In basic firefighter training, we all took a building construction class. We learned how various construction types react during fire conditions and that modern buildings are engineered to be stronger under normal conditions using lighter weight construction materials. Designed to carry specific loads, structural members in today’s buildings are prone to failure if additional loading is placed on them. We also learned that a small failure in a structural member can lead to the failure in the entire engineered system.
PHOTO COURTESY VIRGINIA TASK FORCE 2
Structural collapse often creates debris that must be moved during search and rescue operations. Simple machines — levers, rollers and haul systems — are useful for removing large debris. |
When the supporting structure fails, gravity takes over and we have a collapse; we also have a major incident on our hands. Responding to a building collapse requires coordination among different aspects of the operation, which can include search- and-rescue efforts, fire attack, shoring and stabilizing, hazmat control and scene management. A compromised or partially collapsed structure can present unique and challenging hazards for responders.
Causes & Types of Collapse
Earthquakes, wind, flooding, tidal surge, explosions, increased load and neglect are a few of the main reasons structures fail. Regardless of the cause, the end result is the same: Unsupported materials move until they find something to which they can transfer their weight.
In a pancake collapse, vertical support members fail, causing floors to come to rest on top of one another. Debris piles and pieces of the failed support structure can create small voids within the rubble pile. A lean-to collapse occurs when one side of a building fails and the floor structures fall on that side, creating a larger, wedge-shaped void between the floors. In a v-shape collapse, the floor structures fail, resulting in opposing wedge-shaped voids along the remaining vertical support walls.
The type of collapse depends on the type of construction, building materials and the force applied to the building. When responding to a collapse, identify the new load path—the support structure allowing the weight of the supported area to be transferred to the ground. The load path may be through debris piles, unstable structural members or even vending machines. Keep in mind that unless the entire structure rests completely on the ground, the potential for a secondary collapse always exists.
Every collapsed building presents its own challenges; a two-story wood-frame house collapses differently than a four-story reinforced concrete office building. The structural integrity of the remaining frame must be evaluated prior to search-and-rescue operations.
This task is best left to a structural engineer, but if one is not available, use some common sense to conduct operations safely.
Take a good look at the building’s construction. What materials were used for the superstructure (wood, steel, pre-cast concrete, tensioned concrete)? How were they put together (nailed, bolted, welded, set in place)? How damaged are the supports (twisting, cracking, sheering, buckling)? Is this building going to continue to collapse and if so, in what direction and manner?
In cases of multiple buildings, conduct a building triage: Rate the damage to each building, along with its potential occupancy; complete rescue operations in buildings with low damage and high occupancy loads before those with lower ratings.
PHOTO COURTESY VIRGINIA TASK FORCE 2
A compromised or partially collapsed structure can present unique and challenging hazards for responders. |
Building Stabilization
Rescuer safety is the primary concern during rescue operations in unstable buildings, and shoring is essential to creating that safety.
The sole purpose of a shore is to support a load and transfer its weight to the base. The header (top) and sole (bottom) are very important for the collection and transfer of the load. Example: A shore constructed like the letter “I” captures the load on the top, transfers it through the column and redistributes it to the base. In contrast, a shore constructed like the letter “T” captures more of a load and concentrates it into an area on the base. If this type of shore became quickly loaded by secondary collapse or additional weight above it, there’s a good chance that it would punch a hole through the floor rather than redistribute the added load.
Using temporary shores allows us to conduct initial search operations. Pneumatic rescue struts without the use of air make great temporary shores, as do one-dimensional wooden shores (vertical support only). Note: Start shoring from the point of entry into the building. Shore the window or door you enter from to ensure the opening is still there when you need to exit. Temporary shores can be reused and are not designed to stay in place for the duration of the incident. For rescue operations in the structure, construct more permanent two- and three-dimensional shores. A two-dimensional shore is designed to support against lateral racking in a horizontal direction. Three-dimensional shores are freestanding units that resist racking in multiple horizontal directions.
Shoring allows you to control some of the building’s new load path, but you must monitor shores constantly for signs of overloading (buckling, crushing, cracking). A good shoring system creates a much safer working environment for the rescuers.
Debris Removal
During a collapse rescue, we may need to remove materials from within the collapse. Small, lighter debris can be moved by hand, but what happens if we are faced with a large chunk of concrete or a 2" steel I-beam that needs to be moved? We can signal the crane over, hook it up and lift it away, right? When was the last time you had a crane and an operator right there when you needed them?
