Summary
Varying passive crowds can cause considerable changes in the dynamic properties of civil structures, such as sport venues. The effectiveness of passive control systems for the reduction of vibrations in these structures is limited as the dynamic properties of the structure change depending on the occupancy level and postures. Hence, a semi‐active system is proposed for reducing structural vibrations regardless of the off‐tuning due to passive crowd effects. This paper describes the experimental implementation of a semi‐active control strategy for a pressurized tuned liquid column damper (PTLCD) on a grandstand‐type steel structure. Additionally, an analytical model is proposed for the human–structure–damper system, and numerical results are compared with those obtained experimentally. Only the effects of passive anthropic behavior were considered, and results show that individuals, when sitting, produce more damping in the main structure than when they are standing. Overall, the semi‐active PTLCD had a satisfactory performance for the different configurations considered, achieving reductions in peak and root mean square acceleration of up to 74% and 57% with respect to the grandstand without the control system.
Real‐time hybrid simulations (RTHS) have become an attractive alternative for the study of structural systems by conveniently separating an experimental substructure from a numerical component. Due to the technical and economic benefits of applying fiber‐reinforced elastomeric isolators (FREIs) in unbounded configuration, the analysis of this device using RTHS is gaining interest among researchers. However, there are aspects associated with the complexity of the unbounded isolators that alter the dynamic behavior of the structure. One of these aspects is the rocking effect, which generally is disregarded when conducting RTHS. This paper addresses the role of rocking effects in the representation of isolated structures through RTHS. The results of different RTHS architectures show that when rocking is not taken into account, the base displacement and interstory drifts can be underestimated by more than 50%. Results from the RTHS are compared to shaking table tests (STTs) of a mock‐up structure isolated with unbounded FREIs, with a maximum error less than 8% in peak and root‐mean‐square values of displacement and force.
Introducción: En este artículo se describe la simulación híbrida en tiempo real (RTHS) de un amortiguador no lineal de masa sintonizado (NTMD) y se comparan los resultados con los obtenidos de ensayos experimentales convencionales de una estructura a cortante, de un piso, con el NTMD.
Objetivo: El objetivo de este artículo es valuar la efectividad de una RTHS para estimar el desempeño de un NTMD.
Metodología: La metodología consistió de las siguientes tres etapas: identificación de la estructura principal, diseño del NTMD y evaluación experimental del sistema estructura-NTMD. Para la tercera etapa, se utilizaron RTHS y ensayos sobre mesa vibratoria.
Resultados: Los resultados de los ensayos en mesa vibratoria demostraron que el NTMD redujo el 77% y 63% de las aceleraciones pico y RMS de la estructura principal, con respecto a la estructura sin control. Los valores de estas reducciones obtenidos con RTHS fueron 73% y 63%, respectivamente. Los índices de precisión del sistema de transferencia correspondieron a una amplitud generalizada de 1.01 y un retraso de 2 ms.
Conclusiones: el NTMD, con una razón de masas del 10%, alcanzó reducciones superiores al 60% de la respuesta estructural. La RTHS y el ensayo de mesa vibratoria demostraron que el sistema estructura-NTMD tuvo solo un pico en la respuesta en frecuencia. El ruido en la retroalimentación de la RTHS aumentó el grado de amortiguamiento de la estructura controlada. Finalmente, los resultados experimentales demostraron que la RTHS es una técnica que predice efectivamente la aceleración RMS del sistema estructura-NTMD y puede sobreestimar ligeramente su aceleración pico.
More than 87% of the Colombian population lives in zones of intermediate and high seismic hazard, which has generated an increasing interest toward base isolated structures. Nowadays, this technique has been mainly applied to hospitals and bridges. However, it is necessary to expand the action field of isolators to diverse kind of structures in countries with high seismic hazard. In this direction, the performance of circular unbounded fiber reinforced elastomeric isolators (U-FREI) was studied in a two degrees-of-freedom (DoF), medium scale structure, under seismic excitation. This evaluation was achieved employing a Real-Time Hybrid Simulation (RTHS), which is defined as a modern cyber-physical technique used for the experimental evaluation of complex systems, that treats the system components with predictable behavior as a numerical substructure, and the components that are difficult to model as an experimental substructure. In this case, the main structure was considered as the numerical substructure and a couple of U-FREI was treated as the experimental substructure. The RTHS was evaluated using a set of Current Assessment Measurements, where an accurate tracking of the transfer system was determined. Furthermore, the experimental results were compared with Shaking Table Tests (STT) developed at University of Naples Federico II. Particularly, peak and RMS comparison of force and acceleration signals showed a similar behavior of the RTHS according to the STT results. Overall, both approaches demonstrated that the U-FREI were able to reduce more than the 70% of the structural drift with respect to the fixed structure, and the applied RTHS methodology was verified.
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