Every building is different, and the approaches to safeguarding a structure against earthquake damage remain as diverse as the 13,000 soft-story apartment complexes needing retrofits in the city of L.A.
In our public exchanges at community workshops, professional expos and in face-to-face communication with prospective clients, we inevitably get asked to provide descriptions of a building sight-unseen.
What will you need to do to my building? How long will it take? How much will it cost?
These are all valid and important questions, but they are impossible to answer without actually seeing the property, measuring it and calculating the work to be done based on engineering science.
What is a Soft-Story Structure?
Even though every project is different, there are some similarities inherent in virtually every soft-story retrofit project.
Let’s start by going over some of the characteristics of a soft-story structure – a type of architecture commonly used for apartment buildings, with parking situated on the ground floor and dwelling units built above.
Soft-story structures built in the city to codes dating back to pre-1978 must be retrofitted to provide stabilization in the event of an earthquake.
L.A.’s law represents the nation’s most sweeping seismic regulations, prompted by the death and destruction of previous tremors and the realization that major earthquakes will forever be a part of Southern California life.
The city has been notifying affected property owners by mail, with seismic retrofit notices being sent on a rolling basis, with the city’s largest apartment buildings – those with 16 or more units – getting the first wave of orders. Structures with three or more floors but less than 16 units will come next, followed by all others.
Owners of soft-story buildings will have one year from the date they receive their order to submit either proof that the building doesn’t need retrofitting, or plans for retrofit or demolitions. Within two years, they must obtain permits to get the work done.
All work on soft-story structures must be completed within seven years of receiving an order, the ordinance states.
For most soft-story structures, the installation of steel frame helps to prevent the excessive swaying that can lead to building collapse.
Where to place the frame and how many of them to use are subject to the unique distinctions of each individual building.
Optimum Seismic has its own steel fabrication facility to carefully prepare customized frames designed uniquely for the specifications of each building that we retrofit.
The frames are installed not for weight-bearing support, but to stabilize the building during an earthquake. It’s important that the frames themselves be somewhat flexible. Strategic location of frames can enhance its ability to absorb some of the shock of the earthquake in order to minimize damage.
The University of California at San Diego, home to the world’s largest outdoor shake table, has done repeated tests replicating the effects of a quake on a variety of structures. They recently conducted experiments on the performance of soft-story structures and determined that collapse can happen when a building sways excessively – causing the building to collapse. To see a video of their testing, visit http://jacobsschoolofengineering.blogspot.com/2013/08/shaking-house-down.html.
The steel frames must be secured by foundations, which means they must be firmly connected and rooted into the ground beneath the structure.
Optimum Seismic trenches the area where steel frames are to be installed, then fortifies the area with concrete and rebar. Existing concrete is bonded to the new material with rods, that are inserted into a series of holes drilled into the existing foundation and secured with epoxy. The rebar is then placed inside the trench and all points are firmly secured. Finally, the new concrete is poured into the trench to hold it all together.
The dragline is the term used to describe the means of delivery of earth loads to steel frame. It’s important to make sure that the dragline is properly secured to the structure itself to provide additional support and stability.
We often go in and do a comprehensive securing of the dragline to the structure, which also provides added strength and support.
Educate Yourself about the Law and Your Building
As the Preferred Supplier of the Apartment Association of Greater Los Angeles, Optimum Seismic has been working with AAGLA to help inform members about the new ordinance and to educate them on the steps they need to take to comply with the law. We have been attending community workshops coordinated through AAGLA, spoke recently at the association’s annual Expo, and attended Mayor Eric Garcetti’s 2016 Seismic Retrofit Fair at the Los Angeles Convention Center.
If you have questions about the requirements under the law, the retrofit process or general questions regarding your building, we encourage you to contact us for an evaluation. We are giving $2,000 discounts on engineering to all AAGLA members.
Otherwise, please consider attending one of our upcoming workshops with AAGLA. The workshops are free and open to the public, but RSVPs are required at [email protected] The next two workshops are:
- Koreatown: 6 p.m. Tuesday, July 12 at AAGLA headquarters, 621 S. Westmoreland Ave., Los Angeles. Light refreshments to be served.
- Griffith Park: 12 p.m. Thursday, Aug. 4 at Griffith Park Friendship Auditorium, 3201 Riverside Drive, Los Angeles. Lunch will be served.
Over the course of this year, the organization expects to host meetings throughout the L.A. area. For more information, call AAGLA at 213-384-4131.