October 30, 2020

Exclude Results based on Selection in RISAFloor and RISAFoundation

New to RISAFloor and RISAFoundation is the ability to exclude results by selection. Excluding results from your model is useful when there are certain elements whose results aren’t of interest to you. Removing this clutter from the results will enable you to concentrate on the elements you are most interested in.

Tags: RISAFloor, Results, RISAFoundation, New

June 1, 2011 | RISAFloor, New, Wood, Unbraced Lengths

How to Assign a Wood Roof Member’s Unbraced Length in RISAFloor

In RISAFloor, the beams are susceptible to two forms of buckling; Euler buckling and lateral-torsional buckling. The unbraced length is determined in RISAFloor using the deck properties and framing. Le2 = Lbyy → Defaults to Segment Le1= Lbzz Le-bend-Top → Defined in Deck Properties Le-bend-Bot The rafter is susceptible to two forms of buckling. The first is Euler buckling, which is a column-type buckling about the rafter’s y-axis. The blocking typically braces against this so the Le2 value should be set to the spacing of the blocking (typically 4 feet). It may not be appropriate to consider the decking as bracing against Euler buckling because of the depth of the rafter relative to the depth of the sheathing nail. Le2 is defined in the Beams spreadsheet. The second form of buckling is lateral-torsional buckling, which is a beam-type buckling of the top flange of the rafter. The deck typically braces against this and this value is automatically set based on the Unbraced Length property of the Deck. The deck is nailed to the rafter every 6-feet so that would be a good value to use as the Unbraced Length of the deck. Incidentally, the blocking is also considered (by default)…

June 3, 2025 | Featured, RISA-3D, New, Instability

The Ultimate Guide to Instability Warnings in RISA-3D

Modeling instability can be one of the most frustrating errors to troubleshoot in structural software. Whether you're a new user or a seasoned pro, instability warnings in RISA-3D can bring your workflow to a halt if not properly diagnosed and resolved. This master article brings together all the most common types of instability, provides guidance on identifying the issue, and links to existing resources that walk you through the resolution process. To supplement this written guide, check out the Troubleshooting Mini Tutorial in the RISA Learning Center (RLC). Common Instability Types and How to Resolve Them Below are the five most common causes of instability in a RISA-3D model, along with diagnosis tips and links to deeper resources: 1. Member End Releases at Boundary Conditions Symptom: Instability warnings at the base of columns or ends of beams. Diagnosis: Look for members where moment releases are applied directly at nodes with pinned or fixed boundary conditions. Why It’s a Problem: This removes all rotational fixity at the connection, creating a hinge with no resistance to rotation. Resolution Resource: How do I avoid instability warnings in a RISA-3D model? 2. Pinned End Releases at Every Member Framing into a Single Node Symptom:…

March 26, 2021 | Seismic, RISA-3D, New, Steel, BRBF

Buckling Restrained Braced (BRB) Frames in RISA-3D

The ability to design buckling restrained braced frames has been added to RISA-3D when you integrate your model from RISAFloor. In collaboration with CoreBrace, this new feature came as part of the release of RISA-3D v19.0.0 and RISAFloor v15.0.0. The purpose of buckling restrained braced frames is such that the brace is used as a fuse to dissipate energy during a seismic event. The buckling restrained brace is composed of a steel core and a concrete case. These members are advantageous because the concrete case increases the buckling capacity of the steel core. This enables a more efficient and economical design. The integration of RISAFloor and RISA-3D fits well with the split gravity and lateral design requirements for the BRBF system. The framing members such as columns and beams can be designed in RISAFloor under gravity loads to meet the requirements of them resisting gravity loads without BRB braces. After the model is directed to RISA-3D, users can add BRB braces to perform the lateral load design for the whole system. The buckling restrained braces can be accessed and assigned through the Hot Rolled Steel shape database by selecting the CoreBrace from the Database dropdown menu and selecting BRB as…