Even thought, the conveyor and supporting system were designed in this thesis, the complete product was not created. Optimization and detail level design can be done for the conveyor but if the operation is wanted to ensure the formation of the air cushion between the belt and tube should be studied. The design of air system to the conveyor was not in the scope of this thesis, but for further development it is necessary. Different topics can be categorized as follows:
design of flange connections
design of sealings between the frames
fatigue analysis of steel structures
formation of air cushion
lateral load resistance of the frame when cables are considered
maintenance of the conveyor
method to estimate accurate wind load
method to estimate buckling of the frame under nonlinear stress
optimum height of the pylon
optimum number of cable pairs
point load capacity
redistribution of cable forces in transient design situation
use of different conveying capacities and belt widths
use of longer span lengths
vibration analysis of the frame
Most of the aforementioned topics are related to the functionality and optimization of the conveyor system. However, if the structural strength of the system is considered, the most important aspect to study from the topics is the vibration analysis of the frame. It could be assumed that the slender frame is sensitive for the vibrations due to the wind, especially if the length of the span is increased. The phenomena could be the most limiting issue in the span length of the system.
13 CONCLUSIONS
The design and strength analysis of the frame and supporting system for the air supported conveyor were done in this thesis. The thesis was made for the company, which wanted an estimation of the mass of the conveyor and span length of the supporting system. The thesis was development of a new product, when the methods included design approaches and analytic methods to evaluate the strength properties of constructions. In summary, the used methods were: systematic design, belt conveyor design, analytic calculations and FE-analysis. Due to reason that, there was no experience about the air supported conveyors in the company, the problem of this thesis was seen: how to design the air supported conveyor and the cable stayed supporting system to be strength enough for the affecting loadings?
Further research questions were raised from the problem:
How the conveyor and supporting system are related to each other in the design of the system?
What aspects are influencing loading versus strength capacity of the frame?
The span length of the supporting system determined the maximum loading in the frame. 58 m was selected for the span length of the supporting system. The estimated stress in the frame was 258 MPa. The number of cable pairs in the system affected to the span length.
Next possible span length of 81.2 m would have cause 458 MPa in the frame. On the other hand, the lateral wind load cased the greatest stress. The method to calculate the wind load could give greater loadings than there could actual be.
The loadings in the conveyor were material load, wind load, snow load and dead weight.
The forces from the loadings affected to the cables of the system. The cables were connected to the pylon construction which was under compression. The axial load of 205 kN was obtained for the one column of the pylon. However, in transient design situation the redistribution of the forces and lateral wind load affected 272 kN axial force to the column.
The vertical and lateral loadings affected nonlinear stress distribution in the frame. The plate components were designed to buckle before yielding when the material savings were possible to obtain. The analytic method for the plate buckling considered equally distributed
compression load. The assumption of equally distributed compression was made to simplify the calculations. Due to the nonlinear stress distribution, the plate components become stronger than expected. However, the thicknesses were 4–5 mm when the minimum value for the thickness was 4 mm.
The results in this thesis were: the frame of the conveyor, pylon construction, cables and joints for the cables. The mass of the steel frame was 209 kg/m and the span length of the cable stayed supporting system was 58 m. The designed conveyor utilized the standardized belt, which had the width of 1200 mm and the belt speed of 2.54 m/s. The pylon construction was truss structure with the height of 10 m. The cables were locked coil rope type with the minimum diameter of 18 mm. The connection of the cables to the pylon and the frame was implemented with pin joint type of connection. The supporting structure, the frame of the conveyor and details were forming the complete air supported conveyor with the cable stayed supporting system.
In conclusion, the thesis created the base for the design of the conveyor with the cable stayed supporting system. The following aspects of the system can be considered with the thesis:
design of cable stayed supporting system
design of connections
determination of the loads
manufacturing of the frame
size of the conveyor for needed capacity
strength evaluation of the frame
Even though, the conveyor and supporting system were designed in this thesis, further study is needed. Optimization and detail level design can be done to obtain better design. However, the main considerations should be done for the vibration analysis and formation of air cushion in the conveyor.
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APPENDIX I, 1 PARAMETERS OF THE FRAME
Cross-section, which was used in the calculations
Final cross-section.
APPENDIX I, 2
Conveyor with the belts and material.
APPENDIX II, 1 PYLON CONSTRUCTION
Diagonal beam
APPENDIX II, 2 H-beam
HE A 140 was selected
APPENDIX II, 3 Throat size for the members of the pylon
APPENDIX III, 1 BUCKLING OF THE FRAME TUBE
APPENDIX III, 2
Component under study.
APPENDIX IV, 1 BUCKLING OF THE CHUTE STRUCTURE
APPENDIX IV, 2
Component under study.
APPENDIX V WIND LOAD
APPENDIX VI SNOW LOAD
APPENDIX VII, YIELD LINE THEORY
Normal force capacity
𝑊 = 𝑊 => 𝛾 𝐹𝛿 = ∑ 𝑚 𝐿 𝜃
𝐹𝛿 = 2 ∙ 150 ∙ + 4 ∙ 𝐿 ∙ + + 2 ∙ 16 ∙ + 2 ∙ 440 ∙ + 2 ∙ (440 + 2𝑥) ∙
𝐹 = 𝑡 𝑓
4 𝛾 2 ∙ 150 ∙1
𝑥+ 4 ∙ 𝑥 67+67
𝑥 + 2 ∙ 16 ∙1
𝑥+ 2 ∙ 440 ∙ 1
67+ 2 ∙ (440 + 2𝑥) ∙ 1 67
𝐹 = + + + + + +
𝐹 = + + [𝑁]
Minimum value of the F can be found from the zero value of the derivative (DF=0)
𝐷 + + = 0
+ = 0 => 𝑥 = ±70,887