For photo-voltaic structures, we think about the solar panel as the main component. However, a suitable structural frame is required to provide a stable platform on which the unit can operate. STAAD.Pro structural analysis software offers designers with a system to design their support structure using tools like:

• Advanced modeling
• Section assignment
• Loads and techniques for load application

This article will focus on the second item, section assignment. To model your solar power structures, you can use STAAD to assign custom cold-formed (CF) and hot-rolled sections for analysis and design.

Cold-formed sections

STAAD.Pro is delivered with an extensive library of hot-rolled sections. It also provides a number of databases of cold-formed section profiles. However, one of the benefits of using cold-rolled profiles is that they are almost infinitely variable and can be manufactured to meet the specific requirements of your specific project.

Figure 1: Standard cold-formed sections from various material standards are available in STAAD's section database.

Some of the most common CF section types in the practicing engineer's world and covered in various material standards are as follows:

• Angle (with or without lips)
• Channel (with or without lips)
• Zee or zee purlin (with or without lips)
• Hat
• Tube (SHS and RHS)
• Pipe (CHS)

The section database manager enables proprietary dimensions to be added to the library of available configurations of the same type. All it takes is to unlock the Section Database Manager and add sections above and below with custom dimensions and maintain a similar STAAD name. Also, the physical properties like Area and Moment of Inertia are mandatory to be entered along with the cross-sectional dimensions. However, other properties like section modulus, the radius of gyration, etc., are calculated internally once the model is executed for analysis.

Figure 2: Section database manager in STAAD adds custom sections to the list of available sections.

So, how can you accommodate a custom profile? This is where the Section Wizard utility provided with STAAD.Pro comes in. The Section Builder module is more appropriate for determining the properties of built-up profiles, such as wide flange sections extended with additional profiles, including channels or angles. However, as the name implies, the FreeSketch module provides a method for defining a general profile. Please note that this does use the standard theory for calculating section properties.

Figure 3: The popular Section Wizard tool adds custom sections to the list of available sections.

Also, with user-defined table (UPT) sections, STAAD using AISI code can still design angles, channels, pipes, and tubes as cold-formed members in a straightforward method with a note in the output.

Hot-rolled sections

Ideally, hot-rolled sections are used for roof-mounted PV structures in medium to high rise buildings to resist higher wind load intensity. In such a case, STAAD.Pro has an extensive library of hot-rolled sections from various country material standards.

However, there might be an instance where custom sections or historical sections should be used to design the structure or check the structural integrity. But historical sections in the practicing engineer's world don't fall in the realm of sections available in various material standards.

Figure 4: Profile corner points user-defined table

Custom sections can be built by defining a profile polygon. The profile corner points along the perimeter of the section should be populated and then section properties can be computed. STAAD will populate this information, which will be useful to visualize the section for analysis and design.

The coordinates can be obtained from a CAD drawing or section wizard tool. Section Wizard files saved as user-provided table files can also be exported to STAAD. Custom sections can also be converted to equivalent sections and designed to an optimum degree.

In the final post of this series, we’ll explore the final tool that STAAD.Pro provides for PV mounting structures. The article will focus on loads and techniques for load application.