SEATTLE, Washington -- There are significant changes coming with the new International Building Code (IBC 2018/ASCE 7-16), specifically seismic design load requirements for buildings in high seismic regions.
“While typical building code cycles see maybe 5% to 20% change, the new changes—for some extreme cases—will increase up to 80%,” said Tom Xia, PhD, DCI Engineers Principal, Technical Director and member of the ASCE and Council on Tall Buildings and Urban Habitat (CTBUH). “That is not a minor change.”
Dr. Xia noted there are three major reasons for the design load increase.
1) Changes in seismic ground motion maps and soil coefficients.
2) For Site Class D, the seismic design load will have an additional increase of up to 50% for taller buildings.
3) The new code will eliminate a provision that allows a seismic load reduction of 18% for taller structures.
In general, short buildings on stiffer soils will be less affected while taller buildings on softer soils will be more affected – even Performance Based Design projects will undergo these design load changes, meaning an impact on buildings up to 400 feet tall.
Dr. Xia stressed the importance of project stakeholders knowing not only when states and local jurisdictions will adopt these design load increases but understanding that their project timing is everything.
“The timing of building permit applications is critical,” Dr. Xia stated, specifically pointing out that drawings submitted after the new code is enacted could mean an overhaul in design which was originally designed to the current code – ultimately costing owners valuable time and money.
These code changes will also affect future building retrofits or additions. Buildings designed to current or previous codes may need significant upgrades if a change-of-use triggers the building into the new standard.
DCI Engineers can help determine the actual impact for a given site and building type.
“Project owners should get engineers involved early to review actual impact on the site, on the buildings, and to help with scheduling,” Dr. Xia said. “It’s very technical, and it’s very project-specific-based. But that’s where we can help.”
For more information on design load impacts in your region, call Tom Xia at 206.787.8954 or Patrick Lindblom, Senior Project Manager, at 206.787.8961. You can also find a DCI office near you at dci-engineers.com/locations.
About the Author
Erin Spaulding, Communications Coordinator / Erin comes from a journalism background with an emphasis in feature writing. She enjoys capturing the unique details of a story and is a firm believer that every person (and every project, for that matter) has a story to tell. Erin loves running, fly fishing and learning about unique spaces. Back in Michigan, she owns a little studio condo readapted from an asylum into a mixed-use residential building.