For reasons that will become apparent in a later post, I need to rotate irregular polygons, defined by the coordinates of each corner, by a specified angle, and then split the resulting shape into horizontal trapezoidal layers. I have written an Excel User Defined Function (UDF) to perform this task, and incorporated it with some section properties functions. The spreadsheet (including full open source code) can be downloaded from Section Properties-Layers.
A summary of the functions provided in the spreadsheet is shown in the screenshot below:
The screenshot below shows coordinates defining the cross section of a precast bridge girder (Columns B,C), section properties calculated from coordinates (Column F), coordinates for the section rotated about the centroid by 30 degrees (Columns H, F), and section properties for the rotated shape calculated from the trapezoidal layers (Column K) and directly from coordinates (Column L):
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