Seismic sensitivity assessment of concrete tunnel-form buildings to variations in ground motion characteristics using time scaling of earthquake record approach: a case study

Analytical studies have demonstrated that tunnel-form system possesses relatively high strength and rigidity. However, in seismic evaluations of this system, only peak ground acceleration and spectral acceleration have traditionally been considered as the primary intensity measures representing earthquake ground motions. While this approach aligns with current seismic guidelines, it overlooks the importance of other critical ground motion characteristics. The present study introduces the time scaling of earthquake record method and, for the first time, employs it to modify the primary characteristics of input ground motions for the seismic evaluation of tunnel-form buildings. For the analyzed models of 2-, 5-, and 10-story, the findings reveal that significant duration, peak ground acceleration, and peak ground velocity have direct effects on the seismic responses of the system. Results indicate that, at a given hazard level, accurate predictions of seismic performance and demands require simultaneous consideration of all three parameters. Analyses show that at high hazard levels, an increase in velocity while keeping acceleration and significant duration constant can change the performance level of the system from immediate occupancy to collapse prevention. This highlights the critical role of velocity in seismic performance. Similarly, variations in acceleration and significant duration yielded comparable results. Under constant conditions for the other parameters, increases in acceleration and significant duration led to performance levels of life safety and immediate occupancy in the worst cases, respectively. Accordingly, these parameters rank second and third in importance when estimating seismic performance levels. Furthermore, the findings demonstrate that code-based relationships fail to predict the seismic demands of tunnel-form systems accurately. Consequently, revisions and modifications are necessary to incorporate the effects of ground motion characteristics.