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Seismic displacements control systems on bridges Luís Guerreiro Instituto Superior Técnico

Seismic displacements control systems on bridges Luís Guerreiro Instituto Superior Técnico. T=0.2s. T=0.6s. 5%. 10%. T=1.0s. 15%. 20%. T=2.0s. T=3.0s. The use a very flexible solutions in bridges has been a way to reduce the seismic effects on the piers.

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Seismic displacements control systems on bridges Luís Guerreiro Instituto Superior Técnico

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  1. Seismic displacements control systems on bridges Luís Guerreiro Instituto Superior Técnico

  2. T=0.2s T=0.6s 5% 10% T=1.0s 15% 20% T=2.0s T=3.0s The use a very flexible solutions in bridges has been a way to reduce the seismic effects on the piers. The pay-back is the increase on the seismic displacements. To limit the displacements to acceptable levels, solutions using devices for the control of seismic displacements were developed.

  3. T=0.2s T=0.6s 5% 10% T=1.0s 15% 20% T=2.0s T=3.0s Strategies to control the seismic displacements A – Increase of the Structure stiffness 1 A 0

  4. T=0.2s T=0.6s 5% 10% T=1.0s 15% 20% T=2.0s T=3.0s Strategies to control the seismic displacements B – Energy Dissipation 0 B 2

  5. T=0.2s T=0.6s 5% 10% T=1.0s 15% 20% T=2.0s T=3.0s Strategies to control the seismic displacements A – Increase of the Structure stiffness B – Energy Dissipation 1 A 0 B 2

  6. Seismic Protection Systems: Devices that improve the seismic behavior of structures without explore their ductility. The devices may modify the structure characteristics or improve the dissipation capacity. Classification of the Seismic Protection Systems:  Passive systems – no energy needed  Active systems – need energy to control the structure movement  Semi-Active systems – need energy to modify the characteristics of the system

  7. Passive Systems Active Systems Semi-active systems Base Isolation Dissipation Devices Tunned Mass Dampers Active TMD Active Bracing Adaptative Control Semi-activeTMD Variable stiffness Variable damping Seismic Protection Systems

  8. There are several systems for energy dissipation. The most common are the hysteretic dampers and the viscous dampers. Viscous Damper Hysteretic Damper (www.alga.it) Vasco da Gama Bridge

  9. F F Fy K2 K1 D D Hysteretic dampers use the plastic deformation capacity of steel or other metallic elements. In these systems the force depends on the deformation and the characteristic parameters are: the initial stiffness (K1), the after yielding stiffness (K2) and the yielding force (Fy).

  10. F F F vel vel vel a = 0.10 a = 1.00 a = 1.80 On the viscous dampers the force depends on the velocity of the piston. The force-velocity behavior depends on the fluid characteristics. The following equation may be used: F = C |v|a signal(v) C, a – Characteristics of the damper; v - velocity

  11. F a = 0.10 vel a = 1.00 F vel F a = 1.80 vel • Large increase on the force for low velocity values; • The maximum force tends to a limit. • The force increases linearly with the velocity; • The use of damping coefficient is allowed (z). • Force almost null for low velocity values; • The increases with the velocity with an increasing rate.

  12. On the hysteretic dampers the ratio between the after yielding stiffness (k2) and the initial stiffness, has a strong influence on the force-deformation cycles shape. Other important factor is the yielding force value. In the case of a very high yielding force value, the device remains elastic for most of the time and the energy capacity is limited. Relation k2/k1 Force-Deformation Damping

  13. The shape of the force-deformation cycles of the viscous dampers are affected by the a parameter. Values of a Force-Velocity Force-Deformation Damping

  14. On viscous dampers the parameter C does not affect the cycle force-deformation shape, but increases the area of the cycle. The increase of the C value increases the energy dissipation of the device. Values of C Damping Force on the device Values of C Damping Force on the device

  15. Force-Velocity Relation (Viscous Dampers) a Force (kN) Velocity (m/s)

  16. Force-Displacement Relation Force (kN) a k2/k1 = 1% Velocity (m/s)

  17. Displacement Velocity Force on Damper Force on the structure Viscous Damper

  18. Displacement Velocity Force on Damper Force on the structure Hysteretic Damper

  19. Force on Viscous Damper Force on Hysteretic Damper Comparison

  20. Vasco da Gama Bridge Steel Hysteretic Dampers

  21. Viaduct of “Loureiro” Viscous Damper

  22. “Shock absorbers” Viaduct “Real”

  23. Viaduct over “Ribeira da Laje” and “Rio Grande da Pipa” Viscous Damper

  24. “Baixa” of Mondego River Viaduct (A1) Seismic Retrofitting

  25. Seismic Retrofitting Alhandra Viaduct (A1)

  26. Seismic Retrofitting Alhandra Viaduct (A1)

  27. Bridge over “Vale da Lama” A22 (Via do Infante)

  28. Bridge over “Ribeira do Farelo” A22 (Via do Infante)

  29. Bridge over Arade River A22 (Via do Infante)

  30. Bridge over Arade River A22 (Via do Infante)

  31. Steel Hysteretic Dampers PND and PNUD (ALGA)

  32. Algasism Dampers PND Steel hyteretic Damper PNUD Steel Hysteretic Damper Free for slow motions ( ALGA)

  33. Non Linear Viscous damper (Infanti e Castellano, 2001)

  34. Non Linear Viscous damper Typical model of FIP Viscous dampers behavior (Infanti e Castellano, 2001)

  35. Non Linear Viscous damper Force-Velocity (Infanti e Castellano, 2001)

  36. Seismic displacements control systems on bridges Luís Guerreiro Instituto Superior Técnico

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