Title: Design Friction Loads for Concrete Silos
Author(s): Demetres Briassoulis
Publication: Journal Proceedings
Appears on pages(s): 438-445
Keywords: friction; granular materials; loads (forces); overpressure; pressure;reinforced concrete; silos; structural design.
The friction loads calculated by Janssen’s theory are forced in ACI 313-77 to approach those calculated by Reimbert’s theory, by using a semiempirical approach. The International Silo Association (ISA) recommended practice for design and construction of concrete silos for silage and grain is based on a specialized Janssen theory. The approach used in ISA for the determination of the friction loads on the silo wall follows the same semiempirical procedure as ACI 313, but it is shown, contrary to ACI 313, to yield rather conservative values of friction loads. The actual friction stress resultants calculated by the specialized Janssen theory are shown to be in good agreement with Reimbert’s theory. Thus, there is no need for any type of semiempirical "correction"when the specialized Janssen theory is used for the calculation of the friction loads. It is shown, however, that there is a major difference between Reimbert’s theory and the specialized Janssen theory that affects basically the calculated lateral static pressures. The source of the difference is the assumption on the variation of the pressure ratio. This difference is reflected to a lesser degree on the calculated friction loads.