A Review on Computational Behaviour Analysis of RCC Grain Silo Under Seismic Forces

A Review on Computational Behaviour Analysis of RCC Grain Silo Under Seismic Forces

Prof. Sagar L Belgaonkar1

1Assistant Professor, Civil Engineering Department SGBIT, Belgaum 590010

Prof. Madhuri N Kesarkar2

2Assistant Professor, Civil Engineering Department

Belgaum – 590006

Mr. Nikhil Patil3, Miss Rutuja Gadivaddar4, Miss Varsha Kakatkar5, Miss Vandana Pawar6.

3,4,5,6 Undergraduate Students, Civil Engineering Department, SGBIT,

Belgaum 590010

AbstractRCC silos which are designed to maintain silages and to provide from the elements to improve life span of stored grains. This analysis and design gives more safety to silo during earthquake intensity. In this study circular RCC silo is analyzed and designed for various heights by both manual design and by using staad pro V8i software for influence parameters such as pressure and displacement. Also it has been analyzed for seismic forces for different zones i.e. zone III, zone IV, zone V and the variations in the displacement are studied.

Keywords- R.C.C. Silo, displacement, Seismic forces, Wheat grains.

1. INTRODUCTION
   1. Vessels of different shapes, sizes and material are required in many industries as well as in agricultural field to store granular or powdery materials which hold the same amount of material in a smaller area in terms land. Silo has the features of water tightness and protect against the moisture.
   2. An elevated silo consists of conical roof, a cylindrical shell, conical hopper and could be supported by RCC columns or frames.
   3. RCC silos are generally built for permanent bulk storage as it is an economical storage unit in design and reasonable cost.
   4. Concrete can offer high water resistance; gives protection to stored materials which requires less maintenance and aesthetic look also it is comparatively free from bulking and damaging.
   5. Silos are cantilever structures which are subjected to many unconventional loading. The various types of loads act on these are dead load, wind load, earthquake load etc.
   6. The walls of silos are subjected to normal pressure and vertical and horizontal forces produced by stored material. The magnitude and distribution of pressures at different height depends on the properties of material stored silo and filling condition.
   7. So the careful evaluation of silos is done for the safe design in a seismic area.

   The design of silos is done generally by two methods;

   1. Airys theory
   2. Janssens theory Airys theory

      Airys theory is related to coulombs wedge theory of earth pressure. By which horizontal pressure acting along its circumference and the position of plane of rupture is determined and following parameters can be studied; horizontal pressure, and vertical load and vertical pressure taken by walls.

      Janssens theory

      This theory assumes that the friction between material stored and walls of silo supports large portion of weight of material store and hopper bottom supports only small portion of weight.

      The walls of silo are subjected to direct compression as well as lateral pressure.

2. METHODOLOGY

   The data for numerical example considered for analysis, Type of silo = R.C.C circular silo

   Total height of silo = 18.45m

   Type of material stored = Wheat Density of material stored = 7850N/m3 Diameter of silo = 5m

   Depth of cylindrical portion = 16m Height of conical hopper = 2.25m Opening of hopper bottom =0.5m

   Coefficient of friction, µ= 0.466, µ= 0.444 Angle of repose = 45°

   Type of soil condition = soft soil

   Silo has been analyzed for earthquake forces in staad pro V8i for following zones, i.e. Zone III, Zone IV and Zone V for 10 different filling conditions.

   Impact factor = 1 Damping ratio = 5 %

   Description for models-

   Model 1: R.C.C silo filled with wheat grains up to 2.25m from bottom of hopper.

   Model 2: R.C.C silo filled with wheat grains up to 4.25m from bottom of hopper.

   Model 3: R.C.C silo filled with wheat grains up to 6.25m from bottom of hopper.

   Model 4: R.C.C silo filled with wheat grains up to 8.25m from bottom of hopper.

   Model 5: R.C.C silo filled with wheat grains up to 10.25m from bottom of hopper.

   Model 6: R.C.C silo filled with wheat grains up to 11.97m from bottom of hopper.

   Model 7: R.C.C silo filled with wheat grains up to 12.25m from bottom of hopper.

