Costing of Steelwork

The erection of steelwork is reliant on crane hook time; therefore, multiple small beams will have a disproportionately high erection cost when compared against a large single beam. Tower cranes are the main source of lifting on site. Crane capacity should be factored into the logistics strategy as any individual members that exceed the tower crane capacity will need to be erected by utilizing mobile cranes (with their associated road closures and space requirement). In cost planning buildings, allowances should be made for tower cranes with sufficient capacity to lift the majority (if not all) of the components necessary to construct the building. Where specific specialist lifts are required then allowance needs to be included within the overall building budget (this is not specific to steel framing and should be taken into account when considering the building as a whole). Design requirements to strengthen the frame in response to the building’s security assessment rating will mean increased structural demands on connection details and edge beams, particularly at the lower levels of the building, like provision for column removal without progressive collapse of the building. In most commercial buildings, straightforward steel construction will meet the required vibration performance criteria without modification. However, stiffening may be required to meet particularly onerous floor vibration design criteria, in which case deeper and heavier beams would be needed. In an optimum structural zone where beams work efficiently. However, with the introduction of services and the desire to increase floor-to-ceiling heights, this zone can become compromised. The reduced structural zone leads to making the frameless efficient and increased steel member weights. Site conditions have a direct impact on costs which manifests itself in the erection and package-specific preliminaries costs. In extreme cases the site conditions determine the design solution, eg constructing above railway lines, sites adjacent to or over rivers, or sites with restricted access (double handling). Site-specific preliminaries are influenced by tower crane availability, building height, uniformity of grid, on-site welding requirements, delivery timings and quiet periods. External factors such as currency exchange rates, buoyancy of the market, labour availability and commodity prices all influence market dynamics and as such should be considered at the time of developing the cost plan. It is advisable always to include exchange rates in the basis and assumptions of the cost document.