March 3, 2020

How to Review Your Batch and Envelope Results

RISA-3D provides users a variety of solution options, allowing results to be catered to specific project needs. In many situations it is beneficial to be able to view both the envelope and batch results for a model without having to run two separate solutions. An example of this would be when you want to optimize the member for the maximum forces, but also to be able to further investigate the detail report for a load combination that controls a specific limit state.

When the 'Envelope (Only) of Marked Combinations' option is selected for a model that contains multiple load combinations, the results are enveloped to show only the minimum and maximum results. If the 'Batch Solution of Marked Combinations' option is selected with the Include an Envelope with the Batch checkbox not checked, the results will be displayed for each load combination.

However, with the 'Batch Solution of Marked Combinations' option selected and the 'Include an Envelope with the Batch' selection checked, an envelope and batch solution will both be available.

Once you have this option selected, click Solve. When the model completes the analysis, your results will be available in the Results toolbar.

Toggling between 'Env' and 'Batch' options on the Results toolbar will determine if the spreadsheets for the enveloped or batched results will open, respectively.

Alternatively, results spreadsheets can be accessed by navigating to the Results tab on the Ribbon toolbar.

You also have the option to display Envelope node reactions and node reactions by load combination graphically. You can do this by navigating to the View tab on the Ribbon toolbar and select Results under the View Settings.

In the dialog that appears, you can toggle between the option to Display Results for Load Combination or Envelope. When Envelope is selected, the controlling maximum and minimum reactions for all solved combinations will be shown graphically.

From that same dialog, you may also view member results graphically by selecting the Members tab. You still have the option here to toggle between Display Results for Envelope or Load Combination.

Tags: RISA-3D, Results, New

April 18, 2011 | RISA-3D, Loads, New

Using Sum of Reactions in RISA-3D

RISA-3D will now check your model for errors by summing the reactions in your model and comparing them to the applied loads. This occurs for the global X, Y, and Z directions. If RISA identifies that the reactions do not equal the applied loads then the software will show a warning message to the user. There are three main reasons why this might happen: You have used a Fixed call out in the Boundary Conditions spreadsheet: There are instabilities in your model, causing locked joints: These locked joints may have an actual reaction coming out, but because the program was forced to lock it there is no calculation of this reaction. Fix the instabilities and the message will likely go away. Areas of high rigidity simulating boundary conditions (sometimes referred to as ghost reactions): If you have an area of your model that has a concentrated amount of very stiff elements and/or single elements that have very high stiffness, then these areas may approach the stiffness of a boundary condition and erroneously take load out of your model. Common reasons why this might happen: Setting the E and I values for your Material or Section Set overly high. A rule…

January 15, 2015 | RISA-3D, Plates, New

Approximate Guidelines for Plate Meshing

It is important to submesh plate elements in your model in order to obtain the most accurate results. However, many users wonder what the approximate guidelines for plate dimensions are acceptable. The l/w ratio ≤ 9.0 is the suggested ratio to follow for the length to width relationship. When the plate gets too long and skinny and is above this ratio you get gradual degradation of your plate model. From experience and from plate modeling references a t/w ratio ≤ 3.0 typically gives adequate results. Similar to the l/w ratio, any value above this ratio may affect the accuracy of your results. When the thickness of a plate element becomes too deep, the behavior of the plate and applied load will be more similar to a deep beam. The distribution of strains across depth of the cross section will be nonlinear and significant amount of the load is carried to the supports by drag struts: This is not desirable behavior with plate elements. As the thickness increases beyond the recommended ratios mentioned previously, you may want to consider modeling solid elements in RISA-3D instead. These approximate guidelines are only suggestions based on RISA’s internal testing and plate modeling references. Plate…

May 24, 2010 | RISA-3D, RISA-2D, New, Analysis, Eccentricity

Define a Beam Eccentricity in RISA-3D

When you have a deep column, it is necessary to model the beam so that it connects to the face of the column. This results in an eccentricity at the joint. RISA-3D offers two ways to model this eccentricity. Open the Members Spreadsheet and go to the Advanced tab. There are two options labeled I Offset and J Offset. These represent the offset at the start (I) and end (J) of the member, respectively. You may also specify the I Offset and J Offset by first selecting the beam, and modifying the Additional Properties section of the Properties Grid. For the beam member you can either enter the exact value of the member offset (i.e. half the depth of the column) or you can enter the column member number. If you enter the column member number the program will automatically calculate the offset assuming half the column depth. This feature is very useful because it will automatically update the offset value when you change the column size. Please note that using the offset feature will reduce the total length of your beam by the offset amounts which will affect your design code check calculation. For example, in a portal frame…