Effects of vibration on loads in a corrugated model grain bin

Transcription

1 Effects f vibratin n lads in a crrugated mdel grain bin D. HAO, Q. ZHANG and M.G. BRITTON Department f Agricultural Engineering, University f Manitba, Winnipeg, MB, Canada R3T 5V6. Received 15 February 1993; accepted 24 Nvember Ha, D., Zhang, Q. and Brittn, M.G Effects f vibratin n lads in a crrugated mdel grain bin. Can. Agric. Eng. 36: Experiments were cnducted using a 1.5 m high by m diameter crrugated steel bin t study the effects f vibratin n lads acting n the bin wall. The bin was instrumented with frce and pressure transducers t measure the vertical frces and lateral pres sures. The bin was filled with wheat at 12% wb misture cntent and then vibrated fr 20 minutes at a frequency f 30 Hz and a vertical amplitude f 10 mm (peak t peak). Vibratin increased the lateral pressure near the bin flr frm 2.73 t 3.78 kpa, r 39%, and the resultant vertical frce frm 0.96 t 1.17 kn/m, r 22%. During discharge, n increase in lateral pressure was bserved in the lwer prtin fthe bin which was previusly subject t vibratin, whereas an increase f31 % was measured near the flr in the bin which had nt been subject t vibratin. The maximum lad (static plus dy namic lad) that was experienced by the vibrated bin was slightly higher than that by the nn-vibrated bin. Keywrds: grain, bin, lads, vibratin, discharge. Des experiences n ete effectuees avec un reservir en acier ndule de 1.5 m de hauteur et de m de diametre afin d'etudier les effets de vibratin sur la charge agissant cntre les murs du reservir. Le reserviraete cquipe de transducteurs de frce et de pressin pur mesurer les frces verticales et les pressins laterales. Le reservir a d'abrd ete rempli de bid ayant une teneur en humidite de 12% (base humide)et ensuite ete vibre durant 20 minutes a une frequence de 30 Hz et une amplitude verticale de 10 mm (crete a crete). La vibratin a augmente la pressin laterale pres du plancher du reservir de 2.73 a 3.78 kpa (u 39%), et la frce verticale resultante a augmente de 0.96 a 1.17 kn/m (u 22%). Durant le dechargement, aucune aug mentatin de la pressin laterale a ete bservee dans la partie infeyieure du reservir qui avait ete auparavant sumis a la vibratin, tandisqu'une augmentatin de 31% a ete mesuree pres du plancher du reservirlrsqu'il n'avait pas ete sumisa la vibratin. La charge maximum (statique et dynamique) bservee sur le reservir vibre a 6l6 legerement superieure a celle bservee sur le reservir nn vibre\ INTRODUCTION Grainstragebins may be subject t varius vibratrycndi tins. Pssible surces f vibratin include running machinery (fans, cnveyrs, etc.), wind, earthquake, and ve hicles travelling n nearby rads r railrads. Vibratin impses dynamic (inertial) frces n bin structures. These dynamic frces may lead t structural failures under severe vibratry cnditins such as earthquakes. Under nrmal cn ditins, grain bins are mre likely subject t lw amplitude vibratins which d nt prduce dynamic lads severe enught damage structures. Hwever, lw amplitude vibra tins cause changes in grain prperties, such as higher bulk density and rerientatin f grain kennels. Changes in grain prperties may result in increased grain pressures n the bin structures. Increased pressures due t grain prperty changes are "static" and they cntinue acting n the bin even after vibratin stps. Nne f the existing grain pressure theries takes int accunt the effects f vibratin n bin lads because "there are insufficient data available t predict the magnitude r significance fvibratin induced pressure" (ASAE 1992a). Dynamic analysis f structures under vibratry cnditins has received much attentin in the area f seismic engineer ing (Newmark and Rsenblueth 1971). Hwever, little can be fund in the literature abut lad increases due t prperty changes in grain bins subject t lw amplitude vibratins. This study was aimed