Experimental investigation on semi-active control of base isolation system using magnetorheological dampers for concrete frame structure

The traditional passive base isolation is the most widely used method in the engineering practice for structural control, however, it has the shortcoming that the optimal control frequency band is significantly limited and narrow. For the seismic isolation system designed specifically for large earthquakes, the structural acceleration response may be enlarged under small earthquakes. If the design requirements under small earthquakes are satisfied, the deformation in the isolation layer may become too large to be accepted. Occasionally, it may be destroyed under large earthquakes. In the isolation control system combined with rubber bearing and magnetorheological (MR) damper, the MR damper can provide instantaneous variable damping force to effectively control the structural response at different input magnitudes. In this paper, the control effect of semi-active control and quasi-passive control for the isolation control system is verified by the shaking table test. In regard to semi-active control, the linear quadratic regulator (LQR) classical linear optimal control algorithm by continuous control and switch control strategies are used to control the structural vibration response. Numerical simulation analysis and shaking table test results indicate that isolation control system can effectively overcome the shortcoming due to narrow optimum control band of the passive isolation system, and thus to provide optimal control for different seismic excitations in a wider frequency range. It shows that, even under super large earthquakes, the structure still exhibits the ability to maintain overall stability performance

AMD control analysis and parametric optimization for a wind excited tall building structure

Under the background of one large scale high-rising reinforced concrete structure located in Dalian city, the AMD active control analysis and design against wind loading is carried out. First, the structural computation model and loading modal are established according to the engineering background and design requirement. Then, the parameter optimization for AMD subsystem is conducted under wind excitations. At last, numerical simulation for the structure controlled by AMD system is carried out. The numerical results show that the AMD system with the optimized parameters can achieve a significant effectiveness on suppressing wind induced structural acceleration response, which will also be in favor of addressing occupant comfort issues. In addition, the control effect of Root Mean Square (RMS) response is generally higher than that of the peak response, which may have implications on structural functionality and reliability during its service life span. The analysis and optimum approaches for AMD control analysis as well as corresponding results can also be applicable to similar control problems

Dynamic test and constitutive model of 225 MPa low yield point steel material and its energy absorption ability

Based on Low Yield Point (LYP) steel's attractive features, e.g. relative lower yielding strength, better plasticity performance than traditional structural steel material, the feasibility of utilizing LYP steel material for absorbing blast and impact/shock energy through its plastic deformation is discussed in this paper. Selected 225 MPa class LYP steels made by Chinese An Gang Corp., abbreviated as AQ225, are tested via quasi-static and split Hopkinson pressure bar (SHPB) experiments, respectively. Then, Johnson-Cook dynamic constitutive model is developed through a comprehensive thorough processing of raw test data. Moreover, the reliability of achieved model and its corresponding parameters are discussed. Finally, the dynamic response of a square plate structure made of LYP steel as well as other different types of steel materials, e.g. high-strength HQ600 and normal highstrength low alloy steel Q345, subject to explosive loading is studied through numerical simulations. As a result, the advantages of LYP steel for absorbing blast and impact energy through the accumulated plastic deformation are demonstrated, which provides the basis of utilizing such material for protective structures

Control force characteristics of different control strategies for the wind-excited 76-story benchmark building structure

In accordance with the International Association of Structural Control and Monitoring (IASCM) third generation Vibration Control Benchmark problem, two new control strategies: structural adjacent reaction wall control (STA) and mass-semi-active-damper (AMD-2), are proposed and systematically evaluated and compared with the Benchmark standard-extended active control solutions as well as with the structural interbedded (STI) control strategy. A set of innovative evaluation indices, denoting the direction and energy relations between control forces and its velocity and/or displacement, is proposed to study the phenomena behavior as well as intrinsic mechanism of active control force of each control strategy. Throughout the comparisons among different control strategies, the function of inertia mass of Active Mass Driver/Damper (AMD) system is discussed. The AMD-2 control strategy has been developed based on a comprehensive analysis of STA control strategy, and both strategies are thoroughly evaluated against relevant Benchmark results. Based on a force mechanism and inertia mass ratio impact analysis, the AMD-2 control is shown to be capable of achieving comparable performance at a lower cost but with additional attractive advantages. Furthermore, an improved understanding phenomena behavior as well as the intrinsic mechanism of active control force corresponding to each control strategy realized by different control systems may contribute to selection of suitable control systems for application considerations

Structural swinging motion and its control subject to point source input

Aiming at the practical problem of swinging motion control of hook and similar suspended structure, the innovative Tuned Rotary Inertia Damper (abbreviated as TRID) control system for pendular vibration suppressing, which is based on passive tuning and absorbing control principle, has been proposed recently by structural control group in Harbin Institute of Technology. As an extension to this problem, parameter optimization and impact of control efficiencies subject to point source excitations, e.g. barge ships subject to ocean wave excitations, are carried out in this paper. Firstly, equation of motion for the suspended structure under arbitrary motion excitation is established based on Lagrangian principle, and the theory of TRID control system is analyzed. Secondly, numerical simulation of TRID control for two types of suspended structural motions, planar pendular vibration and spatial cone motion, is conducted, respectively. Then, optimal parameters and impact factors are summarized. Lastly, the abnormal phenomenon of TRID control for structural response in the resonant zone is studied. The combined TRID-TMD control system for suppressing the ideal cone motion mode is proposed to overcome the limitations of single TRID control system, and the effectiveness and feasibility are validated through numerical analysis. The research result of this paper establishes a partial theoretical foundation for anti-swaying of hook structures of large-scale heavy-lifting and pipeline-paving barge ships, subjected to ocean wave excitations

