
August 30, 2019
Vibration Analysis for Steel Joists
RISAFloor v14 includes Steel Joist Vibration Analysis per SJI Technical Digest #5. For more information, check out the video below.
While members (beams and columns) follow conventions tied to their local axes, interpreting results for wall panels, plate elements, and design strips requires a slightly different perspective. These elements deal with both in-plane and out-of-plane behavior, and the sign conventions can change depending on the program and axis orientation. Overview Table of Sign Conventions Element Type Positive Moment (M) Shear (V) Axial (P) Notes Wall Panels – In-Plane Compression in positive local-y face Downward on right face Tension = Positive Applies to in-plane forces only Wall Panels – Out-of-Plane Compression on positive local-y face N/A N/A Defines “positive bending” convention Plates (RISA-3D) Positive Mx or My = Top surface in tension Shear follows right-hand rule Tension = Positive Local Z-axis defaults upward Plates (RISAFoundation) Positive Mz = Top surface in compression Shear follows right-hand rule Tension = Positive Local Z-axis defaults downward Design Strips / Support Lines Sagging = Positive (bottom fiber in tension) Downward on right face Tension = Positive Matches slab design workflows Wall Panels Wall panels report forces in both in-plane and out-of-plane directions. In-plane: Axial = Positive tension Shear = Positive when downward on the right face Out-of-plane: Positive bending = compression on the positive local-y…
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RISAFloor v14 includes Steel Joist Vibration Analysis per SJI Technical Digest #5. For more information, check out the video below.
RISAFloor v14 now includes floor vibration calculations per the 2nd Edition of AISC Design Guide #11. To select this code for your design, simply choose AISC DG 11 2nd Edition in the Beam Vibrations drop-down from the Codes tab within Global Model Settings.
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