13,14 July 2005 Feasibilty/Concept Study Mid Term Status Review CCAT Enclosure Nathan Loewen AMEC Dynamic Structures Ltd. 13 July 2005

Introduction Content of presentation: AMEC Dynamic Structures overview AMEC Dynamic Structures overview Review of enclosure requirements Review of enclosure requirements Technical work Technical work  Enclosure concept – “Calotte” Basic mechanism Basic mechanism Dimensions Dimensions  Structural design Description of analysis Description of analysis  Mechanical design Calotte mechanical system Calotte mechanical system Azimuth mechanical system Azimuth mechanical system Shutter Shutter Crane Crane Conclusions Conclusions

Company Profile AMEC Dynamic Structures Ltd: Located in Vancouver, Canada Located in Vancouver, Canada Design/build steel fabricating firm Design/build steel fabricating firm Specialize in astronomy and entertainment industries Specialize in astronomy and entertainment industries

Enclosure Requirements CCAT Enclosure Requirements Dome diameter: 50m Dome diameter: 50m Aperture diameter: 30m Aperture diameter: 30m Aperture zenith range: 0 – 75 degrees Aperture zenith range: 0 – 75 degrees Azimuth rotation: unlimited Azimuth rotation: unlimited Calotte rotation: 200 degrees Calotte rotation: 200 degrees Key environmental loads: Key environmental loads:  Wind (survival): 65m/s  Snow Load: 100kg/m^2  Ice Load: 25kg/m^2  Seismic: 0.4g ground acceleration

Calotte Enclosure Concept Zen=0 0 Zen=15 0 Zen=30 0 Zen=45 0 Zen=60 0 Zen=75 0 BASE CAP Aperture Ring Interface Ring Azimuth Ring

Calotte Enclosure Dimensions

Structural Design and Analysis General design Steel triangulated frame structure Steel triangulated frame structure Stiffened ring sections at mechanical interfaces Stiffened ring sections at mechanical interfaces Structural Analysis Preliminary FEA of all-steel enclosure Preliminary FEA of all-steel enclosure Members optimized under survival load combinations (gravity, wind, snow, ice) Members optimized under survival load combinations (gravity, wind, snow, ice) Mechanical interfaces modeled with equivalent spring stiffnesses Mechanical interfaces modeled with equivalent spring stiffnesses Total Enclosure Mass Base structure:140 tonne Base structure:140 tonne Cap structure:120 tonne Cap structure:120 tonne Shutter structure:50 tonne Shutter structure:50 tonne Cladding/Girts:80 tonne Cladding/Girts:80 tonne Azimuth mechanical:50 tonne Azimuth mechanical:50 tonne Calotte mechanical:25 tonne Calotte mechanical:25 tonne TOTAL:465 tonne TOTAL:465 tonne Element Plot Gravity Deflections ~7mm max

Mode Shapes Mode 2: 2.0Hz (Mode 3 similar) Mode 1: 1.4Hz Mode 4: 2.9Hz

Structural Material Mechanical interfaces (ring girders, rails, mounts) will be steel Structural shell could be steel or aluminum Steel advantages Steel advantages  Simplifies thermal issues and detailing pertaining to interface with steel mechanical components  Greater design flexibility; allows welding without loss of strength capacity Aluminum advantages Aluminum advantages  Structural shell ~50% lighter, resulting in weight savings of ~100 tonnes  Factor produced aluminum domes are available; discussions with Temcor are ongoing General notes General notes  Costs appear to be similar

Calotte Bearings/Drives The Calotte mechanical interface design (i.e. the bearings and drives at the inclined plane) are considered the highest risk component of the enclosure design Several general concepts for the mechanical design have been developed, and the pros/cons of each concept have been formally traded off The preferred point design is presented here

Calotte Bearing Concept Bogies contain 2 roller sets: Normal rollers oriented perpendicular to plane of rotation Normal rollers oriented perpendicular to plane of rotation Radial rollers oriented perpendicular to axis of rotation Radial rollers oriented perpendicular to axis of rotation Bogies mounted to “cap”, rails mounted to “base” Allows bogies to be accessed from single location at lowest point of interface Allows bogies to be accessed from single location at lowest point of interface Drive assembly independent from bogie assembly Several drive units mounted to base at lowest point of interface; allows redundancy and ease of access Several drive units mounted to base at lowest point of interface; allows redundancy and ease of access Spring-loaded rubber-tired drive rollers are a feasible concept Spring-loaded rubber-tired drive rollers are a feasible concept Direction of Normal Rollers Direction of Radial Rollers Normal Rollers Radial Roller Rubber-Tired Drive Cap Structure Base Structure Rails