at explring the significancef vibra tin induced lads in grain bins. The specific bjectives were: (1) t cmpare lads befre and after a bin had been subject t lw amplitude vibratins; and (2) t determine the effects f previus vibratinn dynamic lads during discharge. EXPERIMENTAL METHODOLOGY A mdel bin 1.5 m high and m diameter, cnstructed frm 0.97 mm thick crrugated galvanized sheet steel, was used fr all tests. Wall crrugatins were 64 mm pitch and 13 mm deep. The bin wall (an pen-end cylinder) was supprted apprximately 5 mm abve a flat flr by three lad transducers placed 120 apart (Fig. 1). The sum f frces measured by these three transducers was the ttal vertical ladcarried by the bin wall. A flexible plasticskirt was taped t the bttm f the wall t prevent grain kernels frm leaking thrugh the clearance between the wall and flr. The bin flr was suspended by three steel rds, each fitted with a integral lad transducer t measure rd tensin (Fig. 1). These three transducers prvided a measurement f the ttal in-bin grain mass, which was equivalent t the ttal vertical wall lad plus flr lad because the bin wall rested n the flr thrugh the three wall-ladtransducers (Fig. 1). All six lad transducers werecalibratedusing dead weights up t 3.9 kn (R2 > 0.99 fr all calibratins). Lateral pressures n the bin wall were measured using diaphragm sensrs munted n the inside surface f the bin wall at six elevatins f 192, 384, 576, 768, 960, and 1152 mm frm the bin flr (the base f the bin wall) (Fig. 1).Tw additinal pressure sensrs were placed n the bin wall 120 apart arund the bin circumference fr measuring circumfer ential pressure distributin at an elevatin f 384 mm abve the flr. CANADIAN AGRICULTURAL ENGINEERING Vl. 36, N. I, January/February/March

2 vibratin device Flr lad transducer Main frame Mdel bin Lateral pressure transducer Vertical wall frce transducer 5 mm gap Bin flr Discharge utlet Hpper cart Fig. 1. Schematic f mdel bin testing system. Each diaphragm pressure sensr had an aluminum dia phragm 0.52 mm thick and 60 mm diameter. This relatively large size f diaphragm and small aspect rati (8.7x 10" ) was used t maximize the accuracy f grain pressure measure ments (Atewlgun et al. 1992). Under the maximum design pressure f 5 kpa, the deflectin at the centre f the dia phragm was calculated t be 74 mm. This small deflectin ensured a linear utput (Atewlgun et al. 1992), and mini mized the strain relieve (bridging) in the grain mass immediately next t the diaphragm (Dale and Rbinsn 1954). Fur strain gauges were munted n the inside surface f the diaphragm. The gauges were temperature cmpensated fr aluminum and cnnected as a full-bridge. All diaphragm sensrs were calibrated using a water clumn up t 4.9 kpa (R2> 0.99 fr all calibratins). The reslutin f the water clumn was 10 Pa. The manner in which grain prduces pressure n a dia phragm sensr might be different frm that f water. Tests were cnducted t cmpare the respnse f the sensrs t grain pressure and water pressure. The sensr was placed in a plastic cntainer f 200 mm diameter and the cntainer was then filled with wheat t a depth f 50 mm. Dead weights were added n the grain surface incrementally. Chi-square test shwed that the pressure-strain curve measured frm the dead lad test had n significant difference (a=5) frm that btained frm the water clumn calibratin. Zhang et al.