Tucson Chapter Dinner Meeting: University of Arizona Student Night - Las Vegas Airport Bridge-NM250 over I-25 and Seismic Isolation of the Giant Magellan Telescope

  • 16 Nov 2017
  • 6:30 PM - 8:30 PM
  • The Tactic Meeting Room, Aloft Tucson University Hotel, 1900 E. Speedway Blvd.
  • 3


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Las Vegas Airport Bridge-NM250 over I-25

This presentation will describe the replacement of a five span bridge that conveys New Mexico State Highway 250 over Interstate 25 in Las Vegas, New Mexico.  The existing bridge had a Sufficiency Rating of 49 as of 2012, and warranted replacement.  However, heavy local industry use from north of the interchange required the NMDOT to reduce the onsite construction time as much as feasible, so Accelerated Bridge Construction was implemented to construct the abutments and pier of a two span replacement bridge in advance of removal of the existing bridge.  This approach required constructing new abutments without disturbing the nearby outer piers supported on shallow spread footings.  The selected solution included excavation of temporary soil nail walls to provide space for construction of micropile-supported full height closed abutments.  The project required close coordination between the structural engineer and the geotechnical engineer to lay out the micropiles, design pile batters to avoid the existing spread footings, and develop a coordinated plan set for construction.  Construction of the substructure began in April 2014 and allowed for the new superstructure to be constructed within a single 45 day closure. 

Seismic Isolation of the Giant Magellan Telescope

Located in the Atacama Desert at an elevation of 2,518 m on Las Campánas Peak in the northern region of Chile, the Giant Magellan Telescope (GMT) is an Extremely Large Telescope (ELT) class observatory set to make history as one of the largest telescopes ever built.  Vast improvements in the fields of optics, control systems, and mirror fabrication technologies have facilitated correspondingly drastic increases in the size and presence of ground-based telescopes previously thought to be impossible.  Size for these observatories has increased to the point where conventional approaches impart seismic demands on the telescope structure and optics that are unmanageable.  With this, a refined approach involving base isolation is being designed to provide seismic protection of a sensitive, invaluable instrument that will revolutionize our understanding of the universe.  This presentation examines the seismic isolation system from both an engineering and logistics perspective and peers into some of the intricacies and structural engineering challenges associated with such an endeavor.

Biographic sketch of Presenters:

Michael Pegnam, PE, has been with Golder Associates Inc. since 2004 and is presently a senior geotechnical consultant and Associate with the firm. He is a specialist in the geotechnical and geologic design of heavy civil and mining projects with 23 years of professional experience.  He has specialty expertise LRFD for Highway Bridge substructure and retaining wall elements, and flexible and rigid pavement design.  Surface transportation clients have included Departments of Transportation in Arizona, New Mexico, and Colorado, and Michael has worked on projects at numerous sites throughout these states.  Mike received a B.S. in geological engineering from the University of Arizona, and an M.S. in geotechnical engineering from University of California – Berkeley.  He is a licensed Professional Engineer in Arizona, New Mexico, and California.

Eric Manuel, PE, MBA, a transplant from Southern California, Eric Manuel attended Arizona State University and obtained his Bachelors of Science Degree in Civil Engineering in 2003.  Passionate about education, Eric has completed all coursework and is preparing his final report in pursuit of a Master’s of Science Degree in Civil Engineering at the University of Arizona.  He is a licensed Civil/Structural Engineer with specialty in high-seismic steel and concrete design at M3 Engineering & Technology Corporation, headquartered in Tucson. 


Please register by Tuesday November 14, 2017

 Menu: Little Italy

Antipasto mixed greens salad with Balsamic dressing, Baked Cheese Tortellini & sliced Grilled Chicken served with garlic marinara sauce, Roasted Rosemary Italian squash & Corn Saute, La Brea assorted rolls and butter spread, freshly brewed ice tea & regular/decaffeinated coffee.

Should you have any special dietary needs, please contact Jessica Carson at to coordinate. 



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