks. Similarly erection times can vary depending on location and complexity of project, but normally are around 300 – 500 tonnes per month using one or two cranes.

References

Steel Construction News: ‘Factors Influencing steelwork Prices’: Issue No 10: Dec 2001: BCSA CORUS

R Taggart: Structural steelwork Fabrication: The Structural Engineer: Volume 64A:No.8: August 1986

National Structural Steelwork Specifications for Building Construction 3rd Edition, London: BCSA with SCI 1994