Restoring an Impaired Concrete Silo

Abstract

A rectangular reinforced concrete grain silo, supported by mill building columns, was impaired by cracking and spalling, as well as major distortions in the walls. A close inspection revealed major exposure and corrosion of the reinforcing bars. Failure of the silo was possible under service conditions; repair was required. Placement of a conventional shotcrete concrete liner was considered but discarded because it required thick walls and double layers of reinforcement that made it heavy and costly. Instead, a welded steel liner made up of continuous horizontal frames, and a composite steel plate for walls, was used because of its light weight, less expensive construction, and smoothness of its walls. Design of the remedial steel liner is discussed at length; various details, such as connections at the corners to achieve continuity and attachments to the concrete silo walls, are given. This innovative solution is ideally suited for repair of silos that are subjected to combined axial tensions and bending moments.