scholarly journals Seismic Design of Steel Frames Equipped by Control Devices

2014 ◽  
Vol 8 (1) ◽  
pp. 300-309 ◽  
Author(s):  
Nikos G. Pnevmatikos ◽  
George Hatzigeorgiou
Keyword(s):  
Response Spectrum ◽  
Control Analysis ◽  
Control Force ◽  
Design Spectrum ◽  
Elastic Range ◽  
Design Philosophy ◽  
Control Devices ◽  
Controlled Structure ◽  
Design Earthquake ◽  
Control Forces

The design philosophy of EC8 is to ensure that in the event of the design earthquake, human lives are protected and no collapse will occur, while extended damages will be observed. This is achieved by ductility and capacity design. This design philosophy drives to an additional cost for repairing damage of structures. On the other hand, it is costly and uneconomic to design structures behaving in elastic range, especially under high level of earthquake excitation. An alternative direction to this strategy, which is examined in this paper, is to design a controlled structure capable to resist a design earthquake loads, remaining in elastic range and thus without damage. The idea behind this philosophy is that one portion of earthquake loading will be resisted by a control system while the rest will be resisted by the structure. The structure, initially, is analyzed and designed according to the current codes. The elastic and design earthquake forces are first calculated according to the elastic and the design spectrum. The required control forces are calculated as the difference between elastic and design forces. The maximum value of capacity of control devices is then compared with the required control force. If the capacity of the controlled devices is higher than the required control force then the control devices are accepted and installed to the structure. Then, the structure is designed according to the design forces. In the case where the maximum available control device capacity is lower than the demanded control force then an additional portion of control forces should be resisted by the building. In that case, an iterative procedure is proposed and a scale factor, 􀀁, that reduces the elastic response spectrum to a new design spectrum, is calculated. The structure is redesigned based on the new design spectrum and then the devices are installed to the structure. The proposed procedure imposes that the controlled structure will behave elastically for the design earthquake and no damage will occur, consequently no additional repair cost will be needed. An initial cost of buying and installing the control devices is required. In order to ensure that the controlled structure behaves elastically, a dynamic control analysis with saturation and time delay control is performed. Following the proposed procedure the numerical results show that the structure remains in elastic and no damage occurs.

Optimum Structural Vibration Control With Bounds on Control Forces

1995 ◽  
Author(s):  
Alexander A. Bolonkin ◽  
Duane E. Veley ◽  
Narendra S. Khot
Keyword(s):  
Control System ◽  
Linear Quadratic Regulator ◽  
Structural Vibration ◽  
Control Force ◽  
Linear Quadratic ◽  
Structural Vibration Control ◽  
Structure Control ◽  
Design Variables ◽  
Control Devices ◽  
Control Forces

Abstract This paper describes an approach for designing a structure-control system based on the linear quadratic regulator (LQR) which suppresses vibrations in structures. Bounds are placed on the control forces to simulate real actuators. The control system is optimized with an objective function of the total weight of the control devices. The design variables are the bounds (which are proportional to the weight of the control devices) on each control force with a constraint on the time to reduce the energy of the vibration to 5% of its initial value. As an example to illustrate the application of an approach, a wing box idealized by rod elements is used. Control systems are designed for this structure using four and eight actuators for several locations.

On the Use of Design Spectrum Compatible Time Histories

1995 ◽  
Vol 11 (1) ◽  
pp. 111-127 ◽  
Author(s):  
Farzad Naeim ◽  
Marshall Lew
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Design Spectrum ◽  
Analysis And Design ◽  
Motion Time ◽  
Expected Performance ◽  
Earthquake Resistant ◽  
Earthquake Resistant Structures ◽  
Time Histories ◽  
Design Earthquake

To a designer of a nonlinear structure, there is nothing more attractive than a real or fictitious ground motion time history whose response spectrum matches the target design spectrum. Frequency-domain scaled, design spectrum compatible time histories (DSCTH) are widely used in analysis and design of special structures, particularly seismic-isolated buildings. Their use has been even mandated by some code provisions. At the first glance, it seems that DSCTH records furnish designers of earthquake resistant structures with a consistency and compatibility bridge between the two very different worlds of elastic and inelastic response. Closer examination, as presented in this paper, reveal however that there are significant potential problems associated with uncontrolled use of DSCTH records in seismic design. It is shown that the use of design spectrum compatible time histories can lead to exaggeration of displacement demand and energy input. This in turn can distort the expected performance of the structure when subjected to design earthquake ground motions.

