# Numerical Study of the Seismic Response of an Instrumented Building with Underground Stories
## 1 Introduction
For example, studies, such as [22; 23], have investigated the effects of the soil-pile-structure interaction on the seismic response of 3D offshore platforms subjected to near-fault ground motions. The authors concluded that the assumption of a rigid base leads to incorrect results and that the material nonlinearity should be considered for a more reliable selection of the structural members' cross-section. Ground motion recordings have also been used to assess the coupling between superstructure, substructure, and free-field motions employing response spectra [5; 24]. Furthermore, significant investigations have been conducted to extract the SSI system's properties through actual recordings from free-field and instrumented buildings [25; 26; 27; 28; 29]. Although such information is essential and different approaches for modeling the linear and nonlinear SSI exists, ranging from simple to complex approaches, there is still uncertainty on whether the more complicated and time-consuming procedures produce substantially more realistic outcomes. Moreover, comparisons of the effect of underground floors on the building's response to real-world data have been seldom reported, given the few instances where instrumentation was already placed in a building when significant or useful events were registered for data processing. While studies, such as [26; 30] have investigated SSI effects through system identification techniques of buildings from earthquake data, only a few studies [16; 17; 21] to the best of the authors' knowledge, have focused on the influence of underground levels in the seismic analysis of buildings and only the former oriented to practical engineering applications. [PERSON] et al. [16] analyzed the impact of foundation modeling on the accuracy of the simulated response of a high-rise building. This study analyzed data from the 1994 Northridge earthquake on a 54-story framed building on alluvial soil with four underground levels located in Los Angeles, USA. The building was instrumented with 20 accelerometers, whose data were the input for the 3D FEM. Different types of foundation support restrictions were evaluated. The results between the real response and the model were compared visually and via frequency content curves from the Fourier transform. The results indicated that all foundation models' responses were similar in shape; however, inter-story drifts tended to be underestimated in cases where the building is fixed at the ground. This type of modeling was shown to be the least accurate. There were no significant differences among other models examined, nor between the models considering the soil springs working only in compression or in combination with tension. On the other hand, the experimental evaluation of existing and new seismic design methodologies plays a fundamental role in deepening our understanding of the seismic response of structures and verifying numerical models. In this way, experimental activities can be one of the most valuable ways to help engineering practice understand, acquire, and employ new knowledge in their designs. In this context, several studies have validated numerical models throughout experimental programs in an effort to correct design approaches. To mention some, [PERSON] [31] developed a fiber-based finite elements model of a half-scale 3D reinforced concrete frame tested under shake table excitations to verify that the software employed in the calibration and fine-tuning of the shaking-table experiment is able to reproduce the response of full-scale structures. [PERSON] et al. [32] conducted an experimental, numerical study to improve the rules for both static and seismic design of light-duty hand-loaded shelving racks. [PERSON] and [PERSON] [33] validated and proposed a novel inertial mass system for shake table experiments throughout dynamic experimental research and advanced numerical modeling.