Analysis of Seismic and Wind-Induced Vibration Responses of a Super-Long Irregular Terminal Structure Under Multi-Point Excitations

The T3 terminal building of an airport consists of a central hall and two side corridors， with a total structural outline dimension of 411 m × 416 m. It is composed of a lower concrete high-rise structure and a top long-span steel structure roof. According to the architectural layout， structural joints are set up on both sides of the corridor， which coincide with the extension line of the long side of the hall， thus dividing the overall building into three structural zones. Given its dimensions （411 m in length and 200 m in width）， the middle area is a highly complex and ultra-long irregular structure. The seismic wave effect and complex and variable wind load distribution should be fully considered， and the seismic and wind-induced response analysis of the structure should be carried out with multi-point excitation.The first three modes of vibration of the structure are horizontal and vertical vibrations in two directions， exhibiting a relatively regular mode shape distribution. These modes are mainly sensitive to seismic effects in the X， Y， and Z directions. When analyzing the traveling wave effects of subsequent multi-point excitations， the main directions of the traveling waves are X and Y， and three seismic waves in the X， Y， and Z directions are simultaneously applied to the structure during each wave propagation. The peak values of the main， secondary， and vertical seismic waves are applied in a ratio of 1∶0.85∶0.65. The total proportion of structural columns with a wave effect coefficient greater than 1.0 is 37%， while that of the roof steel structures is 5%. Due to the good overall stiffness of the steel roof， all gravity loads are transmitted to the structural columns. As a result， the structural columns are more sensitive to seismic motion. The total base reaction force under multi-point excitation is significantly smaller than that under uniform excitation， with a mean ratio of 0.45 between the two. This occurs because， when the traveling wave effect is considered， the vibration phases of individual structural members are inconsistent， leading to partial mutual cancellation during the superposition of base shear forces. The influence coefficients for the structural traveling wave effect are as follows： 1.6 for corner columns， 1.5 for edge columns， and 1.4 for all other columns. The components near the support of the roof steel structure are taken as 1.4， and the rest of the components are taken as 1.2.A numerical wind tunnel analysis was conducted to obtain the wind pressure coefficients on the building surface at various wind direction angles of 0°， 45°， 90°， 135°， and 180°. The results showed a highly irregular wind pressure distribution， resulting from the roof's complex shape and the combination of wind pressure and suction. Therefore， when conducting wind-induced vibration analysis on the roof steel structure， the time-history wind pressure effects at various wind direction angles should be fully considered. Based on the results of wind tunnel numerical analysis， the time-history wind pressure at each point on the roof was extracted and converted into time-history nodal loads applied to the structural analysis model. The analysis showed that the steel roof structure exhibited the maximum vertical displacement under the action of wind pressure time-history loads.Subsequent calculations for the wind vibration coefficient were performed using vertical displacement as the control parameter. The calculated coefficients for the roof steel structure under time-history wind pressure at various wind angles ranged from 1.38 to 1.55. Based on these results， a value of 1.5 is proposed for design purposes.