Bob Duemmel Sponsored by Fire-Dex
Collapse responses have become more and more prevalent in the fire service community. From small departments to large multi-agency teams, shoring operations are taking place more frequently than ever before.
Many times, these operations are being executed without any formal training, or the responders are self-modifying the proven systems and methods of erecting and installing a shoring system.
When a situation requires shoring to create safe work zones, the attention to detail that goes into the process will have a significant impact on the strength and durability of the shores chosen for the operation.
The traditional shores used within the USAR response system are tested by the U.S. Army Corps of Engineers to establish ratings and capability limits for these shores. Structural specialist from the FEMA USAR system take part in this testing, which provides controlled testing data on the various shoring systems.
Shoring should be installed sequentially to minimize the risk to those working in the hazard zones. Exterior shores, if needed, should be installed prior to entry into a structure, followed by any required interior shores to provide the safety zones for operations.
There are three classes of shores, each representing the dimensional capabilities of the shore:
- A Class 1 shore is one-dimensional or often referred to as a spot shore; they work as initial entry shores to provide safety to responders. This class of shore provides very limited lateral stability. This can be hazardous when working in areas which are extremely unstable and those that have greater potential for secondary movement.
- Class 2 shores consist of two or more posts; a vertical shore is an example of this type of shoring. These shores have greater strength and provide more stability than a Class 1 shore, however, they also lack lateral stability.
- A Class 3 shore is braced in two directions providing three-dimensional stability when installed. They can be erected as an individual system or by lacing two Class 2 shores together. This class of shore is the most stable system of the three and it also provides safe havens for rescuers to retreat to in the event of a secondary collapse.
The first step in shoring is to evaluate the structure to determine the best path to enter for rescue operations. The closest point may not be the best path to take. Evaluate the loads that will need to be supported, then once you complete the initial evaluation, you can begin the actual shoring process.
At small or single structure incidents, you may have to rely on your agency’s training to make these choices. At large events where outside resources have been deployed, you may have a structural specialist available to assist in this process.
As in medicine, where there are many types of doctors, there are also many types of engineers; if you choose to utilize local talent to assist in this area of your response, make sure the people you consider are specialized in the structural collapse aspect of their trade.
Recommendations for shoring multi-story buildings follow these guidelines:
- Wood-frame: one undamaged floor to support one damaged floor
- Steel-frame: two undamaged floors to support one damaged floor
- Reinforced concrete: three undamaged floors to support one damaged floor
- Precast concrete: the shoring should extend to the ground
No matter what type of construction you are dealing with at a multi-story structure; your shoring should start directly under the damaged floor and work down.
Nail selection and application
Proper nail selection and placement are important to a well-built shore. A 16d nail is used for dimension lumber to dimension lumber applications. Sinker/cooler nails are preferred over standard 16d nails as they are less apt to split the lumber, and 8d nails are utilized for applying plywood to dimensional lumber.
Duplex (double headed) nails are used at wedges; their design allows the nail to be easily pulled when adjusting the wedges.
With the nails, come the nailing patterns. The nails provide the connections of the shores members to create the system while the lumber provides the strength of the shores. Nail patterns have been tested and engineered to provide the necessary shear strength within the shores. This is an area of assembly where the attention to detail is very important to a quality product.
The best time to develop good work habits are when first learning how to construct a shore. Hand nailing is a good method to reinforce the various patterns. Hand nailing is promoted through the use of duplex nails during training events; the duplex nails allow for the disassembly of the shores when the task is complete, which permits the lumber to be reused for following exercises.
Once you know the specific count of the nail pattern you will be using for a given task, you can then work on the layout. When nailing from one end to the other, many times the patterns tend to shrink in size, with a significant gap being found at the end of the cleat or gusset being nailed in place.
One method to help control the nail spacing is to nail one nail at the end of the item being attached, then one at the opposite end – this allows for proper alignment of the cleat to the surface it is being attached to. Then find the center of the material being attached and calculate the spacing of the outer rows to meet the designated pattern, finishing with the application of the balance of the nails which will be centered in the four nail patterns created by the outer nails, leaving you with a well-spaced five-nail pattern.
The nail patterns will become second nature to the student if practiced repetitively during initial and ongoing training, however, if bad work habits are developed early, they will stick with the first responders.
Gusset and bracing placement
Gussets placement, lateral and diagonal bracing should be done in a manner where they do not make direct contact with the ground, but other bracing material or the structural element the shore is supporting.
In a raker shore, you want the wall plate making full contact with the surface you are supporting. If the gusset plate(s) extend out beyond the dimensional lumber, the load will not be fully placed on the wall plate in this example.
Shoring should also be inspected at various intervals; the traditional time for this is at shift change or every 12 hours. By leaving a visual gap between the bracing and gussets, the inspector can easily identity any compression of the shore. The compression could indicate a potentially dangerous condition from a shore being overloaded by the forces it is attempting to hold in place.
One of my instructors used the phrase “no touchy, no touchy” when he would evaluate our work during training exercise to emphasize the importance of a well-constructed system.
Pinning wall plates in raker shores is an important part of its installation. A vast majority of shoring training is done at training facilities or structures which do not allow for putting pins into the structure. Even if the pins cannot be driven into place as required for an installation of a raker shore, go though the steps of drilling the holes for the pins and placing them in position. This repetitive exposure will benefit the students as they expand their motor memory skills during their training sessions.
Wall plates for raker shores should have at minimum two – 1/2“ anchors to keep the wall plate from riding up the surface it is in contact with.
Habits good and bad are developed from our initial exposure to any subject. If the student has never accomplished a given skill set during training, the odds are very high that they will not accomplish it during an actual response situation.
Sum of all parts
When utilizing or looking to purchase the shoring guides, focus on the most current addition. Sometimes the updates from one addition to another can be minimal and other times major additions and subtraction to the content take place. My suggestion is to buy what you need and not to stockpile boxes of the shoring guides; this will minimize the potential of having spent funding on items that are outdated when the next addition is published.
Many of the items covered in this article may appear to be minor to some, however having observed a number of responses, training sessions, and photos of shores which didn’t have all of the proper components in place was the motivations for this article.
Like most aspects of the emergency response fields, it is the sum total of all parts of the system that makes it successful. Each individual component of a shoring system comes together to provide the safety margins we come to expect when working in a collapse environment. Remember it is the attention to detail which will help to save your life and the lives of others when responding to a collapse incident.