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