Columns

A column inside the wall

The example house, as it stood after Headers, has single studs every 600 mm, the bracing line at mid-height and headers over the openings. Each stud carries its own strip of wall. That works as long as the load arrives spread along the top track.

A porch beam, a roof truss bearing at a single point or a long wall with no joint change the picture: the load arrives concentrated, or the wall needs a stiffer support in the middle. The Column tool places a built-up member there, made of the LSF sections themselves, without switching systems.

The column always lives inside a wall, in place of a stud or against a joint. There is no free-standing column in the middle of a room.

In the example house: a lattice column in the front wall, between the door and window J1, the most heavily loaded stretch of the facade.

Three ways to join sections into a column

An LSF column is built up: two chord sections working together. What changes between the make-ups is how they are tied. In the lattice column, diagonals and struts make the two chords work as an upright truss; in back to back and box, the two sections sit against each other.

The column has no section of its own: it borrows the ones in the project settings. Changing the truss diagonal in the settings also changes the column diagonal.

A compression member, built up from cold-formed sections

NBR 16970, the Brazilian standard for light steel framing, has no item of its own for an "LSF column". For the standard, each chord is a cold-formed member in compression, sometimes in bending, and joining two sections makes a built-up member. All of that is NBR 14762, the Brazilian cold-formed steel standard. NBR 16970-2 adds the displacement limit.

What the standard does not say

The standard does not set the column width, the panel spacing or the diagonal angle. Those numbers belong to the market rule the app loads, with a declared source. In Brazil: 400 mm width, spacing up to 600 mm, diagonal between 30° and 60°. They are a CalcSteel design decision, not an ABNT requirement.

A column where the load arrives, and at the corners

• 400 mm: width, chord axis to chord axis
• 600 mm: maximum spacing between web nodes
• 30° to 60°: diagonal range
• 6 m: maximum span between supports along the wall

1. A column under a point load. Porch beam, truss bearing at one point, garage frame: put the column underneath. Without it, the load lands on one or two single studs, or on the header.
2. L corners, right at the corner. In the AI automatic layout, every L corner gets a column, and every wall longer than 3 m gets at least one corner column. At the corner, the chords of the two walls merge into a box.
3. No stretch of wall longer than 6 m without support. If the gap between joints and columns goes over 6 m, split it: first at the T joints in the middle, then with evenly spaced columns. That is what the AI does on its own.
4. Lattice as the default. It gives stiffness with thin steel: 400 mm wide with 0.95 mm sections in the chords. Back to back and box are for places where the lattice width does not fit, or next to an opening.
5. Diagonal and strut for a tall column. With the PM strut, each chord gets a node in every panel; in the zigzag the nodes alternate from one chord to the other. A closer node means a shorter buckling length about the weak axis. Zigzag saves members in a short, lightly loaded column.
6. Place the column before the truss. Between a column and a truss beam, whichever goes in last governs: a column placed under the beam splits the beam; a beam placed afterwards shortens the column. Decide the order by which one must run through whole.

1. Open the view and arm the tool

Select the front wall and click Open view on its card, in the footer. On the LSF card, click the Column button. The Column box opens next to the card. The tool works in the plan, in the wall view and in 3D; in the view the studs are bigger and the snap is easier to see.

2. Hover over a stud

An amber ghost shows the column before the click: the two chords, the diagonals and the struts, with the width and spacing of the box. It snaps to the nearest stud (the magnet reaches 0.35 m) and grows toward the side of the cursor.

Here the cursor is on the stud between door P1 and window J1, and the column will grow to its left.

3. See a refusal before clicking

To understand the rule, change the Width to 100 mm and hover over the same stud. With chords 100 mm apart and panels up to 600 mm, the diagonal is almost upright, above 60°. The ghost turns red and the box says why, before any click. Set the width back to 400.

4. Click and check the dimensions

With width 400, click. The column appears in orange, the studs that fell between the chords go away, and with Rearrange neighboring studs checked the stretch next to it is split again into equal bays. The tool disarms by itself, and the whole column is a single Ctrl+Z step.

The column stays selected and the footer becomes the column inspector: name, make-up, wall, and the fields you can change without reopening the box.

5. Change the make-up in the footer

In the footer, click the second button, Back to back (I). Diagonals and struts go away and the two sections stay against each other, web to web. The width and spacing fields leave the footer: in back to back they do not exist.

In the example, we go back to Lattice right after, with the first button.

6. Exit and check in 3D

Esc clears the selection and closes the view. In 3D, the column shows in the front wall between the door and J1, with chords, diagonals and struts.

The Column box and the column footer

The box (applies to the next column)

Model, width, spacing and the two checkboxes only show for the lattice column.

The footer (applies to the selected column)

Editable dimensions

With the column selected in the view, the clearance dimensions to each side, the width and the spacing of each panel accept a click and a number, like the other dimensions of the wall view.

The refusals, and what to do

Every refusal shows before the click: the ghost turns red and the box gives the reason. Nothing is saved.

1. "The column would go past the end of the wall." The width does not fit between the stud and the end of the wall. Fix: cursor on the other side of the stud, so the column grows inward.
2. "It lands on a door or window of this wall." A column does not go inside an opening. Fix: place it against the frame stud next to the opening, or move the opening.
3. "It hits another column in this wall." Two columns do not overlap. Fix: a single, wider column, or move them apart.
4. "It is a joint stud: it is already built up and holds the other wall." The joint stud is already a built-up member. Fix: place the column against it, at the abutting station, without replacing it.
5. "The diagonal would fall outside 30° to 60°: change the width or the spacing." Seen in step 3. Fix: width and spacing of the same order of magnitude.
6. Project market without a column rule. Width, spacing and the diagonal range come from the project market rule, and the box only places a column with it. Use a market that brings the rule, such as Brazil.

Chords in compression, braced by the web

Model. Chords, diagonals and struts enter the model as members, all with the column role. Each chord is pinned at the track about the strong axis. The wind on the wall reaches only the PB chords.

Chord buckling. About the strong axis (the chord bending out of the wall plane), the length is the column height. In the other two modes (weak axis and torsion), it is the longest stretch between the web nodes and the strap and blocking lines. The member card shows "entre os nós da alma do pilar" (between the column web nodes).

Checks (NBR 14762:2010).

A column that passes is not a connection that passes

The engine checks the members of the column. The parts that join them, and web crippling of the chord, stay with the design. Check them separately, with the supplier or with your own calculation.

The path, in one line

Wall view → LSF card → Column → make-up, model, width, spacing → cursor over the stud (amber ghost) → click → column footer → Esc → calculate and read PB, PD and PM.

The example so far

• 1: lattice column, PL1-V6, in the front wall
• 400 mm: between chords
• 5: panels of 552 mm
• 8: plates, 1.25 mm