By: Dilip Khatri, PhD, SE | Principal Khatri International Inc.
Los Angeles is on the “Ring of Fire”. The Ring of Fire circles the perimeter of the Pacific Ocean refers to areas of the high seismic activity because of multiple tectonic plates that have been moving/grinding against each other for millions of years. It’s no surprise that we are in the center of seismic activity with total unpredictability. The Earthquake risk element affects every aspect of life in Southern California, most notably our buildings where we live, work, and entertain, because it poses a threat to our very existence.
The Soft Story Ordinance, passed by the City of Los Angeles in 2016, encompasses residential and commercial buildings (4 or more units) that have a weak story line which leads to potential catastrophic circumstances: The entire upper level may collapse on the weak first story. In order to minimize this structural calamity, the Soft Story Ordinance requires building owners to upgrade/fix/enhance their buildings to reduce this risk.
Figure 1 demonstrates this principle and shows the collapse mechanism. It’s no different from having a heavy object on “stilts”. A lateral force applied to the upper floors will cause the structure to tip over. The objective of the Ordinance is not to save the building/property. Rather, the prime and single goal is to save the People inside the building. Many property owners don’t realize this objective, and its important to be clear that the Ordinance is not trying to save property values, it’s main object is Life Safety.
The L.A. Ordinance officially affects approximately 14,000 buildings but that number is changing because new buildings are being added to the list, and other Cities in Los Angeles County are decidedly passing similar Ordinances.
There are several engineering options available to resolve this dangerous condition. At least five repair options are to be considered:
- New Steel Moment Frames
- Strengthening existing Steel Moment Frames
- Strengthening existing Wood Shear Walls
- New Wood Shear Walls
- New Steel Flagpole Columns
Figures 2 and 3 show a few schematics of a Steel Moment Frame and Wood Shear Wall.
My advice to owners is to look at each of these options and evaluate the “best choice” from an economic feasibility standpoint.
Each property is unique and requires personal attention of a structural engineer and contractor. It’s definitely not a “one size fits all” scenario. Look around, shop around, and do some diligence before you commit to a specific solution/vendor approach. The time lines for compliance are 7 Years from the date of notice, 2 Years for plans and permits. If you are interested to learn more about the Soft Story Ordinance, this author has produced an online video for your reference: https://vimeo.com/194302379
Dr. Khatri has 31 years of civil engineering experience involving land development, subdivision, commercial, residential, multi-family, industrial, and educational facilities. Design, construction, and overall management of major infrastructure improvements comprising sewer, water, storm drain, flood control, and grading design.