Influence of the Seismic Excitation Frequencies Content on the Behavior of a Tuned Mass Damper in Low-Rise Building Considering Soil-Structure Interaction

Abstract

The influence of the frecuency content of seismic excitations on the behavior of an optimal tuned mass damper (TMD) is studied in the context of a system with explicit consideration of soil-structure interaction. A stochastic analysis is made in the time domain for two random processes, one considering a broad bandwidth process (BBP) and other considering a narrow bandwidth process (NBP). A structure built over three different types of soil (soft, medium and hard) is considered. For the optimization of the TMD, the minimization of the ratio between the standard deviation of the displacement of the main structure with TMD with respect to a structure without TMD, is used as the target function. It is found that for seismic excitations with high frecuency content, the ratio of the TMD frequencies compared to the fixed base frequency of the structure approaches to 1 as the soil becomes more rigid. It is also observed that the TMD become tuned with the flexible base frequency for all soil types, producing perfect tuning for small mass ratios and detuning gradually for higher mass ratios. On the other hand, the TMD optimal damping ratio increases as the TMD mass ratio is higher, independently of the soil type. The TMD is more efficient for higher values of the TMD mass ratios, especially on soft soil. In structures built over flexible base, that are subjected to low frequency content excitations, the optimal TMD is tuned with the flexible base, independently of the type of soil and the fixed base period of the main structure. The TMD optimal damping is not sensitive to the flexible period for small mass ratios, and reaches its minimum value when it matches with the predominant period of the seismic event. On the other hand, the TMD reaches its maximum efficiency when it is tuned with the flexible period of the soil-structure system, and coincides with the predominant period of the seismic exitation and is higher on soft soil. A deterministic analysis is made using two seismic records, an artificial earthquake compatible with the Chilean code NCh2745 characterized by high frequencies content and other similar to the event in 1985 in Mexico, characterized by low frequencies content. It is seen that the optimal TMD is efficient controlling the response of the structure in all types of soil analyzed.

Optimal TMD design for torsional balance of asymmetrical 3D structures considering soil–structure interaction

“…For the seismic demand, a stochastic stationary Gaussian process is considered. This model is developed according to the works of Espinoza et al 24 and Khatibinia et al 11 and a simplified schematic representation is showed in Figure 2.…”

Análisis de la eficiencia de un amortiguador combinado sintonizado con incertidumbre en los parámetros sometido a excitaciones sísmicas de bajo contenido de frecuencias

“…El periodo predominante del filtro es de 2 s, lo cual representa el estrato del suelo sobre la roca que no interactúa con la estructura. El caso de interacción suelo-estructura puede ser revisado en Espinoza et al (2018b). Los grados de libertad del sistema están definidos por el vector:…”

Soil-structure interaction effects on the seismic performance of frame structures

“…To understand different transient behavior of the frame structure and free field responses, three record earthquakes are considered in this study (Figure5): strong earthquake (Tohoku 2011), medium intensity (Northridge 1994) and low intensity (Kobe 1995). In this way, Espinoza et al (2018) have recently studied the influence of the seismic excitation frequencies on a structure built over different types of soil (soft, medium, hard) considering explicitly of the soil-structure interaction. This study leads to optimize the tuned mass damper of the system considering law and high frequency excitations.…”