Collapse Mechanism Of Single-layer Latticed Cylindrical Shell With Four Edges Supported By Steel Columns Under Severe Earthquakes

With the vigorous development of Chinese large span structures, reticulated shellstructures are applied more and more in extensive range. Because of its reasonablemechanical performance and beautiful forms, the cylindrical lattice shell has beenapplied widely in engineering. At present, the static stability problem of spatialstructure has been well solved, but the research about seismic performance has a longway to go. Substructures, maybe a key factor, are not considered in most studies onseismic performance and failure mechanism. In fact, whether dynamic characteristicof the substructure is considered, the result, the collapse mechanism of the structuresunder severe earthquakes, will become quite different. In some cases, substructurewill amplified the effect of seismic response significantly. Therefore, it is quitenecessary to study the dynamic characteristics deeply with regard to seismic responseand collapse mechanism of the shell with substructures. In this dissertation,single-layer cylindrical latticed shell supported on four edges by steel column aretaken as major research object and the structural response analysis method will beused to study its collapse mechanism. The main research contents and results are asfollows:(1) A three-dimensional model with substructures considering permanent loadand part of live load of the shell is established by3D3S steel design software.Subsequently, the natural vibration characteristics of the structures is analyzed. At last,by parameter analysis, the influence of the parameters, that is rise-span ratio, span andcolumn height, to the first frequency can be obtained.(2) The collapse mechanism of single-layer cylindrical latticed shell which issupported on four edges by steel column is studied by the structural response analysismethod under severe earthquakes. The structural response effect changes with theincrease of PGA through characteristic reaction in load domain. The failure mode andcharacter of the shell is confirmed and can be classified into the following threemodes: strength failure Ⅰ, strength failure Ⅱa and strength failure Ⅱb.(3) A large number of parameter analyses for single-layer latticed cylindricalshells supported on four edges by steel column have been done, which can be used for exploring the geometric parameters’ effect for collapsed mode. The correlationanalysis showed that geometric parameters,including span ratio, length to width ratio,span and the height of columns have influence on the PGA of collapse and the failuremode of the cylindrical shell. The greater the span ratio is, the greater the PGA valuewill be. The greater the length to width ratio is, the greater the PGA value will be. Thelonger the span is, the greater the PGA value will be. The collapse mode of the shellcan be affected by the column height. and the collapse mode of the cylindrical shell isrelated to its first frequency closely.