Research On Optimization Of Truss Beam And Leg Structure Selection For Belt Intermediate Line Of Long Distance Pipe Conveyor

The pipe belt conveyor is more and more widely used in the conveying field of bulk materials such as grain,coal,chemical raw materials,etc.with the advantages of closed conveying,space turning and two-way conveying of materials.At the same time,with the development demand of green and efficient,long distance,large volume and more complex and flexible lines become the development trend of pipe belt conveyor.These trends add difficulty to the structural design of truss beam and leg of pipe belt conveyor,and intensify the influence of steel structure on the cost of the whole machine.Therefore,how to design a lower cost truss beam and leg structure on the premise of meeting the transportation requirements has become a difficult problem in the design of long distance pipe belt conveyor.However,in practical engineering,the section of truss beam and leg profile is often designed according to experience,which leads to the design of the structure is too heavy,resulting in the waste of steel.The middle line of the long distance pipe belt conveyor is the main line,which consumes the most steel and is the main source of cost.In the intermediate line,part of the line needs to cross the river,road and other obstacles,resulting in the length of the truss beam and leg height need to be determined according to the specific line,and the truss beam and leg profile need to be selected separately,this part of the line is a specific section of the line.In addition,the truss beam span of part of the line is continuous and equal,and different spans not only affect the selection of the truss beam profile,but also affect the selection of leg profile,and ultimately affect the overall steel amount of the line,this part of the line is a continuous equal section of the line.In order to save steel cost and provide theoretical basis for engineering application,this paper studies the section selection of truss beam and leg profile in specific section and continuous equal section of intermediate line of long distance pipe belt conveyor from the theoretical point of view.In view of the above problems,this paper carries out the following research work from the theoretical perspective and draws relevant conclusions:(1)Aiming at the selection of truss beams and leg profiles in specific sections of intermediate lines,the dimensionless coefficient method is adopted to design and select the section of truss beams and leg members.Compared with the original design,the section designed by this method uses less steel and makes more full use of section.Firstly,the stress characteristics of the truss beam and leg structure in a specific section of the line are analyzed.Then,the iterative formula of the slenderness ratio of the common section of the truss beam and leg lattice column is derived by using the method of infinite steel coefficient.Finally,the design and selection of the common section of the profile are realized by using the formula.(2)By deducing the internal force calculation formula of the most dangerous members of continuous equal segment truss beams,constraints are provided for the design and selection of truss profiles using optimization algorithm.Firstly,the types and characteristics of loads borne by truss beams are analyzed,and then the formulas for calculating internal forces of various truss beams under different loads are derived.Finally,according to the basic combinations of rods,the formulas for calculating internal forces of the most adverse load combinations of the most dangerous rods are calculated.(3)By deducing and analyzing the critical load calculation formula of double leg and single leg,constraints are provided for the design and selection of leg profiles using optimization algorithm.Firstly,the expression of total potential energy of double leg was obtained according to Ritz method.Then,the equivalent flexural stiffness and shear stiffness of double leg were deduced according to the energy equivalent criterion.Finally,the calculation formula of critical load of double leg was summarized and deduced.For the single leg,the critical load calculation formula obtained by analysis can be approximated by the Euler critical load calculation formula of general solid pressure bar.(4)Aiming at the design and selection of truss beams and leg profiles of continuous equal sections,the design and selection of truss beams and leg profiles were realized by combining NSGA-Ⅱ and genetic algorithm,and the distribution law of the total weight of the line structure and the number of truss segments was obtained,as well as the law of the change of the total weight of the structure with the number of truss segments when the legs of different heights were arranged.Firstly,with the section type of the truss beam profile as the discrete variable and the derived internal force calculation formula as one of the constraint conditions,the multi-objective optimization algorithm NSGA-Ⅱ was used to optimize the total weight and number of segments of the truss beam.Then,with the section model of the leg profile as the discrete variable and the derived critical load calculation formula as one of the constraint conditions,the weight of the leg was optimized based on genetic algorithm.Finally,by combining the two algorithms,the legs corresponding to the Pareto optimal solution set obtained from NSGA-Ⅱoptimization are optimized one by one by using genetic algorithm to realize the design and selection of the continuous equal section of the line truss beam and leg profile,and the distribution law of the overall structure weight and the number of truss beam segments decreases first and then increases when the line is arranged with different spans of the truss beam.And the law that the total weight of the whole structure gradually moves forward with the turning point of the number of truss beam segments decreasing first and then increasing as the leg height of the line layout increases.