Shelf capacity measurement and calculation
logistics equipment, shelves as an important storage equipment is increasingly used in all walks of life, reasonable design, choose shelves becomes more and more important. Beam as important components of the modular shelf, how science choice was also a problem to be solved.
most shelf units of production, design, usually through the calculation of the maximum load of the beam to select the beam model. Bearing capacity calculation of the main beam using the simplified method, for example simplified to simple beam or beams cantilever beam. However, so choose the beam is often inaccurate or value too small, can't meet the need of strength, rigidity and safety, likely to cause accidents; or value too large, resulting in rich strength, stiffness and material waste, to the consumer increases unnecessary investment. Not long ago, Chen Zhai 5 5 extra cold storage shelf collapse accident of Zhengzhou, let us recognize that reasonable necessity and importance of design, choice of shelves.
1 model of loading of goods stored in a shelf of goods goods, the smallest unit, made up of beams and columns. Study on model loading of goods in order to force model for analysis of beam.
in practical applications, modular shelf beams span concentration between 1 000 4 000 mm. Span smaller beams are generally used for small light shelf, cargo, bulk and packaged goods, and placed directly on the beam. In order to protect the goods and post contact and collision in goods set at both ends of the lateral clearance of the placement area.
for large-span beams, mainly for senior and racking, goods stacked on the pallet and then placed on a beam, and cargo handling equipment such as forklifts, stackers access. In order to prevent collisions and easy access to jobs, goods, and goods and set up a security clearance between columns. Meanwhile, taking into account the universality and applicability of the model, beam span larger goods calculated in accordance with each order placed 2 pallets, using 3 trays, or even the ground 1 pallet, experiment check errors are acceptable.
consider delivery grid load model of unity, lateral, horizontal clearance, pallet length and total length of the value.
2 beam constrained shelf space truss is a structure of the degrees of freedom, but in the calculation of beam load when model is simplified to a model calculation. Due to the modular shelf span is much larger than the cross section of the beam size, so the beams can be simplified in the calculations for beam elements in the mechanics of materials, and both ends of the beam degree of constraint is the focus of research.
each end of the beam with 3 degrees of freedom, the translation of x axis and y axis motion and rotation around the z axis, usually is two ends of the beam as a hinged or fixed end. As a hinged handle, 2 endpoints of the Translational degrees of freedom constraints, but does not limit endpoint rotational degrees of freedom. In this case, beams in the axis position of endpoint than the original twist to a certain angle, the endpoint may force may not be transmitted torque; when used as a fixed processing, constrains the beams at each end of all freedom. At beam ends at this time is neither moving nor turning, but you can transfer force and moment.
modular shelf between cross beam and column with a special plug connection, beams by 3 feet or 4 feet hanging piece embedded in the post holes. This connection method allows the axis of the beam around before the force on the one hand has some rotation, on the other hand and bar endpoint can transfer the torque load on the column on the crossbar. Thus, reduced to simple beam ends hinged or fixed end is not realistic. Actual stress effect is part of the beam part hinged and fixed.
assume that the total load of the beam is w, deformation is part of the load of the beam (pW ) in hinged beam deformation and residual load caused by conditions ( (1- p) W) in the clamped condition caused by deformation of the beams, namely, y= y i + y g, y for the deformation of beam, y J-pW size of beam deformation under load conditions of hinged, y g (1- p) W the size of the load in the clamped condition of beam deformation, p hinged under the condition of beam load-sharing percentages can be measured, we get p= 0 71.
when beam deformation of f is known to the bearing load of the beam due to deformation and the load linearly, W= 0 71 W j + 0 29 W g.
among them, the W for the bearing capacity of the beam, W g hinged condition under beams bearing capacity is for the f, W g solid under deformation for f beam bearing.
3 load load a cross of the same beam is 1 the goods which the size of the load, but in the process, because we only get 1 bar as the research object, so loading the cargo load bearing capacity of beam 1 2. Because the beams using high density of steel and iron material and long, so the beams must be considered in the process of calculating the weight of.
when the beam span is smaller, the goods for bulk and packaged goods and placed directly on the crossbar, so goods can be loaded as a uniformly distributed load on the beam in the Middle, and some lateral distance from the left and right columns; for the weight of the beam, in accordance with uniformly distributed load on the beam. When the beam span is large, with a pallet of goods placed in the form of the beam. General think, tray and beam of contact for line contact and non-surface contact, that goods on beam of force concentrated Yu tray of some parts and non-uniform to distribution in whole tray Shang, so in simplified Shi put each tray Shang goods of load according to concentrated force loaded in tray of 2 a support feet Shang, each a concentrated force for whole beam hosted of 1/ 8. for beam of weight, still according to are cloth force loaded Yu whole root beam Shang. Figure a 1 for the lateral clearance, a 2 horizontal clearance, q to the weight load of the beam, q 1 for the loading of goods in accordance with uniform force calculation of cargo load, G/ 8 for the loading of goods in accordance with point force calculations each pallet at the foot of the goods loaded.
force model of large-span beam with small span beam model 4 of computational methods in mechanics of materials known to the maximum maximum bearing stress deformation of beam method and calculation method of deflection method 2. On the beam in the use process, instability characterized by stiffness of beam instability of beam deflection exceeds the allowable deflection. But when the coefficient of the beam flexural or beam span is smaller, the intensity of instability may also occur, namely the stress exceeds the allowable stress of the beam. Must be considered when calculating the beam bearing strength and stiffness requirements, rather than adopt the stress and deflection of law 1.
author used of calculation method is first take beam of ends for hinge support end, then respectively according to stress method and deflection method calculation beam of hosted, last take both of smaller who as hinge support State Xia of beam hosted; Similarly, again take beam of ends for fixed end, get fixed State Xia of beam hosted; last according to Qian paper mentioned of method for overlay, that get has beam of actual hosted.
due to combined shelf in the of beam for 2 tablets lip shaped cold rolled pieces occlusal and into of box shaped parts, according to steel shelf structure design specification subsection 3 2 2 article, calculation full section effective of cold bent steel shelf structure of by pulled, and by pressure or by bent component of strength Shi, can used meter and the cold bent effect of strength design value f , its value by Xia type determine: f = 1 + (12 - 10) &Nbsp;t L n i= 1 i 2 f, coefficients for the ratio of tensile strength and yield point of steel, n for the number of edges contained in section I, section angle corresponding to the I-th on the edges, the length of the center line of the L section, section area and thickness ratio.
in accordance with the standards currently used domestic shelf manufacturers, and in the process to get the maximum deflection of the beam for the beam span 0 5% , the safety coefficient is n= 1 62. Meanwhile, taking into account the actual use of cross beam and column needs to go, if the calculation of bearing capacity of beams is greater than the matching column bearing, you will need to make the corresponding amendment, put the carrying value of the beam as the supporting column of the carrying value.
5 results the author in accordance with the method presented in this paper, chose several different beam cross sections are calculated spans cross the data groups in 1000 4000mm, and by experimental standard load tables for comparison. From that, calculated in accordance with the method presented in this paper bearing bearing with the actual standard error is only for an average of 2 05% , and is an acceptable method, calculation error is very small, can meet the needs of rack selection and bearing capacity calculation.
6 conclusion this paper details the bar hosts and selecting model and calculation method, the method is simple and practical, can greatly improve the accuracy. This method can be used as shelves manufacturing enterprises and design beam series design and bearing capacity calculated according to standards. Of course, calculated from the actual situation, the scaling factor p is a key factor. To create a more accurate calculation of beam load capacity must be through multiple experiments to be closest to the actual p value, to get closer to the actual beam load capacity.
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