A COMPARATIVE ANALYSIS OF INTERLAYER ISOLATION AND BASE ISOLATION UTILIZED IN TWIN-TOWER FRAME SEISMIC ISOLATION STRUCTURES WITH AN ENLARGED PODIUM, CONSIDERING DIFFERENT LENGTH-TO-WIDTH RATIOS AND TOWER HEIGHTS.

Compared to traditional seismic structures, isolated structures offer advantages in safety performance, particularly for complex structures in areas with high earthquake risk. One of these commonly used complex structures is the twin-tower frame seismic isolation structures with an enlarged podium (2TFSLP-SI). Many researchers have conducted studies on the selection of isolation schemes for a 2TFSLP-SI. However, there are few findings on the comparison of the isolation efficiency of such structures under different isolation schemes, particularly when considering various tower heights and the length-to-width ratio. This forms a research gap. The objective of this study is to compare the isolation efficiency of interlayer isolation and base isolation schemes in 2TFSLP-SI, considering three different length-to-width ratios and five different heights of towers. In this study, thirty models of 2TFSLP-SI have been built, which includes the consideration of three length to width ratios (3.3, 1.7, and 5) of towers, five tower heights(20 levels, 17 levels, 14 levels, 11 levels and 8 levels) and two isolation schemes(base and interlayer isolation). These models are built and calculated using ETABS with a maximum horizontal seismic influence coefficient of αmax = 0.45. The response spectrum method and time-history analysis method are used to analyse the models. The story drift data from the time history analysis method is averaged and compared with that from the response spectrum method to get the maximum value as the result. By analysing these data, it can be concluded that the maximum story drift and average story drift are generally lower in the models with interlayer isolation than in those with base isolation. Specifically, for the tower has 20, 17, 14 and 11 floors, the average reduction in the maximum story drift is 16.2%, the average reduction in the mean story drift is 22.8%. However when the tower has eight floors, the maximum story drift of the interlayer isolated structure can be 16.8% higher than that of the base isolated structure in the model with the length- to-width ratio of 1.7. This implies that for these 2TFSLP-SI, the base isolation can only be considered when the tower height h=24m (8 levels). For the tower height h belongs to 33m (11 floors)≤h≤60m (20 floors), priority needs to be given to adopting an interlayer isolation to obtain better isolation efficiency. [ABSTRACT FROM AUTHOR]