Calotte Bearing Concept Polyurethane Radial Roller Steel Normal and Uplift Rollers Bogie Frame Normal Pivot Bearing Central Mount Rolled Wide-Flange Rail Sections Hardened Wear Plates Cap Ribs Base Ribs Bogie Support Frame Rail Supports 1.) Bogie Assembly2.) Bogie & Rails 3.) Structural Interface

Calotte Bearing Concept Radial rollers contained within a double rail Loading switches between inner/outer rail due to gravity load on inclined interface Loading switches between inner/outer rail due to gravity load on inclined interface Load distribution governed by “soft cap” structural properties Load distribution governed by “soft cap” structural properties Gap between rollers and rails Notionally 1” gap Notionally 1” gap Avoids over-constraint Avoids over-constraint Eases fabrication and assembly tolerances Eases fabrication and assembly tolerances

Calotte Interface Analysis Preliminary analysis have investigate load distribution through interface bogies Analysis based on enclosure FEM Analysis based on enclosure FEM Loads include gravity, wind, and forces due to fabrication tolerances Loads include gravity, wind, and forces due to fabrication tolerances Sample results shown below for radial rollers (results include dead loads, external and internal wind loads): Sample results shown below for radial rollers (results include dead loads, external and internal wind loads): Low Point of Interface High Point of Interface Low Point of Interface

Azimuth Bearings/Drives Azimuth bearings/drives Bogies are fixed to foundation, rail surface is mounted to enclosure Bogies are fixed to foundation, rail surface is mounted to enclosure Drive system utilizes rubber-tire drive rollers, spring loaded to maintain friction force Drive system utilizes rubber-tire drive rollers, spring loaded to maintain friction force  Bearing and drive concept is similar to HET/SOAR concepts Not considered a high-risk design issue due to experience with existing designs Not considered a high-risk design issue due to experience with existing designs

Shutter Shutter design variations Fixed vs. Movable Fixed vs. Movable  Movable structure required: fixed shutter blocks too much sky Interior vs. Exterior Interior vs. Exterior  Interior structure preferred: minimizes wind/snow/ice loads on the shutter structure, resulting in lighter shutter structure Azimuth mounted vs. interface mounted Azimuth mounted vs. interface mounted  Azimuth mounted preferred: minimizes load on enclosure structure, and does not require structure to be balanced about rotation axis Sky blockage due to fixed shutter:

Shutter Selected shutter concept is movable, azimuth mounted, internal structure Shutter closes w/aperture pointed to zenith=75 0 Shutter closes w/aperture pointed to zenith=75 0 Shutter structure supported via bogie system on enclosure azimuth ring girder, rotates to open/close shutter Shutter structure supported via bogie system on enclosure azimuth ring girder, rotates to open/close shutter Shutter structure has no drive system: Shutter structure has no drive system:  In open or closed configurations, locking pins fix shutter rotation to enclosure rotation  In transition from open to closed configurations, locking pins or brakes fix shutter rotation to foundation, and enclosure rotates in azimuth to open/close shutter Shutter seals opening via a telescoping annulus ring and an inflatable seal Shutter seals opening via a telescoping annulus ring and an inflatable seal Shutter OPEN Shutter CLOSED

Enclosure Crane Enclosure requirements specify a 2-tonne crane for telescope maintenance Alternate crane options have been considered: An enclosure-mounted retractable gantry crane is currently the preferred option (see figure below) An enclosure-mounted retractable gantry crane is currently the preferred option (see figure below) Alternate concepts include vehicle-mounted jib cranes; access to telescope is either from interior of enclosure or from exterior through open aperture Alternate concepts include vehicle-mounted jib cranes; access to telescope is either from interior of enclosure or from exterior through open aperture

Conclusions Conceptual designs have been developed for the critical aspects of the enclosure design; these appear to offer feasible solutions Very early cost estimates indicate the budget cost is ambitious, but may be achievable Remaining work includes the following: Investigate feasibility of utilizing factory produced aluminum dome structures for enclosure shell Investigate feasibility of utilizing factory produced aluminum dome structures for enclosure shell Increase fidelity of analysis of Calotte mechanical interfaces under operational conditions Increase fidelity of analysis of Calotte mechanical interfaces under operational conditions  Non-linear analysis including full range of load conditions, variations in design parameters  Required in order to reduce risk associated with this issue Develop layout drawings for major aspects of the design Develop layout drawings for major aspects of the design  Structural geometry/connections/cladding details  Mechanical layouts  Sealing at interfaces Cost estimate Cost estimate Reporting Reporting Note: Current Cost Target: $10m