Diagonal bracing is a common technique used in the construction of pole barns and other similar structures. It involves placing diagonal beams or boards between the vertical and horizontal poles to create a triangle shape.
Purpose. The purpose of diagonal bracing is to provide lateral stability to a structure, preventing swaying and improving overall rigidity. It is essential in resisting forces such as wind or seismic activity that can cause lateral displacement or collapse.
From the DCA 6 Commentary, “Diagonal bracing can contribute to the stiffness of the deck and, therefore, cause additional lateral loads on the posts. Since center posts receive more vertical load than corner posts, additional lateral load can cause overstress.”
Diagonal bracing is obstructive in nature as it blocks the location of opening which ultimately affects the aesthetic of the building elevation. It also sometimes hinders the passage for use. Diagonal bracing can be single diagonal or double diagonal as shown in Figure below.
Chevron bracing and cross bracing have the highest resistance to the lateral drift compared to the others; but cross bracing is more costly due to more joints. Therefore chevron is the optimal bracing type.
A deck that is more than 24 inches above grade must resist lateral loads in accordance with the following: Diagonal Bracing. Provide diagonal bracing both parallel and perpendicular to the beam at each post as shown in Figure 18.
However, instead of using two supports per section forming an X, single diagonal bracing does exactly what its name suggests and only uses one. Unlike cross bracing, single diagonal bracing can withstand tension, as well as compression forces.
Diagonal bracing is a structural component of just about any building. It provides lateral stability, preventing the collapse of walls, decks, roofs and many other structural elements.
Let-in bracing is the most widely used bracing system, but this bracing requires the studs be notched so that the brace will be flush with the stud surface. Using diagonal braces, these studs are typically cut at a 45- to 60-degree angle.
A long-standing rule of thumb is to provide bracing for two percent of the compressive force in the flange or member being braced. Although it lacks an explicit consideration of the required bracing stiffness, this approximation is typically conservative.
All decks using horizontal decking should have a diagonal sway brace to prevent racking. You may install a metal "T" brace, which is a long metal strip diagonally across the top of the joists, or install a diagonal deck board across the bottom of the deck frame. Decks using diagonal decking do not require sway bracing.
The angle of a brace should be kept within the range of 30-60 degrees to be efficient. This is a rule of thumbs I have read in some books on structural design.
"It's like whiplash - you're trying to avoid that sudden movement of the head, which can result in serious injury, if not death." The brace position involves bending forward and placing your hands over your head to prepare for a crash, which Eades explains is supposed to help the body during impact.
Cross bracing can be seen in situations like flooring, where cross braces are put between floor joists in order to prevent movement. It is also commonly used for ship making in order to stand against heavy winds or extreme weather.
The diagonal bracing is both to support the deck weight and, together with the horizontal transverse, provide the lateral racking strength. Often, a system of the horizontal diagonals is used to provide racking strength against quartering seas.
The depth of the joists determines if X-bracing is required, and the code basically states that the bracing is required if the joists are greater than 12 inches in depth. When weight is added to the floors above, the joists tend to deflect or bend slightly.
Some skyscrapers by engineer Fazlur Khan, such as the 1969 John Hancock Center, have a distinctive X-bracing exterior, allowing for both higher performance from tall structures and the ability to open up the inside floorplan (and usable floor space) if the architect desires.
One of the main reasons you may have a shaky deck is improper joist spacing. Joists are the horizontal framing parts that support the deck boards. When these are spaced too far apart, they can't support the deck's weight, causing shaky movement.
Cross bracing and/or knee bracing will help keep second-story decks stable. Decks with Narrow Posts: The thicker the posts the more stable the deck. A 6x6 post can support a taller, unbraced deck than a 4x4 post.
In all of these cases, especially timber construction, knee braced connections provided a perfect engineering solution that increased stability of the structure, created rigid connections between elements and reduced the bending span for beams.
Traditional metal braces (the most affordable)
Metal braces are perhaps the most well-known form of braces treatment. They consist of metal brackets and a metal wire that helps shift teeth into optimal alignment. As a result, metal braces are a great option for correcting severe teeth and jaw misalignments.
They should bend as far forward as possible, resting their head against the seat in front if it is within reach and place their hands on the back of their head, with the hands one on top of another (rather than interlocked). Their elbows should then be brought in.
It is preferable to locate bracing at or near the extremities of the structure, in order to resist any torsional effects.