(1991) reprted that the peak lateral pressure near the bttm f a mdel bin ccurred within 0.4 t 0.7 s after the discharge gate was pened. T capture the peak dynamic lads f discharge, a high-speed data acquisitin system, HP 8532A data acquisitin unit cntrlled by a mi crcmputer, was used t recrd utputs frm all lad transducers and pressure sensrs. The data acquisitin unit was capablef taking 20 readings per secnd fr each f the 14 channels. Each test was carried ut in six steps: (1) the bin was filled using a surge hpper centrally lcated 0.8 m abve the bin tp, (2) the grain surface was levelled, (3) the bin was al lwed t settle fr 10 min, (4) the bin was vibrated until the grain surfacestpped mving(abut20 min), (5) the bin was 30 allwed t settle until static pressures and frces became stabilized (abut 2 h), and (6) grain was discharged thrugh a centrally lcated circular rifice, 60 mm in diameter. Lat eral pressures and the ttal vertical frces n the bin wall were recrded frm the beginning f filling t the end f discharge, except that data recrding was paused befre and after vibratin fr changing cmputer diskettes (Fig. 2). Sen sr utputs were recrded every tw secnds during the filling, settling, and vibrating phases. The recrding rate was increased t 20 readings per secnd per channel fr the first 87 s f discharge, and then decreased t 0.5 readings per secnd until the end fdischarge. Tests were als carried ut n the same bin withut being vibrated. Fr bth vibrated and nn-vibrated cnditins, tests were repeated fur times. All tests were perfrmed using Hard Red Spring wheat (cv. Katepwa) at 12% wb misture cntent. Physical prper ties fthe wheat are summarized in Table I. Misture cntent was measured by the air-ven methd (ASAE 1992b). In-bin bulk densities were determined as the ttal in-bin grain mass divided by the grain vlume. Particle density was measured by using an air cmparisn pycnmeter (Mhsenin 1986). Bth the angle f internal frictin and the frictin cefficient f grain n the crrugated wall were measured by using a direct shear device (ASTM 1981). Nrmal pressures used in the direct shear tests ranged frm 9.73 t kpa. Bin vibratin was induced using an ff-centre weight vi bratr which generated a vibratin frequency f 30 Hz and a vertical amplitude f 10 mm (peak t peak). This frequency was chsen based n the bservatins reprted by Duncan (1980) that grund vibratin at distances 5 t 80 m frm (A W 2.0 a. G> - 3 ~. \ 0.5 ^0.4 CO a> u r 0.1 > III Time Fig. 2. Typical measured lateral pressure and vertical frce n the bin wall frm ne test (I: filling; II: 10 min settling; III: 20 min vibrating; IV: 2 h settling; and V: discharge). Lateral pressure was measured at the lwest measuring level (192 mm frm the flr) and the vertical frce was frm ne f the three wall-lad transducers which was apprximately ne third f the ttal vertical frce acting n the bin wall. IV HAO, ZHANG and BRITTON

3 Table I. Physical prperties fwheat used in experiments Misture cntent (% wb ) Bulk density (kg/m ) Particle density (kg/m ) Angle f internal frictin Grain-crrugated steel frictin cefficient * Wet basis + Bulk density befre vibratin $ Bulk density after vibratin ^ 1.4 E 12 i_ , 836* * 1432 c 25.5 S E railways had frequencies ranging frm 5 t 100 Hz. A lw amplitude f 10 mm was used s that the inertial frce wuld nt cause damage t the bin during vibratin and yet the bulk density f grain stabilized in a relatively shrt time perid (within 20 min). Vibratin frequency and amplitude may affect bulk density and kernel re-rientatin. Hwever, n attempt was made t investigate different frequencies r amplitudes in this study because the vibratr was capable f generating nly ne frequency and ne amplitude. The vibratr was placed n the tp f the bin wall. A vibratin analyzer (Mdel 4660'VIBRA/VIEW\ VITEC Inc., Cleveland, OH) was used t measure vibratin frequen cies and amplitudes at 12 randm lcatins n the bin wall and flr t check fr unifrmity f bin vibratin. The meas urements shwed that vibratin was relatively unifrm ver the entire bin with n nticeable difference in frequency amng these 12 lcatins. The lwest amplitude f 8 mm was bserved n the bin flr. Preliminary tests RESULTS AND DISCUSSION Munting diaphragm sensrs n the inside surface f the wall might disturb the grain flw during discharge, thus affecting bin lads. Preliminary tests were perfrmed t measure static and dynamic vertical frces n the bin wall when all pressure