What Is a Jack Beam in PEB and Where Is It Used?

If you've ever looked at a PEB drawing and wondered why one bay has a big horizontal member where a column should be, you've probably met a jack beam. It's one of those parts that doesn't get much attention until a client asks, "Can we remove this column?" That's usually when it becomes the most important member in the building.

So, what is a jack beam? In short, it's a beam that takes the load of a column or rafter that can't come all the way down to the foundation, and passes that load sideways to the columns on either side of it. Let's go through how that works and why designers use it.

What Is a Jack Beam in a Pre-Engineered Building?

A jack beam in PEB is a horizontal structural member, normally a built-up I-section, that picks up a point load from above and carries it across an opening. Think of a normal frame: rafters sit on columns, and columns go to the ground. Now take away one column. The rafter above it still has load coming down, and that load needs somewhere to go. The jack beam is the answer. It spans between the two neighbouring columns, and the frame above rests on it.

You'll also hear it called a PEB jack beam on site, or simply a jack, and the whole arrangement is sometimes referred to as the jack beam structure. Same idea, different names.

Jack Beam Purpose in PEB: Why Use One?

The jack beam purpose in PEB projects comes down to one thing: creating clear, column-free space where the regular frame spacing would put a column in the way.

Common situations:

• Wide sidewall openings. A loading bay or large door in a sidewall may need 10 to 20 metres of clear width, and a column in the middle would block trucks.
• Omitted bays. Sometimes an interior or edge column is removed to give machinery or racking more room.
• Building expansion. When a future extension is planned, the end frame may be supported on a jack beam so the wall can be opened up later.
• Layout changes. Plant layouts change, and a column that made sense in the first drawing may get in the way later.

Without a jack beam you'd need to rethink the entire frame spacing, which usually costs more.

How a Jack Beam Works

Picture a rafter reaction landing on the middle of a beam. That beam now behaves like a simply supported member with a concentrated load, so it bends, deflects and passes shear to the columns at each end.

Those end columns then carry extra load too, which is a point people forget. Moving a column's load onto its neighbours means the neighbours, and their foundations, may need to be stronger. That is one reason a jack beam is never free. You remove one column, but you pay for it in a deeper beam and heavier supports elsewhere.

Where Jack Beams Are Used

You'll see them across many building types:

• Warehouses and godowns needing wide truck openings
• Factories with large machine bays
• Logistics hubs with dock-side clear spans
• Cold storage buildings where internal columns would disturb racking
• Showrooms and workshops that want open floors

For a grain facility, a jack beam can help create a wide loading mouth along one side, though you'd still want to check that the opening doesn't weaken the stacking layout or the roof drainage path.

Jack Beam for EOT Crane Buildings: What You Need to Know

This is where people get confused, so let's be clear. A jack beam is not a crane beam. The PEB crane beam, better known as the crane runway girder, is a separate member. It carries the wheels of an EOT (electric overhead travelling) crane along the length of the shed, and it's designed for moving loads, impact and fatigue.

Still, the two can meet in the same building. In a shed with an EOT crane, the jack beam for EOT crane bays comes into play when a column near the crane zone has to be omitted. The jack beam then supports part of the main frame, and the crane runway system has to be checked around it. Crane loads, brackets and bracing need their own design. Do not assume a normal jack beam can also carry crane reactions. Give your PEB designer the crane capacity, span and duty class at the start, not after the drawings are done.

Also Read : PEB Factory Shed With EOT Crane

Jack Beam Design: What Goes Into It

Jack beam design is more than choosing a deep section. The engineer usually checks:

• Bending and shear from the rafter's point load plus dead and live loads
• Deflection, which is kept tight because the frame above sits on this beam and sagging would affect roofing and alignment
• Lateral stability, since a deep beam with a compression flange can buckle sideways without proper bracing
• Connections, where end plates and bolts must carry large reactions into the columns
• Effect on neighbouring columns and foundations, which now take more load
• Wind and seismic combinations, as with any PEB member

Most PEB software handles the calculations, but the designer still decides where a jack beam makes sense. Standards such as IS 800 and widely used PEB design practice guide the checks. Always have the final design reviewed by a qualified structural engineer.

Jack Beam vs Other PEB Structural Components

To put it in context, here are the main PEB structural components and where the jack beam sits among them:

• Main frames (columns and rafters) carry the primary loads
• Secondary members (purlins and girts) support the roof and wall sheeting
• Bracing gives lateral stability
• Crane beams and brackets serve overhead cranes
• Jack beams pick up loads where a column is removed

A jack beam is special because it breaks the usual rule that every frame has a column running straight down. That also makes it one of the members that deserves extra scrutiny.

Read More: PEB Structure Components Explained

Final Thoughts

A jack beam is a practical trick. It lets a pre-engineered building have open floor space and wide openings without redrawing the whole frame. But it works by moving load around, not by making it disappear, so the neighbouring columns, foundations and bracing all have to cope. If you're planning a shed with a big sidewall opening or an EOT crane, talk to your PEB designer early and be specific about what you need to clear.

Frequently Asked Questions (FAQs)

1. What is a jack beam in PEB?

It's a horizontal beam that supports a rafter or column that doesn't reach the foundation, passing its load to the columns on either side so the space below stays open.

2. Why is a jack beam used in a pre-engineered building?

To remove a column from a bay and create a wide clear opening, such as a truck entrance or an open machine area.

3. Is a jack beam the same as a crane beam?

No. A crane beam, or runway girder, carries the wheels of an EOT crane. A jack beam carries frame loads over an omitted column. They can appear in the same building but are designed separately.

4. Does a jack beam increase construction cost?

Usually yes. The beam is deeper and heavier, and neighbouring columns and foundations may need strengthening. It can still beat the alternative of redesigning the frame.

5. Who should design a jack beam?

A qualified PEB or structural engineer, with the full loading information provided up front, including any crane details.