Seismic Performance of the Inerter and Negative Stiffness–Based Dampers for Vibration Control of Structures

Passive energy dissipation devices or supplemental damping devices have been successfully implemented into structures for controlling the excessive vibrations under wind and seismic excitation. Recent developments in the form of negative stiffness dampers (NSDs) and inerter-based vibration absorbers (IVAs) as potential energy dissipation devices are of considerable interest to researchers. The present study evaluates the performance of the combined NSD and IVA as a possible alternative to the traditional energy dissipation devices such as viscous dampers (VDs) and viscoelastic dampers (VEDs). The mathematical formulation and optimal design of the combined NSD and IVA mechanism are presented. A 20-storey benchmark building is modeled as a multi-degree-of-freedom (MDOF) shear building. The dynamic equations for the MDOF building are written in the state-space form, and a simple optimization approach based on effective modal damping is prescribed. Comparative performance between traditionally applied and novel IVA and NSD is investigated. The design considerations to analyze structures employing combined NSDs and IVAs are developed. It is demonstrated that NSDs and IVA-based passive energy dissipation devices are the most efficient devices in reducing inter-storey drifts and floor accelerations compared with VDs and VEDs using the same damping coefficient.

The implication of outflow structure for the rapid intensification of tropical cyclones under vertical wind shear

The implication of outflow structure for tropical cyclone (TC) rapid intensification (RI) is investigated via a climatological study using the best-track, reanalysis and infrared brightness temperature data during 1980–2019. Composite analyses are performed in a shear-relative framework for the RI events under different strengths of environmental shear. Results show that for the RI events under moderate (4.5–11 m s-1) or strong (> 11 m s-1) environmental shear the RI onset follows a significant increase of upper-level outflow upshear of the storm, which is intimately linked with the increasing active convection upshear. The intensified outflow blocks the upper-level environmental flow and thus decreases the local shear, building an environment favorable for RI. In contrast, the RI under weak environmental shear (< 4.5 m s-1) is found to be less attributed to this outflow-blocking mechanism. Comparison between the RI and non-RI cases under moderate or strong environmental shear reveals that the RI cases tend to have stronger outflow and convection in the upshear flank than the non-RI cases, confirming the importance of outflow blocking on the occurrence of RI. Statistical analysis further indicates that the 24-h future intensity change under moderate or strong shear is more negatively correlated with the local shear than with the environmental shear, implicating the potential of local shear and upshear outflow as predictors to improve the forecasting of TC intensity change and especially RI. Further analysis suggests that the environmental thermodynamic conditions may play an important role in modulating the upshear convection and thus outflow blocking.

On the Effect of Nonlinear Energy Sink Damping in Seismic Vibration Attenuation

Nonlinear Energy Sinks (NESs) have been proposed for passively reducing the amplitude of vibrations in different types of structures. The main advantage of NES over traditional Tuned Mass Dampers (TMDs) lies in its capability to redistribute the vibrating energy inside a primary structure, what effectively reduces the amplitude of the structure oscillations over a wide range of frequencies. However, the performance of an NES can be substantially affected even by small variations on input energy as in the case of buildings under seismic ground excitation. In this work it is shown that the NES energy sensibility can be significantly reduced by properly selecting the NES damping coefficient. A three stories shear building model subject to seismic ground excitation is used to numerically study the effect that NES damping has on its vibration reduction performance.

Critical Response of High-Rise Buildings With Deformation-Concentration Seismic Control System Under Double and Multi Impulses Representing Pulse-Type and Long-Duration Ground Motions

The critical responses are investigated for a high-rise building with a deformation-concentration seismic control system under double and multi impulses representing pulse-type and long-duration ground motions, respectively. The critical responses were studied for an elastic-plastic multi-degree-of-freedom (MDOF) shear building model under a double impulse and a multi impulse in the previous papers. However, it seems difficult to derive the critical response for a realistic three-dimensional (3-D) nonlinear frame model with a deformation-concentration seismic control system under such double and multi impulses. The criteria on the criticality of the double and multi impulses for the elastic-plastic MDOF shear building model derived in the previous research are extended to this realistic controlled 3-D frame model by regarding the sum of base story shear forces of both main and sub buildings as a key quantity. In the analysis, the concepts of “Double Impulse Pushover (DIP)” and “Multi Impulse Pushover (MIP)” introduced before are used effectively for clarifying the progressive performances for the increasing input level. The analyses of total input energy, frame hysteretic energy and damper dissipation energy are conducted and the criticality of the input derived based on the above-mentioned criteria is investigated in detail.

