Research On The Seismic Performance Of Large Diameter Prestressed Silos Based On Storage Material-silo Wall Interaction

Silo is the fastest growing and most widely used form of storage structure since the 20 th century.With the increase of silo storage capacity demand,the diameter and height of silo has been increased,and large diameter prestressed silo has become one of the effective solutions to engineering demand.However,the research on silo seismic problems at home and abroad is not in-depth,and the established codes suggest using additional mass method or load simulation for analysis,which has deviation from the actual seismic response of silo.In this paper,an in-depth study on the modal performance and time-dynamic response of silos under earthquake action is carried out in combination with a large-diameter prestressed silo of 33.6m internal diameter in Shijiazhuang,and the main results are as follows:(1)The three-dimensional finite element model of large-diameter pre-stressed silo was established by simulating the storage material-wall interaction with ANSYS finite element software using the contact algorithm applicable to nonlinear coal storage,and the effect of storage material height and its physical parameters on the dynamic characteristics was studied,and the results showed that the self-oscillation frequency of silo decreased with the increase of storage material height during the operation period,and the self-oscillation frequency of full silo decreased by 26.19% compared with half silo.The first two steps of the empty silo are dominated by the plain vibration type,and the vibration type of the half and full silos are dominated by the storage vibration.Unlike the rigid foundation,the period of pile-soil-silo structure becomes longer,and the vibration pattern appears axial oscillation and overall torsional change,and the pile-soil effect should not be ignored in the dynamic analysis.The maximum difference of moisture content and coal type on the dynamic characteristics of silo is 3.36% and 16.22% respectively,which clearly shows that coal type has a greater influence on the dynamic characteristics of silo.(2)Considering the interaction between storage material and silo wall,the seismic response law of silo for each coal storage height(empty,half and full silo)and each coal type(anthracite,bituminous and lignite)was studied.The results show that the peak dynamic displacement of silos of each coal storage height gradually increases along the silo height,and the maximum inter-story displacement angle is located in the doorway area.The acceleration at the top of the storage bulk silo is reduced compared with that of the empty silo.The analysis of the peak circumferential and vertical stresses shows that the outer side of the silo is more dangerous than the inner side.Compared with the full silo static working condition,the maximum increment of circumferential stress in the full silo under multiple and rare earthquakes increased by 5.18% and 59.18%,respectively,on the outside of the silo.The maximum main tensile stress under rare earthquakes is 3.07 MPa,which is located at the transition between the bottom of the silo wall and the bucket wall,and it is recommended to take corresponding measures to prevent damage.The coal type has a greater impact on the seismic performance of the silo.The dynamic displacement,peak angle of interlayer displacement and acceleration amplification coefficient are the largest for anthracite coal,followed by bituminous coal and the smallest for lignite coal,indicating that lignite coal has the strongest vibration energy dissipation capacity.The change of annular stress and vertical stress of silo for each coal type is more complicated,and both anthracite and bituminous coal have more influence on the annular stress of silo structure than lignite,and the peak size of input seismic excitation affects the annular stress of coal type.As a whole,anthracite coal has the largest peak vertical stress,bituminous coal the second and lignite the smallest.However,the junction of the outer bucket wall and the ring beam is partially opposite under multiple earthquakes,and is the site where the maximum vertical stress peak occurs for each coal type,and this area needs to be strengthened.(3)Considering the interaction between storage material and silo wall,the design equation of side pressure under silo seismic response and the effective mass coefficient values for different coal types were modified based on the proposed static force method.The time course analysis of storage side pressure under seismic response of large diameter silo reveals the distribution law of storage side pressure along the silo height by ground vibration of silo.The results show that: the additional side pressure of ground vibration increases gradually with the silo height,and the maximum value of overpressure coefficient of ground vibration storage material at the top of the silo is 10.22.In the part below 6m height at the bottom of the silo,a relatively small additional pressure is generated,and with reference to the Technical Specification of Steel Silo(GB 50884-2013),the specification at the bottom of the silo is taken to be dangerous.Combined with the numerical simulation results,the calculation formula of additional lateral pressure of coal storage in silo under multi encounter and rare encounter seismic excitation is modified.Considering the bulk coal-silo interaction,the seismic correction method of silo considering coal species is proposed.The results show that:the base reaction force of each coal type is shown to be widely different,based on the proposed static method,combined with the Code for Design of Reinforced Concrete Silos(GB 50077-2017),the simulation results of the base reaction force mean envelope of silos of different coal types under seismic action are calculated,the code values are taken to be conservative,the seismic energy dissipated by the friction of mutual motion of different bulk coals and silos are different,and the effective The values of mass coefficients are revised to0.67,0.66 and 0.62 respectively.The uniform value of effective mass of storage material according to the specification cannot reflect the difference of each storage material,and the participation coefficient of effective mass of different coal types in the seismic design of silo is amended.