Seismic Upgrades: Preplanning, Site Research and Creative Thinking Help Project Teams Devise Best Approach For Projects That Add 'Muscle' to Older Buildings
DPR Construction, Inc.
Building a seismic upgrade is a little like putting together a jigsaw
puzzle. The pieces must be sorted out and then fit together carefully,
in the right order, to complete the picture.
"The process requires a lot of time investigating, measuring and
verifying in the field," says project manager Rene Gonzalez, who
oversaw a series of seismic projects DPR completed for Stanford University
and for Varian Corp. "No matter how you draw it, you'll run into
different stuff all the time. It's a pretty dynamic process."
Brian Balducci, who is managing a structural upgrade for Kaiser in San Diego, agrees, adding that "thorough site investigation and planning are crucial" for handling the unexpected twists and turns that are often encountered on a structural upgrade.
In-depth planning is playing a key role in the success of a particularly complex seismic upgrade that DPR is building for Level 3 Communications' distribution node facility in Portland. Project manager Tim Sissel says the DPR team "spent three months putting together schedules, talking to subs, bringing them into the building," and then devising a plan for how to upgrade the historical, 110-year-old former machine shop building.
In order to make the structure meet the Zone 4 seismic standards, crews had to gut the interior, saving only the unreinforced brick masonry perimeter walls. They then had to rebuild a new structure within the old one. The walls were braced temporarily using eight-inch poles with caissons sunk 15 feet into the ground. At the same time that the interior was demoed, construction crews applied six-inch-thick shotcrete over the temporary braces to shore up the existing walls. They then built a new steel structure within the building perimeter, tied back to the new shotcrete and, finally, removed the braces.
The risks associated with this project were high, which is typical of seismic upgrades performed in historical structures. Daily safety meetings and constant communication have been essential to managing the risk. "We made sure everybody knew exactly what was happening and had a say on any safety issues they were concerned about," Sissel adds. With substantial completion slated for mid-August, the project has maintained a perfect safety record.
Safety of construction crews and the public has also been a big concern on the Kaiser parking garage structural upgrade that DPR is performing at a busy medical facility in San Diego. With the garage remaining open during the upgrade, structural components included strengthening the columns, adding new shear walls as well as foundation supports.
In strengthening the columns, DPR is using a "fiber wrap" system, an emerging technology that Balducci says is more efficient and cost-effective than steel jacketing and concrete encasement and has structural advantages over traditional methods. The wrap is designed to add strength and ductility to existing columns by using a high-strength hybrid fiber/epoxy composite material. The fabric passes through an epoxy-filled mixing basin after which the resin-soaked fabric is physically wrapped three times around the column and newly enhanced column corbels.
While the Kaiser project features a newer system, Gonzalez notes that innovations on seismic projects often stem from the method used rather than the technology. "The ability to think creatively when planning out a seismic upgrade is essential," he notes. "You've got an existing building and you have to figure out how to access things-basically, how to build a building within a building."