Spatial Actuation Effectiveness of Segmented Actuators on Parabolic Cylindrical Panels

2012 ◽  
Author(s):  
S. D. Hu ◽  
H. Li ◽  
H. S. Tzou
Keyword(s):  
Shape Control ◽  
Cylindrical Panel ◽  
Design Parameters ◽  
Modal Control ◽  
Control Force ◽  
Optimal Position ◽  
Meridional Direction ◽  
Cylindrical Panels ◽  
Active Vibration ◽  
Control Forces

With the distinct capability of line-focusing, open parabolic cylindrical panels are commonly used as key components of radar antennas, space reflectors, solar collectors, etc. These structures suffer unexpected vibrations from the fluctuation of base structure, non-uniform heating and air flow. The unwanted vibration will reduce the surface reflecting precision and even result in structure damages. To explore active vibration and shape control of parabolic cylindrical panels, this study focuses on actuation effectiveness induced by segmented piezoelectric patches laminated on a flexible parabolic cylindrical panel. The mathematical model of a parabolic cylindrical panel laminated with distributed actuators is formulated. The segmentation technique is developed and applied to parabolic cylindrical panels, and the piezoelectric layer is segmented uniformly in the meridional direction. The distributed actuator patches induced modal control forces are evaluated. As the area of actuator patch varies in the meridional direction, modal control force divided by actuator area, i.e., actuation effectiveness, is investigated. Spatial actuation effectiveness, including its membrane and bending components are evaluated with respect to design parameters: actuator size and position, shell curvature, shell thickness and vibration mode in case studies. The actuation component induced by the membrane force in the meridional direction mainly contributes to the total actuation effectiveness for lower modes. Average and cancellation effect of various actuator sizes and the optimal actuator position are also discussed. Results suggest that for odd vibration modes, the maximal actuation effectiveness locates at the ridge of the panel; while for even modes, the peak/valley closest to the ridge is the optimal position to obtain the maximal actuation effectiveness. A segmentation scheme of the meridian interval angle 0.0464rad for the investigated standard panel is a preferred tradeoff between the actuation effectiveness and practical feasibility. The modal actuation effectiveness increases with the shell curvature, whereas decreases when the shell thickens.

Vector-Valued Uniform Hazard Spectra

2012 ◽  
Vol 28 (4) ◽  
pp. 1549-1568 ◽  
Author(s):  
Shun-Hao Ni ◽  
De-Yi Zhang ◽  
Wei-Chau Xie ◽  
Mahesh D. Pandey
Keyword(s):  
Seismic Hazard ◽  
Seismic Design ◽  
Hazard Analysis ◽  
Occurrence Rate ◽  
Simultaneous Occurrence ◽  
Uniform Hazard Spectra ◽  
Design Spectrum ◽  
Performance Based Seismic Design ◽  
Design Earthquake ◽  
Vector Valued

Uniform hazard spectra (UHS) have been used as design earthquakes in several design codes. However, as the results from scalar probabilistic seismic hazard analysis (PSHA), UHS do not provide knowledge about the simultaneous occurrence of spectral accelerations at multiple vibration periods. The concept of a single “design earthquake” is then lost on a UHS. In this study, a vector-valued PSHA combined with scalar PSHA is applied to establish an alternative design spectrum, named vector-valued UHS (VUHS). Vector-valued seismic hazard deaggregation (SHD) is also performed to determine the design earthquake in terms of magnitude, distance, and occurrence rate for the VUHS. The proposed VUHS preserves the essence of the UHS and can also be interpreted as a single design earthquake. To simplify the procedure for generating the VUHS, so that they can be easily incorporated into performance-based seismic design, an approximate method is also developed.

