Task Innovative Systems Fluid 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

2 Outline Review of Research Plan Description of Shear Wall FEM –System Identification Shear Wall Seismic Analysis Proposed Damper Configurations Implementation Issues Short-Term Goals

3 Phase I Literature Review (Sept to Dec. 1999) Phase II Initial Analytical Study (Dec to May 2000) Phase III Identification of Practical Issues (Dec to Sept. 2000) Phase IV Final Analytical Study (May 2000 to Dec. 2000) Phase V Recommendations (Jan to March 2001) Review of Research Plan

4 Shear Wall FEM l Wall dimensions: 2.44 m x 2.44 m (8 ft x 8 ft) l Framing: 50.8 mm x mm (2” x 4”) nominal studs spaced at cm (24”) l Waferboard sheathing panels: 1.22 m x 2.44 m (4 ft x 8 ft), 9.53 mm (3/8”) l Nails: 6.35 cm (2.5 in.) 8d galvanized common nails Field and perimeter nail spacing = cm (6 in.) l 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)

5 Sheathing-to-Stud Connector Element Typical Load-Deflection Curve Obtained from Static Cyclic Sheathing Connector Test (Source: Dolan, 1989) Simplified Hysteresis Loop for Sheathing Connector Element

6 System Identification f 1 = 4.18 Hz  1 = 2.1% f 2 = Hz  2 = 7.6% f 3 = Hz  3 = 7.7%

7 Earthquake Loading 1952 Kern County Earthquake Taft record - Lincoln School Tunnel (S69E component)

8 Damper Configuration Piston Head Piston Rod Pinned Connection Pinned Connection Viscous Fluid

9 Hysteretic Behavior of Wall C = 87.6 kN-s/m (500 lb-s/in) No Damper

10 Hysteretic Behavior of Wall (Plotted to same scale) No Damper C = 87.6 kN-s/m (500 lb-s/in)

11 Components of Hysteresis Loop (Plotted to same scale) Wall ContributionDamper Contribution C = 87.6 kN-s/m (500 lb-s/in)

12 Comparison of Components C = 87.6 kN-s/m (500 lb-s/in)

13 Effect of Dampers on Drift Peak drift reduced by 67% Note: 400% increase in damping capacity results in additional 26% reduction in peak drift.

14 Effect of Dampers on Base Shear Peak base shear reduced by 45%

15 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 %

16 Energy Distribution (Plotted to same scale) No Damper C = 87.6 kN-s/m

17 Proposed Damper Configurations Piston Head Piston Rod Pinned Connection Pinned Connection Viscous Fluid Dual let-in rod pin-connected to bottom corner of wall and to damper; Damper pin-connected to upper corner

18 Recently Developed Amplification Systems for Stiff Structures Toggle-Brace System Scissors-Jack System

19 Pre-Fabricated Wall - Prefabricated in a controlled manufacturing environment (similar to Simpson Strong Wall which “drops” into framing) x mm (2 x 6 in.) framing - Damper connections which ensure minimal slip before damper engagement.

20 Possible Damper Connection Details

21 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

22 Damper Engagement (effect of initial wall displacement w/out damper engagement) Implementation Issues FgFg uwuw u s /cos   Gap element uwuw usus u s = 1/16”, 1/8”, 1/4”, 3/8”, 1/2” -u s /cos  C K F g = gap element force

23 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)

24 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.