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transcript
Dr. Naveed Anwar
Smart Systems for Structural Response Control
5th ASEP Convention on Concrete Engineering Practice and Technology (a. concept 16)
Manila, Philippines
19-20 May 2016
Naveed Anwar, PhD
Dr. Naveed Anwar2
Dr. Naveed Anwar3
Smart Everything!
Smart Phone
Smart Car
Smart TV
Smart Home
Smart City
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Smart Cities
Smart Buildings
Smart Structures
Smart Devices
Smart Materials
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Why Smart Structures?
• Excitation fluctuates so Demand fluctuates
• But Capacity is constant
• Therefore level of safety is not consistent
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Why Smart Structures ?
• Typically capacity is designed based on “Peak” estimated demand
• What if peak demand never comes > Un-economical
• What if demand exceeds estimated peak > Un-safe
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Simplest Case – Restressed Beam
• PT is design to balance a specific load value
• It does not work efficiently for any other value of load pattern or value
• What if PT force could change with load?
• >> Smart PT Beam
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Key Fluctuating Excitations
Wind
Earthquake
Vibrating loads
Others: Flood, Temperature, Settlement, Creep, …
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Response Indicators and Response Control
Deformation, Drift
Acceleration
Dissipated energy
Stresses and strains
Stiffness Strength
Damping Ductility
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What a Smart Structure Does?
Ability to change values of response controllers
to modify the response
based on fluctuation of excitement and demand
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Smart Structure
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Smart Structural System
ability to sense any change in external actions
diagnose any problem at critical locations
measure and process data
take appropriate actions to improve system performance while preserving structural integrity, safety, and serviceability
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Smart Structure Devices
Energy Dissipating
Systems
Active or Passive Control Systems
Health Monitoring
Systems
Data Acquisition System
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Applications for Smart Structure Devices
Structures subjected to extraordinary vibrations
Important structures with critical functionality and high safety requirements
Flexible structures with high serviceability requirements
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Research Areas in Smart Structure Technology
Analytical or numerical modeling of control systems.
Experimental investigation of control systems
Properties of smart materials and their applications
Applicability and Full-scale implementation
Development of guidelines and standards for design of smart systems
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Basic Control Principle
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Acknowledgment
• Some material and figures based on:
• Franklin Y. Cheng, Hongping Jiang and Kangyu Lou (2008) Smart Structures –Innovative systems for seismic response control. CRC Press, Taylor & Francis Group, LLC, ISBN-13: 978-0-8493-8532-2
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Equation of Motion
Equation of motion governing lateral response of linear SDF
𝑚 ሷ𝑢 𝑡 + 𝑐 ሶ𝑢 𝑡 + 𝑘𝑢 𝑡 = 𝑃(𝑡)
In terms of frequency of structure and damping ratio
ሷ𝑢 𝑡 + 2𝜉𝜔𝑛 ሶ𝑢 𝑡 + 𝜔𝑛2𝑢(𝑡) = − ሷ𝑢𝑔(𝑡)
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Methods to Solve Equation of Motion
Procedures based on
Interpolation of Excitation
Vector
Closed Form FormulationsClosed Form Formulations
Time Stepping Methods
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Dulhamel’s Integral Solution
Based on considering the arbitrarily varying dynamic force as asequence of infinitesimally short impulses and superposing theanalytical response from each impulse to get total dynamic responsehistory
𝑢 𝑡 =1
𝜔𝐷න0
𝑡
ሷ𝑢𝑔 𝜏 𝑒−𝜉𝜔𝑛 𝑡−𝜏 𝑠𝑖𝑛[𝜔𝐷 𝑡 − 𝜏 ] 𝑑𝜏
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Analytical Solution
Another way to get solution against arbitrary ground motion vector isto decompose it using Fourier series and determine the responseagainst each term in Fourier expansion:
𝑢 𝑡 =𝑚 ሷ𝑢𝑔,𝑚𝑎𝑥
𝑘
1
1 − (𝜔/𝜔𝑛)2
𝑠𝑖𝑛𝜔𝑡 −𝜔
𝜔𝑛𝑠𝑖𝑛𝜔𝑛𝑡
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Reduction of Lateral Displacement
Increasing the damping of the
system
Reducing the intensity of
ground motion experienced by
the system
Increasing the difference between forcing frequency and the natural
frequency of system
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Equation of Motion Using Control System
𝑚+𝑚𝑐 ሷ𝑢 𝑡 + 𝑐 ሶ𝑢 𝑡 + 𝑘𝑢 𝑡 + 𝐹𝐶(𝑡) = −(𝑚 +𝑚𝑐) ሷ𝑢𝑔(𝑡)
FC(t) = force generated by control system
𝐹𝐶(𝑡) = 𝑐𝑐 ሶ𝑢 𝑡 + 𝑘𝑐𝑢 𝑡
Final Form of Equation of motion using Control System
𝑚+𝑚𝑐 ሷ𝑢 𝑡 + (𝑐 + 𝑐𝑐) ሶ𝑢 𝑡 + (𝑘 + 𝑘𝑐)𝑢 𝑡 = −(𝑚 +𝑚𝑐) ሷ𝑢𝑔(𝑡)
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Damping Systems for Dynamic Response Control
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Damping Devices and Systems
Damping devices and systems applied to a lateral load-resisting system
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Damping Devices and Systems
Passive Control Systems
Semi-active Control Systems
Active Control Systems
Hybrid Systems
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Passive Control Systems
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Passive Control Systems
Use Various mechanical devices which reacts to structural vibrations resulting in dissipating a portion of their kinetic energy.
