Reduction Of Structural Response Research Articles

Coupled numerical simulation of liquid sloshing dampers and wind–structure simulation model

Long-span bridges, high-rise buildings, chimneys, or wind turbines are often susceptible to wind-induced vibrations due to their high flexibility and lightweight. Therefore, these structures should be carefully designed to sustain the wind loads. Employing robust solutions for vibration mitigation, such as tuned liquid dampers (TLDs), enables energy dissipation at reduced structural and maintenance costs. This study presents a numerical coupling methodology for evaluating the wind-induced response of slender vertical structures that include a TLD. The methodology is based on coupling a Computational Fluid Dynamics (CFD) model of a TLD, a semi-analytical aerodynamic force model, and a structural model. The coupling is realized in a time-domain fashion by continuously exchanging sloshing forces, aerodynamic forces, and structural response. The highlight is the use of the volume of fluid (VOF) method as a CFD strategy to represent the sloshing damping forces, including an experimental validation. The methodology is applied to (i) a chimney-type structure to mitigate the buffeting and vortex-induced vibrations and (ii) a high-rise building to reduce the acceleration buffeting response for human comfort. In both cases, strategy for TLD predesign is employed based on free- and forced-vibration analysis, an equivalent tuned mass damper model, and wind vibrations, respectively. The results of the dynamic analyses show that there is a significant reduction in structural response for both cases. The outcome of this study is intended to showcase the applicability of CFD for TLD predesign and modeling nonlinear sloshing forces during dynamic analysis as an alternative to experiments. Thus, it is intended to serve academics as well as practitioners.

Shared vibration absorbers for connected SDOF structures

This paper considers the response reduction of structures connected with shared vibration absorbers. The response of two single-degree-of-freedom (SDOF) structures next to each other are minimized by a connected mass damper as an absorber. The optimum values of the damper’s properties are obtained by using metaheuristic algorithms. The objective function is taken as the H2 norm of the regulated outputs, where the regulated outputs are taken as displacements of both structures. To simplify the problems, the stiffness and damping properties of the absorber are taken the same. Genetic algorithms are used to optimize the absorber parameters. Two cases are considered in the numerical examples. The first case is when we have twin buildings, in which each structure’s mass, stiffness, and damping are the same. The second case is when the structure stiffnesses are different, one is the stiff structure, and another is the flexible one. Several dampers’ constraints are considered to see the possibilities of the connected absorber to reduce the structural responses. The simulations of the structures subjected to four selected ground excitations were carried out to show the absorbers’ performance in reducing the structures’ response with different percentages of reductions.

Influence of Liquid Sloshing in the Vertical Limbs of Tuned Liquid Column Dampers on Structural Response Reduction

Influence of Liquid Sloshing in the Vertical Limbs of Tuned Liquid Column Dampers on Structural Response Reduction

Seismic Response Control of Similar Adjacent Structures Connected by Maxwell Dampers

The seismic response analysis of dynamically similar adjacent structures connected by Maxwell dampers is studied. The structural response for four different types of earthquake ground motions is investigated. The formulation of the equations of motion for two adjacent multi-degrees-of-freedom structures connected with Maxwell dampers is presented. The dampers effectiveness is evaluated in terms of hte reduction of structural responses namely displacement, acceleration and base shear force of the connected adjacent structures. A parametric study is carried out to obtain the optimum damper parameter for minimum response of the connected structures. Results show that Maxwell damper is quite effective for seismic response control of either structure by selecting appropriate parameter of damper. Further, lesser damper at appropriate locations can significantly reduce the earthquake response of the connected system.

Seismic Response Control of Parallel Structures Connectd by Passive Shape Memory Alloy Damper

A shape Memory Alloys are a class of novel functional materials that possess unique properties, including shape memory effect, super-elasticity effect, high damping characteristics, high corrosion resistance, temperature dependent Young modulus and extra ordinary fatigue resistance. In super-elastic phase, shape memory alloys are initially austenitic, upon loading, stress-induced martensite is formed, upon unloading, the martensite reverts to austenite at a lower stress level, resulting in the hysteretic behaviour, is more suitable property for energy dissipation device in structural engineering. In this paper, the response behaviour of two parallel structures coupled by passive Shape Memory Alloy dampers under various earthquake ground motion excitations is investigated. The equation of motion for the two parallel, single-degree-of-freedom structures connected by damper is formulated. The effectiveness of damper in terms of the structural response reduction namely, relative displacement and absolute acceleration of coupled structure is investigated. A parametric study is conducted to investigate the optimum parameter of the dampers. Results show that Shape Memory Alloy dampers connecting the parallel structures of different fundamental frequencies, the earthquake induced displacement response of either structure can be reduce effectively, but acceleration response of flexible structure is increases. Thus passive shape memory alloy damper is not much effective for seismic protection of coupled structure concept.

