Design of Tall Buildings: Trends and Achievements for Structural Performance November 7-11, 2016 Bangkok-Thailand Naveed Anwar, PhD Dr. Naveed Anwar Smart Systems for Structural Response Control Everything is getting smarter ! (We hope humans don’t fall behind) Dr. Naveed Anwar 2 Smart Everything ! Smart Phone Smart Car Smart TV Smart Home Smart City Dr. Naveed Anwar 3 Dr. Naveed Anwar 4 •Smart Cities Dr. Naveed Anwar Smart Buildings Smart Structures Smart Devices Smart Materials 5 Dr. Naveed Anwar 6 Why smart structures ? • Excitation fluctuates so Demand fluctuates • But Capacity is constant • Therefore level of safety is not consistent Dr. Naveed Anwar 7 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 Anwar 8 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 Anwar 9 Key Fluctuating Excitations •Wind Earthquake Vibrating loads Others: Flood, Temperature, Settlement, Creep, … Dr. Naveed Anwar 10 Response Indicators and Response Control Deformation, Drift Acceleration Dissipated energy •Stiffness Strength Damping Ductility Stresses and strains Dr. Naveed Anwar 11 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 12 Smart Structure Dr. Naveed Anwar Smart Structural System 1 4 Dr. Naveed Anwar ability to sense any change in external actions 2 diagnose any problem at critical locations 3 measure and process data take appropriate actions to improve system performance while preserving structural integrity, safety, and serviceability 14 Smart Structure Devices Energy Dissipating Systems Dr. Naveed Anwar Active or Passive Control Systems Health Monitoring Systems Data Acquisition System 15 Applications for Smart Structure Devices Structures subjected to extraordinary vibrations 1 2 3 Dr. Naveed Anwar Important structures with critical functionality and high safety requirements Flexible structures with high serviceability requirements 16 Basic Control Principle Dr. Naveed Anwar 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 Anwar 18 Equation of Motion Equation of motion governing lateral response of linear SDF 𝑚𝑢 𝑡 + 𝑐 𝑢 𝑡 + 𝑘𝑢 𝑡 = 𝑃(𝑡) In terms of frequency of structure and damping ratio 𝑢 𝑡 + 2𝜉𝜔𝑛 𝑢 𝑡 + 𝜔𝑛2 𝑢(𝑡) = −𝑢𝑔 (𝑡) Dr. Naveed Anwar 19 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 Dr. Naveed Anwar 20 Equation of Motion Using Control System Equation of motion 𝑚𝑢 𝑡 + 𝑐 𝑢 𝑡 + 𝑘𝑢 𝑡 = 𝑃(𝑡) With Control System 𝒎 + 𝒎𝒄 𝒖 𝒕 + (𝒄 + 𝒄𝒄 )𝒖 𝒕 + (𝒌 + 𝒌𝒄 )𝒖 𝒕 = −(𝒎 + 𝒎𝒄 )𝒖𝒈 (𝒕) Dr. Naveed Anwar 21 Damping Systems for Dynamic Response Control Dr. Naveed Anwar Damping Devices and Systems Damping devices and systems applied to a lateral load-resisting system Dr. Naveed Anwar 23 Damping Devices and Systems Passive Control Systems Dr. Naveed Anwar Semi-active Control Systems Active Control Systems Hybrid Systems 24 Passive Control Systems Dr. Naveed Anwar 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 Anwar 26 Passive Control Systems Tuned Mass Dampers (TMDs) Tuned Liquid Dampers (TLDs) Friction Devices Metallic Yield Devices Viscoelastic Dampers (VE) Fluid Viscous Dampers (FVDs) Dr. Naveed Anwar 27 Tuned Mass Dampers (TMD) Working Mechanism: 𝑚 Externally applied force on main structure can be balanced with the restoring force developed in additionally attached mass-spring-dashpot system Dr. Naveed Anwar 𝑚 𝑚 (a) (b) (c) 28 Tuned Liquid Dampers (TLD) Working Mechanism: 𝑚 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 P (a) (b) Direction of Vibration Dr. Naveed Anwar 29 Friction Devices Working Mechanism: In X-braced dampers, slotted slip joints provide force resistance through friction by brake lining pads installed between the steel plates Dr. Naveed Anwar Beam Column Conversion of kinetic energy of moving bodies in to heat energy. Moment Connections to Braces Brace Links Friction Damper Hinges Direction of Vibration Slotted Slip Joints Friction Damper 30 Metallic Yielding Devices Working Mechanism: Dr. Naveed Anwar Column Seismic design of conventional structures is controlled by their expected post-yield ductility which is a measure of its energydissipating 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 Rods Beam Brace Yielding Damper Rod Rings Direction of Vibration Yielding Damper 31 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 Dr. Naveed Anwar VE Damper Brace Pinned Connections 32 Semi-active Control Systems Dr. Naveed Anwar 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 Anwar 34 Components of Semi-active Control System Vibrating Measuring Sensors Passive Damper Semiactive Control System Control Computers Control Actuators Dr. Naveed Anwar 35 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 Anwar 36 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 Dr. Naveed Anwar Semi-active Tuned Liquid Dampers Is based on mechanism responsible for variable adjustment and tuning of the liquid. Semi-active Friction Dampers 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 Semi-active Vibration Absorbers Use variable orifice valve capable of varying flow of hydraulic damper. Damping capacity is obtained from viscous liquid. 