April 20, 2011
Refining Area Load Distribution in RISA-3D
After solving a model with Member Area Loads, RISA-3D will automatically create Transient Basic Load Cases that allow the user to verify load distribution.
Powerful Tools Don’t Help If They’re Left Unused Many engineers evaluate analysis software based on core modeling and design checks. But once a demo is over, some of the most impactful features are the ones that quietly save time on real projects — especially mid-size jobs where efficiency matters most. These aren’t advanced edge-case tools. They’re everyday features that often go underused. Diaphragm Forces: See Load Paths Instead of Guessing Diaphragm force output is one of the most valuable — and least leveraged — parts of a full building model. Instead of relying on manual distribution or conservative assumptions, engineers can directly see how loads are flowing to vertical elements. For mid-size structures, this clarity can mean: Fewer overdesigned collectors More confidence in lateral load paths Faster review and revisions when layouts change Batch Results: Review Smarter, Not Longer Batch results allow engineers to review multiple load cases, members, or design checks in a single pass. Instead of hunting through individual reports, patterns become obvious quickly. On mid-size jobs, this speeds up: QA/QC reviews Iterative design changes Comparing “before and after” scenarios It’s not about skipping checks — it’s about seeing the full picture sooner. Design Iteration Speed Is the…
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After solving a model with Member Area Loads, RISA-3D will automatically create Transient Basic Load Cases that allow the user to verify load distribution.
RISA-3D will now check your model for errors by summing the reactions in your model and comparing them to the applied loads. This occurs for the global X, Y, and Z directions. If RISA identifies that the reactions do not equal the applied loads then the software will show a warning message to the...
V-Brace frames in RISA-3D seismic design have unbalanced forces shown on both the beams and braces. As brace frames displace under lateral loads, one brace will buckle and its force decreases while the other brace in tension will have an increase of force until it reaches yield.
When a model is solved that contains Member Area Loads, the program automatically attributes them to the applicable members within the defined area of the applied load. The load is attributed to the members as distributed loads that RISA-3D defines as Transient Loads.
RISA-3D now has the ability to define the seismic parameters Rho, Omega and SDS directly into load combinations. If you open the Basic Load Cases spreadsheet and click into the BLC column, the dialog offers the ability to add these values in to factor the load.
Applying seismic loads to structures with rigid diaphragms can be done automatically in RISA-3D. In the image below we have a structure that has rigid diaphragms and the seismic load has already been applied at each diaphragm level.
Continuous tiedown systems are used to help resist overturning forces generated by lateral loads, and can be estimated in RISA-3D using the hold-down database and the strap forces.
When you have a plate model for a slab or wall in RISA-3D, the Internal Force Summation Tool (IFST) is a very useful analysis tool to get exactly the forces that you want to design for. To use the tool, you must:
RISA-3D automatically considers the complex wind combinations required by ASCE 7 using the wind load generator and the load combination generator.
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