EVALUATION METHOD OF PERFORMANCE TO TRANSMIT HORIZONTAL SEISMIC LOADS TO SUBSTRUCTURES OF DOUBLE LAYER TRUSS DOMES BUILT IN HEAVY SNOW REGION CONSIDERING VERTICAL LOAD RESISTANT CAPACITY

Abstract

 This study deals with an evaluation method of performance to transmit horizontal seismic loads to substructures of double layer truss domes built in heavy snowfall region considering the vertical load resistant capacity. The purpose of this study is to propose the evaluation method based on the dynamic analysis of the dome due to horizontal and vertical earthquake motions. Both the static and dynamic characteristics of shell-like structures vary depending on their configuration. However, membrane actions are dominant in those structures. Among efficient spatial structures, which have membrane actions similar to shells, typical examples are single layer reticular domes and double layer domes composed of many straight members, which are subjected to member buckling. After undertaking the static behavior, dynamic buckling behavior is analyzed in order to determine the collapse mechanism of these reticular domes. The present analysis adopts an assumption that members buckle due to compression and yield under tension. The present analysis considers the effects of material nonlinearity of members and the geometrical nonlinearity of the domes.

 The purpose of this study is also to investigate the earthquake response such as the acceleration, the velocity, the displacement and the axial force of the domes subjected to vertical and horizontal earthquake motions. Based on the dynamic response, the practical calculation method is shown to predict the equivalent static load for the earthquake-proof design of the dome. As long as the accuracy verification of the equivalent static load is concerned, the collapse mechanism and the axial stress of the dome subjected to the static loads show a good agreement with the earthquake response analyses subjected to the earthquake motions.

 In the practical calculation method, the distribution and the value of the equivalent static load are calculated by means of the participation vector and the earthquake acceleration response spectrum. The static earthquake-proof design is able to carry out using the equivalent seismic loads practically. In general, it is not easy to predict the distribution of the acceleration response because of the complicated dynamic behavior combined with the vertical and horizontal response of the dome built in heavy snow region. This is a reason why the earthquake static load is required for the earthquake-proof design using the static analysis.

 The characteristic response of the dome occurs subjected to vertical and horizontal earthquake motions. The design seismic coefficient of the applied load distribution considering the snow weight effect is also actually necessary for the safety study in the earthquake proof design. The study proposes the estimation method of calculating the design seismic coefficient for the applied load for the earthquake-proof design of the dome. The coefficient is easily obtained by means of the eigenvalue analysis. The accuracy is also verified by a good agreement with the earthquake response analysis of the dome subjected to the artificial vertical and horizontal earthquake motions varying the PGA. The proposed method can be used to predict the performance to transmit horizontal seismic loads by means of the elastic static analysis of the truss dome subjected to the equivalent static load.