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A Seismic Shift in the International Building Code

Partially collapsed building

Earthquake-damaged building in Chile

Changes associated with the 2018 International Building Code (2018 IBC) are coming soon to Washington State. This will affect all buildings that are submitted for permit after June 30, 2020.

No Three-Month Grace Period in Seattle

Typically there has been a three-month grace period in Seattle between the code change date and enforcement. This allowed projects that were designed using an older code to still be permitted under that code if there is a short delay. We have heard from multiple City of Seattle representatives that there will be no grace period this time. Projects submitted on July 1, 2020, must use the new code.

Changes to Seismic Design

There are significant changes to the way the seismic hazard will be considered in ASCE 7-16, which is referenced by the 2018 IBC. Up to now, the process to determine code-based seismic hazard has been generally straightforward. As long as a site wasn’t on liquefiable ground that would turn to Jell-O in an earthquake, an engineer could produce seismic code parameters for a site based on latitude, longitude, and assessment of soil stiffness, called the Site Class.

In ASCE 7-16 the process for determining seismic hazard is more complex. Site-specific seismic studies will be encouraged for a larger range of site conditions (i.e., Site Classes D, E, and F), which includes sites with generally soft or loose soils even if a liquefaction hazard is not present. Such a study involves complex calculations and computer modeling. A developer may choose to take an “exception” and not perform a site-specific study for an affected site, which the code allows in certain situations. However, they would incur a penalty by taking this exception that could require the structural engineer to use higher seismic values for building design than the current code permits. A cost-benefit analysis will provide important information.

For example, a seven-story building on a soft, non-liquefiable site in Lynnwood might be affected by these new code changes. Taking a code exception for this structure would likely result in a significant increase to the seismic loads used in design, compared to the previous code. However, a relatively simple site-specific seismic hazard analysis could potentially reduce these seismic loads with a minor cost to the project. In Seattle and Bellevue, the benefit of this additional analysis is reduced because of Seattle Basin effects that amplify ground motions.

Key Takeaway

It won’t be straightforward to determine whether a site-specific seismic study or use of a code-based design will save money. Finding the best approach for each project will take more up-front communication between the developer, the structural engineer, and the geotechnical engineer. We suggest engaging the geotechnical engineer early in the design process.

Why an Earthquake Warning System Should Not Be a Priority In The Pacific Northwest

Earthquake_damage_Cadillac_Hotel,_2001_SmallerThe newest and hottest topics when it comes to disaster discussions in Oregon and Washington, as well as on the national level, are an earthquake warning system and earthquake prediction possibilities. They are the new obsession that has come on the heels of the New Yorker articles this summer. While we don’t object to advancing both of these methods to better warn of impending quakes and hopefully save lives, we do think that the discussion is premature, especially here in the northwest.

The first reason is that an earthquake warning system like that in Japan has to be implemented only with a comprehensive, aggressive, and continuous public education program. Without a full understanding of what you should do when your phone emits an ear piercing shriek warning of impending shaking, we risk even greater panic and possibly more casualties. Running out of buildings with unreinforced masonry or weak facades just before the shaking could put people at more risk of falling hazards outside of the buildings. It could also cause major traffic hazards as drivers try desperately to get across or get off bridges and overpasses. Unless we develop a much better awareness of what the public should do when they receive the warning, it may cause more problems than it solves.

But the real issue is that these technologies are acting as the bright shiny objects that are distracting all of us, from the public to the president, from the real issue: our infrastructure is in dire need of upgrades not only to prevent casualties, but also to encourage long term recovery.  We doubt 30 seconds of warning will seem as beneficial when the public doesn’t have wastewater for one to three years.  Further, a warning system that stops surgery or an elevator is not as important as making sure that the hospital or building itself is designed to withstand shaking. Especially in Oregon and Washington, all of our energy and funds need to be focused first on comprehensive and intelligent infrastructure improvements that increase our community resilience. And that needs to happen as quickly as possible. We implore you not to follow the flashing light! Urge our government to focus on the real issues, and encourage your colleagues and neighbors to personally prepare.

