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Should Los Angeles Area Buildings Be Reinforced?

Should Los Angeles Area Buildings Be Reinforced?
 

Earthquakes are usually unexpected events that happen along major fault lines and they can cause catastrophic damage in the blink of an eye.  As we’ve all learned in recent news, however, earthquakes can happen much farther away from those fault lines than most people would suspect. Knowing that such devastation can happen so quickly and without warning, commercial property owners must consider the need to strengthen their existing buildings against the impact of an earthquake.

An earthquake retrofit provides current structures with more much resistance to earthquakes and other seismic activity.  In commercial and industrial buildings, the earthquake retrofitting process typically includes strengthening all weak areas found in roof to wall connections, shear walls, continuity ties, and the roof diaphragm.

Most older buildings may be dramatically unprepared to withstand the force of even low-level tremors. In the past, building codes were less stringent compared to today’s standards.  Therefore, it is a good idea to inspect all buildings constructed before the 1990’s, as they were built prior to the more current structural codes/requirements.  Most commercial property owners will find, after a thorough building inspection, that if their building is more than 10 years old, an earthquake retrofit will be strongly suggested to provide the extra strength needed to withstand future earthquakes.

There are many types of structures that may benefit from an earthquake retrofit, including homes, commercial and industrial buildings, not to mention bridges and dams.  Buildings in the Los Angeles area and along the entire West Coast, are quite diverse in their design structure, age, and style; specific considerations may be needed before being reinforced.  Considerations include the following:

Concrete Tilt-Up & Reinforced Masonry

An earthquake retrofit for buildings like this typically involves adding anchors that interconnect the roof and floor framing directly to the walls and continuity ties throughout the building. Depending on the shape and size of the building, steel brace frames are often added to the structure.  The concrete tilt-up and masonry walls used in commercial properties are extremely heavy and when they tremble and shake in an earthquake, they exert a great deal of force. The main reason that an earthquake retrofit is necessary for these buildings is to ensure the heavy walls will not pull away from the roof and floor framing which it supports.

Soft Story Conditions or “Tuck Under” Apartment Buildings

These buildings have an open first floor (such as ground level parking or underground parking) with one or more floors above (living or business quarters).  These buildings do not easily handle the movement caused by an earthquake, since they do not have any way to resist the lateral forces along the open elevations.  In order to strengthen this type of building, steel moment frames, concrete footing and drag lines must be added to keep the first floor from rotating and collapsing.  For apartment buildings, shear walls are commonly added to the existing walls on the interior areas of the parking stalls for reinforcement.

Un-reinforced Masonry

As with concrete tilt-up and reinforced masonry buildings, an earthquake retrofit for buildings with un-reinforced masonry also requires adding roof and floor wall anchors and continuity ties.  However, an earthquake retrofit for this type of building may also require a new plywood overlay for the roof. In addition, there are often too many openings on the ground level, such as large open storefront windows, in un-reinforced masonry buildings. Therefore, additional strengthening is required; a moment frame or brace frame must be installed or a small opening may need infilling to resist the shear loads.  Some un-reinforced masonry buildings have walls that are too slender and require a fix such as tube steel strongbacks, gunite or epoxy fiber wrapping.

Concrete Buildings More Than Two Stories

Because of their size and weight, these buildings exert a tremendous force.  An earthquake retrofit to reinforce buildings with multiple stories includes a combination of concrete shear walls, gunite, fiber wrapping, steel collectors, and many other types of strengthening systems.

Earthquake retrofitting is done for a variety of reasons, with the most common reason 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.  For additional information regarding an earthquake retrofit inspection for your building, call Saunders Commercial Earthquake Retrofit today!

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(949) 646-0034

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