Wind and Seismic Response Control of Dynamically Similar Adjacent Buildings Connected Using Magneto-Rheological Dampers

Wind and/or earthquake-imposed loadings on two dynamically similar adjacent buildings cause vigorous shaking that can be mitigated using energy dissipating devices. Here, the vibration response control in such adjacent structures interconnected with semi-active magneto-rheological (MR) dampers is studied, which could also be used as a retrofitting measure in existing structures apart from employing them in new constructions. The semi-active nature of the MR damper is modeled using the popular Lyapunov control algorithm owing to its least computational efforts among the other considered control algorithms. The semi-active performance of the MR damper is compared with its two passive states, e.g., passive-off and passive-on, in which voltage applied to the damper is kept constant throughout the occurrence of a hazard, to establish its effectiveness even during the probable electric power failure during the wind or seismic hazards. The performance of the MR damper, in terms of structural response reduction, is compared with other popular energy dissipating devices, such as viscous and friction dampers. Four damper arrangements have been considered to arrive at the most effective configuration for interconnecting the two adjoining structures. Structural responses are recorded in terms of storey displacement, storey acceleration, and storey shear forces. Coupling the two adjacent dynamically similar buildings results in over a 50% reduction in the structural vibration against both wind and earthquake hazards, and this is achieved by not necessarily connecting all the floors of the structures with dampers. The comparative analysis indicates that the semi-active MR damper is more effective for response control than the other passive dampers.

Performance of Structure Equipped AP-TMD Compared with MTMD, ATMD, and PTMD against Earthquake Using Genetic Fuzzy Algorithm

During the past years, different control devices have been introduced and used to reduce the response of structures. This article presents the performance of active-passive tuned mass dampers (AP-TMDs) in the reduction of structural responses and a comparison between the uses of different controllers, including tuned mass damper (TMD), active tuned mass damper (ATMD), and multituned mass damper (MTMD). Analyzing and modeling the structure under four near- and far-field earthquakes are performed in MATLAB and SIMULINK. Finally, the responses of controlled and uncontrolled structures equipped with these controllers are investigated. Fuzzy and genetic-based fuzzy logic controllers are used to determine the control force of ATMD and AP-TMD, respectively. In order to compare the performance of the dampers, the mass ratio of TMDs is fixed in all cases and is taken to be 5%. Damping of the structure is considered equal to 5%. The frequency and damping ratio of TMDs with maximum and RMS displacement optimization criteria are obtained. The mass ratio of TMDs in controlled structures with MTMD and AP-TMD is calculated by numerical analysis. It can be inferred that using control force affects response reduction in both ATMD and AP-TMD controllers significantly. In addition, using AP-TMD can bring the merits of both passive and active systems by providing active control and reducing power requirements for control forces. All controllers are recommended for structural control although AP-TMD reduced maximum and RMS displacement by about 50% in the best case, which has better performance than others. On the other hand, ATMD decreased RMS acceleration by 37.5% on average in four earthquakes compared to the uncontrolled structure.

Seismic resonant metamaterials for the protection of an elastic-plastic SDOF system against vertically propagating seismic shear waves (SH) in nonlinear soil

The paper explores the key mechanisms that govern the dynamic interaction between resonant metamaterials (consisting of multiple unit cells embedded in the soil, with horizontally vibrating internal masses) and an existing nonlinear structure on nonlinear soil. Elastic behavior of the soil and of the SDOF system, representing the structure, is also investigated for comparison. The Real-ESSI Simulator is employed to develop in-plane (2D) finite element (FE) models, and an extensive parametric analysis is conducted to evaluate the influence of key parameters on the protective efficiency of resonant metamaterials. Both artificial and real ground motions are used as seismic excitation, vertically propagated through the soil as shear waves (SH), employing the Domain Reduction Method (DRM). Two protective mechanisms are identified. The first mechanism is related to the inertial interaction of the metamaterials with the surrounding soil, namely, it is the out-of-phase resonant oscillation of the internal metamaterial masses with respect to the soil at periods close to the natural period of the structure. The maximum reduction in structural response is achieved when the resonant period of the metamaterials is equal or a bit larger than the effective period of the structure. The second mechanism is related to the kinematic interaction of the metamaterials with the surrounding soil, namely, the presence of empty unit cells (no internal masses) in the soil next to the structure creates a protective “shadow” zone. This kinematic interaction mechanism becomes effective when the wavelength of the incoming seismic waves is comparable to the size of the metamaterials, and at the same time, the period of the waves is close to the natural period of the structure. When both soil and structural nonlinearities are considered, the effect of metamaterials remains always beneficial, and their action is localized, making them practically harmless to neighboring structures.

