Research On Seismic Design Of Isolated Long-span Space Structure Of An Airport Terminal In High Seismic Region

As a regional transportation hub,airport terminals are of great importance,and it is a hot and difficult research topic to ensure their post-earthquake functionality.Most airport terminals in China are large-span space structures,characterized by large span,large plan size,and complex interlayer structural layout.Seismic isolation technology has gradually been used to improve the seismic performance of airport terminals,with the isolation layer often consisting of different types of isolation bearings.However,there are complex stress issues and design difficulties in the isolation layer.Based on a real case of an airport terminal located in an 8-degree(0.3g)high-intensity seismic area in China,this study starts from the traditional design,elastoplastic analysis,and the influence of key design parameters to study the effect of different combined isolation schemes on the seismic performance of complex airport terminals,aiming to provide reference for the seismic design of complex airport terminals.The main research results and conclusions are as follows:(1)The combined isolation scheme design and seismic performance analysis of the airport terminal in the high intensity area are carried out.This article proposes a cross-layer seismic isolation scheme designed for the features of the structure,such as local basements and uneven distribution of overall mass.The isolation layer consists of natural rubber bearings,lead rubber bearings,and elastic sliding bearings.Based on the traditional design model,that is,elastoplastic model is used for isolation layer and elastic model is used for superstructure,the design index is tested.The structural horizontal seismic decrease coefficient controlled by the isolation layer is 0.27.Under rare earthquakes,the story drift ratio is 1/363.The absolute floor acceleration peak value is 1.635m/s~2.This isolation scheme also has a good effect on controlling the lateral displacement ratio of steel truss roof structure supporting column and structural torsion angle.(2)The elastoplastic model of the structure was established based on ETABS,the seismic response characteristics of the terminal under rare earthquakes were analyzed,and the engineering demand parameters were obtained.Combined with the component vulnerability model,the damage state of various components was evaluated.The results showed that the structural members in the model mainly suffered slight damage,but no moderate or above damage.The combined isolation scheme can effectively reduce the plastic damage of the structure.At the same time,the lateral displacement ratio of concrete column members supporting steel column and steel column of steel truss roof structure is analyzed.It is found that the deformation of concrete column members is much smaller than that of steel column,which can provide relatively rigid supporting conditions for steel column,and the lateral displacement ratio of steel column is controlled within 1/100.The most adverse deformation of the storey which floor slab is discontinuous appears near the floor with large openings after earthquake isolation.(3)Six combinations of isolation schemes were designed within the range of2%to 4.5%of the yield ratio,and the influence of the yield ratio on seismic performance of structure was investigated through dynamic time history analysis.Under medium earthquakes,as the yield ratio increased,the maximum story drift ratio increased from 1/607 to 1/414,the maximum absolute floor acceleration increased from 1.2m/s~2to 1.82m/s~2,and the isolation layer displacement decreased from 133mm to 79mm.When the yield ratio exceeded 4%,the horizontal seismic decrease coefficient of the structure under design-basis earthquake was greater than0.4,which did not meet the design requirement of reducing the design seismic intensity by one degree.Under rare earthquakes,the trend of the maximum story drift ratio in the X direction increases from 1/272 to 1/324 with the decrease of the yield ratio.In the Y direction,the maximum story drift ratio first decreased with the increase of the yield ratio.When the yield ratio reaches 3.5%,the maximum story drift ratio tends to be stable in the Y-direction.The change in yield ratio had little effect on the absolute floor acceleration of the structure,and the values of absolute floor acceleration fluctuated within a small range in the yield ratio range of 2%to4.5%.The trend of isolation layer displacement with the change of yield ratio was the same as that under the medium earthquake,and the isolation layer displacement decreased as the yield ratio increased.