sensrs were remved frm the bin. The measured static and dynamic vertical frces were 0.98 and 1.24 kn/m (frce per unit length f bin circumference), respectively, whereas the crrespnding frces measured in the presence f all eight sensrs were 0.99 and 1.24 kn/m. Static and dynamic resul tant vertical frces measured in the presence f sensrs were nt significantlydifferent (a = 5) frm the crrespnding frces measured in the absence f sensrs. This suggested that munting sensrs n the wall did nt significantly affect the ttal lads n the bin wall. Hwever, the stress field in the vicinity f each sensr might have been altered by the sensr. This study did nt investigate interactins between dia phragm sensrs and grain. Effect f vibratin n static lads Figure 2 shws typical measured lateral pressure and vertical frce frm ne test. The shwn lateral pressure was frm the diaphragm sensr at the lwest measuring level (192 mm frm the flr) and the vertical frce was frm ne f the three wall-lad transducers, which was apprximately ne third f the ttal vertical frce acting n the bin wall. T H- S 0.4 c w 0.2 Q nn vibrated bin vibrated bin Janssen predictin with k=0.4 95% C. I Static lateral pressure (kpa) Fig. 3. Measured static lateral pressures n the bin wall at six depths in a crrugated bin 1.5 m high and m in diameter. facilitate discussin, the pressures r frces measured after the bin was fully filled but befre discharge were referred t as the static pressures r frces, whereas the lads measured during discharge were defined as dynamic lads. Vibratin caused increases in static lateral pressures at all six measuring levels (Fig. 3). Lateral pressure increased mre in the lwer prtin f the bin than in the upper prtin. Fr instance, the lateral pressure at the bttm level increased frm 2.73 t 3.78 kpa, r 39%, whereas the pressure at the tp layer increased frm 1.11 t 1.18 kpa, r 6%. Further statistical analysis shwed that increases in lateral pressure at the tw upper measuring levels were nt significant (a = 5), whereas increases at the tw lwer levels were significant. It was nticed that lateral pressure predicted by Janssen's equa tin (Ketchum 1919)was in gd agreement with pressure in the nn-vibrated bin and was lwer than that in the vibrated bin (Fig. 3). A k-value f 0.4, determined frm the measured angle f internal frictin, was used in Janssen's predictin. The cmmnly accepted explanatin f increasing pres sure is the higher bulk density caused by vibratin (ASAE 1992a). The measured in-bin density was 797 kg/m3 with a standard deviatin (SD) f 14 kg/m3 befre vibratin, and 836 kg/m3 with a SD f7 kg/m after vibratin. This indi cated that the average bulk density increased 5% after vibratin. Because f grain cmpactin caused by vibratin, the grain surface was lwered by 50 mm, therefre, the ttal depth f grain decreased 3%. Accrding t Janssen's equa tin (Ketchum 1919), a 5% increase in bulk density wuld result in a 5% increase in lateral pressure at all depths, whereas a 3% decrease in grain depth wuld cause a 19% decrease in lateral pressure at the tp measuring level and 3% at the bttm. Therefre, the net change in lateral pressure wuld be -14% (decrease) at the tp level and +2% (increase) at the bttm level. The measured results did nt supprt the abve calculatins. This suggests that the bulk density in crease des nt fully explain the increased lateral pressure after vibratin. One pssible cause f increasing lateral pressure was the grain kernel re-rientatin induced by vibratin. Fr a nnspherical particle such as a wheat kernel in the gravitatinal field, the preferred rientatin is achieved when the lngest CANADIAN AGRICULTURAL ENGINEERING Vl. 36.N. I. January/February/March

