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Viscous Damping Devices
Design and Implementation IssuesApril 17, 2006
Mark Sinclair, SE, Degenkolb Engineers
Outline – The Four “C”’s
> C Values How to size the dampers?
> Configuration How and where to place the dampers?
> Columns Critical in damped frame design.
> Connections Things that are different to other systems.
Damper Types
> Viscous
> Friction
> Visco-Elastic
> Hysteretic
Focus on ViscousDampers
> Advantages Multiple suppliers Ducts and services Can offer large stroke capacity Insensitive to temperature Easy to model Dissipate energy at all
displacements
> Limitations Mechanical device, relatively
complex Requires periodic inspection
and testing More expensive than some
other devices
Connections
> Damper Connections Damper and brace to gusset bolted connection.
Damper to extender brace connection.
> Extender Braces Generally included in the damper manufacturers scope
> Stroke Adjustment Either at extender brace location, Tang Plate, or Provide Extra Stroke
> Velocity Exponent
Hysteresis Loop Area Multiplier
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Velocity Exponent, a (F = C x v^a)
Loop
Are
a M
ultip
lier
Velocity Loop AreaExponent Multiplier
0 40.05 3.940.1 3.880.2 3.770.3 3.670.4 3.580.5 3.50.6 3.420.7 3.340.8 3.270.9 3.21 3.14
Connections –Velocity Exponent
F = C x V α
Displ.
Force
Damper Force Velocity EquationF = Damper ForceV = Damper Velocityα = Velocity Exponent
Increase in Damper Force versus Velocity
0
200
400
600
800
1000
1200
0 5 10 15 20 25
Damper Velocity (inches/second)
Dam
per F
orce
(kip
s)
Exponent = 1.0 (Linear)
Exponent = 0.6
Exponent = 0.4
Exponent = 0.1
Exponent = 0 (Friction)
+7%
Design Velocity MCE or Upper Bound Velocity
+32%
+52%
+100%
+0%
Behavior of check valve
Connections
Damper to Gusset Connection
Images from Enidine
Damper to Brace Connection
Photo by Taylor Devices Dampers
Flanged connection.
Threaded connection.
Configuration -HorizontalChevron
> Example: Transbay Terminal San Francisco
> Lower damper force, higher stroke
> Connecting steel more expensive than in-line (50% to 100% of damper cost), offset by less expensive dampers
> Potentially more interruption to services passing overhead
> Narrower tube brace below ceiling line
PUSH
PUSH
Configuration - In-Line Diagonal
> Higher damper force, lower stroke
> Connecting steel less expensive than horizontal chevron (20% to 50% of damper cost)
> Less interruption to services passing overhead
> Damper flange connection may govern wall thickness
Configuration – In-Line Diagonal - Chevron
Configuration – Damper Toggle
Image from Taylor Devices
Braced Frame or Moment Frame?
> Damped Frame = Moment Frame Drifts to 2% plus
Flexural hinges in beams accommodate large rotations
Low axial loads permit large flexural ductilities
Strong column behavior
Low overturning moments
Shallow foundations
> Damped Frame = Braced Frame Lower drifts…..maybe.
High axial loads limit flexural ductility
Gusset plate connections with limited rotation capacity
“Yielding” of axial members, flexural demands often ignored
> Damped Frame is BOTH
Frame Configuration - Stacked
> Axial loads accumulate
> Deep foundations
> Strong column behavior ??
> Column flexural ductility
> Uplift due to net tension
> Convenient for
architectural requirements
> 13% Damper Gusset
Moment Connections
> 27% if using chevron or V
> 29% if using horizontal
dampers
Frame Configuration- Checkerboard
> Distributed dampers spread
overturning loads
> Shallow foundations
> Reduced column axial loads
permit strong column
behavior
> Architectural “Feature”….?
> 31% Damper Gusset
Moment Connections
> 62% if using horizontal
dampers
Frame Configuration- Offset Tower
> Possible compromise
> Spread overturning loads
> Watch offsets
> Shallow foundations
> Set stack height for strong
column behavior and flexural
ductility
> Architectural…?
> 13% Damper Gusset moment
Frame Connections
> 29% if using horizontal
dampers
Configuration – Frame
> V and Inverted V
versus two-story X
> Minimum dampers
per floor Two dampers, configured to
resist torsion.
Gusset Plate MRF Connections
Connections – Gusset Plate Test
Connections – Gusset Plate at 4% Drift
Connections – Gusset Plate Connection Hysteresis
-10 -5 0 5 10-1000
-500
0
500
1000
Column Top Displacement (in.)
App
lied
Load
(kip
s)
-6 -4 -2 0 2 4 6Story Drift Ratio (%)
Spec. 4Model 4
Connections – Gusset Plate Connection Hysteresis
Strong panel zones are easier…
Configuration- Columns
> Critical
> Plastic hinge
locations
> Column axial loads
Configuration – Beam Depth
234
322
333
370
395
437
509
Zx
0.87%15307.21688W14x132
0.67%27504.31528W18x143
0.59%32206.01543W21x132
0.52%40206.71540W24x131
0.47%47604.61264W27x129
0.43%57705.31319W30x132
0.37%78007.61316W36x135
Yield Rotation
IxBf/2tfPnSection
Serviceability
> Low frame stiffness Design for Strength R = 8
Add dampers for Drift
Very flexible frame……
> Issues Check seal travel under wind cycles
Check perceptable movement for occupants
Consider wind lock-up devices
Damper Sizes – “C” Values
> ASCE 7-05 Chapter 18
> Provisions for New
Buildings
Building Linear Mode Shapes
-50.00
0.00
50.00
100.00
150.00
200.00
250.00
-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0.25
Mode Shape
Hei
ght (
ft)
Mode 1
Mode 2
Mode 3
Caltrans District 4 Headquarters Pushover Curves
0
1000
2000
3000
4000
5000
6000
0 10 20 30 40 50 60
Roof Displacement (Penthouse Floor) - inches
Bas
e Sh
ear -
kip
s
Mode 1
Mode 1 fit
Mode 2
Mode 2 fit
Mode 3
Mode 3 fit
Target for 1.5% drift limit
Building Pushover Displaced Shape, Original Estimate
-50
0
50
100
150
200
250
-5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0
Mode Shape
Hei
ght (
ft)
Mode 1
Mode 2
Mode 3
Building Displaced Shapes
-50
0
50
100
150
200
250
-5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
Displacement (inches)
Hei
ght (
ft) Mode 1
Mode 2
Mode 3
SSRS
Caltrans District 4 Headquarters Pushover Curves
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
0 5 10 15 20 25 30 35 40 45
Spectral Displacement (inches)Sp
ectr
al A
ccel
erat
ion
(g)
Mode 1 Fitted
Mode 3 Fitted
Mode 3 Fitted
DBE Spectrum
Site Specific 10% / 50year
X
X
X
5% Damping added from hysteretic damping12% Damping added from viscous damping
5% Damping added from hysteretic damping16% Damping added from viscous damping
0% Damping added from hysteretic damping85% Damping added from viscous damping
MODE 3
MODE 2
MODE 1
Or….
Use Time-History Analysis
Development Opportunities
> Gusset Plate Damper Connections Bolted Bracket +
SidePlate + ?
Gusset Plate + RBS
Column Base + RBS
> Other Devices – e.g. Wall Dampers
> Damage Free Connections
Bolted Bracket Damper Connection
Bolted Brackets by: Steel Cast Solutions (www.steelcastsolutions.com)
Oiles Viscous Wall Damper(from www.oiles.co.jp)
Q&A
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