Dynamic Stability Analysis Of Single-layer Reticulated Shell Considering The Member Imperfection

Reticulated shell structures with light weight, beautiful appearance, good stiffness andloads carrying capacity are widely used in engineering. The stability behaviour, rather thanthe strength of the members is the controlling factor in the design of most single-layerreticulated shell structures. This makes the stability the of single-layer reticulated shellstructures great concern to researchers. The stability behaviour of reticulated shellstructures is very sensitivity to initial imperfections which including member imperfectionsand node imperfections, and therefore the influence of imperfections has been the keyissues of the stability analysis of the structures. A lot of research results on the stabilityanalysis of reticulated shells under static and dynamic loads considering the nodeimperfection have been obtained in demostic and abroad. Up to now, the infulence of themember imperfections to the dynamic stability behaviour of the reticulated shell structureshas not been involved yet.In this paper, the half sine-wave curve is employed to simulate the initial bending ofmembers, and the finite element analysis of member is carried out to decided thereasonable amplitude of the initial bending and the reasonable number of element that amember is divided. The dynamic stability behaviour of a K8single layer reticulated shellstructure with a span of40m is investigated by the software ANSYS. In the analysis, thenode inperfections and the member inperfections are considered. The three dimensionalTaft earthquake waves are applied to the structure, and the ratio method is used to adjustthe acceleration of the earthquake. Based on the geometrical and material nonlinearearthquake reponse of the single layer reticulated shell for different acceleration, the B-Rrule is used to determined the dynamic stability critical acceleration of the structure. Thestability behaviour of the single layer reticulated shell considering only node imperfectionsand considering both node imperfections and member imperfections is compared based onthe numerical analysis result. The influence analysis of the element division, the differentampitude of the initial bending, the direction of the curvature of the initial bending and thedynamic buckling of the members is also carried out. The research results show that whenthe influence of the element division is eliminated the dynamic stability criticialacceleration of the structure reduces10%by the consideration of the member imperfections, while this acceleration reduces25%when one element is used for themember of the structure. Therefore the element division of the members has a greatinfluence to the analysis results. The research results also show that the different amplitudeand direction of the initial bending of the members have little influence to the dynamicstability behaviour of the structure. The dynamic buckling of the member with largeslenderness ratio will reduces the stiffness of the structure, and cause the dynamicinstability of the structure occurs. The weaken of the members attached to the instabilitynode will makes the dynamic instability of the weaken member occurs before the structurelose its dynamic stability, and this causes the dynamic stability critical acceleration of thestructure reduces obviously. The reduced degree depend on the location of the bucklingmember and its buckling time. The earlier the member buckling appears, the greater thereduced degree of the dynamic stability critical acceleration of the structure.