Study On Simplified Model Considering The Effect Of Joint Stiffness In Strong Seismic Failure Analysis Of Single-layer Spherical Reticulated Shells

As a common structural form,reticulated shells are mostly used in high-speed railway stations,airports,stadiums and so on.Since the last century,the research and application of reticulated shells have developed rapidly.Nowadays,most of the single-layer reticulated spherical shells are modeled and analyzed by traditional beam elements.The latticed shell model of beam element has the advantages of simple modeling,fast calculation speed and better accuracy of calculation results.However,although the traditional beam element model has a small deviation under static load,under dynamic load,the traditional beam element model has a larger error.If the beam element model is used,it will not be conducive to the safety of the structure.Therefore,the refined shell element model,as a more accurate result model,has attracted more and more attention of scholars nowadays.However,the refined model of shell element can get more accurate results.Because of its complex modeling and huge number of meshes,it takes a lot of time from modeling to operation.Therefore,many scholars began to build simplified models with accurate results and short time-consuming.According to the above ideas,this paper carries out strong earthquake failure analysis of K6(3)single-layer reticulated spherical shells and obtains the following results:(1)By establishing beam element model and refined shell element model of K6(3)reticulated shell with a span of 21 m,the bearing capacity,deformation and mechanical properties of the two models under static load and strong earthquake are analyzed.The calculation shows that the carrying capacity of the refined shell element model is slightly larger than that of the beam element model under static load,but the carrying capacity of the beam element model under strong earthquake is larger than that of the refined shell element model,and the critical failure load deviation between the two models is large.(2)The refined model of shell element is further studied.Five groups of refined model of spherical joints with different wall thickness and five groups of spherical joints with different outer diameter are established.It is found that the bearing capacity of refined model of shell element increases first and then decreases with the increase of wall thickness ratio of spherical joints to rods under strong earthquakes.The analysis shows that the value of wall thickness ratio of spherical joints to rods should be between 2 and 3.The load-carrying capacity of refined shell element model under strong earthquake decreases with the increase of the ratio of spherical joints to rods' outer diameter.The analysis shows that the ratio of spherical joints to rods' outer diameter should be between 2.6 and 3.(3)Because the refined model of shell element takes a long time to calculate,a simplified model is established on the basis of beam element model in this paper.The simplified model is based on the establishment of equivalent joint area near the joint.Aiming at changing the axial stiffness,bending stiffness and simultaneously changing the axial stiffness and bending stiffness of the equivalent joint area,eight groups,nine groups and eight groups of models are established respectively.By comparing the vertical displacement time history curve of each simplified model with the vertical displacement curve of the refined shell element model,the simplified model is developed.A simplified model with the best fitting degree of the vertical displacement time history curve is presented,which proves the feasibility of the simplified model method.At the same time,the simplified model method can be popularized and applied.