Task 1.4.7 - Innovative SystemsFluid Dampers for Seismic Energy

Dissipation of Woodframe Structures

Michael D. Symans

Kenneth J. Fridley

William F. Cofer

Ying Du

CUREe-Caltech Woodframe Project

Meeting of Element 1 Researchers (Testing and Analysis) San Diego, CA

January 13, 2001

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Outline

• Review of Research Plan• Description of Shear Wall FEM

– System Identification

• Shear Wall Seismic Analysis• Proposed Damper Configurations • Implementation Issues• Short-Term Goals

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• Phase ILiterature Review (Sept. 1999 to Dec. 1999)

• Phase IIInitial Analytical Study (Dec. 1999 to May 2000)

• Phase IIIIdentification of Practical Issues (Dec. 1999 to Sept. 2000)

• Phase IVFinal Analytical Study (May 2000 to Dec. 2000)

• Phase VRecommendations (Jan. 2001 to March 2001)

Review of Research Plan

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Shear Wall FEM Wall dimensions: 2.44 m x 2.44 m (8 ft x 8 ft) Framing: 50.8 mm x 101.6 mm (2” x 4”) nominal studs spaced at 60.96 cm (24”) Waferboard sheathing panels: 1.22 m x 2.44 m (4 ft x 8 ft), 9.53 mm (3/8”) Nails: 6.35 cm (2.5 in.) 8d galvanized common nails Field and perimeter nail spacing = 15.24 cm (6 in.) Mass: 44.5 kN (10 kips) lumped at nodes along top plate at top of studs (wall located at first story of 3-story building)

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Sheathing-to-Stud Connector Element

Typical Load-Deflection Curve Obtained from

Static Cyclic Sheathing Connector Test

(Source: Dolan, 1989)

Hybrid Stewart - Dolan Nail Connector Model

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

-20 -15 -10 -5 0 5 10 15 20

Displacement (mm)

Load (kN)

Simplified Hysteresis Loop for

Sheathing Connector Element

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System Identification

f1 = 4.18 Hz

1 = 2.1%

f2 = 22.35 Hz

2 = 7.6%

f3 = 22.81 Hz

3 = 7.7%

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Earthquake Loading

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0 10 20 30 40 50 60

Time (sec)

Acceleration (g)

1952 Kern County EarthquakeTaft record - Lincoln School Tunnel

(S69E component)

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Damper Configuration

Piston Head

Piston Rod

Pinned Connection

PinnedConnection

Viscous Fluid

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Hysteretic Behavior of Wall

C = 87.6 kN-s/m (500 lb-s/in)

No Damper

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4

Drift Ratio (%)

Base Shear Coefficient

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15

Drift Ratio (%)

Base Shear Coefficient

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Hysteretic Behavior of Wall(Plotted to same scale)

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4

Drift Ratio (%)

Base Shear Coefficient

No Damper

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4

Drift Ratio (%)

Base Shear Coefficient

C = 87.6 kN-s/m (500 lb-s/in)

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Components of Hysteresis Loop(Plotted to same scale)

Wall Contribution Damper Contribution

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15

Drift Ratio (%)

Base Shear Coefficient

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15

Drift Ratio (%)

Damper Force / Weight

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15

Drift Ratio (%)

Wall Force / Weight

C = 87.6 kN-s/m (500 lb-s/in)

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-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15

Drift Ratio (%)

Normalized Force

Wall Force / Weight Damper Force / Weight

Comparison of Components

C = 87.6 kN-s/m (500 lb-s/in)

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Effect of Dampers on Drift

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0 5 10 15Time (sec)

Drift Ratio (%)

No Damper

C = 17.5 kN-s/m

C = 87.6 kN-s/m

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

1 2 3

Wall Condition

Peak Drift Ratio (%)

No Damper

C = 17.5 kN-s/m(-41%)

C = 87.6 kN-s/m(-67%)

Peak drift reduced by 67%Note: 400% increase in damping capacity results in additional 26% reduction in peak drift.

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Effect of Dampers on Base Shear

Peak base shear reduced by 45%

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

1 2 3

Wall Condition

Base Shear Coefficient

No Damper

C = 17.5 kN-s/m(-25%)

C = 87.6 kN-s/m(-45%)

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0 5 10 15

Time (sec)

Base Shear Coefficient

No Damper

C = 17.5 kN-s/m

C = 87.6 kN-s/m

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Energy Distribution

No Damper C = 87.6 kN-s/m

- Inelastic energy dissipation demand reduced by 93 %

- Portion of input energy absorbed by dampers = 82 %

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12 14 16

Time (sec)

Energy (kN-m)

InputInelasticViscousElasticKinetic

0

0.05

0.1

0.15

0.2

0.25

0.3

0 2 4 6 8 10 12 14 16

Time (sec)

Energy (kN-m)

Input

Inelastic

Viscous

Elastic

Kinetic

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Energy Distribution(Plotted to same scale)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12 14 16

Time (sec)

Energy (kN-m)

InputInelasticViscousElasticKinetic

No Damper

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12 14 16

Time (sec)

Energy (kN-m)

Input

Inelastic

Viscous

Elastic

Kinetic

C = 87.6 kN-s/m

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Proposed Damper Configurations

Piston Head

Piston Rod

Pinned Connection

PinnedConnection

Viscous Fluid

Dual let-in rod pin-connected to bottom cornerof wall and to damper;

Damper pin-connected to upper corner

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Recently Developed Amplification Systems for Stiff Structures

Toggle-Brace System Scissors-Jack System

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Pre-Fabricated Wall

- Prefabricated in a controlled manufacturing environment (similar to Simpson Strong Wall which “drops” into framing)

- 50.8 x 152.4 mm (2 x 6 in.) framing

- Damper connections which ensure minimal slip before damper engagement.

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Possible Damper Connection Details

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Implementation Issues

- Taft EQ, C = 87.6 kN-s/m (500 lb-s/in):

- Damper Force Demand = 2.6 kN (580 lb)

- Damper Velocity Demand = 3.0 cm/s (1.2 in/s)

- Damper Stroke Demand = 0.2 cm (0.08 in)

- Off-the-shelf dampers (D-Series; Taylor Devices, Inc.):

- Force capacity = 2 or 8.9 kN (450 lb or 2000 lb)

- Stroke capacity = 5.1, 10.2, 15.2 or 20.3 cm (2, 4, 6, or 8 in.)

- Estimated cost = $300/damper

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Damper Engagement

(effect of initial wall displacement w/out damper engagement)

Implementation Issues

Fg

uwus/cos

Gap element

uw

us

us = 1/16”, 1/8”, 1/4”, 3/8”, 1/2”

-us/cos

C

KFg = gap element force

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Response to Comments from Element 1 Managers

• Sept. 16, 2000 Meeting Comments– Analytical results need to be checked carefully

(Done)– Typical detailing/connection of the dampers should

be considered (In progress)

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Short-Term Goals

• Parametric studies of wall performance

– Various earthquake records and intensities

– Various damper configurations

– Effect of delay in damper engagement

• Development of implementation details

• Analysis of 3-D Woodframe Building with dampers.