For more information contact Allison Pyrch at (360) 816-7398 or Allison.pyrch@hartcrowser.com

Shaken and Stirred: Northwest Earthquake and Tsunami

Washington 9.0 earthquake--Are you ready? Oregon 9.0 Earthquake--Are you ready?Suddenly the Pacific Northwest is on the national stage for its earthquake and tsunami vulnerability, thanks to a New Yorker article. “The Really Big One,” by Kathryn Schulz, has triggered attention from dozens of local papers and news sites. Yet even before the New Yorker shook the Northwest (pun intended), Oregon Public Broadcasting had been featuring Hart Crowser engineer Allison Pyrch in its “Unprepared” series, to alert the region to the impending disaster in hopes that we will get prepared.

Also, Allison recently gave a presentation for the Lake Oswego Sustainability Network: “Surviving a 9.0, Lessons Learned from Japan and Beyond.” If you are involved in emergency management or just plain interested in massive disasters and their aftermaths, settle in for some powerful visuals and easy-to-follow explanations about earthquakes in Japan and Chile, how the 9.0 earthquake and tsunami will happen in the Pacific Northwest, and what you can to do to be resilient.

Watch the whole “Surviving a 9.0” video to get unusual insight into what’s ahead, or if you’re pressed for time, skip to one of these minute points:

  • 9:00 Jan Castle introduces Allison Pyrch 10:56 Allison Pyrch’s presentation begins with how the Pacific Northwest 9.0 earthquake will happen
  • 14:25 Comparing the Japan and Chile quakes “It didn’t stop shaking for a day”
  • 21:45 Fire damage/natural gas 22:30 Water, wastewater, and electrical systems; liquid fuel; natural gas
  • 24:25 Lifelines/infrastructure/airports “PDX will not be up and running”
  • 28:35 Port damage/economics
  • 31:45 How prepared is the Pacific Northwest? When will it happen? “We are 9 ½ months pregnant”
  • 35:00 What will it look like?
  • 37:32 What you can do
  • 40:30 What businesses can do
  • 42:11 Can you be sustainable without being resilient?
  • 43:33 What about a resiliency rating system similar to LEED?
  • 53:30 Will utilities, transportation, hospitals be useable after the 9.0? “We’re toast”
  • 1:01:30 End of Allison’s presentation; additional information from Jan Castle on how to prepare
  • 1:19:19 How sustainability measures in your home lead to resiliency

First Tsunami Safe Haven Building in the United States

Ocosta School Construction

The City of Westport stands sentry at the tip of a narrow peninsula between the expanse of the Pacific Ocean and the protection of Grays Harbor. The Cascadia Subduction Zone, a 700-mile-long earthquake fault zone, lurks approximately 90 miles off the shore. Experts predict this submerged fault zone will release a magnitude-9.0 earthquake and unleash a tsunami that will hit the coasts of British Columbia, Washington, Oregon, and California. The last such “megaquake” struck just over 300 years ago.

As was recently seen in Chile, Indonesia, and Japan, tsunamis ravage low-lying areas such as Westport. There, it is expected that a tsunami from a Cascadia Subduction Zone megaquake could reach the coast in as little as 20 minutes. However, evacuation of Westport and neighboring Ocosta Elementary, Junior and Senior High Schools could take nearly double that time. Therefore, in 2013 residents of the Ocosta School District approved re-construction of an aging elementary school that will include the nation’s first tsunami “refuge” structure.

Construction of the school started in November 2014. The school’s gym has been designed to withstand the impact of a tsunami and the debris it carries, while sheltering nearly 1,000 people on its roof. The roof is 30 feet above the ground (nearly 55 feet above sea level) to keep people dry and safe. The gym’s roof is supported by heavily reinforced concrete towers in each corner that are designed to remain intact during shaking from the initial megaquake, associated aftershocks, and the resulting tsunami surges.

