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Volume 4, Issue 9, September 2014 ISSN: 2277 128X

International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: www.ijarcsse.com

Studies on Economical Design of Bunkers N. Karthiga Shenbagam, Mahesh., Loganayagan. S, N. V. Manjunath, A. S. Ramesh

Assistant Professor Department of Civil Engineering Bannari Amman Institute of Technology, Sathamangalam,

Erode, Tamilnadu, India

Abstract: In order to study the most economical configuration of bunkers to store a given volume of a material, one

hundred and forty five bunkers have been designed by changing the ratio of height to lateral dimensions for storing a

given material, namely, bituminous coal. In this investigation, for each volume, i.e., for 100m3 the length to breadth

ratio is taken constant as 1, 1.2, 1.4, 1.6, 1.8 and 2 and, for each length by breadth ratio, four bunkers having different

breadth by depth ratio have been designed and finally, the most economical size is found out. This method is carried

out for volumes of 120m3, 140m3, 160m3, 180m3, and 200m3also. A program has been developed using C-language

for the design of bunkers, columns and footings and all the bunkers have been designed using this program. All the

designs have been based on the recommendations of I.S 4995 -1974 and I.S 456 – 2000 codes. Based on these designs,

those dimensions of bunkers which will lead to least amount of concrete, steel and total cost to store a given amount of

material have been found out. These findings will be useful for the designers of bunkers.

Keywords: Bunkers, length to breadth ratio, lateral dimensions, bituminous coal, total cost, most economical.

I. INTRODUCTION

Bins are used by a wide range of industries to store bulk solids in quantities ranging from a few tonnes to over one

hundred thousand tones. A bin is an upright container for the storage of bulk granular materials. Shallow bins are usually

called as bunkers and deep bins are usually called as silos. If the depth and breadth of a bin are such that the plane of

rupture meets the surface of the material, before it strikes the opposite side of the bin, it is called a shallow bin or a

bunker. Hopper of bins is four sloping slabs. Bunkers are made from many different structural materials. They can be

constructed of steel or reinforced concrete and may discharge by gravity flow or by mechanical means. Steel bins range

from heavily stiffened flat plate structures to efficient unstiffened shell structures. They can be supported on columns,

load bearing skirts, or they may be hung from floors. Bins with flat bottom are usually supported directly on foundations.

Reinforced concrete is an ideal structural material for the building of permanent bulk-storage facilities for dry

granular like fillings. Initially concrete storage units are economical in design and reasonable in cost. Concrete can offer

the protection to the stored materials, requires little maintenance, is aesthetically pleasing, and is relatively free of certain

structural hazards (such as buckling or denting).

GENERAL CHARACTERISTICS:

Concrete storage units can be designed and built in any shape and size to fit the site or the process for which

they are required. They can be poured monolithically by the use of sliding forms when the walls are high, in single lifts

when they are low, and in rapidly following lifts of fixed forms when they are of moderate height.

OBJECTIVE OF THIS INVESTIGATION:

The main objective of the investigation reported herein is to identify the most economical size of bunkers to

store for a given volume of material.

SCOPE OF THE INVESTIGATION:

The volume of bunkers is varied from 100 m3 to 200 m

3. The material to be stored is taken as bituminous coal,

having an angle of internal friction of 35o and unit weight of 8 kN/m

3.For storing a given volume of material, the effect

of the ratio of height to lateral dimension on the total cost has been studied in depth. The provision of IS: 4995(Part1)-

1974 (Criteria for design of Reinforced Concrete Bins for Storage of Granular and Powdery Materials), IS: 4995(Part II)-

1974 (Criteria for design of Reinforced Concrete Bins for Storage of Granular and Powdery Materials), and IS: 456-2000

(Code of Practice for Plain and Reinforced Concrete) are made use of whenever required. Concrete grade of M20 and

steel of Fe 415 grade are used throughout the investigation for design of bunkers.

ETHODOLOGY:

A program has been developed using C-language for the design of bunkers, columns and footings and all the bunkers

have been designed using this program. All the designs have been based on the recommendations of I.S 4995 -1974 and

I.S 456 – 2000 codes. Estimation of cost of bunkers and its supporting structures are done by using Microsoft excel.

http://www.ijarcsse.com/

Shenbagam et al., International Journal of Advanced Research in Computer Science and Software Engineering 4(9),

September - 2014, pp. 417-429


II. DESIGN CONSIDERATION:

The design process for bunkers is of two types – functional and structural, functional design must provide for adequate

volume, proper protection of the stored materials, and satisfactory methods for filling and discharge. Structural

considerations are stability, strength and control (minimizing) of crack width and deflection. Loads to be considered

include the following:

1. Dead load of the structure itself and items supported by the structure.

2. Live Load forces are taken based on the type of material stored.

Bin design procedures consist of four parts as follows:

i. Determine the strength and flow properties of the bulk solid.

ii. Determine the bin geometry to give the desired capacity, to provide a flow pattern with acceptable flow characteristics

and to ensure that discharge is reliable and predictable. Specialised mechanical feeder design may be required.

iii. Estimate the bin wall loads from the stored material and other loads such as wind, ancillary equipment, thermal, etc.

iv. Design and detail the bin structure.

