In the wake of the 7.1-magnitude earthquake that rocked Southern California on July 5, 2019, it’s more important than ever to think about the importance of post-earthquake inspections for your buildings before it happens to you.
Although the earthquake, which occured near Ridgecrest, California, did not cause any fatalities or major injuries, it did cause major damage to some buildings, knock out power and spark several gas leaks, according to the Los Angeles Times.
After an earthquake has ended and your occupants are out of harm’s way, a post-earthquake inspection is in order. A thorough assessment clears your building for reoccupation and identifies structural damage you need to address before re-entry.
Plan Ahead and Develop Relationships
After experiencing an earthquake, the demand for structural engineers in your region will be high. It’s certainly not the time to be fumbling through Craigslist ad pages for help after the fact.
“Establish a relationship with a good structural engineer beforehand to make sure that when those services are needed, a licensed engineer is on hand to provide a building inspection,” says Andy Thompson, associate principal for Arup, an engineering consulting firm.
There are some cities that offer services that enable this relationship. You may also find contacts through your insurance company or structural engineering associations.
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Once connected, invite an engineer to your facility for a walk-through. Not only does this provide them with familiarity of your building, but they can make suggestions about reinforcement strategies.
It is also important to have your structural drawings available and organized. Often they’re in a state of disorder, which slows down the inspection process. If you have CAD or BIM drawings, make sure you can access them if the IT system goes down.
Proper Building Inspections
Remember that building codes and designs are focused on life safety during an earthquake. There is no absolute guarantee that the structure will be functional afterward.
A proper inspection is the only way to confirm if your building is safe to reoccupy.
“Engineers are looking for an indication that the lateral and vertical strength of the facility has not been compromised by the earthquake," says Thompson. "Is the building as safe as it was prior to the earthquake?”
An engineer starts with a visual evaluation of the building’s exterior, looking for tilting and land shifts. Once inside, damage to structural members is critical to identify. Impaired columns, shear walls, and gravity or lateral supporting systems often imply the building is unsafe.
Minor damage is also pinpointed, such as cracks, ceiling and floor issues, elevator and lighting damage, and roof failures. Note that a structural engineer will not address systems such as mechanical, plumbing, or IT.
There are two types of evaluation methods:
1. Rapid Visual Inspection
This occurs up to 24 hours after an event and uses a red, yellow, and green tag system. A volunteer or state-contracted engineer will take approximately an hour to assess the building’s safety, erring on the conservative side.
2. Detailed Structural Evaluation
These inspections are specific to your situation. They take place several days after an event and a thorough assessment takes one or two days. The time required for an inspection is dependent on your building type – a box store requires a different level of attention than a high-rise building.
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After an earthquake, physical damage on the outside is always apparent. But the inside, internal damage can compromise a building without being highly visible to the naked eye.
“There are cases where a visual inspection cannot reveal the extent of the damage,” says Farzad Naeim, vice president of the structural engineering firm John A. Martin and Associates.
For example, connections in framing may be shaken to the point where they have cracked, weakening their load capacity. This could go unnoticed because framing is usually covered by drywall and other materials.
Consider adding real-time structural health monitoring to address hidden sources of damage. This system of sensors collects data from multiple points around your facility. It triangulates sensor feedback to reveal potential areas of damage and generates a detailed and actionable report with 10-15 minutes of an event.
This can determine if your building is a high or low priority for inspection. It also saves engineers time by directing them to specific locations to evaluate instead of having them walk every corner of the building.
The expertise of the human eye combined with the precision of software can help minimize the downtime of your building. Throughout the process, remember that any time needed for an inspection is well worth ensuring the safety of your occupants.
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This article was published in 2011 by Jennie Morton, an associate editor of BUILDINGS. It was updated on July 8, 2019, by Sarah Kloepple, staff writer.