Summary
Highlights
The final step involves mirroring the generated purlins to the other side of the structure. All purlins are selected by section, and a vertical mirror command is applied using the midpoint of the structure as the mirroring axis. This automatically generates all the purlins for the entire project with the correct orientation. A final structural verification is performed to ensure no issues were introduced.
After inputting the purlins, a quick structural verification is performed to check for any errors. The video then explains that purlins will be modeled on a single portal frame first, then generated for all frames. A vertical mirror will be used to generate purlins for the other side of the structure. The active frame is isolated and viewed in 2D (XZ plane) with profiles deactivated.
The video recalls the process of calculating the spacing between purlins. A small safety distance (20-30 cm) is left at each end of the rafter. The remaining length is then divided into equal segments for purlin placement. The video demonstrates using dimension tools and a calculator to determine the effective length (9.47m) between the initial safety distances. This length is then divided to determine optimal spacing, for example, 1.58m for 6 purlin spaces.
To accurately place purlins, the nodes need to be activated. The rafter is divided using the 'divide bar by distance' tool. First, a node is created at 0.30m from one end (respecting the arrow direction for the offset). The same is done on the other end. Then, additional nodes are created based on the calculated purlin spacing (1.58m), incrementally adding this distance to the previous node's position. This process can be automated using translation commands.
The same translation tool, specifically 'translation with stretching', is used to generate the purlins. First, the desired purlin section (IPE 100) is selected. Then, all the previously created nodes on the single rafter are selected. These nodes are then translated with stretching along the Y-axis by a distance of 6m, four times, to generate the purlins on all four portal frames. This automatically creates the purlin elements.
A crucial step is to ensure the purlins are perpendicular to the rafters. While initially created with their Z-axis aligned with the global Z-axis, the rafter has a slope. The video demonstrates how to calculate the rafter's angle with the horizontal (found to be 6.8 degrees) using the dimension tools in the software. All purlins are then selected, and their gamma angle (rotation) is set to -6.8 degrees to achieve the correct perpendicular orientation relative to the rafter.