Numerical and experimental study of tuned liquid damper effects on suppressing nonlinear vibration of elastic supporting structural platform

© 2020, Springer Nature B.V. A liquid storage container installed on the top of a fixed offshore platform is used as a tuned liquid damper (TLD) to suppress structural vibration through sloshing motion and viscous energy dissipation. To further optimize TLD capability on suppressing vibration and accurately predict nonlinear coupled processes between TLD and offshore platform, a two-way coupling numerical model was developed to investigate the nonlinear vibration of TLD and elastic supporting structural platform (SSP). Meanwhile, laboratory experiments of TLD interaction with the SSP were also conducted on a six-degree-of-freedom motion simulator to validate the developed model. The bottom plate of the SSP was fixed to the motion simulator and subjected to sinusoidal excitation in the horizontal direction. The natural frequency of bare SSP was obtained firstly by shaking table tests at a wide range of external excitation frequencies and finite element modal analysis. The developed numerical model was validated by using the present experimental data in terms of both the roof plate displacements of the SSP and the free surface elevation and waveforms in TLD. Effects of TLD in suppressing the nonlinear vibration of the elastic SSP were further investigated numerically by varying the mass and frequency ratio of TLD to the SSP. Wavelet transform was used to analyze the nonlinear interaction and energy distribution characteristics of the sloshing wave in TLD. It was shown that the peak displacement response of the roof plate had been significantly reduced, and at the same time a frequency shift occurred after TLD installed on the SSP. In addition, the sudden excitation breaks the balance of energy absorption and production in fluids, resulting in larger wave height. Finally, a mass ratio of 2% and a frequency ratio of 1 were found to be optimal by considering the frequency shift and energy dissipation

Evaluation of optimal analysis, design and testing of electromagnetic shunt damper for vibration control of a civil structure

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordThe current study is to find out alternative damping to provide satisfactory vibration suppression performance in civil engineering. Accordingly, electromagnetic actuators and electromagnetic dampers (EMDs) are utilised to generate electromagnetic damping. For further discussion on control of vibration serviceability problem in civil structure, the use of a linear voice coil motor (LVCM) as an EMD is implemented to attenuate unwanted vibration. To induce appropriate electromagnetic damping the terminal ends of the LVCMneed to connect with shunt circuits. The basic resistor series circuit and resistor, inductor and capacitor (RLC) oscillating circuit are employed to connect to the LVCM in term of enhancing the EMD damping. However, a design of the electromagnetic shunt damper (EMSD) is required with the generic HØ and H2 robust optimisation techniques to determine shunt circuit components, in which the results of these optimisations were discussed on the previous author study. For extending the EMSD study, the resulting EMSD is experimentally exploited to a six-storey aluminium frame structure. The random and harmonic excitations are selected to input to the structure to examine the performance of the electromagnetic damping. The finding of the experimental test of the EMSD gives satisfactory vibration suppression performance.Engineering and Physical Sciences Research Council (EPSRC

Symmetry in Structural Health Monitoring

In this Special Issue on symmetry, we mainly discuss the application of symmetry in various structural health monitoring. For example, considering the health monitoring of a known structure, by obtaining the static or dynamic response of the structure, using different signal processing methods, including some advanced filtering methods, to remove the influence of environmental noise, and extract structural feature parameters to determine the safety of the structure. These damage diagnosis methods can also be effectively applied to various types of infrastructure and mechanical equipment. For this reason, the vibration control of various structures and the knowledge of random structure dynamics should be considered, which will promote the rapid development of the structural health monitoring. Among them, signal extraction and evaluation methods are also worthy of study. The improvement of signal acquisition instruments and acquisition methods improves the accuracy of data. A good evaluation method will help to correctly understand the performance with different types of infrastructure and mechanical equipment

Variable friction cladding connection for multi-hazard mitigation

Safety and serviceability design of civil infrastructure, including buildings and energy, lifeline, communication, and transportation systems, is critical in providing and maintaining services and benefits to our communities. In modern society, new constructions tend to be more flexible due to advances in material science and construction technologies. A key challenge in the design of these structures is to meet the motion requirements under operational and extreme loadings. The purpose of a motion-based design (MBD) approach is to ensure that motion requirements are met under the design loads, after which strength requirements are verified and met. A popular method under MBD is the inclusion of supplemental damping systems. For instance, several passive damping systems were introduced over the last decades, demonstrating high effectiveness at reducing seismic vibrations for buildings. These traditional passive control systems, although capable of mitigating targeted loads, are restricted to single hazard one-at-a-time due to their limited performance bandwidth. It follows that they become difficult to implement when multiple excitation inputs are considered either combined or individually, termed multi-hazards. Alternatively, one can use high-performance control systems that include active, semi-active and hybrid control systems, to adapt structural responses under different types of hazards. This work proposes and characterizes a novel high-performance control system termed variable friction cladding connection (VFCC). The VFCC leverages the motion of cladding elements to dissipate energy. It consists of friction plates upon which variable normal force is applied through an adjustable toggle system controlled by a linear actuator. When locked, the device acts as a traditional rigid cladding connection with high stiffness for daily operation and also provides maximum friction force to passively dissipate blast energy transferred to the structure. A rubber bumper is integrated to avoid collision between the structure and cladding elements under high impact loads. The VFCC, once activated under wind and seismic hazards, performs as a semi-active damping device that leverages cladding mass to reduce structural vibrations via a feedback control system. Here, a device prototype is fabricated and tested in laboratory to identify and validate its dynamic behavior. Experimental results show that the device prototype functions as designed and demonstrates its high promise for multi-hazard mitigation. In order to effectively implement the VFCC, an MBD procedure is developed and demonstrated on building examples subjected to multi-hazards. The MBD procedure includes the analytical quantification of hazards, identification of structural motion objectives, and iterative design of cladding connection parameters. The MBD approach is first developed for each hazard individually and then extended to multi-hazard design for blast, wind, and seismic loads. Numerical simulations are conducted on several building examples where the VFCC is simulated under a linear quadratic regulator controller (semi-active case) for wind and seismic loadings, and under a locked position (passive-on case) under blast load. An uncontrolled case with a traditional rigid cladding connection is used to benchmark results, and a passive-on case is simulated under wind and seismic loads also for benchmark purposes. Simulation results show that the designed VFCC is capable of reducing the response of the uncontrolled structures under the prescribed performance objectives under multi-hazard loadings. Overall, this work demonstrates the VFCC\u27s high capability of mitigating multi-hazards by leveraging motion of the cladding system, and the promise of the developed MBD approach enabling its holistic integration at the design phase

