•Physical realizations and mechanical models of inerter are briefly presented.•Inerter-based vibration control systems and their applications are comprehensively reviewed.•The remaining challenges of ...inerter-based vibration control systems are discussed.
Structural vibration control has received considerable research attentions in the past few decades, with special emphasis on developing effective, affordable and applicable control systems to protect the structures against natural or man-made hazards. In 2002, a two-terminal mechanical element, dubbed inerter, was proposed based on the force-current analogy, offering many potentials for upgrading conventional structural vibration control systems. Over the past two decades especially in the recent five years, extensive research efforts have been made for the development of inerter-based vibration control systems. This paper aims to provide a state-of-the-art review on the research and development of inerter-based passive vibration control systems and their applications. It begins with the concept and physical realizations of inerter. The mechanical models of inerter are then presented. Subsequently, this paper reviews the applications of inerter in civil engineering and discusses its benefits comparing to conventional vibration control systems. Finally, some discussions are made on the unresolved problems and the possible topics for future studies.
•Using THPI for offshore platform heave motion control is proposed and investigated.•The control performances of FHP, THP and THPI are derived and compared.•The influences of size and depth of the ...heave plate are parametrically investigated.•A novel hydraulic inerter is proposed to realize the THPI.
The undesirable motions resulting from wave loading can lead to the long-term fatigue damage or even catastrophic sinking of offshore semi-submersible platforms (SSP). It is therefore by all means necessary to suppress the excessive vibrations of SSP. Many methods have been proposed to mitigate the heave motion of offshore platforms, such as using a fixed heave plate (FHP) to increase the draft and damping of the system, or adopting a tuned heave plate (THP) to form a tuned mass damper (TMD) system. In this paper, a novel inerter-based control system, namely a tuned heave plate inerter (THPI), is proposed for control of SSP heave vibrations. In this system, an inerter device, which can transform the linear motion into the high-speed rotational motion and thus significantly amplifies the physical mass of the system, is added to the THP to further improve the performance of conventional THP. Analytical studies are performed to investigate the effectiveness of the proposed method. The mean square heave motions of SSP without control device and with FHP, THP and THPI are stochastically formulated, and the optimal design parameters for THP and THPI are derived. Parametric studies are conducted to investigate the influences of the size and original depth of heave plate on the optimal performances of FHP, THP and THPI. Finally, a novel waterwheel inerter is developed to realize the suggested device. The analytical results show that THPI is more effective to mitigate the heave motion of SSP compared to the conventional methods, and the novel waterwheel inerter is capable of generating a large apparent mass by using a small waterwheel.
Soil–structure interaction (SSI), which characterizes the dynamic interaction between a structure and its surrounding soil, is of great significance to the seismic assessment of structures. Past ...research endeavors have undertaken analytical, numerical, and experimental studies to gain a thorough understanding of the influences of SSI on the seismic responses of a wide array of structures, including but not limited to nuclear power plants, frame structures, bridges, and spatial structures. Thereinto, large-span spatial structures generally have much more complex configurations, and the influences of SSI may be more pronounced. To this end, this paper aims to provide a state-of-the-art review of the SSI in the seismic assessment of large-span spatial structures. It begins with the modelling of soil medium, followed by the research progress of SSI in terms of numerical simulations and experiments. Subsequently, the focus shifts towards high-lighting advancements in understanding the seismic responses of large-span spatial structures considering SSI. Finally, some discussions are made on the unresolved problems and the possible topics for future studies.
•The prototype of a rotational inertia damper (RID) is manufactured and tested.•An equivalent viscous damping ratio of more than 0.4 is realized when the RID is installed in the water.•A mechanical ...model considering inerter nonlinearities is established to accurately predict the behaviors of RID.
An inerter is a two-terminal mechanical device with the property of generating a resisting force that is proportional to the relative acceleration across its terminals. Due to its distinct mass amplification and negative stiffness effects, inerter has been applied to enhance the performance of conventional control systems, e.g. tuned mass damper (TMD) and vibration isolation system (VIS). Very recently, a novel inerter-based damper dubbed rotational inertia damper (RID) that is capable of generating a significant damping force was proposed by the authors to control the vibrations of offshore platforms, and its control effectiveness was examined through analytical studies. In the present study, a RID prototype was manufactured and tested under harmonic excitations for an in-depth understanding and demonstration of its mechanical behaviors. A precise mechanical model considering inerter nonlinearities is proposed to predict the behaviors of the RID, and the corresponding parameters are identified by using a nonlinear least squares method based on the experimental results. The theoretical results predicted by the proposed mechanical model are then compared with the experimental results, good agreements are achieved. The results demonstrate that the developed RID has a good capacity for energy dissipation, and the proposed mechanical model is accurate in predicting the behaviors of the RID.