Computational Aerodynamic Optimization of Wind-Sensitive Irregular Tall Buildings

Wind-induced loads and motions play a critical role in designing tall buildings and their lateral structural systems. Building configuration represented by its outer shape is a key parameter in determining these loads and structural responses. However, contemporary architecture trends towards creating taller buildings with more complex geometrical shapes to offer unique designs that become a signature on the map of the world. As a result, evaluating wind-induced motions on such structures becomes more challenging to be evaluated and predicted. This paper presents a computational performance-based aerodynamic optimization with minor imposed modifications that have little to no impact on architectural and structural design intent. The developed tool aims to assist both architects and engineers to seek a sustainable optimal design decision at the early stage of design by employing different computational technological tools in an automated manner. A computational optimization methodology consisting of a computational fluid dynamic coupled with finite element analysis and embedded within a radial basis function surrogate model is proposed to mitigate wind-induced loads on tall buildings. In addition, a numerical example implementing the proposed methodology on selected case study is presented and discussed. The proposed approach was able to achieve a minimization of 13.83% and 23.12% for along-wind and across-wind loads, respectively, which is translated to a reduction in structural response by 12.95% and 14.31% in maximum deflection for along-wind and across-wind directions, respectively.

Optimal design of multi-storey buildings with tuned mass dampers using genetic algorithms and grey wolf optimization

Two 10-storey benchmark buildings exposed to different earthquakes are considered in the study in order to analyse the performance and capability of the design of the Tuned Mass Damper (TMD) with the optimal properties. Two optimisation algorithms, i.e. the Modified Genetic Algorithm (MGA) and the Grey Wolves Optimization (GWO) method, are used in the investigation. Firstly, the effectiveness of MGA and GWO, under optimally designed TMD system is verified by comparing the results with the ones obtained by other methods. In a second part, the optimum design of TMD system is determined by including mass of TMD as a design variable so as to assess the feasibility of MGA and GWO. The MGA and GWO methods hold the better responses based on the reduction in the displacement, drift and acceleration of all stories subjected to different seismic excitations. The smaller properties of the TMD are attained using the methods of MGA and GWO as compared to the ones obtained by the Den Hartog and Warburton methods based on the objective function. Therefore, the MGA and GWO approaches lead to more practical and efficient solutions, which allows us to design economically the TMD systems rather than that of the other methods based on the reduction of structural responses. The results show that the efficiency of the parameters and modifications can be enhanced by selecting the proper access in the regulation output with requirements to be diminished.

A hybrid metaheuristic method for optimization of active tuned mass dampers

AbstractA metaheuristic‐based tuning methodology for the optimization of active tuned mass dampers (ATMDs) is presented. The methodology considers both physical parameters of ATMDs and controller parameters of the control algorithm. The employed control algorithm is a proportional–integral–derivative type controller. ATMDs are used in structures in the reduction of structural responses resulted from earthquakes. The proposed methodologies must be feasible for real practices in construction, so consider all physical factors such as stroke capacity, limitation of the active control force, the time delay of the generated control signal, and a time‐saving one. A novel hybrid metaheuristic algorithm that combines the specific advantages of four metaheuristics (harmony search, flower pollination algorithm, teaching‐learning‐based optimization and Jaya algorithm) is proposed for the optimization process. The results of the process showed that ATMDs are more effective for high values strike limitations, compared to TMDs. The feasibility and effectiveness of the optimum control method are also demonstrated on a full‐size 76‐story structure.

