7 November 2012, EERI, Rice Chapter

7 November 2012, EERI, Rice Chapter

Introduction to Damping and Dampers

VishnuPhD Candidate

Dept. of Civil and Environmental EngineeringRice University, Houston, TX


Fundamentals

• Three fundamental properties of any structure– Mass, m– Stiffness, k– Damping, c

• Occurs naturally in structures– Microcracks– Microslip among frictional interfaces– Joints


Damping – SDOF system

• SDOF – Single Degree of Freedom System

0 2 4 6 8 10 12 14 16-100

-50

0

50

100

150Single Degree of Freedom System

Time (secs)

Inp

ut a

nd

Ou

tpu

t

Input acceleration

Output - = 5%

Output - = 10%

Output - = 20%


Critical damping


Spectrum


Spectrum

0 1 2 3 40

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

/p

x/x o

0 1 2 3 40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

/p

Ba

se s

he

ar/

We

igh

t

= 1% = 5% = 10% = 20%


Multi Degree of Freedom System


Tuned mass damper


Fluid dampers

Constantinou, MC, Symans, MD, (1999) “Experimental study of seismic response of buildings with supplemental fluid dampers,” The Structural Design of Tall Buildings, Vol. 2, 93-132.

Constantinou, MC, Symans, MD, (1999)


MR dampers (no damper)


MR dampers (1 damper)


MR dampers (>1 damper)


Viscoelastic dampers

Wallace F. Bennet Building, Salt Lake City, Utah, USA

Kaiser Santa Clara Medical Hospital, Santa Clara, California, USA

Symans, MD et al., (2008) “Energy Dissipation Systems for Seismic Applications: Current Practice and Recent Developments,” J. of Struct. Engrg, vol. 134, No.1, 3-21.


Friction dampers

Constantinou, MC and Symans, MD, (1993), “Seismic response of structures with supplemental damping,” The Structural Design of Tall Buildings, vol. 2, 77-92.

Nagarajaiah, S. et al. (1992) “Experimental study of sliding isolated structures with uplift restraint,” J. Struct. Engrg., vol. 118, no. 6, 1666-1682. (page no. 1678).


Friction dampers

Monterey County Govt. Center, Monterey County, California, USA

Patient Tower, Seattle, USA



Damping force - summary

a) Friction Dampersb) Steel yielding

devicec) Viscoelastic

deviced) Viscous device

Constantinou, MC and Symans, MD, (1993), “Seismic response of structures with supplemental damping,” The Structural Design of Tall Buildings, vol. 2, 77-92.

Symans, MD et al., (2008)


Summary

• Supplemental damping can be provided and is very effective.

• When choosing a supplemental damping strategy scaling is a very important phenomenon that needs to be taken into account.

7 November 2012, EERI, Rice Chapter

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