Question
How does the "View by Max" option function for moving load cases? The results from this option differ from the concurrent forces obtained when exporting the beam force table to Excel for moving loads, whereas they match accurately for static load cases.
Answer
First we will start with how the results are displayed for moving load cases
The software provides three viewing options for each moving load cases i.e. "Max," "Min," and "All."
- "Max" displays the results corresponding to the vehicle position that produces the maximum response in a given element. If all elements are selected, it determines the maximum response for each individually. However, the vehicle position that leads to the maximum result may differ across elements.
- "Min" functions similarly but identifies the vehicle position that generates the minimum response in the element.
- "All" presents the absolute maximum values obtained from both the "Max" and "Min" cases for the element.
In the Beam Force table, when reviewing forces for the Moving Load Max case, the table displays the maximum member forces for all six components: axial force, shear forces (Y and Z directions), bending moments (Y and Z directions), and torsion. These maximum force values may correspond to different vehicle positions for each component .To understand this let us take simple example
Consider a simply supported beam as an example:
Here, we can see that the forces vary depending on the vehicle's position, as illustrated below
- When a vehicle is positioned at the midspan, it generates the maximum bending moment.
- When the vehicle is near the support, it results in the maximum shear force.
Since these two maximum forces are produced by different vehicle positions, they do not occur simultaneously.
However, when extracting the beam force table results for the maximum case, both the member forces appear in the data, despite being from different vehicle positions. This leads to an incorrect interpretation of concurrent forces.
On the other hand, using the "View by Max" option works differently. It identifies the vehicle position that generates the maximum member force for the selected element and then calculates the corresponding members forces at that position. This explains why results from Excel do not match those from the "View by Max" option—because the vehicle positions differ.
However, in the absence of moving loads (i.e., when all loads are static), the issue does not arise, as there is only one load position. In such cases, the results from the Excel export match those obtained using the "View by Max" option.