Seismic Response Control of Elevated Water Tank using Base Isolation: A Review

Earthquake events are not something which can be avoidable. The Indian subcontinent has a background marked by devasting quakes. Quakes are generally caused when the stone underground out of nowhere breaks along an issue. Ground shake is caused by seismic waves due to sudden release of energy. The Centre of earthquake vibration is known as epicentre. Due to earthquake millions of lives are lost which can never be affordable. Most of the structures are subjected to vibrations; it causes destruction of country’s infrastructure. In the recent earthquakes many well designed concrete structures have been severely damaged or collapsed. To protect structures from response reduction of structures and important harm under such serious earthquakes has become a vital theme in structural engineering. In this investigation, we evaluated seismic performance of staging system of elevated water storage tank with or without Base Isolation by using SAP2000. From this examination the powers following up on elevated water tank because of seismic powers are determined for zone IV.

Development of a novel tuned liquid damper with floating base for converting deep tanks into effective vibration control devices

Despite the proven effectiveness of tuned liquid dampers (TLDs), readily available liquid storage tanks are rarely utilized for vibration control of laterally-excited structures, as these are deep tanks with low inherent damping. Further, the fluctuation in liquid level in these tanks also causes variation in the fundamental sloshing frequency, leading to detuning. To overcome these problems, a novel TLD with floating base (TLD-FB) is proposed, in which a constant and shallow liquid level is maintained between the free liquid surface and the floating base. The liquid above the floating base acts as a conventional shallow TLD that always remains tuned to the structural frequency. The paper demonstrates how the TLD-FB can be incorporated into a water storage tank system on an example building without disturbing its functionality and achieves structural response reduction, despite water level fluctuations in the tanks.

Hydrodynamic damping enhancement by implementing a novel combined rigid-elastic heave plate

Heave plates are structural components used for reducing the vibrations caused by environmental forces on marine and offshore structures by changing the hydrodynamic properties. The fact that the added mass increase via heave plates does not always lead to the structural response reduction underscores the role of damping in maintaining the vibration amplitude within allowable limits. In the present experimental study, a novel combined rigid-elastic design is used to improve the damping through the velocity increase in the elastic part and added mass creation in the central rigid part. The desired percentage of total added mass and damping can be adjusted by changing the rigid-to-elastic parts diameter ratio, which is the main scope of this experimental research. Frequency of vibration, which affects the elastic edge excited mode shapes, also affects the forming of the vortex shedding. Experimental tests show that the frequency increase generally causes high damping performance provided that the excited mode shapes are axisymmetric, which strongly depends on equivalent stiffness and mass.

Comparative Performance Study of Tuned Liquid Column Ball Damper for Excessive Liquid Displacement on Response Reduction of Structure

The tuned liquid column damper (TLCD) having a uniform cross-sectional tube of U-shaped, occupied with liquid is used as a vibrational response mitigation device. The tuned liquid column ball damper (TLCBD) is a modified TLCD, where, an immovable orifice, positioned at the middle part of the horizontal portion, is replaced by a metal ball. Different studies on the unconstrained optimization performance of TLCBD subjected to the stochastic earthquake have been performed where limitations on the maximum amplitude of liquid present in the vertical portion of the tube were not imposed. In the case of the high magnitude of earthquake and space constraint, the excessive liquid movement might get generated in the vertical portion of the tube which can create challenging circumstances. This can be taken care of by restricting the liquid movement up to a certain limit. The present investigation considers the optimum performance of the structure with TLCBD for mitigating the vibrational response with limited liquid movement in the vertical portion of the tube. A numerical study has been carried out to demonstrate the difference between constrained and unconstrained optimization of structure-TLCBD system. Numerical results show the influence of constraining cases on optimum parameters and performance behavior of the structure-TLCBD system.

Study and Comparison of Seismic Behaviour of Isolator-Damper Hybrid Control System with Conventional Structural Systems

