Finite Ele me nt Ana lysis o f Re a so na b le Fo und a tio n fo r Sup p o rting Silo ’ s To we r Sukima n Nurdin
283
4. Discussion
The a na lytic a l a nd num e ric a l d e sig n stud ie s we re b a se d o n the
sa m e d a ta inp ut. Ne ve rthe le ss b o th o f the m e tho d s usua lly p ro d uc e d iffe re nt
re sults.
4.1 Pa d Fo und a tio n Ac c o rd ing to the a na lytic a l
a nd num e ric a l p re d ic tio ns sho we d tha t the p a d fo und a tio n se e m s
unsa tisfa c to ry to sup p o rt the silo s. The re a re se ve ra l fa c to rs b a se o f
tho se re a so n. In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y
a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring
fa ilure is 1.92 whic h is lo we r tha n the limit va lue o f fa ilure
5 .
2
. In a d d itio n, a t the se c o nd la ye r o f so ils the va lue
o f fa c to r o f sa fe ty d e c re a se d to 1.36 whic h is unsa tisfa c to ry. And a t the
third a nd fo urth la ye r the va lue o f fa c to r o f sa fe ty wa s fluc tua te d to b e
1.63 a nd 1.52 re sp e c tive ly.
The num e ric a l re sult a na lysis a p p e a rs tha t the va lue o f fa c to r o f
sa fe ty a g a inst b e a ring fa ilure slig htly lo we r tha n the a na lytic a l m e tho d . The
fa c to r o f sa fe ty wa s p ro d uc e d b y num e ric a l a na lysis o f 1.25 tha t it is
lo we r tha n the limit va lue o f fa c to r o f sa fe ty. It c a n b e c o nc lud e tha t
num e ric a l m e tho d p ro d uc e s lo we r re sults tha n a na lytic a l d e sig n.
The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d
tha t the se ttle m e nt se e m e d a p ro b le m in the p a d fo und a tio n. It c a n
b e se e n fro m Ta b le 10 tha t the a na lytic a l a nd num e ric a l re sults
p re se nt the se ttle m e nt a b o ut 122m m a nd 41m m re sp e c tive ly. Whic h is the
se ttle m e nt is in c ritic a l c o nd itio n. In a d d itio n, the d iffe re nc e se ttle m e nt
p ro vid e s b y a na lytic a l m e tho d is a p p ro xim a te ly 71.04m m , tha t is c a n
c a use the c ra c k o n the to p o f fo und a tio n a nd will im p a c t the
sta b ility o f the silo s. Whe n the p a ra m e tric stud y b e e n p ro c e ss to
d e c re a se a nd inc re a se o f the stre ng th o f the so il, a c ha ng e o f
se ttle m e nt b y b o th stud y a re 17 a nd 20 re sp e c tive ly, whe re it se e m e d no t
re a lly im p o rta nt e ffe c t o f the se ttle m e nts a s sho wn in ta b le 10 a nd
fig ure 6 a nd 7.
As the lo w o f fa c to r o f sa fe ty in c a se o f p a d fo und a tio n d e sig n, it
se e m s tha t so m e fa c to r c o uld b e a p ro b le m in the te rm o f the p a d
fo und a tio n b e e n a p p lie d . First, p la stic d e fo rm a tio n mig ht b e p re se nt d ue to
the inc o nsiste nc y o f the fa c to r o f sa fe ty in se ve ra l la ye rs, le a d ing to
m o ve m e nt o f the fo und a tio n g re a te r tha n se ttle m e nts; in e xtre m e c a se
fa ilure will o c c ur.
Ano the r p ro b le m tha t c o uld b e o c c ur a nd sho uld b e ta ke n und e r
c o nsid e ra tio n is the no n-unifo rm p la c e m e nt o f fill d uring filling . Whe n
the lo a d fro m the c o nte nt a nd the silo s is o ff c e ntre , a s the re sult, the
p re ssure b ulb will b e d iso rd e r, a s sho wn in fig ure 2. Stro ng wind s a c ting
o n ta ll silo c a n p ro d uc e the sa m e e ffe c t. The lo c a l o ve rstre ssing o f the
fo und a tio n so il m a y c a use tilting , a nd unle ss the p ro b le m is re m e d ie d it m a y
inc re a se with tim e until the silo o ve rturns.