Before the structural design can be carried out, the loads on the bin must be evaluated. Loads from the stored material are

dependent, amongst other things, on the flow pattern, the properties of the stored material and the bin geometry while the

methods of structural analysis and design depend upon the bin geometry and the flow pattern. The importance of Stages i

and ii of the design should not be underestimated. Simplified rules for the functional design of bins and for estimating

wall loads are given in IS 4995-1974.

Design Example:

Volume of bunker =100m3

Dimension of bunker:

Adopt a bunker size 5.35x5.35x2.5m with the depth of 1.2m hopper bottom.

Height of surcharge = =

=1.87m.

Check for volume:

Volume of surcharge =

V1= =17.5m3.

Volume of cylindrical portion = a*b*h.

V2=5.35*5.35*2.5=71.42 m3.

Volume of hopper bottom portion, V3

V3 =

=

V3=11.35 m3.

V=100.27 m3. 100 m

3.

As per IS 4995(part 1)-1974, table 1, the density of bituminous coal is 8kN/m3 and angle of repose is 35°.

Design of Side walls:

Horizontal working pressure p= whcos2φ

p= 8*5.35 cos235=28.71 kN/m

2

Assume the thickness of side wall =230mm.

Effective span =5.35+0.23=5.58m.

L=B

Maximum bending moment at corners is

M=p (L2+B

2-LB)/12 =p (L

2)/12 =(28.71*5.35

2)/12=68.47kNm.

Ultimate design moment, Mu=1.5*68.47

=102.72kNm.

Direct tension in wall,

T=pB/2 (for longer wall)

T=pL/2 (for shorter wall)

T=28.71*(5.35/2)=76.79kN.

Ultimate direct tension in wall, Tu

Tu=1.5*76.79=115.18kN.

Providing a cover of 30mm,

Providing effecting depth=230-30=200mm.

Distance between reinforcement of slap, x=85mm.

Net design moment = Mu-Tu*x

=102.72-(115.18*0.085)=92.93kNm.


September - 2014, pp. 417-429


Based on limiting moment resistance, effective depth required is given by

D= =

=183.5mm <200mm.

Since the depth provided is more. The section is under reinforced. Hence the area of steel required is,

Mu=0.87fyAstd {1-Astfy/bdfck}

92.93*106=0.87*415*A

st*183.5{1-A

st*415/1000*183.5*20}

Ast=1748.18mm2.

Provide 12mm Φ bars,

Ast= mm2.

Spacing S= =

Hence provide 12mmΦ bars at 50mm c/c.

Positive bending moment at centre of span

=

=34.23kNm.

Design ultimate moment=1.5*34.23=51.35kNm.

Mu-Tu*x

=51.35-(115.18*0.085)=41.597kNm

Hence the area of steel required to resist the moment is


41.597*106=0.87*415*A

st*183.5{1-A

st*415/1000*183.5*20}

Ast=680.15mm2.


Ast= mm2.

Spacing S= = 0

Provide 12mm Φ bars at 150mm c/c

Distribution reinforcement = 0.12%bD

=0.0012*1000*210 =252mm2.

Use 8mm Φ bars,

ast= mm2.

Spacing S= =

Hence provide 8mm Φ bars at 175mmc/c

Design of hopper bottom:

Weight of bituminous coal = W=wV

=8*100=800kN.

Weight of sloping hopper bottom (210mm) thick is computed as

Wh=(5.35+0.5/2)√(2.4252+1.5

2)*(4*0.21*25

=287.16kN.

Total load on 4 walls

=800+287.16=1087.16kN

Total load on one wall

=1087.16/4=271.79kN.

