Steady as She Goes
After the engineer completes the size-up, he or she has a few different ways to stabilize the damage, and they fall into two main categories: shoring, as well as strengthening and repairing techniques.
Shoring in general engineering terms means that you're temporarily supporting a structure for workers during construction, renovation or demolition. In search-and-rescue efforts, however, it's a little more specific. Shoring involves temporarily supporting a damaged structure (or at least the damaged part of the structure) that's needed for emergency activities. For instance, keeping a damaged beam stable in order to support the floor as a rescue takes place.
Vertical shores can stabilize things like floors and roofs. You might use a "double T shore" to do this, meaning that two gusseted posts brace the unstable floor above them. Lateral shores are used for walls that are either bulging out or leaning; that requires using diagonal shores to bolster the wall or angled shores to prop them up.
While shoring involves re-supporting damaged parts of the building, repairing and strengthening involves actually fixing the damage. For instance, in a concrete structure you might fix minor cracking by applying an epoxy to the cracks. If the structure is actually showing signs of collapse, however, you might need to strengthen the damaged element by placing new formwork around it and casting new concrete around the entire component. In much the same way, steel or carbon fiber jackets can be used to confine damaged beam-column joints as a way to reinforce them.
Engineers might combine different shoring and repairing and strengthening on each building, but there are some expected failures to look for depending on building types. If you're interested in the specifics, the U.S. Department of Homeland Security publishes a comprehensive field guide on building stabilization and shoring techniques.
Of course, engineers also have other tricks for stabilizing buildings. For lots more information, check out the next page.
Author's Note: How do engineers stabilize buildings for rescue?
So stabilizing buildings sounds all fine and good if you're an engineer, but what I can't get over is how quickly the process must happen. If you're in the midst of a dangerous rescue, you're no doubt doing a size-up, making decisions and carrying out those decisions in the time it takes to read this article.
- Department of Homeland Security. "Field guide for building stabilization and shoring techniques." United States Government. October 2011. (Aug. 28, 2013) http://www.dhs.gov/xlibrary/assets/st/st-120108-final-shoring-guidebook.pdf
- Federal Emergency Management Agency. "Structural Collapse Technician Course." Oct. 12, 2012. (Aug. 28, 2013) http://www.fema.gov/structural-collapse-technician-course-student-manual