   Model 8: R.C.C silo filled with wheat grains up to 14.25m from bottom of hopper.

   Model 9: R.C.C silo filled with wheat grains up to 16.25m from bottom of hopper.

   Model 10: R.C.C silo filled with wheat grains up to 18.25m from bottom of hopper.

   Fig. A showing Model 1 and Model 2

   Fig. B showing Model 3 and Model 4

   Fig. C showing Model 5 and Model 6

   Fig. D showing Model 7 and Model 8

   Fig. E showing Model 9 and Model 10

3. RESULTS AND DISCUSSION

   Table no. 1. Results for displacements of silo under Zone III

   Graph no 1. Comparison of displacements of silo in zone III

   1. 1. The displacement for Model 1 at 2.25 m which is at junction where conical shape changes to circular shape is 78.03% as compared to Model 10, where in Model 10 has the highest displacement among all.
      2. The displacement for Model 1 at 18.25 m is 54.95% as compare to Model 10, where in Model 10 has the highest displacement among all.
      3. The displacement for Model 1 at 11.97 m is 72.43% as compare to Model 10, where in Model 10 has the highest displacement among all.
      4. The variations in displacement for Model 1, Model 3, Model 4, Model 5, Model 6, Model 7 and Model 8 are almost same.
      5. Model 9 and Model 10 have more displacement as compared to other models.

   Table no. 2. Results for displacements of silo under Zone IV

   Graph no 2 Comparison of displacements of silo in zone IV.

   1. The displacement for Model 1 at 2.25 m which is at junction where conical shape changes to circular shape is 85.68% as compared to Model 10, where in Model 10 has the highest displacement among all.
   2. The displacement for Model 1 at 18.25 m is 66.58% as compare to Model 2, where in Model 2 has the highest displacement among all.
   3. The displacement for Model 1 at 11.97 m is 66.75% as compare to Model 2, where in Model 2 has the highest displacement among all.
   4. The variations in displacement for Model 1, Model 3, Model 4, Model 5, Model 6, Model 7, Model 8 and Model 9 are almost same.
   5. Model 2 and Model 10 have more displacement as compared to rest other models.

   Table no. 3. Results for displacements of silo under Zone V

   Graph no 3 Comparison of displacements of silo in zone V.

   1. The displacement for Model 1 at 2.25 m which is at junction where conical shape changes to circular shape is 88.88% as compared to Model 10, where in Model 10 has the highest displacement among all.
   2. The displacement for Model 1 at 18.25 m is 73.81% as compare to Model 10, where in Model 10 has the highest displacement among all.
   3. The displacement for Model 1 at 11.97 m is 85.52% as compare to Model 10, where in Model 10 has the highest displacement among all.
   4. The variations in displacement for Model 1 to 8 are almost same.
   5. Model 9 and Model 10 have more displacement as compared to other models.
4. CONCLUSION

1. Maximum displacements in zone III and zon V occurs in Model 10 where the R.C.C silo is filled with wheat grains up to 18.25m from bottom of hopper. Whereas in zone IV maximum displacement occurs in Model 2 i.e., R.C.C silo filled with wheat grains up to 4.25m from bottom of hopper.
2. The value of maximum displacement in comparison to all models for Zone V is 61.654mm which is 1.83 times greater than the displacements for the models of zone IV.
3. In zone III model 10 shows maximum displacement of 36.80 mm for fully filled wheat grains. In zone IV Model 2 shows maximum displacement of 45.567mm for wheat grains filled up to 4.25m from bottom of hopper. In zone V Model 10 shows

   maximum displacement of 61.654mm for fully filled wheat grains.

4. The Maximum displacement in zone IV occurs in Model 2 because of the variations of stiffness and mass on the walls of silos.
5. At critical height of 11.97m the variation of displacement in all models for zone III and zone V are nearly same whereas in zone IV in Model 2 the variation is more compared to other models because of the pressure intensity governed at that point.
6. It is observed that the behavior of rcc silo will change its behavior due the effect of natural period for different zones and the modes have affect on the displacements.

REFERENCES

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