October 26, 2018
What’s New in the NBC 2015?
The 2015 NBC compliant codes have been implemented into RISA-3D v17.0, RISAFloor v13.0 and RISAFoundation V.11.0!
Welcome to a high-level walkthrough of dynamic analysis in RISA-3D! This guide introduces essential aspects of modeling dynamics, focusing on natural frequencies, mode shapes, and the impact of dynamic behavior on structural integrity. The Dynamics Scenario Imagine we’re tasked with evaluating the stability of a cantilevered pedestrian bridge that spans over a city street. The bridge is connected to a building on one side and features decorative panels and a lightweight canopy. The concern? Wind gusts and foot traffic could cause the bridge to vibrate. Our goal is to understand its dynamic properties—natural frequencies and mode shapes—and assess whether it can handle these dynamic forces without compromising structural stability. We start by setting up dynamic mass for each load case: Canopy Load: Applied uniformly along the length of the bridge to account for wind effects. Pedestrian Load: Simulated at intervals along the span to reflect walking traffic. Decorative Panels: Modeled with specific weights on each side. Once mass and stiffness are set, RISA-3D enables us to simulate how the structure behaves dynamically, revealing which parts might be sensitive to specific frequencies or forces. Running the Eigensolution Analysis In RISA-3D, we use an eigensolution to identify: Natural Frequencies (intrinsic vibration rates…
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The 2015 NBC compliant codes have been implemented into RISA-3D v17.0, RISAFloor v13.0 and RISAFoundation V.11.0!
The 2016 edition of ASCE Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16) is now available in RISA-3D v17.0, RISAFloor v13.0, and RISAFoundation v11.0!
Eurocode lateral torsional buckling capacity is calculated per equations in Annex F in the ENV 1993-1-1:1992. This calculation uses variables C1, C2 and C3. Since there is no generic formula in the Eurocode to calculate the moment gradient factor, C1, RISA will use the widely accepted López, Yong...
With the initial implementation of wood wall design in RISA-3D, the wall aspect ratio was calculated as the full height of the wall divided by the width of the region.This was intended to accommodate balloon framed multi-story walls that were drawn as one continuous wall stack. With recent...
With the recent release of RISA-3D v17 the program now offers the user the option to use Chord Straps between floors of a wood shear wall building in lieu of using hold downs. Chord Straps are a great option for transferring tension load between floors of a multi-floor building and can be installed...
RISA-3D v17.0 now has the ability to model partial fixity member end releases. Partial fixity end releases can be utilized in RISA to model the behavior of a partially restrained or semi-rigid connection that cannot be idealized as fully fixed or pinned. Partially restrained connections are common...
The new AWC NDS 2018 code has been implemented into RISA-3D v17.0 and RISAFloor v13.0. To select this code for your design, simply choose this code from the Codes tab within Model Settings.
RISA-3D v15 includes "analysis offsets" which moves the centroid of the member for analysis allowing for flexibility in how members are designed. Let's use a WT brace to demonstrate how this feature can be utilized. When you model a WT brace it exists at the member centroid, which means that no...
In a previous article we discussed how the Analysis Offsets feature in RISA-3D works and how it can be used to model members at top of steel. In this article, we will discuss some specific situations and how the results change with the analysis offset set as top of member (local -y axis).
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