ANALISIS RESPON DINAMIK TANAH BERPOTENSI LIKUIFAKSI PADA UNDERPASS YOGYAKARTA INTERNATIONAL AIRPORT (YIA)

Underpass Yogyakarta International Airport (YIA) terletak di pesisir pantai selatan jawa dekat dengan pertemuan lempeng tektonik. Kondisi geologi di lokasi Underpass YIA termasuk formasi geologi endapan alluvial, dimana sepanjang underpass ditemukan lapisan tanah berupa lempung pasiran dan pasir. Aktivitas seismik serta kondisi geologi dan geoteknik menyebabkan wilayah Underpass YIA rentan terhadap gempa bumi berpotensi likuifaksi. Penelitian ini bertujuan untuk menganalisis respon dinamik tiap lapisan tanah berpotensi likuifaksi dengan ragam spektrum Multi Degree of Freedom serta memodelkan lapisan tanah berupa shear building. Evaluasi bawah permukaan didasarkan pada data pengeboran dan N-SPT serta data tanah pada 5 titik di sepanjang Underpass YIA. Nilai percepatan batuan dasar ditentukan berdasarkan peta gempa SNI 1726-2012. Piranti lunak MATLAB digunakan sebagai alat bantu dalam perhitungan analisis perilaku dinamik. Hasil analisis menunjukkan bahwa nilai simpangan tiap lapisan tanah semakin mendekati permukaan cenderung semakin besar karena nilai kekakuan tanah semakin mengecil. Kekakuan tanah yang semakin kecil menghasilkan nilai frekuensi sudut semakin kecil dan periode getar semakin besar mendekati permukaan tanah. Hasil analisis menunjukkan adanya potensi likuifaksi pada kedalaman 4-6 m dari permukaan tanah jika terjadi gempa bumi dengan nilai percepatan muka tanah maksimum (amax) lebih besar dari 0,44g.

Análise de confiabilidade estrutural em sinais de excitação randômica aplicando métodos estatístico linear-experimental e da bioengenharia

Este trabalho demonstra um estudo de métodos estatísticos lineares-experimental e do sistema imunológico artificial de seleção negativa, aplicados a excitação randômica de um sistema dinâmico estrutural. No desenvolvimento deste trabalho foi desenvolvido uma estrutura shear building de dois andares excitado randomicamente, e a falha foi causada por uma perturbação externa aleatória, cujo sinal ruidoso foi tratado pelo filtro de Wiener e posteriormente aplicado o método estatístico linear-experimental e sistema imunológico artificial de seleção negativa. O resultado de ambas as aplicações permitiu uma análise direcionada e objetiva, demonstrando que o espectro do sinal contém níveis qualitativos e quantitativos de grande significância em aplicações na engenharia.

Study on the Sensitive Factors of Structural Nonlinear Damage Based on the Innovation Series

Constructing a damage-sensitive factor (DSF) is one of the key steps in structural damage detection. In this paper, innovation series extracted from the auto-regressive conditional heteroscedasticity (ARCH) model are proposed to construct a DSF, which is defined as the standard deviation of innovation (SDI). A three-story shear building structure is used to demonstrate and verify the performance of the proposed method, and the results are compared with the standard deviation of the residuals (SDR) based on an auto-regressive (AR) model. In the proposed method, the AR model is established using the acceleration responses obtained from the reference and test states. The residual series are then extracted for fitting the SDR. Subsequently, the ARCH model is constructed based on the residual series from the AR model, and a new DSF of SDI is defined. This study focuses on analyzing the accuracy of fitting AR model and ARCH model to vibration response data via the normal probability distribution, and identifying the characteristics of the residual and innovation series. The mean squared error (MSE) is used as the loss function to calculate the loss on residual and innovation series from the AR model and ARCH model, respectively. The results demonstrate that the SDR can be used for nonlinear damage detection. However, the proposed SDI can provide more accurate nonlinear damage identification and is robust to varying environmental condition and small damages. Thus, the innovation series developed based on ARCH model are promising for expressing and constructing nonlinear DSFs.

Seismic Assessment of 10-Story Building Using Tuned Mass Damper

In this paper, optimum parameters of Tuned Mass Dampers (TMD) are considered to control the responses of 10-story shear building under harmonic loading and 22 set of seismic records of FEMA-P695. The criterion used to obtain the optimum parameters is to select mass ratio, the frequency (tuning) and damping ratio that would result in smallest lateral displacements. State-space equations of motion are presented to compute the structural responses by developing a MATLAB file. A 10-story shear building is presented as a case study to assess the effects of TMDs on the multi-story structures. The results indicate that using TMD can reduce structural responses up to the average 20% under earthquake excitation and up to 90% under harmonic loadings. TMDs are not always effective under any type of ground motion; therefore, being aware of the given location is significant to design TMDs properly.