Built Up (Tapered) vs Hot Rolled Frames

Most pre-engineered metal building frames are either made from built up members or hot rolled members. A brief description and comparison of the pros and cons of the two frames are provided below.

Built Up Sections Basics

• Fabricated by welding plates of varying thicknesses together to form a beam

• Typically seen in wide (60+ ft) buildings

• More expensive to manufacture, but significant weight/cost savings in wide buildings

Hot Rolled Section Basics

• Typically I beam sections for metal buildings

• Most common option for buildings less than 50-60 ft wide

• Less expensive to manufacture, but additional steel can be a big expense on wider buildings

Price

• Built up section have larger production costs

• Hot rolled sections are typically less expensive than built up sections for smaller buildings

• Built up member weight savings offsets the increased production cost at building widths of ~50-60 ft

  • Buildings wider than 60 ft are almost always more economical to make from built up sections

Design Optimization

For metal buildings, the load increases as you make your way up the column.

• Hot rolled members are uniformly sized throughout the column length

  • The bottom portion of the column is over-designed since it is carrying a much smaller load

• Built up members can be optimized to increase in thickness as the load increases as the building increases in height

  • Using tapered sections and the minimum required thicknesses for flanges and webs results in members designed near 100% capacity along the entire section

• Built up members are often preferred for buildings with integrated cranes because the web and flange thicknesses can be adjusted for crane loads

QA/QC

• Built up beams require quality assurance techniques on the welds, drilled holes and other connection details

  • Forces must be distributed through the connections from the flanges to the web

Corrosion

• Built up members are more prone to corrosion

  • Connections are more prone to corrosion than a solid piece

Availability

• Designers must ensure that a hot rolled section is locally available before finalizing the design

  • May require additional increase in cost if larger section is required due to availability

• Built up members can be made from plate which is one of the most readily available materials