Model Validation and Simulation

The Bauhaus Summer School series provides an international forum for an exchange of methods and skills related to the interaction between different disciplines of modern engineering science. The 2012 civil engineering course was held in August over two weeks at Bauhaus-Universität Weimar. The overall aim was the exchange of research and modern scientific approaches in the field of model validation and simulation between well-known experts acting as lecturers and active students. Besides these educational intentions the social and cultural component of the meeting has been in the focus. 48 graduate and doctoral students from 20 different countries and 22 lecturers from 12 countries attended this summer school. Among other aspects, this activity can be considered successful as it raised the sensitivity towards both the significance of research in civil engineering and the role of intercultural exchange. This volume summarizes and publishes some of the results: abstracts of key note papers presented by the experts and selected student research works. The overview reflects the quality of this summer school. Furthermore the individual contributions confirm that for active students this event has been a research forum and a special opportunity to learn from the experiences of the researchers in terms of methodology and strategies for research implementation in their current work

Novel Approaches for Structural Health Monitoring

The thirty-plus years of progress in the field of structural health monitoring (SHM) have left a paramount impact on our everyday lives. Be it for the monitoring of fixed- and rotary-wing aircrafts, for the preservation of the cultural and architectural heritage, or for the predictive maintenance of long-span bridges or wind farms, SHM has shaped the framework of many engineering fields. Given the current state of quantitative and principled methodologies, it is nowadays possible to rapidly and consistently evaluate the structural safety of industrial machines, modern concrete buildings, historical masonry complexes, etc., to test their capability and to serve their intended purpose. However, old unsolved problematics as well as new challenges exist. Furthermore, unprecedented conditions, such as stricter safety requirements and ageing civil infrastructure, pose new challenges for confrontation. Therefore, this Special Issue gathers the main contributions of academics and practitioners in civil, aerospace, and mechanical engineering to provide a common ground for structural health monitoring in dealing with old and new aspects of this ever-growing research field

Analysis and design of non-linear seismic isolation systems for building structures—An overview

In this paper, the development of non-linear building isolation systems is overviewed. The study summarizes commonly used linear building isolation systems in two categories, which are building base isolation systems and building inter-storey isolation systems. Typical isolators including Lead-Rubber Bearings Friction Pendulum Bearings inter-storey viscous damper and Tuned Mass Damper are reviewed. The analysis and design of linear building isolation systems are also reported. After that, non-linear building isolation systems are introduced from two aspects based on their dynamic characteristics. They are (i) non-linear stiffness isolators including Quasi-Zero Stiffness isolators and Non-linear Energy Sink and (ii) non-linear damping isolators including power-law viscous dampers and magnetorheological dampers. Practical implementations of these non-linear isolators are introduced. Finally, the analysis and design of non-linear building isolation systems are discussed. Traditional equivalent linearization approaches and advanced non-linear frequency design approaches are introduced. The promising applications of the non-linear frequency design approaches to building isolation systems are also demonstrated in this review paper

Passive, semi-active, active and hybrid mass dampers: A literature review with associated applications on building-like structures

In this paper, a state-of-the-art literature review is presented emphasising on the development of control variants for mass damper schemes on building-like structures. Additionally, a systematic literature review is conducted addressing three relevant questions: What type of mass damper is preferable by the associated industry? How are mass dampers distributed around the world? Is industry following research? Through the systematic literature review, updated lists of mass damper implementations and control algorithm applications in real-life structures were compiled. 208 case-studies are discussed in total. It is found that, 63% of them refer to passive tuned mass dampers, 31% to hybrid mass dampers, 4.0% to active mass dampers and only 2% to semi-active mass dampers. Regarding control algorithms, controllers of 24 structures driving semi-active, active or hybrid mass dampers are presented. It is concluded that the industry considerably lags behind latest structural control research both regarding implementations and overall management