COLLAPSE SEARCH AND RESCUE OPERATiONS: TACTICS AND PROCEDURES
Part 8: Door Shore and Interior Rake Variations
The door shore can be used to shore and stabilize any access way or doorway, even if breaching of walls has been undertaken. Usually, it is done to shore up a damaged or unstable existing doorway, and it is well suited for buildings with a masonry face.
After a serious collapse, the majority of masonry in the structure has been subjected to some type of stress. While masonry has excellent compressive strength values, its tensile strength is minimal. As a result, all masonry walls in a structure that has been subjected to the stresses of collapse must be thoroughly checked for damage. If an area or doorway is to be used as a means of egress and the walls show signs of stress, then the area must be shored up for safety reasons.
When shoring up these doorways in a typical brick-and-joist-constructed building, 4 x 4s generally are sufficient. Each situation is different, and size-up must be performed according to the specific situation; therefore, larger-size lumber may be needed.
Larger-size lumber is needed if the doorway is more than four feet wide or if an extensive amount of material above the shore must be supported. In these situations, 4 x 6s or even 6 x 6s may have to be used, especially in heavier commercial occupancies. bracing can be installed for greater strength and stability. For wider door openings, corner braces also can be installed.
If the door that is to be shored is not used for access or egress, then diagonal
VARIATIONS IN INTERIOR RAKE SHORING
Since all collapse situations are different and many of the hazards are unique to the specific conditions created by the collapse, variations in the ways rake shores are erected and used will be inevitable.
DOOR SHORE
1. Bottom plate. Install the bottom plate first to force the door jamb into the frame, keeping the opening tight. Cut off close to the plate the wedges used to keep the plate tight to eliminate any possible tripping hazards.
2. Header. Install the header next. The wedges should be on the opposite side of the bottom plate. This helps keep the shore stable. Install the header as level as possible; shim it tight to the top of the frame, if necessary.
3. Posts. Install the two posts next, the one under the top wedges first in case any problems occur and those wedges loosen up.
4. Bottom of posts. Tighten up the wedges on both sides; make sure there is no trip hazard. If necessary, cut these wedges close to the 4 x 4s to prevent this problem.
5. Corner brace. If additional support is needed or if the opening to be shored is more than four feet wide, install 45-degree angle braces, which typically are used in the construction industry to stabilize open framework. Using the steel framing square, you can easily determine the angles. The angles of the most common lengths are already calculated in the table located along the center of the back of the tongue. This information makes it simple to put in these braces, which should take relatively little time to install. Make sure you cut an inch and one-half return on the ends of the braces so that cleats can be installed.
6. Brace cleats. To make sure the braces hold securely, nail the cleats to the header and posts. Make sure they are long enough to be effective and anchored using the five-anchor pattern (see Fire Engineering, October 1993, p. 81).
Several options used successfully bycollapse rescue personnel are discussed below. As in every emergency, “ad libbing” is done continually. As long as the basic elements of the shore (wall plate, sole plate, rake, cleats, wedges, and diagonal braces) are installed properly and the fundamentals of load stress and transfer are followed, the shores will hold effectively.
INTERIOR RAKE VARIATIONS
Two angles. Illustrated are the recommended angle of 45 degrees (front) and the 30-degree angle, the lowest recommended angle (back). As you can see, the 30-degree-angle piece uses up more material, and longer lumber is needed for these rakes. Another situation that arises with the 30-degree-angle rake is that the top angle and the bottom angle are different, which can cause a little confusion in emergency situations with inexperienced personnel. Also, it is more difficult to determine the length of the 30degree-angle rake than the 45-degree-angle. For this reason and because both angles are the same with the 45-degree rake, it is generally recommended that this size angle be used whenever possible.
Hard surfaces. If for some reason, such as in the case of a large commercial building, it is difficult to brace the sole plate and the floor is concrete, other options are available. Sole plates can be 2 x 4s instead of 4 x 4s. They can be anchored to the floor quickly using poweractuated hammers. Be sure to use all safety precautions recommended for these tools; they can be extremely dangerous if not used properly. If this option is used, you will have to anchor additional cleats to the 2×4 sole plate—one should be at the front of the plate butted against the wall plate; this cleat should be at least two feet long and nailed down using the five-anchor pattern.
Another cleat will have to be installed directly behind the base of the rake itself. After leaving room for the wedges, nail the cleat down using the same nailing method. The length of the cleat should be at least four feet, if possible, to give the shore maximum holding strength.
Plywood. The use of plywood in front of the rake shore may be warranted in some situations. Generally, if a masonry wall is involved in a collapse, the remainder of the wall will be unstable: Many of the blocks or bricks may be loose or the mortar around them may be cracked. If this is the case, the plywood will support a much larger area than the rake itself normally would. If the base of the plywood is in contact with the floor, it also will help promote additional stabilization of the shore. It is recommended that the plywood be at least one inch thick.
ANCHORING METHODS
1. There are two common methods ot bracing the sole plate of the rake shore.
METHOD A. This method can be used in a large open area where the sole plate Is not large enough to reach a substantial anchoring point. A larger cross beam can be run at a right angle to the sole plate (plates, if more than one shore is to be erected, which Is normally the case) to increase strength and stability. The cross beam is butted tight to the sole plates, and another 4 x 4 is run from the point of each plate to a substantial anchoring point. This additional bracing Is then wedged tight to lock the shores together.
METHOD 8. This method is used when the sole plates are long enough to reach a substantial anchoring point, which often will be another wall. Make sure that the wall you are bracing against is stable and can handle the additional pressures applied to it. At this point, wedge the sole plate tight to the wall and anchor an additional brace to the sole plate directly behind the rake itself. Wedge it tight to secure the rake in place and transfer the loads from the damaged wall safely to the floor.
