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LIGO Science Education Center Kinetic Pendulum Wall Exhibit Preliminary Design Review

LIGO Science Education Center Kinetic Pendulum Wall Exhibit Preliminary Design Review 27 April 2006. Project Deliverables. Engineering CAD realization of the Kinetic Exhibit concept, suitable for fabrication and installation, including: Design of structural supports and interface attachments

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LIGO Science Education Center Kinetic Pendulum Wall Exhibit Preliminary Design Review

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  1. LIGO Science Education Center Kinetic Pendulum Wall Exhibit Preliminary Design Review 27 April 2006

  2. Project Deliverables • Engineering CAD realization of the Kinetic Exhibit concept, suitable for fabrication and installation, including: • Design of structural supports and interface attachments • Design of moving elements • Design of bearing and axle attachments and supports • Design of magnet attachments and adjustments • Design of a manual interaction mechanism for visitor excitation of the exhibit • Design of a secure, manually-activated locking mechanism to restrain elements and prevent damage under extreme weather conditions • Specification of bearings, magnets, elastomeric bumpers, lubricants, and other special materials and hardware • Specification of surface finishes and material treatments (coatings, anodizing, etc.) • Design of special fixtures or tooling required for installation and continuing operational maintenance (as required) • Supporting analyses of moments, loads and stresses for static, dynamic and wind conditions, including verification of compatibility with the building structural interface • Installation, alignment and commissioning procedures • Cost estimation and value engineering, as required, to maintain final project within allocated budget • Supporting estimates of installation, life cycle, and maintenance costs • Prototype or first-article fabrication and associated qualification testing, if required

  3. Complete Exhibit • 120 Pendulums across 100’ • Magnetically coupled

  4. Truss Assembly • Design • 12 Trusses across building • Each truss • 10 Pendulums on 10” centers • 3 axle supports • Welded structural steel • 1 Truss per building structure section (8’4”) • Truss feet to be located close to vertical I-beams for strength • Issues • End pendulums are 16” from edge of siding • Pendulum/I-beam spacing/coverage • Attachment method of Trusses to rails TBD

  5. Building Interface • Design • Stringers • 2 structural steel channels • Welded to vertical W6x20 I-beams • Issues • Specify and weld stringers prior to painting? • Hanger/gussets for stringers

  6. Pendulum Assembly • Design • Pendulum • 4”x6”x.125”x27’ • 6061-T6 Aluminum • Clear anodized • Natural period ~9s • Stiffener plates • 6”x12”x.125” • 6061-T6 Aluminum • Clear anodized • Riveted to pendulum • Issues • Refine stiffener plate dimensions • Vibrations due to bumper impact? • Fabrication procedure for bearing mount

  7. Axle and Attachments • Design • Axle • 1.5” Diameter • 99” Long • 17-4 PH H1150 Stainless steel • Supports • 4 Pendulums between supports • 1 Pendulum overhangs each end support • 2”x4”x.125” Wall structural steel tubing • is a candidate • Issues • Axle attachment design • If tubing is selected, welds must be water-tight • Channel does not require water-tight welds

  8. Bearings and Magnets • Design • Bearings • Piloted flange bearing • Collet-type shaft connection • Life expectancy >>100 years • Magnets • 2 per pendulum (likely) • Ceramic magnet • 4”x6” Footprint • Attachments • Sheet metal covers • Issues • Bearings • Lubrication/service interval • Cost • Corrosion resistance • Magnets • Thickness to be determined • Adjustability required for final unit?

  9. Excitation Mechanism • Design • Excitation plate • Offset from pendulum by flanged tube • Issues • Ropes tangling in pendulum • Add rope guides? • Elastic cords to limit forces? • Limits to abuse by visitors Ropes to ground

  10. Locking Mechanism • Design • 12 Locking mechanism assemblies • Rollers contact pendulums • UHMW or similar • Issues • Axle stiffness • Retain desired preload for all pendulums

  11. Locked Locking Mechanism Locking mechanism – stored up • Issues • Storage • View obstruction • Deployment • Must push 10 pendulums into position • Manual powered winch • Visible rope or cable Free

  12. Locking Mechanism Locking mechanism – stored down • Issues • Storage • View obstruction • Deployment • Must push 10 pendulums into position • Manual powered winch • Visible rope or cable Free Locked

  13. Upper Lower Bumpers • Design • Loading-dock type bumper • D-shaped cross-section • Elastomer material • Issues • Upper bumpers extend forward from roof line • Vibration/noise due to pendulum impact • Material selection for damping, weather resistance

  14. Analysis - Stress • Pendulum under side wind loading • Model and assumptions • Analyze lower section only and cut in half based on symmetry • Bearing flange rigidly supports thrust load • Pressure due to wind determined using ASCE 7-05 • “Minimum Design Loads for Buildings and Structures” • Yield strength • 40,000 psi • Max stress • 16,300 psi

  15. Analysis - Displacement • Pendulum under side wind loading • Model and assumptions • Analyze lower section only and cut in half based on symmetry • Bearing flange rigidly supports thrust load • Pressure due to wind determined using ASCE 7-05 • “Minimum Design Loads for Buildings and Structures” • End deflection • 2.3”

  16. Analysis - Stress • Bumper impact scenario • Model and assumptions • Analyze lower section only and cut in half based on symmetry • Wind acts on the pendulum above the pivot only, normal to the front surface • Pendulum accelerates through its entire range of motion • Pendulum impacts the upper bumper at maximum velocity • Bumper absorbs zero energy • Pendulum acts as two simply-supported flexures to momentarily store impact energy • Upper and lower pendulum stiffnesses determined via FEA • Resulting deflections/forces are calculated • Yield strength • 40,000 psi • Max stress • 26,500 psi

  17. Impact bearing loads Pendulum weights Analysis - Stress • Axle under bumper impact loading • Model and assumptions • Cut in half at center • Axle supports are rigid • Bearing loads applied • Pendulum weights • Loads due to pendulum impacts • All pendulums impact simultaneously • VERY conservative • Bumper energy absorption will reduce stresses to acceptable level • Yield strength • 126,000 psi • Max stress • 140,000 psi

  18. Y Z X Building Loads • Model and assumptions • Loads • Weight of pendulums, supports, etc. • Wind loads - horizontal at 45° • Distribution • Across vertical I-beams at stringer • elevations: 244” and 284” • Rx = -56959 (lbf) • RY = -21158 (lbf) • RZ = 56959 (lbf) • Magnitude R = 83285 (lbf) • Issues • Building compatibility to be verified • by Mckee and Deville

  19. Installation Procedure • Design • Truss assembly can be assembled on the ground • Fixture will be made to allow truss assembly to be picked up with extended-boom fork lift • Issues • Fastening method for truss assemblies • Magnet adjustment in field, if necessary

  20. Preliminary Cost Estimation • Issues • Bearing selection, materials • Truss fabrication method • Lock-down method • Refined and verified cost estimates on all items

  21. Prototype • Design • 5 Pendulums • Sliding stiffeners • Mild steel • Suspended from scaffolding • Adjustments • Pivot position - 12” range • Pendulum spacing • Magnet position, quantity, size • Tests • Response/coupling • Impact vibrations • Bumper performance • Lateral locking friction • Single pendulum fabricated • per “final” design • Issues • Alternative bearing selection • Risks

  22. Questions/Issues • How close to the edge of the building do the end pendulums need to be? • Can the pendulum range of motion be asymmetrical? • Verify that the west (4) vertical W6x20 I-beams will not have any front skin. • Clarify the walkway locations. • Is there access to the sides of the vertical W6x20 I-beams? • Verify the roof overhang detail.

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