Proceedings of the 7th International Working Conference an Stored-product Protection - Yolume 2

A hanging steel silo

Wang Rongshuar' and Yang Shizhong''

Abstract

Steel s110 is one of the main gram storage containers. Alltypes of steel s110sm use can be styled Placing Steel Silo; itis placed on the supportmg bed or foundation Itsdisadvantages are: (1) steel strength used only about onethird because of the buckling of It; (2) the pressure appliedto the silo wall by the stored matenal WIll be doubled at timeof unloading accordmg to the Silo Code. So, more steel andfund are needed for construction. In order to overcome thetwo disadvantages above mentioned of the Placing Steel S110,the Hanging Steel S110was designed. It is hung at Its topcircumference. In tlusl case, less steel and capitals areneeded for the construction of the Hangmg Steel S110 TheNational Patent Bureau has awarded the writer a patent rightfor this design.

Introduction

The steel silo technology has been used for storing granularmaterials in China since the begmmng of 80's, and itattracted many scholars to concentrate their attention instudying on this technology.It is well known that the steel s110 belongs to thm-shell

structure, and when the friction of the storage matenal tothe s110wall apphes axial compression, it IS easy to buckle.The structure design of steel SIlo is controlled by bucklingcondmons mstead of by strength conditions and ItS bucklingcritical compressive stress IS very smaller than ItS strength.On the other hand, axial tension IS not to cause buckling, sothat the structural design of steel SIlo IS determined by ItSstrength conditions instead of by Its bucklmg condmonsAll types of steel silo used now can be styled the placing

steel s110 that is located at the supporting bed or the s110foundation. The fnction of the stored material makes It tobe compressed in axial direction. The disadvantages of theplacing steel s110are: (1) steel strength used only about onethIrd because of the buckling of It, (2) the pressure applied

IZhengzhou Gram Science Research & Design Institute under theMmistry of Domestic Trade, 153 Nanyang Road, Zhengzhou450053, China

2Forelgn Capital Management Office, Mnustry of Internal Trade, 45Fuxmgmennei St , Benmg , Chma

to the silo wall by the storage material mcreases one timeswhen unloading according to the silo code. With unloading ofthe storage material, the dynamic pressure on the silo wallexerted by the storage material changes very much whichmay result m the buckhng of the Hanging Steel S110. So,more steel and capitals are needed for construction toguarantee the safety of the Placing Steel S110.In order to overcome the two disadvantages above

mentioned of the Placing Steel Silo, the Hanging Steel Silowas designed.

Model of the Hanging Steel Silo

The sketch drawing of the Hanging Steel Silo IS shown inFig. 1. Mam idea 1S that we manage to make s110wall behung at Its top circumference, IS this status in, the storagematerial friction to the silo shell shall make It axial tensile.As we know, axial tension will not cause the silo shellbuckhng, so, we can reasonably make use of the strength ofsteel to design the s110wall. And in order to hang the SIlowall, a compression support bin with radial steel cantilevertrusses for hanging silo wall and openmgs for grain flowingin and out are set up in the center of the hanging steel silo.ThIS bin can be used as the pressure reduction pipe todecrease the dynamic actions as far as possible whenunloading the storage materials. And this bin can also beused for the ventilation of the whole s110.

1 s-to bose

2 Ploc.ng St" ..1 S,loJ 5.10 roof

4 Hongohg Steel S,lo5 supper t b,n

b s'tgeo\ trl)SS

7 COt'loeoct,og JOInt

8 hon9,ng Jo,nt9 open,ngJO .ol"t11 .9ut'l>[

Note

Fig. 1. Diagram of the placing steel silo and the hangingsteel Silo.

In a word, the Hanging Steel Silo can overcome the twodisadvantages of the Placmg Steel Silo mentioned aboveTherefore, less steel and capitals are needed for theconstruction of the Hanging Steel S110.

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Proceedings of the 7th lnternoiumal Workmg Conference on Stored-product Protection - Yolume 2

The basic structural elements

Main structural elements are a compression support bin,radial steel cantilever trusses set on the bin for hangmg ofthe steel silo and a tensile steel silo.These structure elements are descnbed respectively as

follows:The compresswn support bin.On the compression support bin are set the ramal steel

cantilever trusses to hang the steel silo, so, It IS the pillarstrength of the whole silo. On the compression support bm,opemngs are also designed m all directions and variousheights. Through these openmgs, the storage matenal flowsmside or outside the compression support bin to unload orload the steel silo.In consideration of too low strength of bnck and stone,

concrete structure WIllbe used for the compression supportbm. The diameter of the compression support bin, Dl , willbe Do/4 - Do/3, and Willnot be smaller than Zm, m wluch ,Do ISthe diameter of the steel silo The compression supportbin ISsupported by the foundation.The compression support bm can be used as the pressure

