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What is a Splice Plate?

A splice plate is a metal connector used to join and reinforce two sections of structural components, such as beams or trusses, ensuring stability and strength in construction. By distributing load and stress, it's crucial for the integrity of buildings and bridges. Ever wondered how these unseen heroes hold our world together? Join us as we explore the unseen backbone of modern architecture.
B. Turner
B. Turner

In construct, a splice plate is a thick metal sheet used used to reinforce the connection between structural steel beams. The joint between two pieces of steel is known as a splice, and each splice must be carefully reinforced to ensure a secure bond. Despite the high strength of steel beams and columns, a weak splice between two beams can compromise the structural integrity of an entire building. Adding a splice plate minimizes the risk of failure and helps improve safety for building occupants.

Steel erectors utilize splicing for a number of reasons. In some cases, there are simply no beams available that are long enough for a particular application. In others, a full-length beam may be too difficult to transport to the job site, or even to get in or out of the building. Finally, beam splices can help workers erect steel around obstructions, or maneuver them through the building without damaging surrounding surfaces.


After two beams are positioned as needed, the splice plate is centered along the spliced area. It may be placed on the web, or the beam, or on the chords, depending on installer access and engineer recommendations. Sometimes a single splice plate is used to secure the two beams, while other applications require two splice plates for a more secure hold.

The plates come pre-drilled with holes from the manufacturer. Installers lay the plate on the splice, then insert heavy bolts into each hole. A steel nut holds the end of the bolt in place and prevents the plate from moving. Some engineers may also require workers to weld the perimeter of the splice plate to maximize the strength and durability of the connection.

Splice plates provide a much more secure hold between two beams than bolts or welding alone. The forces applied to the beam are spread out over a much larger area than they would be with bolts, as the plate helps to distribute loads beyond the splice. These plates also reduce the risk that the beams will twist or warp at the connection point over time, which helps to extend the life of the structure.

Most building codes provide specific requirements for the use of splice plates. Engineers refer to these codes to determine the size, thickness, material and type of fasteners that must be used for splicing. The engineer may also perform calculations based on the forces and loads the splice will support to help him determine the best splice plate design.

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Discussion Comments


What is the difference between a splice plate and a gusset plate?


I am joining two beams for a indoor roof with a splice plate. One plate is welded to one beam top of one and the bottom of another with bolts to connect. Does the plate need to be sealed with welding from moisture and if not, will rust start to destroy the welded half in time, shortening the building's life?


@kentuckycat - As I understand flange and splice plates, I believe that you are right. I have always heard of flanges in reference to pipes rather than beams.

The article says that splice plates can be connected to the web, beam, or chords. What do these terms mean? My initial guess would be the beam is the long straight section, but I don't have any idea what either of the other two terms would refer to.

Also, I've seen wood structures with things similar to splice plates. They are square metal pieces with a lot of holes. They are usually connected with several nails to hold together two wooden beams. Are these also called splice plates, or is that only to refer to metal beams?


Has anyone here ever heard of a flange plate? I was reading about flange plates the other day, and now I'm wondering how it is the same or different from a splice plate.

After reading this article, my understanding is that a flange plate is more often used to combine things like sections of pipe rather than beams. I think the flanges go in between the metal rather than being bolted or welded onto the sides. Is this right, or have I not understood the differences correctly?


I see splice plates every day when I cross the bridge to go to work. I always think it is amazing that a simple piece of metal like that can hold together thousands of pounds of steel beams not to mention all of the cars passing over the bridge.

Out of curiosity, does anyone know what the longest a steel beam can be while still being structurally stable? Does it differ depending on the use? I could see where a bridge may benefit from having longer beams where a normal building could get by with having a few shorter beams spliced together. I'd be interested to know how the length applies to skyscrapers, too.


Is anyone here old enough to remember playing with an Erector set as a kid? Reading this article reminded me of that. Even though I had no idea they were called splice plates at the time, you could use a special piece to combine two pieces into a longer section.

It's a shame great thinking toys like this have been replaced with more modern kits where kids aren't as encouraged to make designs outside of what the box says.

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