In ETABS non-uniform loads can be assigned to shell elements via Assign > Shell Loads > Non-uniform. This option allows the user to assign non-uniform loads in any direction based on global coordinates.

As an example below, assume we want to assign a triangular load to a 24 ft. long and 12ft high wall and located in the X-Z plane.

The load will have magnitude of 1000lb/ft at the base and zero at top of the wall.

The values for A, and B are zero since the load will not change in the X or Y directions. The equations to solve are:

Cz + D = 1000 at z = 0 ft
Cz + D = 0 at z = 12 ft

Solving the system above: D = 1000 and C = -83.33

After running the analysis, we can check reactions using basic statics to make sure the load has been correctly applied.

Total load = 1000*24*12/2=144,000 lbs or 144 kips

Reaction at top of the wall =144*4/12=48 kips or 24 kips at each support
Reaction at bottom of the wall=144*8/12= 96 kips or 48kips at each support

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