After the quake has subsided and your occupants are out of harm’s way, a post-earthquake inspection is in order. This assessment clears your building for reoccupation and identifies structural damage you need to address.
After an earthquake, the demand for structural engineers is high. It’s certainly not the time to be combing through the phonebook for help.
“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.
Some cities offer services that facilitate this relationship. You may also find contacts through your insurance company or structural engineering associations.
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 disarray, which impedes the inspection process. If you have CAD or BIM drawings, make sure you can access them if the IT system goes down.
The Inspection Process
Remember that building codes and design are focused on life safety during an earthquake. There are no guarantees from either that the structure will be functional afterward.
An 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:
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.
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.
After an earthquake, the most adverse damage will always show itself. But internal damage that also compromises a building can be difficult to spot.
“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.
Jennie Morton (firstname.lastname@example.org) is associate editor of BUILDINGS.