Then tanθ =1.5/2.425

Θ=tan-1

(1.5/2.425)=31.74 and cosecθ=1.9

Direct tension in sloping wall = Wtcosecθ

= 340.71×1.9

= 565.58 × 58 KN

Working tension per meter run = 647.349 /5.35

=120.9 KN/m run

Design of ultimate tension = 1.5 × 120.9

= 181.499 KN

Area of reinforcement for resisting direct tension is,


September - 2014, pp. 417-429


Ast = (181.499×103 ) / (0.87 ×415)

= 502.69mm2

Spacing S, = ast / Ast × 100

= (120.9/502.69) ×1000

= 240.45 mm

Provide 12mm Φ bars @ 225 mm c/c in the direction of sloping faces

Ast = ast / s × 1000

Ast = (120.9 / 225) × 1000

= 537.3.2mm2

Normal component of coal pressure @ centre of slab is,

Pn = w.hp [cos2 θ + cos

2 φ. Sin

2 θ]

Where,

W = 8 KN/m2

hp = [5.35 + (0.5 × 1.5 ) + (0.5 × 1.87) ]

hp = 6.95 m

θ = 37.07 ° & φ = 35

°

Pn = 8 × 6.95 [cos 2 37.07 + cos

2 35. Sin

2 37.07]

= 48.78 KN/ m2

Working pressure = Pn = 848.78 KN/ m2

Normal component due to weight of sloping slab,

= wd. cos θ

= 0.21 × 25 cos 37.07

= 4.19 KN / m2

Total normal pressure P = Pn + wd. Cos θ

P = 48.78 + 4.19

P = 52.97 KN / m2

Effective Design moment, L1 = ((5+0.5) / 2) + 0.21 = 2.96m

Maximum negative bending moment, M

= P. (L1 2 + B1

2 -L1B1)/12

=pL12/12=52.97*2.96

2/12=38.67kNm

Ultimate design moment=1.5*38.67

=58kNm.

Limiting moment of resistance, Mu limit

=0.138fckbd2=0.138*20*1000*176.65

2.

=86.13kNm>58kNm.

Since Mu<Mulimit

The section is under reinforced section.


58*106=0.87*415*A

st*183.5{1-A

st*415/1000*183.5*20}

Ast=985.15mm2.


Ast= mm2.

Spacing S= = 0


Maximum positive bending moment at centre is = P. (L1 2 +-2B1

2 +2L1B1)/12

= (52.97*2.7252)/12=32.77kNm

Ultimate bending moment = 1.5*32.77

=49.17kNm.

Area of reinforcement steel required is


49.17*106=0.87*415*A

st*183.5{1-A

st*415/1000*183.5*20}

Ast=810.6mm2.


Ast= mm2.

Spacing S= = 0



September - 2014, pp. 417-429


Edge beams:

Provide edge beams of 300x300mm connecting the corner columns as the top and the junction of vertical walls and

sloping slab with 4 numbers of 12mm Φ bars.