Requires no external power source and are capable of generating large damping forces with increasing structural response
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Passive Control Systems
Tuned Mass Dampers (TMDs)
Tuned Liquid Dampers (TLDs)
Friction Devices
Metallic Yield Devices
Viscoelastic Dampers (VE)
Fluid Viscous Dampers (FVDs)
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Tuned Mass Dampers (TMD)
𝑚𝐷
𝑚𝐷
𝑚𝐷
(a) (b) (c)
Working Mechanism:
Externally applied forceon main structure can bebalanced with therestoring force developedin additionally attachedmass-spring-dashpotsystem
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Tuned Liquid Dampers (TLD)
Working Mechanism:
Same as TMD with a differencethat water or any other liquid isused as the mass and therestoring force is generated byweight of sloshing liquid inside acontainer
𝑚𝐷
Direction of Vibration
P
(a) (b)
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Friction Devices
Working Mechanism:
Conversion of kinetic energy ofmoving bodies in to heat energy.In X-braced dampers, slottedslip joints provide forceresistance through friction bybrake lining pads installedbetween the steel plates
Direction of Vibration
Beam
Co
lum
n
Brace
Friction
Damper
Hinges
Links
Moment
Connections to
Braces
Friction Damper
Slotted Slip
Joints
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Metallic Yielding Devices
Seismic design of conventionalstructures is controlled by theirexpected post-yield ductilitywhich is a measure of itsenergy-dissipating capacity. Thisled to the idea that additionalmetallic devices capable ofexhibiting stable hystereticbehavior can be used to absorbenergy of main structure Direction of Vibration
Beam
Co
lum
n
Brace
Yielding
Damper
Rods
Rod Rings
Yielding Damper
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Viscoelastic Dampers
Working Mechanism
Viscoelastic (VE) dampers arebased on the use of VEmaterials which dissipateseismic energy through theirshear deformation whensubjected to vibrations
Brace
VE
Damper
Pinned Connections
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Viscoelastic Dampers
Working Mechanism
FVDs comprise of a dashpotrepresenting the energy-dissipation by conversion ofkinetic energy to heat as a resultof moving piston casingdeformations in a viscous fluid
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Semi-active Control Systems
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Semi-active Control Systems
Referred as controllable or intelligent systems.
Working principle is “computer processes the vibration measurements comingfrom sensors and generates the command for control actuator to modify theproperties of passive damper according to requirement”
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Components of Semi-active Control System
Semi-active
Control System
Vibrating Measuring
Sensors
Control Computers
Control Actuators
Passive Damper
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Advantages & Limitations of Semi-active Control Systems
Advantages:
Additional adaptive system which collects and process the information about response of main structure and modifies the damper’s property based on this information.
Economically combine the advantage of both passive and active control systems
Limitations:
Control capacity is limited by the maximum capacity of their constituent passive device
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Common Semi-active Control Systems
Semi-active Tuned Mass Dampers
Actuator generates the control force
which is required to develop optimum
amount of damping in TMD
Semi-active Tuned Liquid Dampers
Semi-active Friction Dampers
Semi-active Vibration Absorbers
Is based on mechanism
responsible for variable adjustment
and tuning of the liquid.
Electric motor is used to operate the
actuator applying compression force to
interface. Efficient control system us used to adjust this
force to achieve performance
Use variable orifice valve capable of varying flow of
hydraulic damper. Damping capacity is
obtained from viscous liquid.
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Common Semi-active Control Systems
Electrorheological Dampers
Based on smart ER fluids containing
dielectric particles. In the presence of electric fields,
dielectric materials polarized and
increased resistance to flow
Semi-active Stiffness Control
Devices
Magnetorheological Dampers
Semi-active Viscous Fluid Damper
Consist of hydraulic cylinder, double
acting piston rod, solenoid control valve and connecting tube. Opening or closing of control valve results
in system optimization
Use smart MR fluids and contain micron-sized magnetically
polarizable particles suspended in any
viscous liquid. Magnetic field
controls particle behaviour
Use the opening or closing of a
solenoid valve to regulate the
amount of the fluid through a bypass loop, according to commands from control algorithm
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Active Control Systems
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Active Control Systems
Use electrohydraulic actuators which generate optimum amount of control force based on actual measured response of main structure
Effective Control on Structure Response
Adaptability to Ground Motion
Characteristics
Suitability to Use for any
Control Objectives
Ability to Suppress
Responses Against Wide
Range of Frequencies
Advantages
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Schematic Diagram of Active Control Systems
Measurements Controller Measurements
Sensors
Earthquake
Excitations
Structural
Response
Sensors
Control Signal
Actuators
Control Forces
Structure
Power
Supply
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Common Types of Active Control Systems
Active Mass
Damper (AMD)
Active Tendon Systems
Active Brace Systems
Pulse Generation
Systems
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Active Mass Dampers (AMD)
Natural extensions of TMDswith the addition of anactive control mechanism.
