Seismic codes govern structural design to prevent damage to buildings and structures during an earthquake. It’s common knowledge that buildings must conform to specific seismic codes, but your chemical storage tanks also have seismic regulations. Any facility in a seismically active region, including everywhere along the Pacific Rim, must pay careful attention to the safety measures established in the International Building Code.
The recent updates to the IBC have corresponding changes to the ways that chemical storage tanks are secured. Let’s review these changes so you can get a better understanding of the code.
Storage Tanks and Self-supporting Structures
It can be confusing which parts of the code you need to be concerned with. As it pertains to storage tanks, the requirements in the ASCE in chapter 15 should be adhered to, and not chapter 13, which mentions vessels supported by a building. Essentially, the difference has to do with whether the tank is self-supporting or not.
To find the specific seismic code that relates to chemical storage tanks, refer to the 2018 IBC and the American Society of Civil Engineers (ASCE) 7-16, chapter 15.7, which covers “tanks and vessels that are supported within buildings.” This refers to any self-supporting structures that carry gravity loads and resist the forces of earthquakes or other seismic activity.
Changes to 2018 IBC
The updates to the latest specifications are relatively minor, but they are significant. Here are a few key points to note:
- Wind Loads — Section 1609 now has updated wind speed maps, including maps for the state of Hawaii. Terminology for describing wind speeds has been changed again: ultimate design wind speeds are now called basic design wind speeds. Except in hurricane areas, wind speeds have reduced by about 10%. At high altitude locations, wind pressures can be considering the reduced density altitude, thereby decreasing wind forces.
- Earthquake Loads — The site coefficients contained in the IBC have now been brought into alignment with the newest generation of ground motion attenuation equations. You must provide a site-specific hazard analysis report. If one isn’t provided, higher seismic coefficients may have to be used.
- Seismic Maps — The IBC seismic maps have been updated to match new maps in the 2015 NEHRP Provisions and 2016 ASCE 7 standard.
- Tsunami Loads — There are many coastal communities in the western United States and on islands in the Pacific Ocean that need tsunami-resistant design of critical infrastructure and essential facilities. New IBC Section 1615, Tsunami Loads, has been added to address the design of these facilities. If your project is in a tsunami area, a special calculation is required, as Poly Processing’s standard system does not cover tsunami design.
These changes are the prevailing code for plants nationwide starting January 1, 2020.
Updated requirements only apply to new tanks built after the code goes into effect.
Poly Processing and Seismic Calculations
Poly Processing has built a calculation system to handle seismic code issues, whether you need a wet stamp, calculations for a permit, or data for budgeting and planning. Calculations are address-specific (now more than ever), so the end user’s address is necessary for us to provide you with the correct calculations.
Poly Processing has long-standing relationships with reliable third-party engineers that extend beyond 30 years. As a result, we can ensure that quality tank restraint systems are done correctly per state code. A qualified third-party engineer provides the design and certification stamps of all Poly Processing tanks requiring a certified seismic restraint system.
Even in areas of the United States with minimal seismic or wind activity, we typically see specifications for restraints. We’ve created restraint systems for almost every type of tank that we offer, whether it’s a vertical tank, IMFO (Integrally Molded Flanged Outlet) tank, sloped bottom tank, cone-bottom tank, SAFE-Tank double-walled tank system, or a tank in a secondary containment tank. Each seismic calculation is site-specific, so it’s important that you have a company working for you who is experienced in each region.
Proper seismic and wind restraints are a key component in operating a safe, long-lasting chemical storage system. The third-party engineer ensures that the design meets the current IBC requirements to give you peace of mind. The third-party engineer also backs the restraint system calculations and handles any questions with the IBC reviewer.