volume h a/b ratio h/b ratio a b

100 2.5 1.0 0.5 5.35 5.35

100 4.3 1.0 1.0 4.40 4.40

100 5.8 1.0 1.5 3.86 3.86

100 7.1 1.0 2.0 3.54 3.54


100 2.3 1.2 0.5 6.00 4.90

100 4.0 1.2 1.0 4.90 4.10

100 5.4 1.2 1.5 4.30 3.70

100 6.6 1.2 2.0 4.00 3.30


100 2.4 1.4 0.5 6.20 4.50

100 4.0 1.4 1.0 5.20 3.80

100 5.1 1.4 1.5 4.80 3.40

100 6.30 1.4 2.0 4.35 3.12


100 2.2 1.6 0.5 6.80 4.20

100 3.5 1.6 1 5.80 3.70

100 4.9 1.6 1.5 5.20 3.20

100 5.90 1.6 2.0 4.75 3.00


100 1.89 1.8 0.5 7.45 4.10

100 3.5 1.8 1.0 6.20 3.40

100 4.6 1.8 1.5 5.60 3.10

100 5.8 1.8 2.0 5.00 2.85


100 2.05 2.0 0.5 7.60 3.80

100 3.3 2.0 1.0 6.60 3.30

100 4.4 2.0 1.5 5.90 3.00

100 5.5 2.0 2.0 5.50 2.70

TABLE 1

TABLE 2

TABLE 3

TABLE 4

TABLE 5

TABLE 6


September - 2014, pp. 417-429



120 2.9 1.0 0.5 5.50 5.50

120 4.4 1.0 1.0 4.40 4.40

120 6.1 1.0 1.5 4.15 4.15

120 7.42 1.0 2.0 3.80 3.80


120 2.75 1.2 0.5 6.00 5.20

120 4.4 1.2 1.0 5.20 4.25

120 5.7 1.2 1.5 4.72 3.80

120 7.0 1.2 2.0 4.20 3.58


120 2.5 1.4 0.5 6.70 4.80

120 3.9 1.4 1.0 5.80 4.10

120 5.4 1.4 1.5 5.10 3.60

120 6.5 1.4 2.0 4.76 3.30


120 2.4 1.6 0.5 7.20 4.50

120 3.8 1.6 1.0 6.20 3.90

120 5.1 1.6 1.5 5.60 3.40

120 6.3 1.6 2.0 5.05 3.20


120 2.3 1.8 0.5 7.60 4.30

120 3.8 1.8 1.0 6.50 3.66

120 4.9 1.8 1.5 6.00 3.25

120 6.1 1.8 2.0 5.50 3.00


120 2.1 2.0 0.5 8.20 4.10

120 3.6 2.0 1.0 6.90 3.50

120 4.7 2.0 1.5 6.32 3.20

120 5.9 2.0 2.0 5.75 2.90

TABLE 7

TABLE 8

TABLE 9

TABLE 10

TABLE 11

TABLE 12


September - 2014, pp. 417-429



140 2.8 1.0 0.5 6.00 6.00

140 4.9 1.0 1.0 4.90 4.90

140 6.6 1.0 1.5 4.30 4.30

140 7.8 1.0 2.0 4.00 4.00


140 2.8 1.2 0.5 6.50 5.40

140 4.6 1.2 1.0 5.50 4.50

140 6.0 1.2 1.5 4.99 4.00

140 7.4 1.2 2.0 4.40 3.80


140 2.8 1.4 0.5 6.90 5.10

140 4.4 1.4 1.0 6.00 4.20

140 5.6 1.4 1.5 5.50 3.80

140 7.0 1.4 2.00 4.94 3.50


140 2.4 1.6 0.5 7.80 4.80

140 4.2 1.6 1.0 6.50 4.00

140 5.5 1.6 1.5 5.80 3.60

140 6.9 1.6 2 5.35 3.25


140 2.4 1.8 0.5 8.18 4.43

140 4.0 1.8 1.0 6.84 3.85

140 5.2 1.8 1.5 6.20 3.50

140 6.4 1.8 2.0 5.75 3.20


140 2.3 2.0 0.5 8.60 4.25

140 3.6 2.0 1.0 7.50 3.70

140 5.0 2.0 1.5 6.70 3.30

140 6.1 2.0 2.0 6.10 3.10

TABLE 13

TABLE 14

TABLE 15

TABLE 16

TABLE 17

TABLE 18


September - 2014, pp. 417-429



160 3.2 1.0 0.5 6.10 6.10

160 5.2 1.0 1.0 5.10 5.10

160 7.0 1.0 1.5 4.50 4.50

160 8.2 1.0 2.0 4.19 4.19


160 3.0 1.2 0.5 6.70 5.80

160 4.8 1.2 1.0 5.60 4.86

160 6.3 1.2 1.5 5.20 4.20

160 7.8 1.2 2.0 4.60 4.00


160 2.9 1.4 0.5 7.28 5.30

160 4.4 1.4 1.0 6.45 4.45

160 5.8 1.4 1.5 5.75 4.00

160 7.3 1.4 2.0 5.15 3.70


160 2.5 1.6 0.5 7.90 5.20

160 4.4 1.6 1.0 6.75 4.20

160 5.8 1.6 1.5 6.00 3.80

160 6.8 1.6 2.0 5.75 3.49


160 2.5 1.8 0.5 8.60 4.70

160 4.1 1.8 1.0 7.20 4.10

160 5.4 1.8 1.5 6.50 3.70

160 6.7 1.8 2.0 5.95 3.40


160 2.3 2.0 0.5 9.00 4.60

160 4.0 2.0 1.0 7.78 3.80

160 5.2 2.0 1.5 7.00 3.50

160 6.3 2.0 2.0 6.55 3.20

TABLE 19

TABLE 20

TABLE 21

TABLE 22

TABLE 23

TABLE 24


September - 2014, pp. 417-429



180 3.3 1.0 0.5 6.40 6.40

180 5.4 1.0 1.0 5.30 5.30

180 7.0 1.0 1.5 4.75 4.75

180 8.8 1.0 2.0 4.30 4.30


180 3.1 1.2 0.5 7.00 6.00

180 5.0 1.2 1.0 5.90 5.02

180 6.5 1.2 1.5 5.40 4.40