•A novel inerter-based vibration isolation system (IVIS) is proposed for floating platforms.•Analytical studies are performed to investigate the control performance of IVIS.•The IVIS performs better ...in terms of the control performance and effective frequency band.•The IVIS is more practical since it can realize the best performance by adjusting its inertance.
This paper develops an inerter-based vibration isolation system (IVIS) for heave motion mitigation of semi-submersible platforms (SSPs) subjected to sea waves. An analytical model of a classical SSP equipped with IVIS is first established and validated by comparing the heave response amplitude operator (RAO) with the previous experimental and numerical results, and the corresponding equations of motion are derived. Optimization analyses are performed to search for the optimum inertance-to-mass ratio of IVIS by minimizing the heave motion standard deviation of the SSP. A case study is carried out to demonstrate the control performance of IVIS in the frequency and time domains. The results indicate that the proposed IVIS is more effective and has a wider effective frequency range compared to the conventional vibration isolation system (VIS). By introducing a parallel-connected inerter, the reduction ratio of the receiving body can be further improved by more than 23%. More importantly, the IVIS can achieve the best control performance under different wave conditions by adjusting the inertance in the system. The proposed IVIS is an attractive alternative to the conventional vibration isolation systems for offshore platforms.
Electricity transmission system is well recognized as a lifeline system in the modern society, and its failures in past major earthquakes have aroused the concern about its seismic vulnerability. In ...the present study, fragility curves are developed to assess the vulnerability of a typical transmission tower subjected to near-field ground motions. A probabilistic seismic demand model (PSDM) is constructed for the transmission tower in terms of the maximum inter-segment drift ratio (ISDR) and the spectral acceleration (Sa) at the fundamental period of the structure. Pushover analysis is performed to define the capacity limit states for the transmission tower, which are serviceability, damage control and collapse prevention in this research. The data for the PSDM are acquired by using incremental dynamic analyses (IDAs) of a suite of seismic records. Additionally, the influence of the seismic incident angles and the coupling effect between the transmission tower and lines on the structural fragility are further investigated. The results quantify the seismic vulnerability of the transmission tower and demonstrate the influence of the seismic incident angles and the dynamic coupling effect between the transmission tower and lines.
•A new probabilistic seismic demand model is constructed for the transmission tower•Fragility curves are developed for the transmission tower subjected to near-field ground motions•Influence of the seismic incident angles and the dynamic coupling effect on the structural fragility are investigated.
•Rotational inertia dampers are proposed to control both the heave and pitch motions of SSP.•Performances of fixed heave plate (FHP), tuned heave plate (THP) and RID are studied and compared.•The ...RIDs can provide almost the same or even better control performance with a smaller physical mass.
Semi-submersible platforms (SSPs) are widely applied for energy mining in the ocean. During its service life, SSP may be subjected to excessive heave and pitch motions induced by sea waves, which in turn may result in fatigue problems of structural components or even catastrophic capsizing of the platform. It is therefore important to mitigate the heave and pitch motions of SSP by all means. In the present study, a novel inerter-based control system, rotational inertia damper (RID), is proposed to simultaneously mitigate the heave and pitch motions of SSP in the shallow sea. The responses of SSP equipped with RID systems subjected to six typical wave conditions are calculated in the frequency and time domains respectively based on the developed analytical models and Simulink models. For comparison, the models and responses of SSP without and with traditional control devices, i.e. fixed heave plate (FHP) and tuned heave plate (THP), are also developed and calculated. The results reveal that the RID system can achieve almost the same or even better control effectiveness compared to the conventional systems with a much smaller additional mass to the SSP especially when the SSP is under harsher waves.
•Full-scale tests of a latticed steel tubular transmission tower are performed.•A buckling and softening failure model is developed to capture behaviors of members.•Numerical simulations are ...conducted to reproduce the failures of the tower in the tests.
