An earthquake retrofit definitely can strengthen existing commercial properties, providing more resistance to seismic activity, including devastating earthquakes. For most commercial buildings, this process typically consists of a variety of steps, including strengthening weak connections found in shear walls, roof to wall connections, continuity ties, and the roof diaphragm. Earthquakes are unexpected events that happen along major fault lines, but seismic activity can happen much farther away from those fault lines than most people realize. More often than not, older buildings are dramatically unprepared to withstand the force of even low-level tremors. Therefore, most buildings up and down the West Coast, from Washington state to southern California should all be evaluated for the potential need of an earthquake retrofit.
Buildings that are more than 20 years old will likely need to be reinforced with a earthquake retrofit.
In the past, many buildings were constructed under the concept of “build it and forget it”, but as we know today, that is a downright dangerous way to handle commercial property maintenance. The lifespan of a structure is largely determined by design, engineering, materials, and the environment, however there simply is no man-made structure that doesn’t require some form of ongoing maintenance.
It is possible to avoid structural failure providing the materials used are not stressed beyond their capacity. While earthquake building codes in areas prone to seismic activity have become more sophisticated in recent years, older buildings are still vulnerable to seismic activity. Generally speaking, buildings constructed before 1987 are not considered to be engineered well enough to withstand the strain of an earthquake shock. In fact, an entire community of aging buildings that have not been retrofitted will easily become a deadly disaster area, especially when the “BIG ONE” occurs.
Building codes in the past were far less demanding, therefore it is recommended that buildings constructed prior to the 1990’s (before the current structural codes and requirements were developed) should be inspected and reinforced as necessary. Many types of structures may benefit from an earthquake retrofit, including buildings, bridges and dams. There are many buildings along the West Coast, including in the Bay Area, that would benefit from an earthquake retrofit; they are diverse in their design structure, style and age, therefore experienced professionals should complete a thorough evaluation to include all necessary considerations, before completing an earthquake retrofitting plan.
Depending on the type of building in need of reinforcement, professional contractors specializing in earthquake retrofitting can evaluate and make appropriate suggestions:
- Un-reinforced Masonry (URM) – An earthquake retrofit for buildings with un-reinforced masonry typically requires adding roof and floor wall anchors and continuity ties. In addition, an earthquake retrofit will usually require a new plywood overlay for the roof. Often, in these types of buildings, there are openings, such as a large open storefront window, which require strengthening. This situation can be resolved by infilling the smaller openings or installing a moment frame or brace frame to resist the shear loads. Some URM properties have walls that are too slender, and they will require a fix such as tube steel strongbacks, gunite or epoxy fiber wrapping.
- Concrete Tilt-Up & Reinforced Masonry (CMU) – An earthquake retrofit for buildings like this generally includes adding anchors that interconnect the roof and floor framing to the walls, along with continuity ties throughout the building. Sometimes due to the size and shape of the building, steel brace frames are necessary to strengthen the structure. The concrete tilt-up and masonry walls used in commercial properties are very heavy and when they are shaken during in an earthquake, they exert a great deal of force. The main purpose of an earthquake retrofit for these buildings is to keep the heavy walls from pulling away from the roof and floor framing which it supports.
- Concrete Buildings (more than two stories) – These taller buildings exert a great deal of force, as well, due to their weight. An earthquake retrofit to reinforce buildings with multiple stories typically includes a combination of concrete shear walls, gunite, fiber wrapping, steel collectors, and many other types of strengthening systems. The concept is the same as URM’s, as far as strengthening connections and adding shear strength.
- Soft Story or “Tuck Under” Apartment Buildings – These are buildings have an open first floor (such as ground level parking or subterranean parking) with another floor above (living or business quarters). These buildings tend to perform poorly in an earthquake because there is no way to resist the lateral forces along the open elevations. Strengthening these buildings usually includes adding a steel moment frame, concrete footing and drag lines to keep the first floor from rotating and collapsing during the rocking and rolling of any seismic activity. With apartment buildings, shear walls are commonly added to the existing walls on the interior areas of the parking stalls for reinforcement.
Earthquake retrofitting is done for a variety of reasons, with the most common being to ensure the safety and security of a building’s employees, machinery and inventory. While it is nice to imagine that all buildings in danger zones were built right the first time, that is simply not the reality. To find out more about whether your commercial property should be reinforced for earthquakes and tremors, be sure to contact Saunders Seismic Commercial Retrofit for additional information. The professional team at Saunders Seismic Commercial Retrofit can provide a thorough building evaluation and they can address structural maintenance, earthquake retrofitting, and roof condensation conditions. To get more information regarding the updated building codes/requirements for commercial properties in the Bay Area, call Saunders Seismic Commercial Retrofit today!