To replace the pure active control device from the AMD control system : benchmark model based analysis

Based on the background of the International Association of Structural Control and Monitoring (IASCM) 3rd generation Vibration Control Benchmark problem, two new control strategies: structural adjacent reaction wall control (subsequently called “STA”) and mass-semi-active-damper (subsequently referred to as "AMD-2"), will be proposed and evaluated and compared with the Benchmark standard-extended active control solutions. A set of innovative evaluation indices, denoting the direction and energy relations between control forces and its velocity and/or displacement, will be proposed to study the phenomena behavior as well as intrinsic mechanism of active control force of each control strategy. Throughout comparisons among different control strategies, the function of inertia mass of AMD system will be discussed. The AMD-2 control strategy will be developed based on comprehensive analysis of STA control strategy, and both strategies will be intensively evaluated against relevant Benchmark results. Based on force mechanism and inertia mass ratio impact analysis, the AMD-2 control is shown to be capable of achieving comparative performance at lower cost but with attractive advantages

Modeling and dynamical performance of the electromagnetic mass driver system for structural vibration control

This paper presents the designing, theoretical modeling and dynamical testing of an innovative Electromagnetic Mass Driver (subsequently called the "EMD") system for structural vibration control. Firstly, a set of bench-scale EMD system was developed. Then, based on the electromagnetic field theory, the Kirchhoff's circuit law, and the analogous analysis, electro-mechanical models of the EMD system were developed, which utilizes the control voltage and relative velocity to predict active control force generated by the EMD system. To validate these models, as well as to examine the dynamic performance of the EMD system, a series of tests under open-loop control mode and closed-loop control mode were carried out. All the test results show that the EMD system functions linearly under low levels of input voltage and low frequencies. Furthermore, step inputs based transient response of the EMD system was also examined. The results show the EMD system is a fast and well controllable actuator. At last, all the experimental results were compared with theoretical predications based on the proposed electro-mechanical model. Successful experimental validation of the force-voltage relationship lays out the foundation for structural vibration control utilizing such kind of innovative EMD system

(Numerical simulation on shock waves generated by explosive mixture gas from large nuclear blast load generator based on equivalent-energy prinaciple)

Based on the nonlinear explicit dynamic finite element program LS-DYNA and the multimaterial Euler algorithm, the shock wave propagations were numerically simulated for the two explosion resources of the TNT dynamite and the acetylene- air gaseous mixture in free air field, respectively. The overpressures of the shock waves and the propagation principles were compared between the two blast-loading methods. Based on the equivalent-explosion energy, a formula for calculating the nominal scale distance of gas explosion was obtained in terms of overpressure. The results show that the Euler method can be used to calculate the propagation process of two kinds of explosion sources and the numerical results agree well with the ones based on the empirical equations. With the increasing of the propagation distances, the overpressures decrease sharply and the overpressure relative error between the two load methods decreases gradually. When the shock wave overpressure was lower than 0.5 MPa, the acetylene-air gaseous mixture can replace the chemical dynamite for generating blast shock waves by the large nuclear blast load generator

Compressive behavior of a novel hexagonal nodes-based 3D chiral auxetic structure

The energy absorption capacity of materials with negative Poisson’s ratio (NPR) is attracting interest from both industry and academia due to the excellent impact resistance of the local shrinkage of materials. However, understanding the compressive behavior of 3D auxetic structures at different strain rates and developing design methods are challenging tasks due to the limited literature and insufficient data. This paper presents a study on the behavior of Poisson’s ratio of an advanced 3D chiral structure, which is formed of two orthogonally positioned 2D hexagonal nodes-based chiral structures. Firstly, both theoretical analysis and numerical simulations are conducted to identify the Poisson’s ratio of 2D chiral structures. The same theoretical value of −1 is obtained for 2D chiral structures with a bending-dominated ligaments assumption. Thereafter, the Poisson’s ratio of 3D chiral structures is determined numerically using a low-speed loaded model composed of 5 × 5 × 8 3D unit cells for eliminating the boundary effects. The results show that impact velocity can strongly affect the energy absorption and deformation behavior of the proposed 3D chiral structure. Increasing the beam radius results in reduced energy absorption capability. However, the energy absorption capability of the 3D chiral structure is not sensitive to the yield strength of nodes. Impact direction affects the energy absorption performance of the 3D chiral structure, depending on the crushing strain. The research results could be used to optimize the design of the proposed novel 3D chiral honeycombs for various applications, such as impact energy absorbers and vibration-resistant dampers

In-plane crashworthiness of chiral honeycombs

In-plane dynamic crushing and energy-absorption capabilities of chiral honeycombs are studied numerically invoking Finite Element (FE) code ABAQUS®/Explicit. Chiral honeycombs are characterized by a non-intuitive negative in-plane Poisson’s ratio ρ (auxeticity), for hexagonal chiral honeycombs, which exhibits a theoretic value of −1 (Prall and Lakes, 1997). The effects of topology parameters, stiffness ratio of ligament to node, impact velocity and impact mass on structural crashworthiness are studied based on a fixed-size model and a convergence study is also carried out to minimize the meshing induced result error. The numerical results show that increasing values of topology parameters give rise to better crashworthiness of chiral honeycombs which is dependent on boundary conditions. Specific energy absorption of chiral honeycomb is independent of relative stiffness after reaching a critical value. High velocity impact loading has dramatic effect on energy absorption of chiral honeycomb which is relatively independent of low velocity impact loading and impact mass