CFD-Based Hydrodynamic Analysis for a Ship Sailing Along a Bank in Restricted Waters

2013 ◽  
Vol 155 (A2) ◽  
Keyword(s):  
Flow Field ◽  
Physical Mechanism ◽  
Control Force ◽  
Hydrodynamic Analysis ◽  
Bank Effect ◽  
Ship Steering ◽  
Control Devices ◽  
Cfd Method ◽  
And Control ◽  
Water Depths

For a ship navigating along a bank in restricted waters, it is usually accompanied by obvious bank effect which may cause ship-bank collision. In order to avoid collision, it is necessary to provide control force and moment by using control devices such as a rudder. In this paper, CFD method is applied to numerically simulate the viscous flow around a ship appended with a rudder sailing along a bank. Systematical simulations are carried out for the hull-rudder system with different rudder angles at different ship-bank distances and water depths. The flow field features and the hydrodynamic forces of the hull-rudder system are obtained and analysed. This study is of significance for revealing the physical mechanism behind the bank effect and providing guidance for ship steering and control in restricted waters.

scholarly journals Control Force Recalculation for Balancing Problems

2019 ◽  
Vol 19 (05) ◽  
pp. 1941010
Author(s):  
Bálint Bodor ◽  
László Bencsik ◽  
Tamás Insperger
Keyword(s):  
Optimization Problem ◽  
Control Mechanism ◽  
Numerical Differentiation ◽  
Open Loop ◽  
Second Step ◽  
Control Force ◽  
New Approach ◽  
Numerical Errors ◽  
Linearized System ◽  
Control Forces

Understanding the mechanism of human balancing is a scientifically challenging task. In order to describe the nature of the underlying control mechanism, the control force has to be determined experimentally. A main feature of balancing tasks is that the open-loop system is unstable. Therefore, reconstruction of the trajectories using the measured control force is difficult, since measurement inaccuracies, noise and numerical errors increase exponentially with time. In order to overcome this problem, a new approach is proposed in this paper. In the presented technique, first the solution of the linearized system is used. As a second step, an optimization problem is solved which is based on a variational principle. A main advantage of the method is that there is no need for the numerical differentiation of the measured data for the calculation of the control forces, which is the main source of the numerical errors. The method is demonstrated in case of a human stick balancing.

Design, Optimization and Nonlinear Response Control Analysis of the Mega Sub-Controlled Structural System (MSCSS) Under Earthquake Action

2020 ◽  
Vol 14 (03) ◽  
pp. 2050013
Author(s):  
Mustapha Abdulhadi ◽  
Zhang Xun’an ◽  
Buqiao Fan ◽  
Muhammad Moman
Keyword(s):  
Structural Response ◽  
Frame Structure ◽  
Control Analysis ◽  
Percentage Reduction ◽  
Optimal Arrangement ◽  
Control Effectiveness ◽  
Rubber Bearing ◽  
Earthquake Action ◽  
Controlled Structure ◽  
Rubber Bearings

The lately proposed mega sub-controlled structure (MSCSS) remarkably improved the seismic resistance ability and reduced vibration effects much more than the mega substructure (MSS). However, the controlling effectiveness and its optimization remain a significant concern. In this paper, a new configuration of MSCSS is analyzed in which viscous dampers are optimally arranged between mega-frame and substructural frame and optimal damper parameters are investigated. Also, rubber bearings are designed and introduced at the top of the additional column to ease the horizontal constraints between the additional column and mega-floor beam and improve the structural design of MSCSS, so that the structure has a larger span and further reduces the structural response. The result showed that optimal parameters of the damper and its optimal arrangement have a significant influence in the control effectiveness of MSCSS. Furthermore, the addition of a rubber bearing at the top of the additional column improves the mechanical behavior of the column and further reduces the acceleration response of both the mega-frame structure and the substructure. This paper also shows that the percentage reduction of the acceleration is more within the substructure than at the mega-frame structure. The seismic response of this structure under El Centro is less than the Taft (NE) wave and the percentage reduction is more under the Taft wave than under the El Centro wave.