4 (a) 1.4 Grain kernel 1.2 r 0.8 h 0.6 <d a Rankine nn vibrated vibrated 95% C.I Lateral t vertical pressure rati (k-value) (b) \ / Grain kernel Fig. 5. Lateral t vertical pressure ratis (k-values) btained by fitting average measured static lateral pressures t Janssen's equatin. Lateral expansin Fig. 4. A hypthetical spacial arrangement f grain kernels: (a) frce relatinship; and (b) tendency f lateral expansin during vibratin. axis cincides with the hrizntal directin. When wheat is placed int a bin, nt all kernels are in the preferred rienta tin. Vibratin tends t re-rient grain kernels t their preferred rientatin. This kernel re-rientatin induces a tendency fr lateral expansin within the grain mass, as illustrated in Fig. 4b fr a hypthetical situatin. Any lateral expansinis resisted by the bin wall, thus lateral pressuren the wall increases. Cnsiderthe hypthetical situatin shwn in Fig. 4a. A tw-kernel aggregate is subject t a vertical frce (Fv) frm a kernel abve it and is supprted by tw kernels underneath it. Frm the frce equilibrium equatin, the relatinship betweenthe verticalfrce, Fv,and the lateral frce, Ff can be written as: Fv Fh = 2tana h;i- wherea is the angle between the lngest axis f a kerneland a hrizntal plane. The lateral frce, F/,, increases with de creasing angle a as vibratin re-rients the kernels t their preferred psitin even if the vertical frce, Fv, remains cnstant. Many tw-kernel aggregates may exist in a grain bulk. The verall effect f increased hrizntal frces, F/,, frm all aggregates in the grain bulk is an increase in lateral pressure n the bin wall. Equatin 1 suggests that the lateral t vertical pressure rati (k-value) increases as vibratin re-rients kernels t the 32 (1) preferred rientatin. The measured static pressure data were fitted t Janssen's equatin (Ketchum 1919) t determine k-values at the six measuring levels. It was assumed that the cefficient f frictin between grain and the bin wall was cnstant and the vertical stress in the grain mass was unifrm acrss the bin diameter. The fitted k-value decreased frm the tp t the bttm befre and after vibratin. After vibratin, the k-value increased slightly in the upper prtin f the bin and significantly in the lwer prtin (Fig. 5). The k-value at the bttm level increased frm 0.32 t 0.45, r 41%. The k-value averaged ver all six measuring levels was 0.40 befre vibratin and 0.46 after vibratin, i.e., vibratin caused an increase f 15% in the average k-value. It was nticed that the average k-value befre vibratin was almst the same as the Rankine cefficient [(l-sin< >)/(l+sin< ))]. This implies that it may nt be apprpriate t use the Rankine lateral t vertical pressure rati fr bins which were pre viusly subject t vibratin. Vertical lad shifted frm the flr t the wall after the bin was vibrated. The increase in the vertical lad n the wall was 0.21 kn/m (frm 0.96 t 1.17 kn/m), r 22%, after vibratin. Effect f vibratin n dynamic lads during discharge Vibratin changes flwability f grain in the bin, thus affect ing dynamic lads during discharge. Fr the nn-vibrated bin, the lateral pressure in the lwer part f the bin increased sharply immediately after the discharge gate waspened and a slight pressure change was bserved at the tp level. Whereas, fr the vibrated bin, the lateral pressure in the lwer part f the bin stayed nearly cnstant and the pressure at the tp layer increased slightly at the initial stage f discharge (Fig. 6). Smaller increases in lateral pressure during dis charge in the vibrated bin mightbe attributed t the existence f a funnel flw mde, because grain was cnslidated by vibratin and became mre difficult t flw. An attempt was made t bserve the flw mde by inserting twenty 2-mm diameter and 45-mm lng steel rds int the grain mass thrugh small hles in the wall. The rdswereevenly placed at heights frm 197 t 1413 mm (measured frm the flr). HAO, ZHANG and BRITTON

