A DESIGN STUDY ON REINFORCED CONCRETE SILOS FOR REHABILITATION AND RETROFITTING

Abstract

Thermal stresses are regularly experienced by silos due to the temperature of their stored material clashing with the atmospheric temperature on site. This is most prominent in the case of hot stored material conflicting with cold winter temperatures. In Reinforced Concrete (R.C) silos these stresses are experienced as tensile stresses in a circular outwards direction and are to be resisted by the vertically placed steel reinforcement bars. Thermal stresses are however, rarely discussed and brought up in discussion regarding R.C silos unlike the more known stresses due to weight of stored material, wind, and seismic action. This leads them to often be neglected leading to silos being under designed and issues such as cracking begin to emerge during the silo’s operation phase. The need for retrofitting arises to keep the silo operational and to prevent future damages that might cause complete structural failure. Depending on the retrofitting technique selected however this can lead to high costs, notable additional load being placed on the silo, large time periods where the silo cannot be operated, and the reduction of the silos maximum storage capacity. Carbon Fiber Reinforced Polymers (CFRP) are composite materials consisting of carbon fibers that have proven to be an efficient and lightweight solution for the repair of deteriorated structures in the construction industry. For silos specifically they can be attached externally leading to minimum disturbance of operations and no reduction in storage capacity. Their high strength and light weight have led to them being widely used in developing countries but they find themselves being underutilized in Pakistan. This project highlights the significance of thermal stresses on the design of an R.C silo by using commonly used design codes as well as showcases the capability of CFRP to act as a competent retrofitting technique that is sufficient to deal with said thermal stresses.