July 11, 2017

Base Plate Connection Design now Available

This video tutorial will show you how to design a base plate in RISAConnection for both gravity and lateral loads. You can automatically transfer your column end forces from RISAFloor or RISA-3D into RISAConnection.

Tags: New, RISAConnection, Base Plate

June 28, 2016 | Seismic, New, RISAConnection, News, Brace Connection, Integration

Seismic Brace Connection Integration with RISA-3D

RISAConnection version 6.0 has introduced the ability to design vertical brace connections per the seismic design provisions of the AISC 341-10 Seismic Design Manual. Now you can export Vertical Diagonal Brace Connections and Vertical Chevron Brace Connections from RISA-3D into RISAConnection as either Ordinary Concentric Braced Frames (OCBF) or Special Concentric Braced Frames (SCBF). See post for information on How to Model a Seismic Vertical Brace Connection in the stand alone version of RISAConnection. Link: Seismic Brace Connections now Available RISA-3D Input and Design: 1. First, you must create and apply a Seismic vertical brace Connection Rule to your member in RISA-3D. The application rules are the same as for non-seismic vertical braces. 2. You must also create and apply an appropriate Seismic Design Rule. For OCBF, select a “Minimal” Frame Ductility. For SCBF, select “High” Frame Ductility. 3. Solve the RISA-3D model. Note that you must solve for RISA-3D Seismic Detailing results. If your solution does not include Seismic Detailing results, you will not be able to export the correct brace axial forces into RISAConnection. 4. Solve the Connections within RISA-3D to see a summary of the connection design. 5. For details on the connection design, use the Director…

May 16, 2019 | RISA-3D, New, News, Analysis, Eccentricity

Pinned Beams in Semi-Rigid Diaphragms

When using semi-rigid diaphragms in a RISAFloor/RISA-3D model, it is possible to see negative moments at the ends of pinned beams as a result of the link between the semi-rigid diaphragm and the beam-column connection. In RISAFloor, semi-rigid diaphragms utilize internal rigid links to create a 12in by 12in “rigid zone” around the column location in order to spread the load from the column out to the diaphragm. This prevents the load from being applied to the diaphragm at just the single node (which is unrealistic) that represents the column to slab attachment. Although this assumption achieves a smooth load application between the column and the slab, it can result in “spikes” in member end forces that are unexpected if the member end falls within the “rigid zone”. Note: When developing semi-rigid diaphragms in RISAFloor/RISA-3D, a 12in by 12in footprint was chosen because it was assumed that most columns would fall within that region. Additionally, a specific footprint was chosen (rather than one determined by the explicit size of a column) which allows RISAFloor to continue with the design and optimization routines without having to re-iterate the mesh. When this situation arises, engineers can either determine that these spikes are…

October 9, 2013 | RISA-3D, New, Analysis

What is the Tau b Factor and how does it affect my analysis?

When solving a RISA-3D model with hot rolled steel members under the AISC 360-05 (13th Edition) or AISC 360-10 (14th Edition) codes you may find references to a factor called Tau_b. To understand what this factor is you should first be familiar with the Stiffness Adjustment in RISA-3D, then see the AISC 360-10 Specification, Section C2.3.2: “An additional factor, Tau_b, shall be applied to the flexural stiffnesses of all members whose flexural stiffnesses are considered to contribute to the stability of the structure” Link: Stiffness Adjustment in RISA-3D By applying this factor in addition to the 0.80 factor to flexural stiffness (EI) of the members the deflections for those members increase significantly. This code provision is only intended to be applied to members whose flexural stiffness contributes to the stability of the structure though, such as beams and columns within moment frames. The calculation of Tau_b is a function of the ratio of axial force in the member to its axial yield strength. For members where this ratio is less than 0.5 (members which are less than 50% stressed axially) the value of Tau_b is 1.0, which means that is has no impact on the member stiffness. For members which…