Tutorial 2 of 7 · Beginner · about 20 minutes

Loads and load combinations

This tutorial adds the loads of a real building to the frame of Your first frame: dead, live, roof snow and wind load cases, member, area and point loads, wind and snow generated to ASCE 7-22, and the LRFD and ASD load combinations.

1. Create the load cases #

On the Loads tab, click Load cases. Every case has a name and a kind; the kind tells ILX Structures which load factors apply to it when it makes the combinations.

Pick the case you are about to load in the active case selector before you apply a load: new loads go to that case.

2. Apply member loads #

1. Select the Level 2 beams and click Distributed load.
2. Enter a uniform load, or a load that varies from one end to the other, with the start and end distances along the member if it covers only part of it. Pick the direction (gravity, or along a local or global axis) and the load case.
3. For a single load on a member, use Point load on member with its distance from the start.

3. Apply area loads #

Floor and roof loads are easier as pressures than as member loads:

1. Click Area load.
2. Pick the panel outline (the beams around a bay) or the plates of a slab, and enter the pressure in pounds per square foot, for example 50 psf of live load in case L.
3. ILX Structures spreads the pressure to the supporting beams by their tributary areas. The arrows in the 3D view show the result.

4. Point loads at nodes #

Nodal load applies forces and moments in any direction to the selected nodes, for example a column load from above or an equipment reaction.

5. Generate wind loads to ASCE 7-22 #

1. Click Wind / Snow / Seismic generators and open the Wind tab.
2. Enter the basic wind speed, the risk category, the exposure, the topographic and directionality factors, the enclosure and the building dimensions.
3. Pick the load case W and the direction, and click Generate. The story forces of the main wind force resisting system are applied at each level and listed in the Loads table.

6. Generate snow loads, with drifts #

1. In the same window, open the Snow tab.
2. Enter the ground snow load, the exposure and thermal conditions, the roof slope and surface, and the roof members or plan area.
3. Generate the balanced roof snow in case S. Where a lower roof meets a taller part, add the drift: ILX Structures works out its height and width from the ASCE 7-22 rules and applies it as a load that varies along the members.

7. Make the load combinations #

1. Click Generate ASCE 7-22 LRFD. ILX Structures makes the strength combinations of ASCE 7-22 from the kinds of your load cases, so a model without snow gets no snow combinations.
2. For serviceability or allowable stress design, click Generate ASCE 7-22 ASD as well.
3. Open Combinations to review them: every factor is shown and can be edited, and you can add your own.

8. Run and compare #

Run the analysis, then pick a combination, or the envelope of all combinations, in the result case selector on the Results tab. The envelope shows the largest and smallest value of every result over all the combinations, which is what the member design uses.

Tips #

• Pattern live loading places live load on alternate bays to find the worst moments in continuous beams.
• The Loads table lists every load of every case; edit values there directly.
• Turn the Loads display on or off on the View tab to keep the 3D view readable.

Screens in the app may differ slightly from the words here as the app gains features; the steps stay the same. Questions: services@ilxstudio.com.