5 Q_ JZ *~> 1_ 3 m w L. Q. " 2.0 i_ *- D Time (s) Nn-v!brated bin c.0 E fc CO Fig. 6. Typical measured dynamic lateral pressures n the bin wall at three depths during discharge. (Tp: 1152 mm frm the bin flr; Middle: 768 mm frm bin flr; and Bttm: 192 mm frm bin flr). Fig Nn-Vibrated Bin tlme=0 s tlme=1 s time=10 s 1.4 Vibrated Bin 1.2 tlme=0 s tlme=1 s time=10 s Lateral pressure (kpa) 8. Average measured lateral pressure prfiles at different stages f discharge. withut vibratin 1040 mm with vibratin Fig. 7. Observed flw regins at 10 s f discharge. Fr the nn-vibrated bin, all rds tilted frm the beginning f discharge, which indicated that grain near the wall mved and mass flw ccurred in the entire bin. Fr the vibrated bin, nt all rds tilted during discharge. Fr example, after the initial 10s (an arbitrarily chsen time), rds in the upper part (1150 mm abve the flr) tilted, whereas, rds in the lwer part did nt tilt until the grain depth became clse t r lwer than the elevatins f the measuring pints, which shwed that grain did nt mve alng the wall (funnel flw) in this regin. Schematics f flw regins cnstructed frm the bserved rd mvements are shwn in Fig. 7 fr a discharge time f 10s. At thisparticular time,the height f the stagnant grain regin in the vibrated bin was 11 % greater than that in the nn-vibrated bin. A greater regin f stagnant grain means a smaller mass flw regin and a smaller increase in lads (Gaylrd and Gay lrd 1984). The measured pattern f lateral pressure distributin agreed with the bservatins f flw mde. Fr the vibrated bin, the lateral pressure at the tp level increased at the beginning f discharge (1 s), while pressures at all ther levels stayed belw the static pressure all the time (Fig. 8). This demnstrated that mass flw ccurred nly in the tp prtin f the bin while funnel flw existed in the lwer prtin. Fr the nn-vibrated bin, lateral pressure increased nticeably in the lwer prtin f the bin at the beginningf discharge (1 s) (Fig. 8). As the pressure peak travelled up wards, pressures in all depths became higher than the static pressure (10 s). Figure 9 shws the measured vertical wall frce fr a typical frce transducer (the vertical frce measured by ne transducer was apprximately ne-third f the ttal vertical wall lad). Fr bth vibrated and nn-vibrated cnditins, the ttal vertical frce n the wall increased sharply when dis charge started, but the vertical frce fr the nn-vibrated bin increased mre (frm 0.30 t 0.40 kn/m, r 33%) than fr the vibrated bin (frm 0.36 t 0.40 kn/m, r 11 %). Regardlessf the higher static vertical frce fr the vibrated bin, the peak dynamic frces were almst the same fr bth bins apprxi mately 50 s after discharge (Fig. 9). Times f peak discharge lads Fr the vibrated bin, the time f peak lateral pressure varied frm 1 s at the tp measuring level (1152 mm frm the flr) t 54 s at the furth measuring level (576 mm frm the flr), and n pressure peak ccurred belw the furth measuring level (Table II). An ppsite trend was bserved fr the nn-vibrated bin. The lateral pressure reached the peak at the bttm earlierthan at the tp (TableII).The peak pressure at the lwest measuring level (192 mm frm the flr) ccurred later than the level abve it because the lwest measuring level was lcated belw the stagnant grain zne. Analysis f variance indicated that the time f peak lateral pressure fr the vibrated bin was significantly (a = 5) shrter in the CANADIAN AGRICULTURAL ENGINEERING Vl. 36, N. 1, January/February/March

6 Z J* W Fig. 9. ^tt TTVt 'IWI»l ^ ^it u -- nn-vibrated bin vibrated bin Time (s) Typical measured vertical frces frm ne transducer which was apprximately ne third fthe ttal vertical frce n the wall. Table II. Measured times f peak lateral pressures during discharge Measuring Height* Withut vibratin With vibratin Vibratin re-distributed vertical lad frm the bin flr t the wall. The ttal vertical frce n the bin wall increased frm 0.96 t 1.17 kn/m, r 22%. The bulk density and the average lateral t vertical pressure rati (k-value) increased 5% and 15%, respectively, after vibratin. This suggests that