Study On Elasto-plastic Seismic Performance Of Suspendomes

Suspendome is a new type large-span space structure with superior capability. In this paper, characteristics of the elasto-plastic response under the intensity of fortification and rare earthquake as well as problems of seismic design of this kind of structures are studied. Specifically, the main work includes the following four aspects:(1) Intensity measure of artificial seismic waves are studied. The seismic response caused by different artificial seismic waves, which were generated by the same response spectrum and modulated according to a single intensity measure(IM), varies distinctly. Besides, the variations of seismic response are sensitive to the natural vibration period of structures and durations of artificial seismic waves. An improved response spectrum IM is put forward. When the amplitudes of artificial seismic waves were modulated by the improved IM, differences of structural seismic responses caused by different artificial seismic waves are reduced obviously, and the level varies lightly with the natural vibration period of structures In addition, the variations of structural seismic responses under artificial seismic waves with different durations reduced significantly by using the improved IM.(2) Efficiency of segmentation for round steel bar beam element is studied. It shows that, when the rod is divided into four three-node beam elements and the ratio of the length of end element to that of the central unit is1:4, response of elasto-plastic buckling under compression and bending can be efficiently simulated. The effect of member’s initial curvature on buckling capacity and elasto-plastic seismic response is analyzed.In case of the larger intensity earthquake, the seismic response of the structure will vary greatly according to the shape, direction and peak value of initial curvature. In addition, displacement response’s difference (DRD) method is put forward in order to find the critical point of dynamic instability.(3) By means of24suspendome models, effect of initial pretension of cable-bar system, rigidity and symmetry of substructure, connection condition of abutments, rise-span ratio and criteria of cross section checking on the structural elasto-plastic dynamic behaviors are analyzed. The results reveal that, for most of models, the members with residual plastic strains mainly located in the central of the roof under the intensity of fortification and rare earthquakes. The dynamic behaviors of suspendomes are more sensitive to the symmetry of substructure and the rise-span ratio of roof. A reference index, the ratio of residual ultimate bearing capacity, is put forward in order to evaluate the damage level of suspendomes. It reveals that the ratio of residual ultimate bearing capacity for the suspendome under7-degree rare earthquake is very high. However, it reduces much under8-degree rare earthquake. Furthermore, by the analysis of the ratio of residual ultimate bearing capacity of24suspendome models, it is suggested that the member’s cross sections of the upper reticulated shell should be checked against frequent earthquake in7-degree district and the intensity of fortification earthquake in8-degree district.(4) Changes of cable force in suspendomes after the intensity of fortification and rare earthquakes are investigated. It shows that, after the intensity of fortification earthquakes, the cable force does not change in most of those models designed according to elastic behavior in7-degree frequent earthquake, and the changes of cable force in most of those models designed according to elastic behavior in8-degree frequent earthquake, are less than10%. After rare earthquakes, the changes of cable force in most of those models designed according to elastic behavior in7-degree frequent earthquake are less than10%, and in most of those models designed according to elastic behavior in8-degree frequent earthquake are more than20%and some cables may even be totally relaxed. When according to elastic behavior in7-degree the intensity of fortification earthquake, the changes of cable force reduce much. Cable layout, asymmetry of substructure and the rise-span ratio of upper dome are important influence factors to the loss of cable force. It is suggested that the ratio of cable force’s loss can be regard as a reference index for performance-based seismic design of suspendomes.