(storage material to steel silo wall) reduction pipe and forthe ventilation of the whole silo.The radial steel cantilever trusses set on the compressionsupport binThe radial steel cantilever trusses are set upon the upper

part of the compression support bin to hang the HangingSteel Silo and support the root of the Hanging Steel SIlo.They are rooted in the upper and lower ring beams, whichare inlaid in the near-top part of the compression supportbm.The tenstle steel siloSteel plates welding or other fittmg method can be used

for the construction of the Hangmg Steel SIlo wallHowever, the LIPP Patent SIlo wall should not be used forthe Hanging Steel SIlowall, as ItS rollmg construction jointsare not favorable to endure tension action. The topcIrcumference of the Hanging Steel SIlo is hangmg under theradial steel cantilever trusses set on the compreSSIonbm;the bottom of the Hangmg Steel Silo is connected with thebase bed. The diameter and heIghts of the Hangmg SteelSIlo WIll be determmed accormng to the applIcationconmtIOnsand the conmtions of the foundatIOnbed

Work Principle

Loading, unloading operations

When loading, the storage material goes mto thecompreSSIon support bm from the top conveyor of theHanging Steel SIlo, and ItS level nses gradually When thematenal level IS higher than the bottom openmgs on thecompression bm, the matenal flows mto the Hangmg Steel

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SIlo through the bottom openmgs on the compresston supportbm After a penod of time, the material level in the bmnses again, the above procedure repeats time and agam fromthe lower opemngs on the bm to the upper opemngssuccessively until the silo becomes full of gram last throughthe highest openings on the bin. Of course, the bin alsobecomes full of gram.When unloadmg, as the storage matenal flows out of the

silo hopper, the material level drops gradually. When it islower than the highest opemngs on the bin, the matenal inthe silo flows mto the bin. After a penod of time, thematenallevel m the bin drops again, above process repeatstime and agam from the upper openmgs on the bin to thelower openmgs successively, until the silo becomes emptylast through the lowest openmgs on the bm, finally the binalso becomes empty

Structure mechanical status

When the silo and bin are empty, the silo is subjected tothe lateral wmd load and transfers It to the Trusses at thesilo top circumference and the base bed at the silo bottom.When the SIloand bin are filled With the storage material,

the matenallateral pressure produces circumferential tensilestress m the silo wall, but It produces circurnferentialcompressive stress in the bm wall. The storage matenalvertical Inction produces vertical tension in the SIlo wall,but to the bin wall, produces vertical compression. That isto say, the Hangmg Steel SIlo is tensile m both directionsand the concrete bm is compressive m both directions.Accordmg to the strength theory, these stress statuses arerespectively favorable to the steel silo and the concrete bm.Furthermore, when unloading, as the material flows

through the bin, Its dynamic effects on the Hanging SteelSIlo will be near zero. ThIScondition ISalso favorable to thesteel silo.

Construction Details

The steel silo hanging on the cantilever trusses

As shown in FIg. 2, a tensIle nng of angle iron is set up atthe outer jomts of the cantilever trusses. The steel silo ISconnected WIth a wmg of the angle Iron nng by means ofhigh strength bolts.

The steel silo connecting with the base bed at itsbottom

As shown in Fig. 2, a band plate rmg ISwelded WIth theembedded parts in the base bed. The steel sIlo bottom ISbolted to the band plate nng and the bolt hole on the steelsIlo will be ellipSOIdalto allow the steel sIlowall move up anddown freely.

Proceedings of the 7th Iruemaiumal Working Conference on Stored-product Protection - Volume 2

NotE'

1 st!?!?1 truss

2 .r on ongl!?

3 Horoq,ng Steel $,10

4 h'gh s+rength bo't

5 band pto t e r ,nq

b eMbedded r:cr+7 bol+

8 "eld,ng

Fig. 2 0 Structure details of the top and the bottom end of thehanging steel s110

Procedure in Construction

o Construction of the base bed.o Slip fore or prefabncated construction of the compressionsupport bin.

o Assembly of jack hft frame.o LIft the cantilever trusses and the steel silo wall everytime hfts a certam height, assembles a CIrcle plate of thesteel silo wall, which IS pre-assembled on the ground.

o After assembly and lift of the whole steel silo fuushed,manages to anchor the cantilever trusses to thecompression support bm at the exact posi tion

o Layout the roof plates of the steel silo.

Conclusion

The Hanging Steel SIlo has advantages of structuralproperties, as It is tensile 10 both direction and thecompression bm IS compressive in both directions. So we canreasonably make use of the mechamcal properties of steeland concrete materials, and the storage material unloadingdynamic effects to the hanging Steel SIlo will be near zero.Also the compression support bin with many openings can beused for ventilation, therefore, the hanging Steel Silo is notonly less expensive, but also safer. However theconstruction penod of the Hanging Steel SIlo may be a little

longer.

References

M . L. Reimbert and A. M. Reimbert, 1976. SIlo Theoryand Practice, Trans Tech Pubhcations, Germany, 239p.

Sun Xunfang etc. 1979. Material Mechamcs (in Chmese);People's Education Press, Belling, 442p.

Zhou Iiajun etc, 1988 Design Code for RemforcedConcrete SIlo (GBJ77 - 85) (in Chinese). Chma Iihua

Press, Belling, 52p.

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