A 21st Century Iconic Glulam Structure: Cathedral of Christ the Light

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Deborah Chambers
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1 A 21st Century Iconic Glulam Structure: Cathedral of Christ the Light Paul C. Gilham, P.E., S.E. Chief Engineer Western Wood Structures, Inc. Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board.

The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/ CES), Provider #G516.

2 The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/ CES), Provider #G516. Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-aia members are available upon request. This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

3 Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited. Wood Products Council

4 Course Description Architecturally stunning, the Cathedral of Christ the Light features a space-frame structure comprised of a glulam and steel-rod skeleton veiled with a glass skin. Twentysix, 110-foot glulam Douglas-fir ribs curve to the roof to form the framework for the sanctuary superstructure, while 724 closely spaced glulam louver members interconnect and provide lateral bracing for inner ribs. Through the use of advanced seismic techniques, including base isolation, the structure has been designed to withstand a 1,000-year earthquake. This presentation examines the Cathedral s structural design, specification, fabrication and erection, highlighting the technologies, connections and engineering that made this project one of the most iconic timber structures of the 21st century.

5 Learning Objectives 1. Discover the capability of glulam framing to fulfill architectural goals in large structures. 2. Discuss the design and coordination efforts necessary to provide an iconic glulam structure that meets specific performance criteria. 3. Highlight structural design and specification procedures unique to glulam systems and members. 4. Review a variety of phases and aspects of this project, including fabrication of timber elements, permit approvals, inspection and budgeting.

6 Innovative Use of Glulam in the Oakland Cathedral Oakland California Christ the Light Cathedral - Design and Construction Team Catholic Cathedral Corporation of the East Bay Owner Conversion Management Associates Project manager Kendall Heaton Architects Architect of Record Skidmore Owings and Merrill LLP Design Architect Skidmore Owings and Merrill LLP Structural Engineer Webcor Builders General Contractor Western Wood Structures, Inc. Glulam supplier and erector Enclos Corp Glazing Supplier and Installer

7 Design Goals Architectural Light as the Central Focus Light could be the key to create a contemporary design that was still evocative of the Church s two millenium-old traditions With the alter as the focus of the 1500 seat sanctuary, The architects chose a more fluid, curvilinear, minimalist space for the overall design of the cathedral s sanctuary

8 Design Goals Architectural

9 Design Goals Architectural Design Life of 300 years. We felt that the 300 year standard applied not only to the cathedral s structural integrity but equally to the aesthetic that that building should be architecturally worthy of lasting at least until the 24 th century.

10 Design Goals Architectural Wood, rather than steel, was chosen to form the cathedral s supporting lattice because of its warmth and reference to light and well as its religious significance. The architects felt that Douglas Fir framing would provide a natural, renewable, more beautiful, and equally earthquake-proof structural skin to support the outermost glass skin Wood also proved to be a pivotal, economic advantage that would ultimately win SOM the design contract. Craig Hartman, FAIA, SOM

11 Design Goals Architectural Building Shape was comprised of a Vesica Pisces interior and conical exterior

12 Design Goals Structural Building life of 300 years Withstand a 1000 year earthquake event. The site is located 4.7 km from the Hayward Fault and 25 km from the San Andreas Fault To an engineer, locating a 110 foot high cathedral made of delicate materials so close to an active fault line and expecting it to survive a 1000 year earthquake like the 1906 Earthquake that is the ultimate challenge Mark Sarkisian, S.E. SOM

13 Unique Specifications Mock-up of structural system

14 Unique Specifications Mock-up of structural system

15 Unique Specifications Testing of mock-up

16 Unique Specifications Premium, no putty appearance grade at Ribs and Mullions

17 Unique Specifications Industrial, Sanded louvers

18 Unique Specifications Construction Phase Survey of Program of Cathedral Superstructure required surveys for: Curved Glued laminated timber ribs Straight Glued laminated Mullions Final tolerance of 1 in or out, up or down.

19 Structural Aspects Code Issues Tension Only Ductility Structural System not included in CBC => Peer Review required: Ductility Testing of Tension Members Non-Linear Push-Over analysis Time History Seismic Analysis Base Isolation to reduce seismic motion Pre-tensioning of tension members

20 Structural Aspects Code Issues Base Isolation Double Concave Friction Pendulum Isolators

21 Structural Aspects Code Issues Base Isolation Double Concave Friction Pendulum Isolators

22 Structural Aspects Code Issues Base Isolation Double Concave Friction Pendulum Isolators

23 Structural Aspects Code Issues Ductility Testing of Tension Members

24 Structural Aspects Code Issues Ductility Testing of Tension Members

25 Structural Aspects Code Issues Pre-tensioning of tension members Determine required torque to obtain specified load Develop tensioning sequence to eliminate load interference Adjust specified loads for ambient rod temperature Monitor rod forces with Strain gages.

26 Structural Aspects

27 Structural Aspects

28 Structural Aspects Code Issues Pre-tensioning of tension members Adjust specified loads for ambient rod temperature Monitor rod forces with Strain gages.

29 Innovative Use of Glulam in the Oakland Cathedral Oakland California Glulam manufacturing and fabrication methods Autocad modeling of structure Detailing of steel and glulam assemblies Manufacturing, Fabrication and pre-assembly of Glulam members