37 Common Semi-active Control Systems Electrorheological Dampers Semi-active Stiffness Control Devices Magnetorheological Dampers Semi-active Viscous Fluid Damper Based on smart ER fluids containing dielectric particles. In the presence of electric fields, dielectric materials polarized and increased resistance to flow 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 micronsized 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 38 Active Control Systems Dr. Naveed Anwar Active Control Systems Use electrohydraulic actuators which generate optimum amount of control force based on actual measured response of main structure Advantages Effective Control on Structure Response Dr. Naveed Anwar Adaptability to Ground Motion Characteristics Suitability to Use for any Control Objectives Ability to Suppress Responses Against Wide Range of Frequencies 40 Schematic Diagram of Active Control Systems Measurements Controller Measurements Control Signal Sensors Power Supply Actuators Sensors Control Forces Earthquake Excitations Dr. Naveed Anwar Structure Structural Response 41 Common Types of Active Control Systems Active Mass Damper (AMD) Active Tendon Systems Active Brace Systems Pulse Generation Systems Dr. Naveed Anwar 42 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 Anwar 43 Structure with AMD Model & Free Body Diagram for Structures with AMD Dr. Naveed Anwar 44 Active Tendons System  Consist of a set of pre-stressed tendons subjected to controllable tensile forces.  Under seismic excitation, interstory 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 x(t) Active tendon α Actuator ẍg (t) u(t) Schematic Diagram of Active Tendon System Dr. Naveed Anwar 45 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, Kbraces 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 Anwar 46 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 47 Hybrid Systems Dr. Naveed Anwar Common Hybrid Systems Hybrid Mass Dampers Hybrid Base-Isolation System Hybrid Damper-Actuator Bracing Control Intelligent Hybrid Control Systems Dr. Naveed Anwar 49 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 Anwar 50 Hybrid Base-Isolation System  Combines base isolation system with an active control system.  Active tendon system is installed on a baseisolated structure Hybrid system with base isolation and actuators Dr. Naveed Anwar 51 Hybrid Damper Actuator Bracing Control Combines a hybrid device with an actuator resulting in increased efficiency and control on structural response Dr. Naveed Anwar 52 Intelligent Hybrid Control Systems Excitations - + Structure Z(t) Response >>TR Response TR?? Yes Z (t) or Z˚(t) No Z (t) = 0 Or Z˚ (t) = 0 Feedback Gain Working Mechanism of Single Stage Intelligent Hybrid System Dr. Naveed Anwar 53 Intelligent Hybrid Control Systems Ground Motion Stage 2 Stage 1 Structure Stage 3 Structure Damper Damper Structure Actuator Damper Actuator Will Adjusted feedback gain Response Response > 2nd Threshold > Ist Threshold No Yes No Yes Working Mechanism of Three Stage Intelligent Hybrid System Dr. Naveed Anwar 54 Base Isolation Systems for Seismic Response Control Dr. Naveed Anwar Base Isolation Systems for Seismic Response Control  Tend to reduce the energy transfer from ground acceleration to structure. Most Important Component Bearing Elastomeric Bearings Dr. Naveed Anwar Sliding Type Bearings 56 Common Types of Bearings Elastomeric Bearings Lead-Plug Bearings High-Damper Rubber Bearings Friction Pendulum Bearings Pot-Type Bearings Dr. Naveed Anwar 57 Types of Bearing Elastomeric Bearings Dr. Naveed Anwar Lead-Plug Bearings 58 Types of Bearing Friction Pendulum Bearing Dr. Naveed Anwar Friction Pendulum Bearing with Double Concave 59 Types of Bearing Top Plate with Stainless Surface Seal Piston with Teflon-Coated Surface at the top Elastomer Base Pot Typical Plot Type Bearing Dr. Naveed Anwar 60 Sensing and Data Acquisition Systems Dr. Naveed Anwar Components of Data Acquisition Systems Sensors Data Acquisition System Control Computer Dr. Naveed Anwar Signal Conditioning Unit 62 Schematic of Analog Sensing and Data Acquisition System Smart Seismic Structure Sensors Signal Conditioner Actuators Analog Computer Dr. Naveed Anwar 63 Schematic of Digital Sensing and Data Acquisition System Smart Seismic Structure Signal Conditioner Sensors Actuators D/A Boards Dr. Naveed Anwar Digital Controller A/D Boards 64 Components of Data Acquisition and Digital Control Systems Smart Structure Signal Conditioner Sensors Amplifier Filter Multiplexer Actuator(s) Dr. Naveed Anwar Control Computer A/D Observer Controller D/A Data Recorder Display 65 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 Anwar 66 Dr. Naveed Anwar View publication stats 67