Loads

All loads live in a single load case and act simultaneously. To compare scenarios, save each one as a project file or share link.

Sign convention in one line

Global x points right, global z points down. A positive Fz or fz in global coordinates is therefore a downward, gravity-type load; a positive moment My is counter-clockwise on screen. Details in Coordinate system & sign conventions.

Nodal loads

Loads tab → Add nodal load, or click a node → Add load. Choose Force/Moment:

Field	Meaning	Unit
Fx	horizontal force (+ → right)	force unit
Fz	vertical force (+ → down)	force unit
My	moment about y	moment unit

Components are always in the global coordinate system. A live arrow preview in the dialog shows the resulting direction and magnitude. Several nodal loads on one node are allowed and simply add up.

Prescribed displacements (support settlements)

In the same dialog choose Prescribed displacement (or click a supported node → Prescribe displacement). Fields switch to:

Field	Meaning	Unit
Dx	imposed horizontal displacement	length unit
Dz	imposed vertical displacement (+ → down)	length unit
Ry	imposed rotation	rad

A value can only be entered for a DOF that is restrained at that node—only supports can be moved. Each node can have one prescribed displacement; edit it rather than adding a second. In a statically determinate structure a settlement produces displacements but no internal forces; in an indeterminate one it produces both.

Element loads

Loads tab → Add element load, or click an element → Add load. Pick the Load type; the dialog shows a live preview of the load on the element.

Uniformly distributed load

Field	Meaning	Unit
fx	load per length along x	force / length
fz	load per length along z	force / length
LCS	tick to interpret fx, fz in the element's local axes	–

The most common case is a vertical gravity load: fz > 0, LCS off. For an inclined member, a load perpendicular to the member (e.g. wind on a rafter) is fz with LCS on; a vertical load per metre of horizontal projection is not available directly—convert it to per metre of member length first.

Trapezoidal load

Field	Meaning
f1x, f1z	intensity at the start node
f2x, f2z	intensity at the end node

Intensities vary linearly between the ends. A triangular load is simply f1z = 0. Trapezoidal loads are always in the element's local system (the LCS box is locked on); for horizontal elements local and global z coincide, so this only matters for inclined members.

Concentrated load

A point force or moment somewhere along an element—no extra node needed.

Field	Meaning
Fx, Fz, My	force / moment components
Load position from start node	distance from the initial node, 0 ≤ a ≤ L
LCS	components in local axes

The shear diagram jumps by Fz and the moment diagram gets a kink at the load position; the moment value there is labelled automatically.

Temperature load

Field	Meaning
ΔTc – axial temperature change	uniform change over the whole section → elongation $\alpha\,\Delta T_c\,L$
ΔTb − ΔTt – bottom minus top fibre	temperature difference across the depth → curvature $\alpha\,(\Delta T_b - \Delta T_t)/h$

Temperature loads use the material's α and the section height h. A positive ΔTb − ΔTt (bottom warmer) makes the element hog (bend upward). In a statically determinate structure temperature causes only displacements; restraint (fixed ends, continuity, redundant members) turns it into internal forces.

Editing and removing loads

• Loads appear as chips in the Nodes / Elements tables and as rows in the Loads tab, where components (and the LCS flag) are edited in place.
• Double-click a load in the viewer, or click it and choose Edit load, to open the edit dialog.
• Select a load and press Delete, or use the trash icon.
• Loads attached to a node or element are deleted with it, and are copied with it when you copy & paste.

What is not available

• Load cases and combinations — one case only.
• Self-weight — enter it as a UDL: $f_z = \rho\,g\,A$ (e.g. IPE 200: 7850 × 9.81 × 0.00285 ≈ 0.22 kN/m).
• Global-coordinate trapezoidal loads on inclined members.