San Diego Main Public Library Dome Wins National Architecture and Engineering Award
June 11, 2014 from American Institute of Steel Construction
(Chicago, IL) – San Diego’s Main Public Library Dome has earned national recognition in the 2014 Innovative Design in Engineering and Architecture with Structural Steel awards program (IDEAS2). In honor of this achievement, members of the project team will be presented with awards from the American Institute of Steel Construction (AISC) during a ceremony at the dome, in the Qualcomm Dome Terrace, on Friday, June 13, at 2 p.m.
Conducted annually by AISC, the IDEAS2 awards recognize outstanding achievement in engineering and architecture on structural steel projects across the country. The IDEAS2 award is the highest, most prestigious honor bestowed on building projects by the structural steel industry in the U.S. and recognizes the importance of teamwork, coordination and collaboration in fostering successful construction projects.
The dome’s project team members include:
Owner: City of San Diego Main Library, San Diego
Architects: Rob Wellington Quigley Architects, San Diego; Tucker Sadler, San Diego
Structural Engineer: Endrestudio, Emeryville, Calif.
Construction Engineer: Hassett Engineering, Inc., Castro Valley, Calif.
General Contractor: Turner Construction, San Diego
Steel Fabricator, Erector and Detailer: SME Steel Contractors, Inc., West Jordan, Utah (AISC Member/AISC Certified Fabricator/Advanced Certified Steel Erector)
Bender-Roller: Albina Pipe Bending Company, Inc., Tualatin, Ore. (AISC Member)
The San Diego Main Public Library Dome is a National award winner in the category of projects Less than $15 Million, making it one of only three projects around the country to receive the National honor. Each year, the IDEAS2 awards honor National and Merit award winners in three categories, based on constructed value: projects less than $15 million; projects $15 million to $75 million; and projects greater than $75 million. Each project is judged on its use of structural steel from both an architectural and structural engineering perspective, with an emphasis on: creative solutions to project’s program requirements; applications of innovative design approaches in areas such as connections, gravity systems, lateral load resisting systems, fire protection and blast; aesthetic and visual impact of the project; innovative use of architecturally exposed structural steel (AESS); technical or architectural advances in the use of the steel; and the use of innovative design and construction methods.
A 140-ft diameter post-tensioned steel-leaved dome serves as a beacon for San Diego’s 10-story, $185 million downtown main library, and adds a new focal point to the city’s skyline.
“A prominent structure in the San Diego skyline, this is a monument to steel as a building material, providing both aesthetic and functional benefits to the many patrons of this iconic library,” commented Chad Clinehens, P.E., executive vice president of ZweigWhite in Fayetteville, Ark., and a judge in the competition.
Conceptual designs of the dome spanned eight years and explored six different circumferential and segmented options. The final scheme resulted in eight intersecting post-tensioned, moon-shaped truss elements with a saddle-shaped cable net on each. Adjacent to the dome, the vertical stair tower forms a strong structural core that anchors the two wings of the building. Thrusting outward and upward from this anchor are projecting triangulated arms that catch a few of the dome rib bases. The computer model of the dome enlisted more than 6,000 “tension only” members and required programs written specifically for post-processing filtering.
The dome, believed to be the largest steel post-tensioned segmental dome in the world, rises 221 ft above ground level to provide shade and acclimatize the reading room. It is constructed of more than 3,000 individual steel members, weighing 285 tons in all, and is clad in 1,500 perforated aluminum panels to shade the eighth floor reading room beneath it. The dome is made up of eight unique truss “ribs” that rise from base to apex in varying heights (from 72 ft to 113 ft) and eight “sail” structures located between the ribs.
Sails are oriented in plan with a pinwheel configuration, an effect created by offsetting each of the sails’ vertical leading edges to the outside of the ribs, while the sails’ trailing vertical edges are connected to the inside rib surfaces. Each sail has an external pipe grid that is spherical at the upper part of the dome. However, the spheres are tipped vertically and horizontally so the center of each sail does not coincide with the center of the dome. Unfurled, the largest sail is 123 ft by 53 ft wide and comprised of 175 hollow structural sections (HSS) and 60 cable segments.
