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1. Abstract:

Octagonal structural street light pole (single and double cross arm) has widely used around the world. This kind of poles has a high ratio of height to horizontal space. It means this kind of structural pole are highly wind sensitive compared to any other structure. Here in this paper we calculated the static loading of this structure and in dynamic case we also calculated the wind loading of this structure.

2. Introduction:

The octagonal street light pole structure is one of the most used lightning poles in the world. Though it has some disadvantages like high height to horizontal space ratio, in wind loading it vibrates more due to this reason. Due to its light weight and less manufacturing complexity it has some advantages in industrial purpose.in this paper we basically confirmed that, the given structure and the design is suitable to sustain any kind of mechanical forces into its range. And to check its failure in structure like any kind of fatigue might be appear into it or not. We analyzed both the static and dynamic load tests virtually in CATIA V5R20 software. Mathematically we also calculated the mechanical force experienced in by the structure. This kind of design validation and simulation is very much important to get the best design

3. Objective:

3.1. To discuss the main parameters required to design a octagonal structural street light pole (6m). 3.2.To present the 3d model of the said product.

3.3. To obtain its virtual simulation in software tools.

3.4. To obtain its characteristics or behavior i-n wind loading (Dynamic case) study.

4. Technical specification: Table (A)

Hight of pole	6000 mm
Number of sections	1
Material of construction	Structural steel
Base diameter	135 mm
Top diameter	76 mm
Wall thickness	3.1 mm
Base plate dimensions	L=225 mm; B=225 mm; t=12 mm
Bas plate PCD	225 mm
Number of foundation bolts	4
Type and dimension of foundation bolt	M20, 700 mm lg.
Cross arm length	1000 mm

 

5 Mathematical calculations:

The load test simulations are given in this paper but due make this report easily understandable some of the mathematical calculations are given here. These are basically for static loading lateral load test and deflection, vertical load test and deflection and for dynamic case study the deflection and elastic limitation of the structure in wind loading is given here.

The mathematical calculations are classified into two parts, those are ‘Static case’ and ‘Dynamic case’.

6. Static case:

6.1. Deflection due to lateral load:

Considering the cross section of the pole through its axis and three axis XYZ are given into consideration. This method is used to determine the deflection or deformation of the structural pole.

Where ‘M’ and ‘m’ are the moments due to applied unit dummy load in the transverse direction along the height of the pole, ‘E’ is the modulus of elasticity and H_p is the pole height.

Assuming that a point load ‘P’ is acting at the top of the pole. The moment of inertia ‘I’ expressed as;

I= CD³t

Here C is a constant, ‘D’ is the avg. diameter of the pole.

The bottom and top diameter of the pole are designated as D_b and D_t  respectively. Then the slope of the pole is expressed as,

The lateral displacement d lat  at a distance z_d from the top of the pole due to the application of lateral load ‘P’ at a distance Z p from the top of the pole is expressed as;

The lower limit of the integral has to be changed as z_d or z_p depending upon the location of deflection measuring point is below the load point application. Solving the above integral equation by partial fraction, the above equation can be expressed as;

Where ‘V’ is the vertical load applied and dlat is the deflection due to lateral load shown previously. Thus the lateral displacement due to vertical load d vert through moment ‘M’ at a distance z_d from the top of the pole is expressed as;

Substituting the value of constants in the above integral equation, the deflection due to vertical load d vert is obtained as;

7. Dynamic case:

7.1. Wind load testing:

Here we are calculating the wind loading case for calculating the force exerted on the pole structure then by applying the force the virtual simulation of the pole is shown in this paper with the help of CATIA V5R20 software tool.

The average wind speed in India for 6 months is 6.7 miles per hour approximately which is equivalent to 10.7826 km/hr. For making this structure a very reliable one we are calculating the deformation under a very high value of wind speed if it will sustain on that loading then it will be clear to us that the structure has a strength enough to sustain any kind of wind speed without failure.

Note: Here in terms of calculating the wind loading (0.85) stands for the average air mass at 6 m height.

8. Simulation results:

Here the load testing in various condition like static and dynamic case study is given from the generated result of Catia, in this simulation result basically it is shown that the designed structure can sustain in a high range of longitudinal and vertical force in case of static loading and also the sustainability of this structure in wind loading also.

Final element analysis (FEA) performed of the part in Catia V5R20 is compared with the eleastic limit of the material of load in both von mises stress, shear strength, and principle stress and the deformation in loading. If the computed results are lesser than the elastic limit than the design shall not fail under the computed maximum loading that is 739.83N.

8.1. FEA (Final element analysis) results:

Fig: Von Mises stress as computed in FEA for single cross arm pole

 

Fig: Von Mises stress as computed in FEA for double cross arm pole

 

Fig: Translational displacement for single cross arm octagonal street light pole

 

Fig: Translational displacement for double cross arm street light pole

 

Fig: Principal Shearing stress distribution (Single cross arm street light pole)

 

Fig: Principal shearing stress distribution (Double cross arm street light pole)

The under given table compares the induced value of Von mises stress, Principal shearing stress distribution and their maximum limit computed by Finite element analysis with the elastic limit of the material and enlists the evaluated factor of safety.

The below table shows the comparison between the maximum value of the sustained loads and material’s maximum elastic limit.

9. Table (B)

Quantity	Computed maximum value	Elastic limit	Remarks
Von Mises Stress	3.03e+007 pa (S CA) 3.01e+007 pa (DCA)	8.41e+008 pa	Design is safe
Principal shearing stress	1.64e+007 pa (SCA) 2.5e+007 pa (DCA)	5.4e+008 pa	Design is safe
Principal tensile stress	2.37e+007 pa (SCA) 2.22e+007 pa (DCA)	8.41e+008 pa	Design is safe

 

10. Conclusion:

As the table ‘B’ suggests that the design parameters like Von Mises Stress, Principal shearing stress and the Principal tensile stress both are within the elastic limit of the material. When the factor of safety is considered from 1.1 to 1.5 it is suggesting that the design shall withstand the applied load 739.83 N without any failure.

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