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

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1 Volume 4, Issue 9, September 2014 ISSN: X International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: 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 100m 3 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 200m 3 also. 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 and I.S 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 m 3 to 200 m 3. The material to be stored is taken as bituminous coal, having an angle of internal friction of 35 o 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) (Criteria for design of Reinforced Concrete Bins for Storage of Granular and Powdery Materials), IS: 4995(Part II) (Criteria for design of Reinforced Concrete Bins for Storage of Granular and Powdery Materials), and IS: (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 and I.S codes. Estimation of cost of bunkers and its supporting structures are done by using Microsoft excel. 2014, IJARCSSE All Rights Reserved Page 417

2 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 Design Example: Volume of bunker =100m 3 Dimension of bunker: Adopt a bunker size 5.35x5.35x2.5m with the depth of 1.2m hopper bottom. Height of surcharge = = Check for volume: Volume of surcharge = =1.87m. V 1 = =17.5m 3. Volume of cylindrical portion = a*b*h. V 2 =5.35*5.35*2.5=71.42 m 3. Volume of hopper bottom portion, V 3 V 3 = = V 3 =11.35 m 3. V= m m 3. As per IS 4995(part 1)-1974, table 1, the density of bituminous coal is 8kN/m 3 and angle of repose is 35. Design of Side walls: Horizontal working pressure p= whcos 2 φ p= 8*5.35 cos 2 35=28.71 kn/m 2 Assume the thickness of side wall =230mm. Effective span = =5.58m. L=B Maximum bending moment at corners is M=p (L 2 +B 2 -LB)/12 =p (L 2 )/12 =(28.71* )/12=68.47kNm. Ultimate design moment, M u =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, T u 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 = M u -T u *x = (115.18*0.085)=92.93kNm. 2014, IJARCSSE All Rights Reserved Page 418

3 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, M u =0.87f y A st d {1-A st f y /bdf ck } 92.93*10 6 =0.87*415*A st *183.5{1-A st *415/1000*183.5*20} A st = mm 2. Provide 12mm Φ bars, A st = mm 2. 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. M u -T u *x =51.35-(115.18*0.085)=41.597kNm Hence the area of steel required to resist the moment is M u =0.87f y A st d {1-A st f y /bdf ck } *10 6 =0.87*415*A st *183.5{1-A st *415/1000*183.5*20} A st =680.15mm 2. Provide 12mm Φ bars, A st = mm 2. Spacing S= = 0 Provide 12mm Φ bars at 150mm c/c Distribution reinforcement = 0.12%bD =0.0012*1000*210 =252mm 2. Use 8mm Φ bars, a st = mm 2. 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 W h =( /2) ( )*(4*0.21*25 =287.16kN. Total load on 4 walls = = kN Total load on one wall = /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 = W t cosecθ = = KN Working tension per meter run = /5.35 =120.9 KN/m run Design of ultimate tension = = KN Area of reinforcement for resisting direct tension is, 2014, IJARCSSE All Rights Reserved Page 419

4 A st = ( ) / ( ) = mm 2 Spacing S, = a st / A st 100 = (120.9/502.69) 1000 = mm Provide 12mm Φ 225 mm c/c in the direction of sloping faces A st = a st / s 1000 A st = (120.9 / 225) 1000 = mm 2 Normal component of coal centre of slab is, P n = w.h p [cos 2 θ + cos 2 φ. Sin 2 θ] Where, W = 8 KN/m 2 h p = [ ( ) + ( ) ] h p = 6.95 m θ = & φ = 35 P n = [cos cos Sin ] = KN/ m 2 Working pressure = P n = KN/ m 2 Normal component due to weight of sloping slab, = wd. cos θ = cos = 4.19 KN / m 2 Total normal pressure P = P n + wd. Cos θ P = P = KN / m 2 Effective Design moment, L 1 = ((5+0.5) / 2) = 2.96m Maximum negative bending moment, M = P. (L B 1 2 -L 1 B 1 )/12 =pl 1 2 /12=52.97* /12=38.67kNm Ultimate design moment=1.5*38.67 =58kNm. Limiting moment of resistance, M u limit =0.138f ck bd 2 =0.138*20*1000* =86.13kNm>58kNm. Since M u <M ulimit The section is under reinforced section. M u =0.87f y A st d {1-A st f y /bdf ck } 58*10 6 =0.87*415*A st *183.5{1-A st *415/1000*183.5*20} A st =985.15mm 2. Provide 12mm Φ bars, A st = mm 2. Spacing S= = 0 Provide 12mm Φ bars at 100mm c/c Maximum positive bending moment at centre is = P. (L B L 1 B 1 )/12 = (52.97* )/12=32.77kNm Ultimate bending moment = 1.5*32.77 =49.17kNm. Area of reinforcement steel required is M u =0.87f y A st d {1-A st f y /bdf ck } 49.17*10 6 =0.87*415*A st *183.5{1-A st *415/1000*183.5*20} A st =810.6mm 2. Provide 12mm Φ bars, A st = mm 2. Spacing S= = 0 Provide 12mm Φ bars at 100mm c/c 2014, IJARCSSE All Rights Reserved Page 420

5 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. TABLE TABLE TABLE TABLE TABLE TABLE , IJARCSSE All Rights Reserved Page 421

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11 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 m 3. Rate of Steel: RS.50 per kgf. Rate of Formwork: Rs. 150 per m , IJARCSSE All Rights Reserved Page 427

12 275 8 nos of 32 mm 125mm c/c Dwg 1: Column details. 16 mm dia mm c/c mm dia mm c/c 16 mm dia mm c/c mm dia mm c/c Dwg 2: Bunker reinforcement details mmm dia mm c/c Dwg 3: Foundation details. 2014, IJARCSSE All Rights Reserved Page 428

13 IV. CONCLUSION From the above Figures it is concluded that for storing Bituminous coal for various volumes from 100m 3 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: (Code of Practice for Plain and Reinforced Concrete) 2014, IJARCSSE All Rights Reserved Page 429