concept of silo design

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Engineering Design Solutions

Design of Silo of 150 Cu. M Capacity

1. Scope of the Project 1. Design & Analysis of Silos 2. Support structure-fabrication drawings 3. Platform, staircase & Access ladder Drawings.

2. Methodology for SILO Design Load consideration

The container and its supporting structure are subjected to the following loads Permanent loads

The self-weight of the container, support structure, access ladders and platforms The in-service loads

Gravity loads from stored material Access ladders and their fixings should be designed to withstand a

minimum live load of 1.5 KN (150 kg). Loads induced by flow of stored material (Dynamic) Concentric and eccentric discharge or filling of the container (Dynamic) Impact caused by falling material (Dynamic) Internal gas or air pressure, or suction, including pressure from pressurized

delivery systems. Loads associated with potential impact of vehicles, loaders or trains where

these enter into the container area and could create a risk of collapse Environmental loads

Wind loads The weight of at least two persons on the roof. Seismic loads (Modal)

Rescue loads The weight of at least two persons on the roof The weight of the rescue equipment The load required to lift the person being rescued

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Silo design calculation including plate thickness required for silo cylinder and cone portion.

As suggested by customer thickness of 8mm for cone and 6mm for cylinder section will be considered,

We will determine wind speed and calculate the wind pressure distribution around the structure.

Checking the deformation at the various points on silo due to internal pressure acting on the inner surface.

Checking for the failure of silo at joint due to shear.

Supporting structure design calculation.

Considering the weight acting on the multiple frames that includes the self-weight of the silo, weight of the material and the wind load, the design is carried out. This includes:

Considering the square section frame, the bending stress and the shear stress are analyzed. Check is done for allowable compressive stresses also.

Lateral deflection is checked, that is buckling analysis is carried out. Both the axial and lateral deflections are checked for calculated load and maximum

deflection is checked. Analyzing the natural frequency of the structure supporting the load (Modal) Carrying out the modal analysis to determine the fundamental mode of vibrations and

also check various modes. (Modal) Linear dynamic analysis is carried out for time varying loads (Dynamic)

Supporting structure fabrication details.

Square section beams are used for the supporting the structure. Depending upon the total load and the stresses generated, the cross sections are designed and drawings will be given for the same.

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Foundation plan and load data details.

The foundation depth required for putting foundation is provided and also the type of foundation to be put will also be provided.

Platform, staircase and access ladder fabrication details. Structures providing access, such as fixed platforms, walkways, stairways, and ladders, will be designed to eliminate or minimize the risk of slips, trips or falls and 2D drawings will be given.

Access ladders and their fixings will be designed to withstand a minimum live load of 1.5 KN (150 kg).

Guard railing will be provided around the edges of platforms and walkways where there is a risk of person falling.

Corrosion prevention

Accumulation of water and material on the structural members can result in their corrosion leading to eventual structural collapse. The design should prevent, or if this is not practicable minimize, the water and material traps inside and outside the bulk container. This can be achieved by means of the following

Position steel angles and channels with their legs pointing downward Allow for sloping surfaces to drain water Seal joints by continuous rather than intermittent welds Overlap joints in a way that will avoid accumulation of water and material Provide drain holes (e.g. cut the corner of gusset plates to allow drainage of water) IS 2062 copper for atmospheric corrosion resistance material may be used.

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Design: Wind Load Analysis

Design wind speed:-

V2 = Vb x K1 x K2 x K3 Vb = basic wind speed in m/s K1 = Risk co-efficient = 0.91 K2 = THS Factor = 1.02 K3 = Topography Factor = 1

Terrain Category: 2(Open Terrain with scattered obstruction of height between 1.5 to 1.0m) Class of building: B (Structure having mass dimension between 20m to 40m)

Design Wind Pressure = 0.6 Vz2 Exposure factor at all joints =1

The wind load on a building shall be calculated for the building on a whole. Wind load on a building = Cf * Ae * Pd, where Cf = Force co-efficient Ae= Effective frontal area Pd = Design wind pressure

The value of Cf = 0.5 for circular shape.IS:875

Wind load at each floor is distributed among the columns at that floor according to their relative stiffness.

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Earthquake Design Consideration The building will be designed for horizontal seismic force only. The structure is analyzed as an equivalent static approach employing the use of a seismic co-efficient method. a) Basic Seismic co-efficient (0) To give the basic design acceleration on a fraction or the acceleration due to gravity. b) Importance Factor (I) To modify the basic seismic co-efficient and seismic zone factor, depending upon the importance of structure. c) Soil Foundation System Factor () To modify the 0 seismic zone factor depending upon soil foundation system. d) Design Horizontal Seismic Co-efficient (h) Seismic co-efficient taken for design.

Earthquake Load Consideration Earthquake Zone : II Basic horizontal seismic co-efficient 0 : 0.01 Co-efficient depend upon soil foundation system() (Hand soil) : 1.0 Importance Factor(I) : 1.5 Design value of horizontal seismic co-efficient h = * I * 0 = 0.015

Base shear calculation The base shear is given by Vb = K * C* h * V K = Performance Factor according to structure framing system = 1 C=Co-efficient determining the flexibility structure depends upon the number of storey of building = 0.75. h = Design seismic co-efficient W = Total DL + 25% of LL

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Base shear calculation and its distribution among floor Base Shear Vb = 19 * C* h * W The distribution or forces along with the height or the building is given by Qi =Vb * (Wi *hi2) / (Wi *hi2)

Analysis:

Wind Load Analysis

Total Vertical Moment

concept of silo design

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