Studies On The Static And Seismic Behaviors Of The Spherical Reticulated Shell In Triad-Overlapped Revolvingly Retractable Roofs

With the rapid economic and social development of China in recent years,more and more engineering applications of retractable roof structures have been adopted.Based on the Fukuoka dome in Japan,this paper studies the static and seismic performances of a type of large-span spherical reticulated shell in triad-overlapped revolvingly retractable roofs that has not been applied in China.The main work and conclusions of the paper are as follows:1.The static performances of multiple 200-meter-span double-layer spherical reticulated shell models with different rise-span ratio,thickness,expansion rate of bottom expansion areas and substructure rigidity are analysed.The results show that,when the expansion rate of bottom expansion areas is greater than 0.28,the vertical reaction forces in design values of the surrounding supports are all pressure,which can meet the condition of self-supporting;the support reaction forces in the bottom expansion areas are significantly higher than those in the main shell area,so the trolleys in the bottom expansion areas should be arranged more densely and the trolleys in the main shell area can be relatively sparse.The difference in the support reaction forces in the bottom expansion areas can be significantly reduced when increasing the expansion rate of bottom expansion areas.2.Under the vertical loads or the most unfavorable wind load,the "oblique arch effect"connecting to two bottom expansion areas and the "outer tensile(compressed)ring effect" in the area of bottom supports appear in the reticulated shell,and internal force concentrations also occur significantly at the turning point between the main shell and the bottom expansion areas.The change in the stiffness of the substructure has little effect on the internal forces and deformations of the reticulated shell.The steel consumption and deformation of the reticulated shell are very sensitive to the change in its rise-span ratio when it is less than 0.15,and the structural deformation cannot even be effectively reduced by increasing the thickness of the reticulated shell.A high stability bearing capacity is observed for the single reticulated shell.3.The effects of 8-degree frequently-occurred earthquake show no great importance in the cross-section check of the lattice shell members.The time-history analysis of the elasto-plastic seismic response of the structure revealed that weak areas of the reticulated shell near the turning point between the main shell and the bottom expansion areas or the bottom supports(the former is dominant)are observed under 8-degree fortification intensity and 7-degree or 8-degree rarely-occurred earthquakes,which tend to cause the structure to collapse.The elastic response spectrum method was used to analyze the large-span single double-layer spherical reticulated shell model.The results reveal that the main reason for the formation of weak areas lies in the large difference between the internal forces under the most adverse condition of the non-seismic design of the section and the most unfavorable internal forces under the checking condition of the fortification intensity and rarely-occurred earthquakes.Further analysis shows that the internal forces of the members in the weak areas is greatly contributed by the second and 11th modes.4.The basic model is strengthened by three measures:the smooth transition at the turning point between the main shell and the bottom expansion areas,the "elastic design under the fortification intensity earthquake",and the artificial adjustment of the cross-sectional specifications of the buckling belt members.The time-history analysis results show that the strengthened model can not effectively prevent the structure from collapsing under rarely-occurred earthquakes.5.Taking the modes that mainly contribute to the seismic response of the weak area members as the object,adopt the method of amplifying the seismic internal forces of these modes to strengthen the members of the weak areas in a targeted manner.The analysis found that if the cross-section check of the lattice shell members can be satisfied under about 10.0 times the benchmark(under frequently-occurred earthquakes)modal forces,then it can effectively ensure that the structure will not collapse under rarely-occurred earthquakes,and the steel consumption of the reticulated shell is about 5.2%higher than that under non-seismic design.