Due to its discontinuous circular form and peaked pinnacle, the dome behaves as a series of intersecting three‐hinged arches. At the base, each rib is supported on a large pin that allows the ribs to rotate or expand with increasing temperature, and each pin falls on a fixed rectangular grid. Four of the sails were configured at equal plan angles and the other four were configured at different angles, giving a unique condition at each connection.
The erection process was challenging not only because of its inconsistent geometry, but also because large curved trusses had to be lifted and erected after their assembly. In addition, the fabricator and erector, SME Steel, expressed the desire to erect the sails in one piece.
Each sail was assembled with tubes, cables and intricate parts all welded and bolted on the ground. Due to the curvature of each sail, ground assembly would require temporary racks to support the sail parts. Furthermore, working off of aerial lifts would be both cumbersome and costly. Instead, a temporary ramp was proposed in order to hold the members in place and provide access for the work. The ramp followed, as closely as practicable, the curvature of the sails. The erection crew could then work on the decked platform under much safer conditions. Posts protruded through the deck, where needed, to support the shop‐assemblies that were shipped to the site.
Once the sails were assembled, they each needed a picking scheme. The upper end of the sail was ultimately hung with four lines when erected into the dome ribs. However, in order to get the sail in position, it required a second crane to lift the sail from its resting position on the sail rack. The lower crane was fitted with two rolling blocks on four lower pick points. Once the sail was high enough, the lower hook elevation remained constant as the upper crane continued to lift, until the four upper lines were all engaged. The lower lines were then released so that the sail was hanging true, ready to erect.
Erection of the sails was expected to be difficult due to the many connection points between the two ribs. However, after the first sail was erected, more specific geometry checks were done on the racks before picking, and this eased the erection. SME planned its schemes well in advance with the erection engineering team, Hassett Engineering, Inc., and also included input from structural engineer Endrestudio, based on its knowledge of the analysis and final design. Many different options were considered, and collaboration was crucial for each step of the process. There was important constructive criticism given from the field crew throughout the assembly of this new San Diego landmark. The constant communication within the erection team greatly accelerated the erection process, allowing the project to be a success for all parties as well as the public.
The 12 IDEAS2 winners for 2014 were chosen from nearly 100 submissions received from architectural and engineering and other project team member firms throughout the U.S. Each submission is reviewed and award winners are selected by a nationally recognized panel of design and construction industry professionals.
The IDEAS2 award dates back more than 70 years to the earliest years of AISC’s existence. And about this year’s winning dome, Roger E. Ferch, P.E., president of AISC, said, “The entire San Diego Main Public Library Dome project team has shown how structural steel can be used to create structures that combine beauty and practicality. The result is a structure that serves its library, city and patrons extremely well, while providing an example of what can be achieved when designing and constructing projects with steel.”
High-resolution images of the San Diego Main Public Library Dome are available upon request by contacting AISC’s Tasha Weiss at 312.670.5439, [email protected]. For more information about the IDEAS2 awards and to view all of this year’s winners, visit www.aisc.org/ideas2.
Photo Credit: Rob Quigley
For more information contact:
American Institute of Steel Construction
The American Institute of Steel Construction, headquartered in Chicago, is a not-for-profit technical institute and trade association established in 1921 to serve the structural steel design community and construction industry. AISC’s mission is to make structural steel the material of choice by being the leader in structural steel-related technical and market-building activities, including: specification and code development, research, education, technical assistance, quality certification, standardization, and market development. AISC has a long tradition of service to the steel construction industry of providing timely and reliable information.
130 East Randolph St. Suite 2000
Chicago IL 60601
Fax: 312.626.2402 www.aisc.org