If two o r m o re silo s a re c o nstruc te d to o c lo se to e a c h o the r,
c o nse q ue ntly, the p re ssure b ulb will o ve rla p , a s sho wn in fig ure 3. Be c a use
o f p re ssure a re a d d itive , the re sulting p re ssure b ulb will b e m uc h la rg e r a nd
will e xte nd to g re a te r d e p ths. In the o ve rla p zo ne , the so il will b e
sub je c te d to hig he r stre sse s a nd the fo und a tio n in this re g io n will b e
se ttling m o re , c a using the silo s to tilt to wa rd e a c h o the r.
Jurna l SMARTe k, Vo l. 9 No . 4. No p e m b e r 2011: 271 - 286
284 The c o nstruc tio n c o st fo r the p a d
fo und a tio n will b e ve ry e xp e nsive , b e c a use it is re q uire d la rg e a m o unt o f
c o nc re te a nd lo ng tim e c o nstruc tio n p ro c e ss. It is a lso re q uire d a d va nc e o f
site inve stig a tio n to se c ure o f sta b ility o f the silo s in lo ng -te rm p e rio d . And
the sp a c e c o uld b e a p ro b le m fo r c o nstruc ting the p a d in the site d ue to
the limita tio n o f the a re a .
4.2 Strip Fo und a tio n As c a n b e e n se e n fro m the
a na lytic a l a nd num e ric a l p re d ic tio ns, tha t sho we d the strip fo und a tio n
se e m s fe a sib le to sup p o rt the silo s in te rm o f fa c to r o f sa fe ty. The re a re
se ve ra l fa c to rs b a se o f tho se re a so n. In te rm o f b e a ring c a p a c ity fa c to r
p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty
a g a inst b e a ring fa ilure is 4.2 whic h is sa tisfa c to ry. In a d d itio n, a t the se c o nd
la ye r o f so ils the va lue o f fa c to r o f sa fe ty d e c re a se d to 3.0 whic h is
sa tisfa c to ry. And a t the third a nd fo urth la ye r the va lue o f fa c to r o f
sa fe ty wa s c o nsiste nc e d e c re a se in 3.6 a nd 3.5 re sp e c tive ly. Ho we ve r, the
num e ric a l re sult a na lysis a p p e a rs tha t the va lue o f fa c to r o f sa fe ty a g a inst
b e a ring fa ilure lo we r tha n the a na lytic a l m e tho d . The fa c to r o f
sa fe ty wa s p ro d uc e d b y num e ric a l a na lysis a p p ro xim a te ly 2.6 tha t it is
ne a r to the limit va lue o f fa c to r o f sa fe ty o f 2.5. It se e m s tha t the
num e ric a l m e tho d p ro d uc e s lo we r re sults tha n a na lytic a l d e sig n.
The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d
tha t the se ttle m e nt is b ig c a se tha t re a lly a p ro b le m in te rm o f strip
fo und a tio n b e e n a p p lie d . It c a n b e se e n fro m Ta b le 12 tha t the a na lytic a l
a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 137m m a nd 98m m
re sp e c tive ly. Whic h is the se ttle m e nt is in c ritic a l c o nd itio n. In o the r ha nd , the
d iffe re nc e se ttle m e nt sho we d b y a na lytic a l m e tho d is ve ry hig h tha t it is
a p p ro xim a te ly 85m m , tha t it is c a n c a use the c ra c k o n the to p o f
fo und a tio n a nd will im p a c t the sta b ility o f the struc ture o f the silo s. In
e xtre m e c a se c a n c a use the fa ilure o f the silo s.
As the hig h o f the se ttle m e nt a nd the d iffe re nc e se ttle m e nt
p re d ic te d in strip fo und a tio n d e sig n, it c a n b e c o nc lud e tha t the strip
fo und a tio n unfe a sib le fo r the silo s. Furthe rm o re , nine silo s b uild in the ro w
re q uire s la rg e o f sp a c e a lo ng the d o c ks, unfo rtuna te ly, lim ite d sp a c e is
a p ro b le m in the site d ue to e xisting struc ture .
The c o nstruc tio n c o st fo r the strip fo und a tio n will b e ve ry
e xp e nsive , b e c a use it is re q uire d la rg e a m o unt o f c o nc re te a nd lo ng tim e
c o nstruc tio n p ro c e ss. It is a lso re q uire d a d va nc e o f site inve stig a tio n to
se c ure o f sta b ility o f the silo s in lo ng - te rm p e rio d .
