Impact of New Codes in Silos Design

Impact of the new codes for design of Cement silos Khaled Eid, PE M.Eng. Head of Steel Department RHI Egypt, Consultant Engineer.

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Abstract

The new Euro code BS EN 1991-4 actions on silos has significant impact when compared to other commonly used codes such as the Din 1055 part 6 or ACI313-18 when considering the eccentric discharge , previous codes states only there will be significant wall moment without stating how to calculate it. This paper will highlight the impact of the asymmetric loading in designing silos with eccentric discharge by presenting a practical case study comparison for a 14000 m3 raw meal homo inverted cone silo 52 meter height and 23 meter diameter designed by ACI and the new Euro code, keeping the same wall thickness to identify the effect on pre stressing, conventional steel reinforcement, cost and design time.

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Introduction

Silos is generally used in storing granular and powder material in industrial planet most of the large silos are in cement planet, silos either concrete or steel filled from top by either conveyors, bucket elevators or airlift and discharged from the bottom by either from the center or eccentric through discharge gates as in inverted cone silos which is our case study The designer should consider the construction method which is usually constructed by the slip form technology Design of silos in the past was based only on static pressure with no allowance to of pressure difference due to material flow which resulting to a bending moment stress, there is no direct software for predicting the walls stress on silos during filling and discharge that makes the silo design requires a very specialized mechanical/structural skills. Footing should be noticed for any differential settlement will cause significant redistribution of loads the remain supports, there were many reported case of silo collapse plus many other unreported. According to silo geometry there are 4 types classification types. 1. Slender silo: where 2≤hc/dc 2. Intermediate slenderness silos where 1.0