MAIN PORTAL FRAME

2 COLUMNS + 2 PITCHED RAFTERS (PORTAL) — FEALiTE2D

⬡ FRAME GEOMETRY

Column height H (m)

Column spacing L (m)

Roof rise f (m) — from the column tops to the ridge

Base connection

⬡ SECTIONS

Column section

Iy = 25,170 cm⁴ · A = 149.1 cm²

Rafter section

Iy = 23,130 cm⁴ · A = 84.5 cm²

Young's modulus E (N/mm²)

⬡ ROOF LOADS

Uniform distribuită Concentrată (pane)

Uniform load (kN/m, downwards)

Applied vertically, downwards, on both pitched rafters (per linear metre of rafter).

Horizontal wind force — left eaves (kN)

Applied horizontally at the top of the left-hand column. A positive value pushes the hall to the right (→); a negative one to the left.

Tool information

What this page computes

The calculator solves an industrial-hall portal frame — two columns and two inclined rafters forming a gable roof — by the finite-element method (the FEALiTE2D engine). It is the typical structural form of an industrial hall or a steel warehouse.

What is special about a portal frame

Unlike the frame with horizontal beams, here the rafters are inclined and meet at the ridge. This geometry introduces horizontal forces at the column bases (thrust) even under vertical load: the gable roof "pushes" the columns outward, and how this thrust is resisted depends on the base support.

The frame can be supported:

pinned at the base — the columns can rotate at the foundation; the base moment is zero, but the horizontal displacements and the thrust are larger
fixed at the base — the foundation carries moment; a stiffer frame, but more heavily loaded foundations

What the analysis returns

The model has five nodes (the two column bases, the two eaves corners, the ridge) and returns:

The moment, shear and axial force diagrams on the columns and rafters
The deflected shape of the frame
The reactions — including the horizontal thrust, essential for designing the foundations

Input data

Geometry — the span, the column height, the roof slope.
The sections of the columns and rafters — taken from the profile catalogue (with real \(I_y\) and \(A\), \(E = 210\,000\) N/mm²).
The base support type — pinned or fixed.
The loads — uniform on the rafters (snow, cladding) or point loads at nodes (from purlins).

Assumptions and limitations

A linear-elastic first-order analysis; for slender halls, second-order effects and frame buckling may govern and require a separate check.
A plane (2D) model: a single transverse frame; longitudinal bracing and diaphragm action are not included.
It does not treat the lateral instability of the rafters (lateral-torsional buckling) — see lateral-torsional buckling.
It gives the internal forces; the member checks are done separately.

Fixed-base frame (finite element) — a frame with horizontal beams, multiple storeys
Continuous beam (finite element) — for beams
Bending and compression (steel) — checking the columns
Lateral-torsional buckling (steel) — the stability of the inclined rafters