When HRS is needed alongside LGS
The typical situations
Section titled “The typical situations”Long spans
Section titled “Long spans”A truss solves a lot, but there is a point at which the structural depth or the number of members is no longer economic. Manufacturers’ data also sets limits: on the usual machines, for example, the clear span of a truss goes to a defined size.
Concentrated loads
Section titled “Concentrated loads”A large force delivered at one point: a column from above, a plant item, a transfer member. A thin-walled section would only carry that boxed or with many members. Built-up sections.
Large transfer openings
Section titled “Large transfer openings”A wide window, a garage door, an open façade. The span of the lintel and the load above it together can settle the question.
An open ground floor
Section titled “An open ground floor”Where the walls of the upper storeys do not continue down and have to be transferred.
A space without intermediate support
Section titled “A space without intermediate support”Hall-like spaces where the internal columns have to go.
What decides
Section titled “What decides”Member count and erection time
Section titled “Member count and erection time”If the thin-walled solution needs many members and many screws, that shows in labour hours.
Structural depth
Section titled “Structural depth”Where the available depth is tight, a more compact section is better.
A thick section can be protected with a coating; for a thin-walled one another route has to be chosen. Fire design.
Simplicity of the connections
Section titled “Simplicity of the connections”A connection receiving a large force is simpler to solve with thick plate.
A mixed structure is not a compromise
Section titled “A mixed structure is not a compromise”In a well-designed building it is natural for the main members to be hot-rolled and the infill structure thin-walled. Each material then works where it is best.
What to watch: the junction. Different material thicknesses, different fixing methods, different tolerances. Where steel meets concrete · Welded and bolted connections.
The point
Section titled “The point”Switching is not a failure of the technology but the result of the design. A good structure changes material where the other solution becomes cheaper.