4.3 Pile Fo und a tio n Ac c o rd ing to the a na lytic a l
re sult tha t p ile fo und a tio n is fe a sib le fo r the silo s, whic h the se ttle m e nt
p re d ic te d is a p p ro xim a te ly 21m m tha t is c a n b e ne g le c te d , So tha t the
re sults o b ta ine d p ro ve tha t the p ile fo und a tio n is c o nsid e re d to the m o st
fe a sib le c ho ic e fo r sup p o rt the silo s. Furthe rm o re , the num e ric a l
p re d ic tio ns sho we d a s sa m e a s a na lytic a l p re d ic tio n tha t the p ile
fo und a tio n se e m s sa tisfa c to ry to sup p o rt the silo s. In the o the r ha nd ,
c he c king b y Euro c o d e tha t a ll the c o nd itio ns ha d b e e n sa tisfie d fo r the
sa fe ty o f the struc ture . Tha t m e a ns tha t the little d iffe re nc e in p re d ic tio n
b e twe e n num e ric a l a nd a na lytic a l is no t re a lly sig nific a nt tha t c a n a ffe c t
Finite Ele me nt Ana lysis o f Re a so na b le Fo und a tio n fo r Sup p o rting Silo ’ s To we r Sukima n Nurdin
285 the struc ture . It c o uld b e c o nc lud e a s
sa tisfa c to ry. In te rm o f b e a ring c a p a c ity
fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f
fa c to r sa fe ty a g a inst b e a ring fa ilure is 2.73 whic h is hig he r tha n the limit
va lue tha t ha ve b e e n g ive n
5 .
2 .
Ho we ve r, a t the p ile g ro up a na lysis, the va lue o f fa c to r o f sa fe ty is ve ry
hig h a p p ro xim a te ly 9.6 whic h it is sa tisfa c to ry. In o the r ha nd , num e ric a l
p re d ic tio n is ra the r p e ssim istic whe re the fa c to r o f sa fe ty wa s p re se nte d
a p p ro xim a te ly 1.75. The fa c to r tha t c a use d the lo w o f fa c to r sa fe ty
p ro d uc e b y num e ric a l c o uld b e the la c k o f so il info rm a tio n tha t p re se nte d
a nd the c o nse rva tive a ssum p tio n tha t b e e n c ho se n in o rd e r to c a rry o ut the
d e sig n p ro c e d ure . In a d d itio n, the g ro und wa te r le ve l wa s b e e n ta ke n
ra the r c o nse rva tive , while it ha s im p o rta nt e ffe c t o n ultim a te b e a ring
c a p a c ity o f fo und a tio n. With the hig h g ro und wa te r le ve ls, the e ffe c tive
stre sse s in the g ro und a re lo we r tha n whe n the so ils im m e d ia te ly b e lo w the
fo und a tio n a re d ry, a nd the ultim a te b e a ring c a p a c ity is re d uc e d .
The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d
tha t the se ttle m e nt is no t re a lly a p ro b le m in the p ile fo und a tio n. It c a n
b e se e n fro m Ta b le 14 tha t the a na lytic a l a nd num e ric a l re sults
p re se nt the se ttle m e nt a b o ut 21m m a nd 19.1m m re sp e c tive ly. Whic h it is
c a n b e ne g le c te d . The d iffe re nc e a b o ut the p re d ic tio n o f the
se ttle m e nt a na lysis b y b o th m e tho d s is a p p ro xim a te ly 10.
Ma ny typ e s o f p ile fo r sup p o rt the silo s struc ture a re a va ila b le . Drive n
a nd c a st in p la c e s p ile s a re e c o no m ic a l fo r la nd struc ture . But the
g ro und he a ve a nd the vib ra tio n a sso c ia te d with the insta lla tio n c a n
c a use d e sta b iliza tio n o f q ua y wa ll. Bo re d a nd c a st in the p la c e a re the
c he a p e st typ e s o f the p ile , whic h it is p o ssib le to b e c ho se n b e c a use it will
ke e p the c o st o f fo und a tio n e ffic ie ntly.
The c o nstruc tio n c o st fo r the p ile fo und a tio n will b e c he a p e r tha n
o the r typ e s o f fo und a tio n, b e c a use it is no t re q uire d la rg e a m o unt o f
c o nc re te a nd sho rt tim e c o nstruc tio n p ro c e ss.
5. Conclusion