Because of the potential for over 10 feet of scour (soil erosion adjacent to the building) caused by tsunami surges and liquefaction of the native sandy soils, the gymnasium is supported on nearly 50-foot deep piles. The remainder of the school is supported on shorter piles designed to withstand earthquake shaking and liquefaction, but not necessarily tsunami surge forces.

Links below lead to more information on the Ocosta building and general tsunami research. Note that the maps on the last link (Project Safe Haven) illustrate how impossible it would be to escape a tsunami in the Ocosta area.

Rooftop Refuge Washington Disaster News, Washington Military Department Emergency Management Division
Grays Harbor County school to build first U.S. vertical-tsunami refuge Seattle Times
First tsunami-proof building to be built in Westport Komo News
Rising above the risk: America’s first tsunami refuge the Geological Society of America
Project Safe Haven: Tsunami Vertical Evacuation in Washington State

Geotechnical Lessons from the Tohoku Earthquake

Japan landslide area

Rockslide (background) and flood protection (foreground) in Ishinomaki City, Japan (Photo: Dave Swanson, Reid Middleton)

The magnitude 7.3 earthquake that struck Japan six days ago is a reminder of the more devastating magnitude 9.0 earthquake that struck March 11, 2011. In an earlier post we mentioned a reconnaissance team that traveled to Miyagi Prefecture in Japan in May 2011 after the earthquake and tsunami.

In the landslide area photo above from 2011, the light colored rock slope failed even with reinforcement that protected the slope to the left. The entire land area settled, which allowed Tsunami and high tide water access to the shoreline. Fortunately, in this area the Tsunami water was not as high as other areas, so the buildings weren’t washed away. Blue tarp temporarily protects the river bank from overtopping at high tide.

Doug Lindquist of Hart Crowser had these observations about the geotechnical damage:
Damage generally happened in known geologic hazard areas (tsunami zones, areas near past landslides, liquefiable areas, and reclaimed land).
• Liquefaction damage was extensive even 150 kilometers away from the fault rupture. (Seattle is about 100 kilometers from the Cascadia Subduction Zone.)
• Ground improvement measures are effective.
• Engineering methods can reasonably estimate the liquefaction hazard.
• Newer structures performed well when designed considering known geologic hazards.

As the reconnaissance team report reminds us, a similar earthquake will happen along the Cascadia Subduction Zone, off the coastline from northern California to British Columbia. The impacts of this event on our communities and industry will depend on the actions we take now to prepare for it. The lessons learned from Japan can be applied in our own communities.

For more details on the reconnaissance team’s findings, along with some fascinating photographs, see the report here.

Driving on Styrofoam, Building on Pillows

Geofoam at SR 519

Geofoam at SR 519

You may have seen this recent blog headline: In New York, Buildings ‘Sleep’ on These Giant Red Pillows. Since that headline was called out in an engineering-related notice, you might have assumed it had something to do with seismic stability or that it was related to geotechnical engineering. After all, a recent Washington State Department of Transportation project (SR 519) used giant blocks of styrofoam in the foundation for access ramps and pedestrian areas.

To be more specific, SR 519 had the first application of geofoam approved by the Seattle Department of Transportation. Geofoam, or lightweight expanded polystyrene, is essentially a type of Styrofoam, and is used as lightweight fill in areas where heavier materials would be problematic. For the SR 519 project, using Geofoam helped protect hundred-year-old utilities. Meanwhile, highrises now can have huge rubber or fluid-filled shock absorbers, or Teflon-coated pegs.

But if you clicked on that blog headline about pillows expecting to see an earthquake engineering technology, you would have been delightfully wrong. The blog entry is about a stunning art installation, not about engineering. Although you might wonder whether there is an underlying truth to the art.

Take a look.