For the most part, we must rely on simple machines to remove large debris. Simple machines can accomplish a lot of work with little to no equipment; they were the central concept behind construction of the Egyptian pyramids. Simple machines include levers, rollers and haul systems, all of which you can use very easily to move large objects out of your way. For example, you can lift a large piece of debris by using levers to place pieces of pipe under it. The pipe will act as rollers and the concrete can be pushed or pulled out of the way.
Air bags are another lifting tool at our disposal. Always calculate the approximate weight of the object so you can select the correct air bags. Steel weighs around 490 lbs. per cubic foot; concrete weighs about 150 lbs. per cubic foot.
Mechanical advantage systems easily reduce the amount of force necessary to move large weights. During a recent training class, I was introduced to a new mechanical advantage system called the Georgia Haul. This 27:1 system, designed to move a large block of concrete, consisted of 27 students and 1 rope; it very easily accomplished the task. Sometimes the simplest system works the best.
PHOTO COURTESY VIRGINIA TASK FORCE 2
Making entry though concrete is difficult. You can use saws or drills to weaken the concrete, then use small chippers or large breakers to fracture off pieces to create an opening. |
Making Entry
Occasionally, the only way to get inside a collapsed structure to conduct interior operations is to go through an obstacle. Some materials are easier to get through than others. Wood is easy to cut through, while steel and concrete are more difficult.
Specialized tools can make these jobs a little easier. Burning equipment works very well on metals. Such tools operate by taking a small section of the metal out of its solid form and removing it from the rest of the piece. Oxy/acetylene, oxy/gasoline, exothermic and plasma units can efficiently cut steel and other metals, but you must answer a few questions first: What will happen when I make the cut? Does the obstacle support any load? How heavy will the piece be that I am burning off? Where will it fall? Are there any combustibles in the burning area that may ignite? Is the burning tool set up for the material? Different tip sizes and pressure settings exist for different materials, and these tools do require some amount of skill to operate effectively.
Concrete removal techniques are a little different. Drills, saws, chippers and breakers work to take the concrete material out of compression and put it into sheer. Sawing or drilling weakens the concrete’s ability to dissipate force throughout its mass. Once concrete is weakened, you can use small chippers or large breakers to fracture off pieces to create an opening. The exposed rebar can then be cut using saws or specialized rebar cutters. The final step is to enlarge the opening to allow rescuers to make entry.
PHOTO RALPH TROWBRIDGE
Cutting into concrete and other materials can produce particles that irritate your respiratory system. When responding to a structure collapse, wear an air-purifying respirator with at least P-100 cartridges. |
Rescuer Safety
Remember: Your safety is the first priority; take proper steps to safeguard it. Structural collapse is an inherently dangerous environment, and can involve caustic gases and dust, including asbestos, which can still be found in many buildings. Your respiratory system, if unprotected, will suffer the most damage. Wear an air-purifying respirator with at least P-100 cartridges. In addition, ensure that hazmat personnel are on site as force protection in keeping all rescuers safe.
Managing the Incident
During a structural collapse response, you must establish a well thought-out command structure. In most cases, the response will involve multiple agencies, whether it’s neighboring departments, local contractors or outside resources. Large-scale incidents may involve federal agencies you’ve never worked with before, such as a FEMA US&R team or the FBI. This is why it’s so very important to use the National Incident Management System (NIMS). Following the NIMS model simplifies the addition of outside resources as they arrive. To ensure smooth operations in such situations, train in incident management as much as tool use.
Collapse Rescue Rests on You
Dealing with a structural collapse requires training, tools and equipment not normally associated with firefighting. This article is just a brief overview of some of the information contained in the Structural Collapse Technician Level training program (NFPA 1670), which involves approximately 80 hours of instruction. Students walk away from the program tired and sore, but with a wealth of knowledge and experience for future incidents.
Structural collapse training can apply to situations besides building collapse, including fires in commercial buildings and mayday situations. Federal US&R task forces have undergone collapse training, and now some states are putting teams in place as well. But these teams are not the first-in resources to the incident; your engine or ladder company is. You will be the ones responsible for the most lives saved. You will be the ones in the most amount of danger. Train, equip and protect yourselves so that you can save those you serve. KTF-RFB.
Bob Hnatko is a firefighter/specialist with the Special Operations Division of the Chesapeake (Va.) Fire Department and the commercial programs director for Spec Rescue International. He also serves as a hazmat specialist with the Southside Region Virginia State Hazardous Materials Response Team and as a rescue specialist on FEMA’s Virginia Task Force 2.