In this paper, in addition to introduce a hybrid structural system contained local isolators and dampers, its behavior and functional capabilities were studied on a conventional structure. For this purpose, an RC frame building with six-story was designed based on valid codes and then, in four cases based on the number of spans, it was split into two separate adjacent frames. Base isolation was done underneath the columns of one frame, while the bottom connections of the other frame’s columns were remained fixed and viscous dampers provided the connection of two adjacent frames on the same floors. Nonlinear time history analysis (NTHA) under three near-fault and three far-fault earthquakes and frequency-domain analysis are performed. Displacement, drift, acceleration and shear forces of the stories in the four proposed hybrid cases with two limited cases, full base-isolated and full base-fixed frames, as well as nonlinear hysteresis behavior of a damper and an isolator are assessed. The results showed that using the novel hybrid control method in most cases can mitigate deteriorating effects of all types of seismic motions observed in the conventional structural systems. However, among them, two cases (2 isolated columns -5 fixed columns and 3 isolated columns -4 fixed columns) had the best significant influence on seismic performance and structural response reduction. Furthermore, frequency response functions of displacement and acceleration with respect to ground acceleration demonstrated that the two proposed cases further suppress the responses of the limited cases, over a wide range of frequencies including all natural frequencies. Due to decrease about 50-70% in the number of base isolators (compared to full isolation) lead to considerable construction cost savings. In spite of the limitation of ASCE7-10 code on separately using base isolators and dampers on structure, applying the proposed combination technique of these two dissipating devices can overcome the limitation.

2D dynamic structure-soil-structure interaction: A case study of Millikan Library Building

Dynamic structure-soil-structure interaction (SSSI) effects with large separation distance are investigated based on a case study of Millikan Library Building. The numerical results are obtained by two-dimensional (2D) anti-plane model and in-plane model using indirect boundary element method (IBEM) for any incident direction of seismic waves. It's shown that the SSSI effects may be detrimental or beneficial, and the amplification and reduction of structural response compared to the stand-alone structure may be up to 40% and 30%, respectively in the case of Millikan Library Building. The structural response is sensitive to adjacent building's parameters. Both for anti-plane model and in-plane model, more similar or heavier adjacent building has more significant influence. Moreover, beyond what was previously known, the SSSI effects may persist up to large separation distance, e.g., the amplification may be up to 36% when separation distance is up to b/λequ ≈ 2.5 (b ≈ 410 m). Of course, the detrimental or beneficial effects are not constant but appear alternately with variation of the separation distance, which should be considered comprehensively in the prediction of seismic response for design.

Semi-Active Control Performance Index for magneto-rheological dampers considering s-structure interaction

In this study, an instantaneous optimal control performance index for structures with magneto-rheological (MR) dampers is analytically defined. Absolute acceleration and absolute velocity feedback are implemented to this simple performance index. The performance index is another application of instantaneous optimal control algorithms. A three story structure incorporating an MR damper is presented as a numerical example. Modified Bouc Wen damper force model is used for obtaining the MR damper force. The electrical current need for the operation of the MR damper is taken into account by using a piece wise invertible MR damper model. Near fault earthquakes are used in the dynamic simulations. Seismic energy-based evaluations are carried out. Uncontrolled structural response reduction performance and power requirement of the MR damper is investigated. The analysis shows that proposed performance index is effective in reducing uncontrolled structural seismic responses.

Performance of 2-D Frame Equipped With Base isolation System under Dynamic Loadings

Building responses have become a major concern in design research. Passive control techniques are implemented to improve structure efficiency. The present research aims to assess the efficiency of base isolation system for a 2D frame and to enhance the performance of structures that are subjected to seismic ground excitations and ground vibrations induced by blast. Two moments of resistant RC frames were studied and output of the isolator (Lead / Rubber Bearing) was observed to reduce structural responses. In SAP2000 non-linear dynamic analysis is conducted to compare normal and irregular moment-resistant frames and structural responses with and without passive control techniques. Isolators are constructed based on time of isolation. Reduction of structural responses is assessed by passive control techniques, and comparative analysis is performed. Mitigating systemic retaliation is affected by the implementation of passive control system.

Seismic control performance indices for magneto-rheological dampers considering simple soil-structure interaction

In this study, two instantaneous optimal control performance indices for seismic control of structures incorporating magneto-rheological (MR) dampers are analytically defined. One of the time dependent performance index uses conventional state vector considering simple soil structure interaction (SSI). However, absolute displacement and absolute velocities are added to the conventional state vector terms and eventually to the other one. SSI effects are also included simply in the second performance index. The response reduction performance of these simple indices is compared with the linear quadratic regulator control (LQR). A three story ¼-scaled structure incorporating an MR damper is taken into account as a numerical example. The power requirement of the MR damper is considered by using an MR damper model which is piece wise invertible. It is obtained from numerical results that the proposed performance indices are as effective as LQR algorithm in uncontrolled seismic structural response reduction performance. However taking SSI effects into account increases structural responses and decreases control effectiveness slightly.