To replace rotten wooden ramps with metal framed ramps

We have being trying to obtain funding to cover our skatepark with a roof to protect the wooden ramps. As yet we have not been able to complete this fundraising and so we wish to replace some of the wooden ramps that never get the sun and so have rotted with ramps that are metals framed and in some cases where they will never dry out have special metal surfaces.We also wish to purchase some smaller, moveable ramps that can alter the layout of the park periodically by being moved around.