INVESTIGATION INTO THE STABILITY OF LARGE SCALE THIN-WALLED STEEL CYLINDRICAL SHELLS UNDER SEVERE DISASTER OF ICE AND SNOW

The south China suffered a disaster of severe ice and snow in 2008,which caused many steel structures to fail.The large-scale thin-walled steel cylindrical shells widely used in the chemical or electric power engineering as the key facilities in the system are always located some beams internally to support the equipments.Consequently,the shell wall is subjected to local axial compression from the beam and the circumferentially uniformly distributed overall axial compression resulting from the self-weight of the upper part and the roof.The structure has accumulated some stress and deformation under the combined loads. Once it suffers the severe disaster of ice and snow additionally,there will be great load of snow quickly accumulating on the roof with large area and the connecting pipes,which causes the failure.Based on the process of construction and service and in consideration of loading path,the overall uniformly distributed axial compression is firstly applied then the local axial compression,thirdly the uniform axial compression is applied which simulates the great load of ice and snow.The nonlinear stability analyses of 112 cylinders with the initial weld imperfection are conducted.The investigation indicates that the buckling bearing capacity of the cylinder decreases as the initial overall load magnitude increases;the ratio of cylinder buckling bearing capacity under snow against the buckling design bearing capacity under overall uniform compression increases as the amplitude of the imperfection increases,and the post-buckling bearing capacity increases.The bearing capacity against snow increases slightly when the cylindrical shell stores slurry in the lower part.Based on numerous computation results,the design recommendation of the cylindrical shells subjected to the significant load of snow is proposed in consideration of loading history.