Ultimate capacity evaluation is of vital importance for electricity transmission tower-line systems, which are well recognized as the lifeline engineering in modern society. Undoubtedly, full-scale tests are the most effective and straightforward method for an in-depth understanding of the structural ultimate capacity. In the present study, full-scale tests of a latticed steel tubular transmission tower are performed with emphasis on the failure mechanism of the tower under extreme wind load. Structural responses, ultimate capacity and failure mechanism of the transmission tower in the tests are presented and discussed, respectively. Numerical simulations are then carried out to reproduce the failure of the transmission tower in the tests. In the finite element (FE) model, a buckling and softening failure model is developed to capture the behaviors of the transmission tower. Finally, numerical results are investigated and compared with those obtained in the full-scale tests. Experimental and numerical results demonstrate that the latticed steel tubular transmission tower is designed with enough capacity to resist the designed loads, and the buckling failures of leg members are the dominant cause of the collapse of the transmission tower. Additionally, the developed buckling and softening failure model can accurately reproduce the displacements, ultimate capacity and failure mechanism of the transmission tower. This research can extend the current state of knowledge concerning full-scale tests of latticed transmission towers, and provide a more comprehensive understanding of the performance of latticed steel tubular transmission towers under extreme loads.
•Effects of ground motion parameters and structural damping on the optimal design of inerter-based TMDs were investigated;•Design formulas were proposed to estimate the optimal parameters of ...inerter-based TMDs;•The accuracy of proposed formulas was validated;•Control effectiveness of inerter-based TMDs under real earthquake records was examined.
Tuned mass dampers (TMDs) are widely adopted to control the adverse vibrations of engineering structures. To further improve the effectiveness of TMD, inerter was introduced into TMD recently to form inerter-based TMD systems. Similar to TMD, inerter-based TMDs should be carefully designed (optimized) in order to get their best control performances. In the previous studies on using inerter-based devices for seismic induced vibration control, the external excitation was normally simplified as a white noise and the inherent structural damping was ignored. However, it is well known that seismic excitation cannot be simply assumed as a white noise and damping always exists in the structure. The parameters obtained by the previous optimization procedures thus do not necessarily result in the best performance of the device. In the present study, the equations of motion of a single-degree-of-freedom (SDOF) structure equipped with three types of inerter-based TMDs subjected to seismic excitation are firstly developed. Instead of using a white noise as input, the filtered Kanai-Tajimi spectrum, which is characterized by the site damping and frequency, is adopted to model seismic ground motion. Then the effects of site damping, site frequency and structural damping on the inerter-based TMDs are comprehensively investigated and formulas are proposed to estimate the optimal parameters. Lastly, the responses of a structure without control and controlled by an inerter-based TMD under simulated and recorded earthquake ground motions are analysed by using MATLAB/Simulink. Numerical results show that the optimal parameters of inerter-based TMDs are significantly dependent on the site frequency and structural damping, while the site damping has little influence. Moreover, the accuracy of the proposed formulas is validated, and the control effectiveness of the inerter-based TMD is confirmed.
•The IEEE pre-approved record and its filtered version can provide different results.•Ground motion variations should be considered in evaluation of transmission towers.•Artificial ground motions may ...be inadequate for evaluation of transmission towers.•Transmission towers are highly non-ductile.•Performance of transmission towers is sensitive to the ground motion amplitude.
Electricity transmission towers are vital in minimizing the risk of disruption of power supply after earthquakes. However, no guidelines currently exist for seismic performance evaluations of electricity transmission towers. Considering electricity transmission towers should have the same desirable performance as electric substations, this research team assessed seismic performance of transmission towers using the Institute of Electrical and Electronics Engineers (IEEE) recommended document for seismic design of substations (IEEE 693). A representative existing system was identified as the prototype. A computer model was developed for Response History Analyses (RHA) of the prototype. Three suites of ground motions matching the IEEE 693 required response spectrum were considered, consisting of one suite of three pre-approved empirical and random records and another two suites of records selected based on different criteria. It was found that the prototype designed according to the equivalent static force method meets the qualification requirements of IEEE 693. Additionally, it was found that a filtered version of the pre-approved empirical record to accommodate the limitations of some shake tables do not always provide results consistent with the un-filtered record. Moreover, analysis results reveal that different historic records selected matching the same target spectrum cause different responses in the prototype, suggesting the need to consider variation of ground motions. Further, it was found that the artificial ground motions may not always be adequate for analyses of transmission towers depending on what criterion is used in record selection. Last, it was found that failure of the prototype is highly non-ductile and seismic performance of the prototype is very sensitive to the amplitude of the input ground motions.
