During tender stage, time is often at a premium and various early assessments are required to be made to enable a subcontractor to produce a tender price in time for bid submission. The attached spreadsheet performs a budgetary function to analyse the hook time and ultimately determine how many tower cranes are required over a given programme period, to then allow a price to be obtained from specialist in the market. The entry data is relatively simple and is made up of 2 sheets within the Excel file.

The “Calculations” sheet defines and quantifies the duties the tower cranes will perform. The “Analysis” sheet carries forward this information into a calculation of hook time, programme period input, and ultimately determines the tower crane number based around a satisfactory “utilisation” figure. From experience, I prefer the utilisation number not to exceed 0.8, despite the theoretical limit of 1.0 being possible. However, the mechanical availability is the risk factor, which despite allowance for downtime due to wind, and efficiency of the machine downtime itself, is the fundamental variable. Personally, I like to see utilisation no higher than 0.8 for that purpose.