RISA | Tips & Tricks | RISA-3D (16)

November 19, 2024

How to Run a Basic Dynamic Eigensolution in RISA-3D?

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…

September 27, 2018

Using Analysis Offsets in RISA-3D

Have you ever wondered what the Analysis Offset feature does? Let’s take a look at how this feature can be used to model members at top of steel.

September 13, 2018

Steel Design per AISC 15th Edition Steel Manual now Available

The new AISC 360-16 15th Edition changes have been implemented into RISA-3D v17.0 and RISAFloor v13.0.

August 23, 2018

P-Delta Instability with Gravity Only Loads

“Why am I receiving a P-Delta instability error when I run my DL + LL load combination? I don’t see this error when I run my lateral load only combination.”

August 16, 2018

Modeling Cables in RISA-3D

One of the support questions we get most often is, “How can I model a cable element in RISA-3D?” Cables that are straight and experience only axial loading can be easily modeled. When modeling structures with cables (such as guyed structures) the cables can be modeled as tension only and doing so...

August 2, 2018

Governing Load Combinations for Shear in Concrete Columns

For concrete column members, the load combination producing the maximum shear code check is reported in the Detail Report and corresponding Results spreadsheet. Since concrete is evaluated based on a batch solution, this can be useful when shear governs the design.

July 19, 2018

Designing Multi-Material Models for ASD & LRFD with one solution

RISA-3D includes material specific checkboxes on the Design tab of the Load Combinations spreadsheet that allow you to define the load combinations that shall be checked for members of different materials.

July 12, 2018

Plate Elements Available in Material Takeoff

RISA-3D now includes plate elements in the Material Takeoff.

June 28, 2018

A Deeper Understanding of Deflection and Member Deflection Ratios

There are many different types deflection values calculated by RISA-3D. Let’s take a deeper dive into each.

June 21, 2018

Beam Deflection Ratio Options

RISA-3D v16.0.4 introduces an enhancement that will allow for more control over the beam deflection ratio through Deflection Ratio Options. As part of the member properties, you can now designate the ends of single and multi-span beams as a cantilever or supported. This will determine whether the...

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