Magnetostrictive Microactuations and Modal Sensitivities of Thin Magnetoelastic Shells

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
W. K. Chai ◽  
H. S. Tzou ◽  
S. M. Arnold ◽  
H.-J. Lee
Keyword(s):  
Cylindrical Shell ◽  
Transverse Mode ◽  
Control Force ◽  
Control Actions ◽  
Spatially Distributed ◽  
Longitudinal Bending ◽  
Shell Panel ◽  
Magnetostrictive Actuator ◽  
Membrane Bending ◽  
Control Forces

This study is to evaluate distributed microscopic actuation characteristics and control actions of segmented magnetostrictive actuator patches laminated on a flexible cylindrical shell panel. A mathematical model and its modal domain governing equations of the cylindrical shell panel laminated with distributed magnetostrictive actuator patches are presented first, followed by the formulation of distributed magnetostrictive control forces and microcontrol actions including circumferential membrane∕bending and longitudinal bending control components. Transverse mode shape functions with simply supported boundary conditions are used in the modal control force expressions and the microcontrol action analyses. Control effectives and spatial characteristics of distributed actuators depend on applied magnetic fields and on geometrical (e.g., spatial segmentation, location, and shape) and material (i.e., various actuator materials) properties. Spatially distributed magnetoelectromechanical actuation characteristics contributed by circumferential membrane∕bending and longitudinal bending control actions are investigated. Distributed control forces and microactuations of a magnetostrictive actuator patch at various locations are analyzed, and modal-dependent spatial control effectiveness is evaluated.

On Selection of Control Parameters for H∞ Output Feedback

2005 ◽  
Author(s):  
Chang-Ching Chang ◽  
Chi-Chang Lin
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Output Feedback ◽  
Delay Time ◽  
Output Feedback Control ◽  
Feedback Gain ◽  
Control Force ◽  
Control Parameters ◽  
Structural Responses ◽  
Control Forces

In this paper, an H∞ direct output feedback control algorithm through minimizing the entropy, a performance index measuring the tradeoff between H∞ optimality and H2 optimality, is employed to design the control system in reducing structural responses due to dynamic loads such as earthquakes. The control forces are obtained from the multiplication of direct output measurements by a pre-calculated time-invariant feedback gain matrix. To achieve optimal control performance, the strategy to select both control parameters γ and α is extensively investigated. The decrease of γ or increase of α results in better control effectiveness, but larger control force requirement. For a single degree-of-freedom (SDOF) damped structure, exact solutions of output feedback gains and control parameters are derived. It can be proved analytically that the LQR control is a special case of the proposed H∞ control. Direct velocity feedback control is effective in reducing structural responses with very small number of sensors and controllers compared with the DOFs of the structure. In active control of a real structure, control force execution time delay cannot be avoided. Relatively small delay time not only can render the control ineffective, but also may cause system instability. In this study, explicit formulas to calculate maximum allowable delay time and critical control parameters are derived for the design of a stable control system. Some solutions are also proposed to increase the maximum allowable delay time.

Semi-Active Control of Structural Systems Aiming to Approximate the Performance of the Targeted Active Control Law: Output Emulation Approach

2013 ◽  
Author(s):  
Kazuhiko Hiramoto ◽  
Taichi Matsuoka ◽  
Katsuaki Sunakoda
Keyword(s):  
Control System ◽  
Active Control ◽  
Variable Parameter ◽  
Control Law ◽  
Structural Systems ◽  
Control Force ◽  
Control Performance ◽  
Control Devices ◽  
Active Control System ◽  
Control Output

As a method for semi-active control of structural systems, the active-control-based method that emulates the control force of a targeted active control law by semi-active control devices has been studied. In the active-control-based method, the semi-active control devices are not necessarily able to generate the targeted active control force because of the dissipative nature of those devices. In such a situation, the meaning of the targeted active control law becomes unclear in the sense of the control performance achieved by the resulting semi-active control system. In this study, a new semi-active control strategy that approximates the control output (not the control force) of the targeted active control is proposed. The variable parameter of the semi-active control device is selected at every time instant so that the predicted control output of the semi-active control system becomes close to the corresponding predicted control output of the targeted active control as much as possible. Parameters of the targeted active control law are optimized in the premise of the above “output emulation” strategy so that the control performance of the semi-active control becomes good and the “error” of the achieved control performance between the targeted active control and the semi-active control becomes small.

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