We add and replace hoops on stave and poured concrete silos. Standard silo hoops come in 9/16" thickness and have a minimum yield strength of 40,000 PSI.
On a poured concrete silo the necessity to add hoops is evidenced when a silo shows signs of stress, often vertical cracks. However, on a stave silo the bottom hoops generally deteriorate faster than the others. For this reason we often only replace approximately the bottom 10 feet.