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Dr. Naveed Anwar
Smart Systems for Structural Response Control
Design of Tall Buildings: Trends and Achievements for Structural Performance
Bangkok-Thailand
November 7-11, 2016
Naveed Anwar, PhD
Dr. Naveed Anwar2
Everything is getting smarter !
(We hope humans don’t fall behind)
Dr. Naveed Anwar3
Smart Everything !
Smart Phone
Smart Car
Smart TV
Smart Home
Smart City
Dr. Naveed Anwar4
Dr. Naveed Anwar5
•Smart Cities
Smart Buildings
Smart Structures
Smart Devices
Smart Materials
Dr. Naveed Anwar6
Dr. Naveed Anwar7
Why smart structures ?
• Excitation fluctuates so Demand fluctuates
• But Capacity is constant
• Therefore level of safety is not consistent
Dr. Naveed Anwar8
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
Dr. Naveed Anwar9
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
Dr. Naveed Anwar10
Key Fluctuating Excitations
•Wind
Earthquake
Vibrating loads
Others: Flood, Temperature, Settlement, Creep, …
Dr. Naveed Anwar11
Response Indicators and Response Control
Deformation, Drift
Acceleration
Dissipated energy
Stresses and strains
•Stiffness Strength
Damping Ductility
Dr. Naveed Anwar12
What a smart structure does?
Ability to change values of
response controllers
to modify the response
based on fluctuation of
excitement and demand
Dr. Naveed Anwar
Smart Structure
Dr. Naveed Anwar14
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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2
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4
Dr. Naveed Anwar15
Smart Structure Devices
Energy Dissipating
Systems
Active or Passive Control Systems
Health Monitoring
Systems
Data Acquisition
System
Dr. Naveed Anwar16
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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Dr. Naveed Anwar
Basic Control Principle
Dr. Naveed Anwar18
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
Dr. Naveed Anwar19
Equation of Motion
Equation of motion governing lateral response of linear SDF
𝑚 𝑢 𝑡 + 𝑐 𝑢 𝑡 + 𝑘𝑢 𝑡 = 𝑃(𝑡)
In terms of frequency of structure and damping ratio
𝑢 𝑡 + 2𝜉𝜔𝑛 𝑢 𝑡 + 𝜔𝑛2𝑢(𝑡) = − 𝑢𝑔(𝑡)
Dr. Naveed Anwar20
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
With Control System
𝒎+𝒎𝒄 𝒖 𝒕 + (𝒄 + 𝒄𝒄) 𝒖 𝒕 + (𝒌 + 𝒌𝒄)𝒖 𝒕 = −(𝒎 +𝒎𝒄) 𝒖𝒈(𝒕)
Equation of motion
𝑚 𝑢 𝑡 + 𝑐 𝑢 𝑡 + 𝑘𝑢 𝑡 = 𝑃(𝑡)
Dr. Naveed Anwar
Damping Systems for Dynamic Response Control
Dr. Naveed Anwar23
Damping Devices and Systems
Damping devices and systems applied to a lateral load-resisting system
Dr. Naveed Anwar24
Damping Devices and Systems
Passive Control Systems
Semi-active Control Systems
Active Control Systems
Hybrid Systems
Dr. Naveed Anwar
Passive Control Systems
Dr. Naveed Anwar26
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
Dr. Naveed Anwar27
Passive Control Systems
Tuned Mass
Dampers
(TMDs)
Tuned Liquid
Dampers
(TLDs)
Friction
Devices
Metallic Yield
DevicesViscoelastic
Dampers (VE)
Fluid Viscous
Dampers
(FVDs)
Dr. Naveed Anwar28
Tuned Mass Dampers (TMD)
𝑚
𝑚
𝑚
(a) (b) (c)
Working Mechanism:
Externally applied
force on main
structure can be
balanced with the
restoring force
developed in
additionally attached
mass-spring-dashpot
system
Dr. Naveed Anwar29
Tuned Liquid Dampers (TLD)
Working Mechanism:
Same as TMD with a
difference that water or
any other liquid is used
as the mass and the
restoring force is
generated by weight of
sloshing liquid inside a
container
𝑚
Direction of Vibration
P
(a) (b)
Dr. Naveed Anwar30
Friction Devices
Working Mechanism:
Conversion of kinetic
energy of moving bodies
in to heat energy.
In X-braced dampers,
slotted slip joints provide
force resistance through
friction by brake lining
pads installed between
the steel plates Direction of Vibration
Beam
Co
lum
n
Brace
Friction
Damper
Hinges
Links
Moment
Connections to
Braces
Friction Damper
Slotted Slip
Joints
Dr. Naveed Anwar31
Metallic Yielding Devices
Working Mechanism:
Seismic design of
conventional structures is
controlled by their expected
post-yield ductility which is a
measure of its energy-
dissipating capacity. This led
to the idea that additional metallic devices capable of
exhibiting stable hysteretic
behavior can be used to
absorb energy of main
structure
Direction of Vibration
Beam
Co
lum
n
Brace
Yielding
Damper
Rods
Rod Rings
Yielding Damper
Dr. Naveed Anwar32
Viscoelastic Dampers
Working Mechanism
Viscoelastic (VE)
dampers are based on
the use of VE materials
which dissipate seismic
energy through their
shear deformation when
subjected to vibrations
Brace
VE
Damper
Pinned Connections
Dr. Naveed Anwar
Semi-active Control Systems
Dr. Naveed Anwar34
Semi-active Control Systems
Referred as controllable or intelligent
systems.
