The Calculation Theory Of Ultimate Load Capacity Of Steel Gantry In Passive Flexible Shield

Our country has a vast territory,a large number of mountains,complex natural environment conditions,landslides,debris flows,rockfalls and other natural disasters occur from time to time.When the slope is relatively steep,and normal protection methods can not be applied,or cost too much,the passive flexible shield becomes one of the first consideration because the advantages about high adaptability,low economic cost and good protection performance.Since the steel gantry plays a major role in carrying load during the impact of rockfall on the passive flexible shield.Considering the impact of rockfall angle in any situation,this paper studies the stress condition of steel gantry,imposed on point load in different diirections,which main work is as follows.(1)In consideration of the plastic deformation of the material,the stress of steel gantry is analyzed.The force imposed on the structure leading to four plastic hinges is the ultimate load capacity of the structure.The formulas for calculating the ultimate load capacity of steel gantry under the action of oblique forces in different directions(the angle between oblique forces and vertical direction are derived),the formulas for bending moment of steel gantry in each stage from elasticity to plasticity are both derived.(2)According to an engineering example of a passive flexible shield,the geometrical parameters of the steel gantry is available.Considering to the classification of the impact angle derived from the theory,while some angles are determined,the theoretical results of ultimate load capacity of the steel gantry are obtained by substituting the calculation formula.(3)According to the parameters of engineering examples,the finite element model of the steel gantry is established by using finite element software ANSYS.Considering to the classification of impact angle of rockfall derived from theory,a multi-group calculation model is established.Referring to the bending moment diagram and plastic stress cloud diagram of the model,load-displacement curve of the structure,analyzing and summarizing the emergence of the plastic hinge of the model,and also the ultimate load capacity of the steel gantry is obtainend.(4)Comparing to the numerical results with the theoretical results,the errors of the two results are calculated to verify the correctness of the theoretical derivation of the ultimate load capacity.