When Los Angeles made its soft-story retrofit program it was with the intention to prevent loss of line during the seismic activities and event of earthquakes. The LA soft-story retrofit program included two retrofit ordinances protecting the buildings. Ordinance 183893 and ordinance 184081 started to roll out in 2015 and were meant to keep soft-story apartment buildings from collapsing in case any earthquake shakes. Around the city of Los Angeles city officials completed an assessment of structures and buildings which they stated were built to keep soft-story apartment buildings from collapsing during an even of earthquake and compiled a list of over 150.000 apartment complexes.
Notices Of Compliance
Notices of Compliance were sent out to the property owners that specified the purposes and deadlines for compelling the retrofitting works. Now when the program is in its 5th year of existence many problems are found. The wording Since the Los Angeles retrofit program passed out, a number of companies came into the market, offering retrofitting services. Most of these attract customers by promising construction costs and “cheap” prices. But do we actually realize what do those “cheap prices” mean? Note, although these kinds of Retrofitting services may meet the standards of the city according to the ordinances, there is a big chance that they may not be enough secure and trusted to protect your apartment.
Is the Cheapest Solution Secure?
When it comes to soft-story retrofit, you will come approach with the three used solutions, such as cantilever columns (SCCS/OCCS), shear walls, and Moment Frames (OMF/SMF). Out of the three mentioned, there are cantilevered columns, which are considered the cheapest option and that’s why the most widely used, but are they enough to protect your building from a large earthquake. Also know, that about 95% of retrofit plans approved by the Department of Building and Safety using cantilever columns are inadequate. Simply installing some reinforced steel columns may seem like the best solution of the surface, but they are not an effective solution on their own.
Issues Retrofitting Companies Are Overlooking
In our years of experience working on residential and commercial buildings, we have come across a number of issues retrofitting companies are overlooking. During the initial inspection, too many contractors do not peel back the stucco to examine the existing wood frame. Once we can see the wood frame, we are often surprised. Water damage, dry rot, and termites can cause decay in the existing beams and joints. One of the biggest problems with the “minimum” requirement of the new ordinances is that not enough is being done to provide an adequate connection between the existing structure and the new components being added.
Why “Value Engineering” Isn’t Working
Many of the newer retrofitting companies are focusing on “value engineering” over making the building’s structure better. One of the areas that are affected by this is the connections between systems. In some instances, the connection from the cantilevered column and the moment frames is not large enough to disperse the forces of a major earthquake properly. Cantilevered columns work fine in a smaller apartment complex, no more than 10 dwellings. But in larger buildings, 30 dwellings or more than two stories, they will not keep the building from sustaining damage. The connections between the moment frames and the cantilever columns need to be larger and spaced out evenly in the bigger structures. This will allow the systems to handle the force of an earthquake without collapsing. If the two systems are not designed to work together, the building may remain standing but it will sustain damage that could have been prevented.
Special Moment Frame Systems
The Structural Engineers Association of Southern California (SEAOSC) hosted the Safer Cities Technical Summit. A respected engineer in the field voiced his concerns over the huge amount of retrofit engineering plans that are being approved with fundamental flaws. A major concern that the speaker highlighted is the lack of reinforcement along the perpendicular plane on the majority of retrofit solutions. Most soft-story retrofit plans only address the potential seismic vulnerabilities of soft, weak, or open-front walls, and do not consider the vulnerabilities of the entire building. Cantilever columns do not provide enough support on the main dragline.
During the shaking caused by an earthquake, a building doesn’t just move from side-to-side. It oscillates, so during a major earthquake, it wants to move perpendicular to the dragline. A CCS is not going to be strong enough to withstand or transfer those types of seismic forces. To prevent extensive damage in this situation a Special Moment Frame System is required.
Existing Components Need To Determine The Retrofit
Apartment buildings often have leaky plumbing, or just are built before 1978 and suffer from old age. Existing wood subfloors grow brittle with age or decay from moisture. Aging joists may be full of knots that are ready to crack at any time. These components need proper reinforcement to withstand the forces of a major earthquake. By just peeling back the stucco, we can determine the condition of the existing structure and use that information to create a thorough retrofit solution. Cantilever columns are the ideal solution for some buildings, just not all. Remember, the goal of the soft-story retrofit program is to save lives and property during a major earthquake. A secondary goal to keep in mind should be to prevent your tenants from being homeless after an earthquake. You should pay attention to the cost of the work to be done, but that cost should not be what determines the safety of your residents. At the Army Of Builders, our professional team will work with you to create a retrofit solution that will prevent harm to your tenants and your building while being cost-effective.