Working principle is “computer processes
the vibration measurements coming from
sensors and generates the command for
control actuator to modify the properties
of passive damper according to
requirement”
Passive
Processor to change properties
Semi Active
Dr. Naveed Anwar35
Components of Semi-active Control System
Semi-active Control System
Vibrating Measuring
Sensors
Control Computers
Control Actuators
Passive Damper
Dr. Naveed Anwar36
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
Dr. Naveed Anwar37
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.
Dr. Naveed Anwar38
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
Dr. Naveed Anwar
Active Control Systems
Dr. Naveed Anwar40
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
Dr. Naveed Anwar41
Schematic Diagram of Active Control Systems
Measurements Controller Measurements
Sensors
Earthquake
Excitations
Structural
Response
Sensors
Control Signal
Actuators
Control Forces
Structure
Power
Supply
Dr. Naveed Anwar42
Common Types of Active Control Systems
Active Mass Damper (AMD)
Active Tendon Systems
Active Brace Systems
Pulse Generation Systems
Dr. Naveed Anwar43
Active Mass Dampers (AMD)
Natural extensions of
TMDs with the addition of
an active control
mechanism.
Motion of passive TMD is
now controlled by the
actuator to generate
control forces.
Comparison of Smart Structures with AMD and TMD
Dr. Naveed Anwar44
Structure with AMD
Model & Free Body Diagram for Structures with AMD
Dr. Naveed Anwar45
Active Tendons System
Consist of a set of pre-stressed
tendons subjected to controllable
tensile forces.
Under seismic excitation, inter-
story drifts are produced causing
the relative movement between
actuator piston and cylinder,
resulting in variable tensile forces
in pre-stressed tendons. Which
provides the desirable control
forces to achieve response control
α
x(t)
ẍg (t)u(t)
Active
tendon
Actuator
Schematic Diagram of Active Tendon System
Dr. Naveed Anwar46
Active Braced Systems
This system uses the existing
structural braces to
develop an active control
system by adding actuator
Different types of bracing
systems (diagonal, K-
braces and X-braces) can
be used in conjunction with
hydraulic actuators
capable of generating a
large control force.Active Bracing System with Hydraulic Actuator
Dr. Naveed Anwar47
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
Dr. Naveed Anwar
Hybrid Systems
Dr. Naveed Anwar49
Common Hybrid Systems
Hybrid Mass Dampers
Hybrid Base-Isolation System
Hybrid Damper-Actuator Bracing Control
Intelligent Hybrid Control Systems
Dr. Naveed Anwar50
Hybrid Mass Dampers (HMD’s)
Combines passive TMD with an active control actuator.
The actuator generates a control force which adjusts the properties of TMD resulting in an increase in AMD’s efficiency
Hybrid Mass Damper
Dr. Naveed Anwar51
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
Dr. Naveed Anwar52
Hybrid Damper Actuator Bracing Control
Combines a hybrid
device with an actuator
resulting in increased
efficiency and control on
structural response
Dr. Naveed Anwar53
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
Dr. Naveed Anwar54
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
Dr. Naveed Anwar
Base Isolation Systems for Seismic Response Control
Dr. Naveed Anwar56
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
Dr. Naveed Anwar57
Common Types of Bearings
Elastomeric Bearings
Lead-Plug Bearings
High-Damper Rubber Bearings
Friction Pendulum Bearings
Pot-Type Bearings
Dr. Naveed Anwar58
Types of Bearing
Elastomeric Bearings Lead-Plug Bearings
Dr. Naveed Anwar59
Types of Bearing
Friction Pendulum Bearing Friction Pendulum Bearing with Double Concave
Dr. Naveed Anwar60
Types of Bearing
Piston with Teflon-Coated
Surface at the topElastomer Base Pot
Seal
Top Plate with Stainless Surface
Typical Plot Type Bearing
Dr. Naveed Anwar
Sensing and Data Acquisition Systems
Dr. Naveed Anwar62
Components of Data Acquisition Systems
Data Acquisition
System
Sensors
Signal Conditioning
Unit
Control Computer
Dr. Naveed Anwar63
Schematic of Analog Sensing and Data Acquisition System
Smart Seismic
StructureSensors
Actuators
Signal
Conditioner
Analog Computer
Dr. Naveed Anwar64
Schematic of Digital Sensing and Data Acquisition System
Smart Seismic
StructureSensors
Actuators
Signal
Conditioner
A/D
Boards
Digital
Controller
D/A
Boards
Dr. Naveed Anwar65
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
Dr. Naveed Anwar66
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 earhquales and strong winds
Dr. Naveed Anwar67