using a higher k-value in predicting vibratin induced lads might be mre imprtant than using a higher bulk density value. Fr the nn-vibrated bin, lateral pressure increased at all measuring levels (192 t 1152 mm frm the flr) during discharge. The maximum pressure was 1.43 times higher than that befre discharge, which ccurred at a measuring level 384 mm frm the flr. Fr the vibrated bin, pressure increases were negligible during discharge. Hwever, the maximum lateral pressure and vertical frce n the wall which the vibrated bin experienced were 3.78 kpa and 1.50 kn/m, respectively, slightly higher than thse experienced by the nn-vibrated bin (the nn-vibrated bin experienced a maximum pressure f 3.57 kpa and vertical frce f 1.42 kn/m). It was cncluded frm this study that lw amplitude vibra tin had significant effects n bth static and dynamic lads in grain strage bins. Further research shuld be cnducted t systematically investigate bin lads as affected by vibratin characteristics (e.g., frequency, amplitude, and directin), bin cnfiguratin, discharge rate, and prperties f stred grain. :vel (mm) Mean* (SD) Mean* (SD) (s) (s) (s) (s) (9.9) 1 (0.4) (2.9) 1 (0.6) (0.5) 25 (18.3) (0.5) 54 (24.4) () _* (9.4) J * Mean f fur replicatins + Measured frm the flr $ N pressure peak ccurred upper tw layers and lnger in the lwer layers than thse fr the nn-vibrated bin in the crrespnding layers. The time f peak vertical resultant frce was significantly affected (a =5) by vibratin. The vertical resultant frce reached the peak in 0.8 s fr the vibrated bin, which was 10 times faster than fr the nn-vibratin bin (8 s). SUMMARY AND CONCLUSIONS Static lads and dynamic lads during discharge were meas ured in a crrugated mdel bin 1.5 m high and m diameter filled with wheat at 12% wb misture cntent. The bin was vibrated fr 20 minutes in the vertical directin at a frequency f 30 Hz and amplitude f 10mm after it was filled. Vibratin induced significant increases in static lateral pressure in the lwer prtin f the bin. The lateral pressure at the bttm measuring level (192 mm abve the bin flr) increased frm 2.73 t 3.78 kpa, r 39%. Static lateral pressure in the upper prtin f the bin was nt significantly affected by vibratin. ACKNOWLEDGEMENT We thank the Natural Science and Engineering Research Cuncil f Canada fr the financial assistance and Westeel fr the supply f the mdel bin. REFERENCES ASAE. 1992a. ASAE EP433 - Lads exerted by free-flwing grain n bins. In ASAEStandards, 39th ed., St. Jseph, MI: ASAE. ASAE. 1992b. ASAE S Misture measurement - ungrund grain and seeds. In ASAE Standards, 39th ed., 404. St. Jseph, MI: ASAE. ASTM Natural building stnes: sil and rck. In Annual Bk fastm Standards, Part 19. Philadelphia, PA: American Sciety fr Testing and Materials. Atewlgun, A.O., G.L. Riskwski and N.L. Buck An in-mass transducer fr measuring the static pressure rati (k) in grain strage bins. Transactins f ASAE 35(5): Dale, A.C. and R.N. Rbinsn Pressure in deep grain strage structures. Agricultural Engineering 35(8): Duncan, W The field f measurement f the transmissin f vibratin frm railway traffic. In Grund Mvement and Structures, J.D. Geddes (ed), New Yrk, NY: Jhn Wiley & Sns. Gaylrd, E. H. and C. N. Gaylrd Design fsteel Bins fr Strage f Bulk Slids. Englewd Cliff, NJ: Prentice-Hill, Inc. 34 HAO. ZHANG and BRITTON

7 Ketchum, M.S The Design f Walls, Bins and Grain Newmark, N.M. and E. Rsenblueth Fundamentalsf Elevatrs. New Yrk, NY: McGraw-Hill Bk Earthquake Engineering. Englewd Cliffs, NJ: Prentice Cmpany, Inc. Hall Inc. Publisher. Mhsenin, N.N Physical Prperties f Plant and Zhang, Q., M.G. Brittn and R. Jaremek Discharge Animal Materials, 2nd ed. New Yrk, NY: Grdn and lads in smth and crrugated walled mdel bins fr Breach Science Publishers. wheat, barley and canla. ASAE Paper N St. Jseph, MLASAE. CANADIAN AGRICULTURAL ENGINEERING Vl. 36, N. 1, January/February/March