Introduction to Earthquake Engineering Introduction to Seismic Control

Transcription

1 Introduction to Earthquake Engineering Introduction to Seismic Control Prof. Dr.-Ing. Uwe E. Dorka published: October 2014

2 Introduction Conventional Structures can be earthquake safe, but they are not configured for earthquakes and therefore, too many are lost 2

3 Introduction A multitude of small details in columns, corners or connections decide whether a building will survive or not 3

4 Introduction Quality control is overwhelmed by this requirement. Its like a game of chance, even for the same type of building in the same location 4

5 Introduction Therefore, we need new structural concepts adapted to earthquakes A feasible approach is Structural Control 5

6 What is Structural Control? Basic Idea: To control the response of a structure to dynamic loading by introducing special mechanisms into the structural system with suitable control devices. Active Control Passive Control From Magonette & Marazzi (1) 6

7 What is Structural Control? Definition: The subjected to dynamic loading Such variables may be displacements or their time derivatives (velocities, accelerations) and/or forces can be achieved in and the For mode control, a structural system is needed that has clearly defined modes For rigid body control, a structural system must consist of an assemblage of rigid bodies 7

8 Mode Control Concepts Controlled braces From: Preumont (4) From: Preumont (4) 8

9 Mode Control Concepts Controled tendons From: Preumont (4) From: Preumont (4) From Magonette & Marazzi (1) 9

10 Mode Control Concepts Base isolation From: Preumont (4) From: Preumont (4) 10

11 Mode Control Concepts Tuned Mass Dampers - TMDs From Soong (3) 11

12 Mode Control Concepts Tuned Mass Dampers - TMDs Den Hartog s Solution From: Soong (3) 12

13 Mode Control Concepts semi-active TMDs Photo: Japan Iron & Steel Federation 13

14 Structural Control for Earthquake Excitation Need mechanism suitable for base excitation Goal: Reduction of horizontal motion and control over internal forces Conventional structure Rigid body assemblage Total Hyde Elastic (potential) Viscous Inertial (kinetic) Control of rigid body mechanisms 14

15 Structural Control for Earthquake Excitation Rigid body mechanisms: Hyde System Pagoda System Tendon System Base Isolation 15

16 Base Isolation The Gates of Hell Auguste Rodin 16

17 Base Isolation The Gates of Hell Auguste Rodin 17

18 Pagoda System 18

19 Hyde System 19

20 Hyde System 20

21 Tendon System Tendons with passive or semi-active devices control the motion of rigid bodies 21

22 Tendon System Early retrofit in Solofra, Italy 22

23 Tendon System Early retrofit in Solofra, Italy 23

24 Structural Control is : Added damping Added damping and stiffness Or any conventional structural system with additional devices: in such structures! The first step in structural control is to select a structural concept that is controllable! The following are conventional structural systems and therfore not controllable: 24

25 Added Damping (Not Structural Control) - Applying viscous dampers 25

26 Added Damping (Not Structural Control) - Applying hysteretic dampers All Pictures from: Soong (3) 26

27 Added Damping versus Structural Control Added Damping Seismic Control Total Hyde Elastic (potential) Viscous Inertial (kinetic) Added Damping: Seismic Control: Vibrations are not eliminated. Limited effect on internal forces and displacements Vibrations are eliminated (rigid body motion). Full control over internal forces and substantial reduction of displacements 27

28 References (1) G. Magonette, F. Marazzi Active Control Experiment of a large scale cable-stayed bridge mock-up Third International Symposium on Cable Dynamics, Trondheim, Svezia, August (2) Petersen Dynamik der Baukonstruktionen Vieweg (3) Soong & Dargush Passive Energy Dissipation Systems in Structural Engineering John Wiley & Sons (4) Preumont Vibration Control of Active Structures Kluwer Academic Puplishers 28