Applications
Large Towers and Satellite Dish Structures
Large communication towers, power transmission line lattice towers and satellite dish structures generate high overturning moment loads. These loads are sometimes difficult to manage with single pad foundation as the sq/m size of the pad becomes prohibitive. In addition the options of excact location are somtimes limited in position and available area withing the easement or land space. By introducing a piled sub-foundation system the area size and mass of the concrete pile cap can be kept to a minimum. This is particularly helpful where the leased easement is confined and space is at a premium.
A screwpile sub-foundation solution provides tower design engineers with the ability to limit the sq/m area needed by converting the large overturning moments produced by wind loads into compression and tension loads that are distributed below ground by the piling system.
Piling layouts are generally installed inside a mass concrete foundation linking all the piles together in a stiffened situation. The concrete pile cap may consist of a 3-4-6-8-12 pile configuration with some screwpiles being installed vertically and others on raked angles to cater for some shear loads.
Tower design engineers are encouraged to utilize the passive soil pressures acting on the pile cap to cater for most of the shear forces as this is by far the most economical method. The screwpiling sub-foundation system will transfer any compression and tension loads down into the ground in accordance with the cyclic wind loads. This is ideal where significant wind loads are expected.
Power transmission lines generate large overturning forces on a structures foundation systems due to cable drag in windy conditions.
Communication tower movement must be kept to an absolute minimum as limits tower movement are a critical component in signal reception.
Satellite dishes have large sail areas and signal lock sensitivity that cannot be exceeded.
As with all towers foundation deflection must be kept to an absolute minimum.
A comprehensive deep geotechnical assessment for each tower location is necessary for the sub-foundation systems engineering design and certification. Screwpile Australia through its associated consulting engineering company Foundation Engineering Pty Ltd offers a turnkey approach in geo-testing, foundation design, piling installation, structural engineering certification and onsite project management.
