In RISA-3D, moving load results are generated by simulating a load that moves across a structure in defined increments. These loads are often used for designing bridges, cranes, or other structures where dynamic loads shift across the structure over time. Moving loads are complex because they involve numerous load steps, each with its own set of internal forces and deflections.
Due to the large number of iterations, RISA-3D envelopes moving load results, meaning only the maximum and minimum values for each member or section are shown. This helps simplify the output and avoids an overwhelming volume of data. However, to view individual load steps for detailed analysis, a different approach must be used.
Viewing and Creating Moving Load Steps in Load Combinations
To review moving load results such as deflections and force diagrams step by step in RISA-3D, you need to generate load combinations that reflect individual moving load steps. Here’s how you can view and create these steps:
- Identify the Desired Moving Load Step: First, you must determine which moving load step you want to investigate in detail. This can be done by reviewing the envelope results and noting the governing load combination and step number in the "LC" column. For instance, "LC 3-2" refers to Load Combination 3, Step 2.
- Generate Static Point Loads: To view results for specific steps, you can convert the moving load into static point loads. This is done using the Point Loads from Moving Load feature:
- Click on the Point Moving icon in the Home tab.
- Select the Basic Load Case where the static point loads should be added.
- Choose the Moving Load or Load Combination from which the point loads will be generated.
- Select the Step you wish to investigate and click Apply.
- Solve the New Load Combination: Once the static point loads are created, you can form a new load combination that includes these static loads and solve it to see the detailed results (member forces, deflections, etc.) at that specific load step.
Other Applications When this is Useful
Moving load step results are not just useful for reviewing forces and deflections—they play a critical role in integrating with other tools and software. Here’s how:
- Integration with RISAConnection: RISA-3D automatically envelopes moving load results, which presents a challenge when integrating with RISAConnection. Since RISAConnection requires discrete results for each load combination, you will need to create a load combination that is a discrete point of the moving load to allow for integration.
- View Step Deflections: While moving loads typically show enveloped results, you can use the point load method outlined above to display deflections for specific steps. This allows you to dive deeper into the behavior of the structure at any given step, which is useful for more detailed analysis.
Have more questions about moving loads in RISA-3D? Contact our support team or explore our Help File for further assistance.