Motion of passive TMD isnow controlled by theactuator to generate controlforces.
Comparison of Smart Structures with AMD and TMD
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Structure with AMD
Model & Free Body Diagram for Structures with AMD
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Active Tendons System
Consist of a set of pre-stressed tendonssubjected to controllable tensile forces.
Under seismic excitation, inter-storydrifts are produced causing the relativemovement between actuator piston andcylinder, resulting in variable tensileforces in pre-stressed tendons. Whichprovides the desirable control forces toachieve response control
α
x(t)
ẍg (t)u(t)
Active
tendon
Actuator
Schematic Diagram of Active Tendon System
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Active Braced Systems
This system uses the existing structuralbraces to develop an active controlsystem by adding actuator
Different types of bracing systems(diagonal, K-braces and X-braces) can beused in conjunction with hydraulicactuators capable of generating a largecontrol force.
Active Bracing System with Hydraulic Actuator
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Pulse Generation Systems
These systems (instead of hydraulic actuators) are based on pulse generators, which use pneumatic mechanisms to generate active control forces.
As soon as the detection of large relative velocity at any installation point, the pneumatic actuator activated and produce the control force in direction opposite to applied velocity.
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Limitations of Active Control Systems
Requires significant amount of external power
supply and complex sensing and signal
processing
Actuators capable of producing large control
forces is key requirement
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Hybrid Systems
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Common Hybrid Systems
Hybrid Mass Dampers
Hybrid Base-Isolation System
Hybrid Damper-Actuator Bracing
Control
Intelligent Hybrid Control
Systems
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Hybrid Mass Dampers (HMD’s)
Combines passive TMD with anactive control actuator.
The actuator generates a controlforce which adjusts the propertiesof TMD resulting in an increase inAMD’s efficiency
Hybrid Mass Damper
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Hybrid Base-Isolation System
Combines base isolation system with an active control system.
Active tendon system is installed on a base-isolated structure
Hybrid system with base isolation and actuators
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Hybrid Damper Actuator Bracing Control
Combines a hybrid device withan actuator resulting inincreased efficiency andcontrol on structural response
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Intelligent Hybrid Control Systems
Structure
Response > TR ?
Z (t) = 0
Or
Z˚ (t) = 0Z (t) or Z˚(t)
Feedback Gain
Z(t)Excitations
No
Structure
Response > TR ?
Z (t) = 0
Or
Z˚ (t) = 0Z (t) or Z˚(t)
Feedback Gain
Z(t)
No
Yes
+-
Working Mechanism of Single Stage Intelligent Hybrid System
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Intelligent Hybrid Control Systems
Working Mechanism of Three Stage Intelligent Hybrid System
Structure
> Ist Threshold
Structure
> 2nd
Threshold
Structure
Damper Damper Actuator Damper Actuator
Ground Motion
Stage 1 Stage 2 Stage 3
Response Response
NoYesNo Yes
Will Adjusted feedback gain
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Base Isolation Systems for Seismic Response Control
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Base Isolation Systems for Seismic Response Control
Tend to reduce the energy transfer from ground acceleration to structure.
Bearing
Elastomeric Bearings
Sliding Type Bearings
Most Important Component
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Common Types of Bearings
Elastomeric Bearings
Lead-Plug Bearings
High-Damper Rubber
Bearings
Friction Pendulum Bearings
Pot-Type
Bearings
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Types of Bearing
Elastomeric Bearings Lead-Plug Bearings
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Types of Bearing
Friction Pendulum Bearing Friction Pendulum Bearing with Double Concave
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Types of Bearing
Piston with Teflon-Coated
Surface at the topElastomer Base Pot
Seal
Top Plate with Stainless Surface
Typical Plot Type Bearing
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Sensing and Data Acquisition Systems
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Components of Data Acquisition Systems
Data Acquisition
System
Sensors
Signal Conditioning
Unit
Control Computer
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Schematic of Analog Sensing and Data Acquisition System
Smart Seismic
StructureSensors
Actuators
Signal
Conditioner
Analog Computer
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Schematic of Digital Sensing and Data Acquisition System
Smart Seismic
StructureSensors
Actuators
Signal
Conditioner
A/D
Boards
Digital
Controller
D/A
Boards
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Components of Data Acquisition and Digital Control Systems
Sensors
Actuator(s)
Amplifier
Filter
Multiplexer
Signal Conditioner
A/D
Observer
Controller
D/A
Data
Recorder
Display
Smart Structure
Control Computer
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Smart structures use smart devices and materials to add some intelligence to adapt, react, adjust,
respond and handle multiple demands, and levels as and when needed
Help to make the structures safer, specially for earthquakes and strong winds
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