November 15, 2017

Beam Skip Loading now Available

Basic Description

Pattern based skip loading has recently been added into RISAFloor beam design. This can be turned on or off using the checkbox in the Solution tab of the (Global) Model Settings shown below.

This new feature applies to continuous beams that span over multiple supports. The various types of live loading will be included or excluded per span in various patterns in an effort to produce the worst case shear, moment and reactions.

This complies with the “Partial Loading” requirements of ASCE 7-10/16 Section 4.3.3.

Load Patterns Utilized

The various live load patterns used for skip loading are shown in the images / patterns shown below.

Pattern A: Full Load on Beam

Pattern B: Intended to produce the maximum positive moments for center span (and every other odd span)

Pattern C: Intended to produce the maximum negative moment for cantilevers and/or maximum positive moment on the off-center span beams (and ever other even span beam).

Pattern D: Two adjacent bays loaded with one bay skipped in between. This is intended to produce the maximum reaction for the first interior supports.

Pattern E: Two adjacent bays loaded with one bay skipped in between. This is intended to produce the maximum reaction for the supports that don’t get covered by pattern d.

Controlling the Load Diagrams in the Detail Report

When viewing the detail report for a beam that is subject to skip loading, the report may be manipulated to show you exactly what loading was used for each “Load Pattern”. This is only available when viewing a live load category where skip loading is applicable (Live Load, Live Load Special, Roof Live Load, Snow Load, and Rain Load). It is NOT available for the display of Load Combinations, only Load Categories.

Merely click on the Patterns drop down menu to change which load patterns get displayed.

This drop down menu will affect the displayed load, shear, moment and deflection diagrams. It does NOT affect the summary code checks which are based on all the various load cases.

The displayed loads, shears, moments and deflections will update based on the pattern selected.

Detail Report Summary

The member detail report has a summary for beam identifying which pattern controlled the calculations of the reported beam results. This includes the bending check, the shear check, the deflection check and the maximum reactions at the starting and ending supports for the beam.

Analysis

Multi-span beams are included in the analysis of the overall floor solution with their full loading (case a). However, for their individual design results, the program uses a separate internal beam solver to automatically check the various load patterns which may produce a maximum moment, shear or reaction for the beam.

In the images shown in this article, the supports are shown as pinned. This is to represent a rigid vertical column support with no rotational stiffness. In the actual analysis, supports are viewed as springs based on actual column or girder stiffness.

Tags: RISAFloor ES, Loads, RISAFloor, New, Skip Loading

June 17, 2016 | Seismic, New, RISAConnection

Why Do Seismic Brace Story Forces Change My Existing Code Checks?

It is possible for seismic (OCBF or SCBF) vertical braced connections to have some limit state code checks lower than those for the same non-seismic connection. This is due to the assumptions that RISAConnection makes when calculating the axial load in the beam. Non-seismic vertical brace connections only have a single beam axial load input value. Because seismic vertical brace connections require separate frame analyses of the various possible load directions, it is not appropriate to use a single input brace axial load for all load direction cases. Doing so could cause un-conservative results. Therefore, RISAConnection calculates the beam axial load for each loading direction case. Story Force and Beam Axial Force Calculation The beam axial load calculation is done for each applicable loading direction case. To see the details of these calculations, please see the Seismic Load Distribution on the new Seismic tab of the results report. The procedure is based on that used in example 5.3.5 of the AISC Seismic Design Manual. It is determined using simple statics and the following assumption: The input connection is mirrored on the other side of the bay with an equal and opposite braced connection. Assuming this assumption, the story force and…

December 15, 2020 | RISA-3D, RISAFloor, New, Cold Formed Steel

WEBINAR: Design of Cold-Formed Steel Buildings in RISA

More and more, commercial buildings are being designed as combined-use structures that handle everything from parking and retail, to apartments and other living spaces. With these requirements, structural engineers are asked to provide a safe, strong and non-combustible framing system that can also achieve the desired overall building height. Combining non-combustible materials such as cold-formed steel with masonry and hot-rolled steel results in higher building heights for these structures at an economical price. The RISA Building Suite now includes robust features aimed at designing these building types that rely heavily on cold-formed steel. In this webinar, attendees will: Understand the benefits and efficiencies of using cold-formed steel for multi-story buildings Learn to layout a multi-story building utilizing cold-formed steel walls, hot rolled steel framing and masonry walls using RISAFloor. Learn to design cold-formed steel wall panels for gravity and shear loading according to appropriate building codes with RISA-3D. To register, click the button below: Register Tags:…

October 3, 2017 | New, RISAConnection, Integration

Detach an Integrated RISAConnection Model

RISAFloor, RISA-3D, and Revit can export connection rule and loading information to streamline the design process for a project with numerous connections. This process helps to quickly create connections with the member shape, geometry, and loading information from the original program. However, there may be times where you want to change some of the exported information. This is now available! To take full control of your RISAConnection model, simply click on the Detach button on the Home tab of the ribbon toolbar: Once you click this, RISAConnection will present you with the following message to warn you that this will break connection with the original program (RISAFloor, RISA-3D, or Revit). Please note that you cannot re-attach a model once it is detached. After it is detached, you now have full control over all of the inputs so you can fully customize the connections in your model!…