Study On Performance-Based Seismic Design Of Lamella Single-Layer Spherical Lattice Shell

Spatial latticed shell structures are always used in buildings, which have long spans and a lot of people in, such as gymnasiums and theaters, therefore, the losses of those buildings caused by earthquakes are very terrible, even if the buildings don't collapse. Considering that question, we adopt the performance-based design theory in the seismic design of spherical lattice shell. In this paper, 'performance' is minimization of lifecycle-costs, which is the basic requirement of 'cost-effectiveness criterion'.The lifecycle-cost of a latticed shell structure includes initial fabrication cost, maintenance cost and failure loss. Initial fabrication cost and maintenance cost can be easily confirmed by the scale of project, but the failure loss can only be confirmed when the failure mechanism of a latticed shell structure is clear. Therefore, we analyze the dynamic responses of many lamella single-layer spherical lattice shells with different spans and different ratios of rise to span under earthquakes with different peak values. By those analyses, we realize that lamella single-layer spherical lattice shells have two kinds of dynamical failure mechanism, and that the structures' damage degree can be determined by their maximal nodal displacements.Based on researches above, this paper divides the failure degree to five levels (good, slight failure, middling failure, bad failure, and collapse). Considering the possible error by man-made division, we adopt degree function of membership, based on fuzzy mathematics, to assess the failure degree. By this method, we can describe the failure degree as the degrees of membership to the five failure levels.The failure loss of a structure can be subdivided into direct failure loss and indirect failure loss. Direct failure loss is only influenced by the structure's failure degree, so we build a parallel table, between the levels of failure degree with the direct failure losses, with which we can get a structure's direct failure loss by calculating the degrees of membership to the five failure levels. But the indirect failure loss is also related to the purpose of a structure, so we adopt a B coefficient to consider the influence of different structures.By theory deducing, we certify that the spatial truss structural, which is collocated in the full stress principle, has the biggest stiffness, and then a full stress adjusting optional method is proposed. The method quotes controlling coefficient λ to adjust the control stress of full stress design, and obtains the structural schemes of full stress design with different coefficient λ.. Then the lifecycle-costs of these schemes are calculated, and we can obtain the optimum scheme.By carefully analyzing the actual design method, we find that structure'simportance coefficient is the reciprocal value of the controlling coefficient which is used in the full stress adjusting optional method. Therefore, this paper calculates all the best controlling coefficients of 150 lamella single-layer spherical lattice shells with different spans, different ratios of rise to span, and different B coefficients. Those best controlling coefficients can be translated to the importance coefficients, which can be the reference for engineering designers.