180 8.2 1.2 2.0 4.90 4.00


180 2.8 1.4 0.5 7.70 5.70

180 4.8 1.4 1.0 6.45 4.70

180 6.1 1.4 1.5 5.90 4.20

180 7.8 1.4 2.0 5.35 3.80


180 2.8 1.6 0.5 8.20 5.20

180 4.4 1.6 1.0 7.20 4.40

180 6.0 1.6 1.5 6.25 4.00

180 7.2 1.6 2 5.80 3.70


180 2.6 1.8 0.5 8.90 4.90

180 4.4 1.8 1.0 7.50 4.20

180 5.7 1.8 1.5 6.80 3.80

180 7.1 1.8 2.0 6.20 3.50


180 2.5 1.9 0.5 9.20 4.80

180 4.1 2.0 1.0 8.10 4.00

180 5.5 2.0 1.5 7.20 3.62

180 6.7 2.0 2.0 6.75 3.30

TABLE 25

TABLE 26

TABLE 27

TABLE 28

TABLE 29

TABLE 30


September - 2014, pp. 417-429



200 3.5 1.0 0.5 6.55 6.55

200 5.6 1.0 1.0 5.50 5.50

200 7.4 1.0 1.5 4.90 4.90

200 9.0 1.0 2.0 4.50 4.50


200 3.3 1.2 0.5 7.40 6.00

200 5.0 1.2 1.0 6.40 5.20

200 7.1 1.2 1.5 5.40 4.60

200 8.5 1.2 2.0 5.00 4.20


200 3.0 1.4 0.5 7.90 5.85

200 4.9 1.4 1.0 6.80 4.80

200 6.3 1.4 1.5 6.20 4.30

200 8.0 1.4 2.0 5.50 4.00


200 2.9 1.6 0.5 8.50 5.40

200 4.7 1.6 1.0 7.40 4.50

200 6.2 1.6 1.5 6.57 4.10

200 7.5 1.6 2.0 6.10 3.79


200 7.8 1.8 2.2 6.30 3.50

200 8.6 1.8 2.5 6.00 3.40

200 8.9 1.8 2.7 6.00 3.30

200 9.6 1.8 3.0 5.80 3.20


200 7.4 2.0 2.2 6.72 3.40

200 7.9 2.0 2.4 6.60 3.30

200 8.5 2.0 2.6 6.40 3.20

200 9.1 2.0 2.9 6.20 3.10

TABLE 31

TABLE 32

TABLE 33

TABLE 34

TABLE 35

TABLE 36


September - 2014, pp. 417-429


III. COST COMPARISON OF R.C.C BUNKERS WITH VARIOUS H/B RATIO

For the purpose of cost comparison, the rates are adopted as per the prevailing rates at Sathyamangalam during the period

of October 2011 and the rates are given below

Rate of concrete: Rs.5000 per m3.

Rate of Steel: RS.50 per kgf.

Rate of Formwork: Rs. 150 per m2.


September - 2014, pp. 417-429


8 nos of 32 mm dia @ 125mm c/c

275

275

Dwg 1: Column details.

300

4000

180

16 mm dia bars

@200 mm c/c

16 mm dia bars

@150 mm c/c

16 mm dia bars

@100 mm c/c

16 mm dia bars

@200 mm c/c

Dwg 2: Bunker reinforcement details

32 mmm dia bars @250 mm c/c

3000

275

500425

Dwg 3: Foundation details.


September - 2014, pp. 417-429


IV. CONCLUSION

From the above Figures it is concluded that for storing Bituminous coal for various volumes from 100m3 t 200m

3 the

most economical h/b ratio of 0.5 and l/b ratio of 1 is found to be economical. As the ratio of h/b ratio increases the total

cost of construction of the storage structure also increases.

ACKNOWLEDGEMENT

The authors thank the Management and the Principal, and the HOD of Bannari Amman Institute of Technology,

Sathyamangalam.

REFERENCES

[1] “N.Krishna Raju”, Advanced Reinforced Concrete Structures.

[2] “Bhavikatti.V”, Advanced Reinforced Concrete Structures.

[3] “O.P Jain and Jai Krishna” Plain and reinforced Concrete Volume-II.

[4] IS: 4995(Part1)-1974 (Criteria for design of Reinforced Concrete Bins for Storage of Granular and Powdery

Materials),

[5] IS: 4995(Part II)-1974 (Criteria for design of Reinforced Concrete Bins for Storage of Granular and Powdery

Materials).

[6] IS: 456-2000 (Code of Practice for Plain and Reinforced Concrete)

Documents

Studies on Economical Design of Bunkers - IJARCSSEijarcsse.com/Before_August_2017/docs/papers/Volume_4/9_September...from heavily stiffened flat plate structures to efficient ... strength