Although many people think that earthquakes only happen near fault lines, we have seen time and time again that they actually can happen at any time and in any place. Past building codes standards were not as stringent as they are today; over the last 30+ years, state and local building codes have been updated to increase safety and to minimize destruction from seismic activity. Unfortunately, however, many older commercial buildings remain dangerously unprepared to withstand the mighty shaking of a powerful temblor. For those older structures, an earthquake retrofit can strengthen the entire building. Often, the roof-to-wall connectors are found to be inadequate and in need of strengthening, in addition to reinforcing continuity ties and the roof diaphragm.
For those who currently own a commercial building that was built before 1990, especially in California, a thorough property inspection should be completed to ensure that the building is strong enough to withstand the incredible force of strong seismic activity. While commercial buildings certainly can benefit from a retrofit, other structures, such as dams and bridges, can be strengthened as well.
In California, commercial buildings vary in their design and style and there are several different building types that need special considerations in the retrofit process.
- Concrete Tilt-Up & Reinforced Masonry (CRM) Construction – Walls built using this construction method are very heavy. When the earth begins to shake, the walls exert an amazing amount of force. Seismic retrofitting commercial properties built using these construction methods typically involves adding anchors that interconnect the roof and floor framing to the walls. By doing so, the heavy walls will not pull away from the roof and floor framing during an earthquake.
- Un-reinforced Masonry (URM) Construction – Any buildings with un-reinforced masonry should have roof and floor wall anchors added, along with the addition of continuity ties. If the walls are not thick enough, special work will be needed to ensure they are strong enough. If a building has a large open window or too many openings, additional reinforcement and strengthening is necessary to resist the shear loads.
- Concrete Buildings with Multiple Stories – Due to their incredible weight, this type of building exerts tremendous force during a major earthquake. An earthquake retrofit for older multi-story properties often includes several different strengthening systems. Based on any weaknesses found during a thorough building inspection, a combination of concrete sheer walls, steel collectors, gunite and fiber wrapping may be used for reinforcement.
- “Tuck Under” Apartment Buildings – “Tuck Under” buildings have an open first level that is used for parking, with one or more additional levels above that are used for living or business spaces. These properties do not fare well during an earthquake because the first level is unable to resist the lateral forces when the earth begins to rock and roll. In order to ensure that this type of building does not twist and collapse, retrofitting often includes adding a steel moment frame, along with drag lines and concrete footing. Additional strengthening may also include adding sheer walls to the existing interior walls of the parking areas.
There are many reasons why commercial property owners decide that an earthquake retrofit should be done. Typically, the most compelling reason to schedule a retrofit is to ensure that tenants, employees and customers will be safe during powerful seismic activity. Call the professional team at Saunders Commercial Seismic Retrofit today to find out more about seismic retrofitting and to determine whether your Bay Area commercial property is currently strong enough to withstand the tremendous force of a powerful quake.