How Sophisticated Testing and Engineering leads to cost effective light gauge steel trusses

A common misconception is that all light gauge steel roof trusses spanning the same distance and with the same loads use the same amount of steel. This is not true. Smart research and development in trusses and sophisticated software can provide reductions in steel usage of up to 50% compared to less efficient light gauge steel trusses.

The ENDUROCADD® design software has been developed over 20 years as a design tool for the proprietary BHP Steel / BlueScope Steel light gauge steel framing system which is now marketed as the ENDUROFRAME® building system.  Over this period the system has responded to changes in building construction, design standards and regulatory requirements.

Extensive testing on the performance of connections and entire roof truss assemblies as carried out at the BlueScope Steel NATA-accredited laboratory in western Sydney to develop values which are used in the ENDUROCADD® software.

Open	Open

The ENDUROCADD® software is used in over 10 countries overseas and here in Australia supporting a wide variety of manufacturers producing trusses for residential and light commercial applications.  Each year, this leads to a vast number truss shapes and types being designed and installed around the world. (in the order of 200,000 trusses p.a. with an estimated 2 million trusses over 20 years).  This very strong user base provides strong corroborating evidence that trusses satisfy the theoretical strength and serviceability criteria we have developed through testing and calculations.

The ENDUROCADD® software complies with the ABCB Protocol for Structural Software which requires independent verification by a third party to ensure that the calculations carried out by structural software packages comply with the Building Code of Australia and the relevant Australian design standards.  

A software package that complies with the ABCB Protocol for Structural Software ensures that buildings that fall within the scope of the protocol can be signed off by a Trained Software User, and not an engineer, saving time and money.

In Australia, the ENDUROCADD® software was used as a test case by the ABCB in drafting the requirements of the Protocol. A decade ago, we chose Swinburne University as the Compliance Certifier and were the first system to be certified. Subsequently several large timber truss manufacturers have had their software compliance certified. As of writing, the ENDUROCADD® software is the only light gauge steel software package that has been independently checked and confirmed to comply with the BCA and relevant Australian standards relating to cold formed steel design.

Currently, the ENDUROCADD® software is the only light gauge steel software package that has been independently checked and confirmed to comply with the BCA and relevant Australian standards relating to cold formed steel design.

The ENDUROCADD® software shows a complete design that is transparent, human readable and tests every load case defined in the loading standard which we believe to be unique amongst framing software packages.  The ENDUROCADD® software runs analysis and design for all members and connections which, in a typical truss, will have 32 primary load cases, 53 combination strength cases and 37 serviceability load cases so that all required load conditions are tested. This provides confidence that trusses are structurally sound.

All connections have been tested in accordance with the provisions of AS4600 at BlueScope’s NATA accredited laboratory and appropriate safety factors applied according to the variability and number of tests conducted.

The screw types are shown on the connections drawings produced by ENDUROCADD® specifically for the connections used in the particular job.  There are many connection options which include multiples of screws and various gusset plates to vary the connection capacity. The number of screws that need to be inserted in each truss chord-web connection is inkjet marked on the parts to avoid any confusion and chord-chord are generated by the ENDUROCADD® software which are used by assemblers to determine the connections to be used.  As there are about 2000 different connections we don’t produce a standard document for these, however all of the connections required for a specific job are generated in a summary sheet and provided to the truss fabricators. 

We believe the number of truss connections is the most of any light gauge steel framing system and reduces the chance that connections are the determining factor in the truss strength and performance which, in turn, increases the cost effectiveness of the truss system. It is always cheaper to to increase the capacity of a connection with a few screws than it is to increase the gauge used in the roof truss.

Boxing is inserted on the reverse side of the truss to the webs and is precision cut to length to strengthen the truss chord where it is required. The darker section demonstrates the sections of truss chords that are boxed. In many cases chord boxing does not need to extend along the entire length of the chord. This part is manufactured together with the truss and unlike in-plane trusses, the boxing can extend across multiple sections of chords and webs.

Boxing segments of chords and webs means that specific sections of the truss can be strengthened without requiring the gauge of all truss components to be increased. This can reduce the amount of steel used in trusses as thinner gauges can be used.

We also provide posters which go onto the factory wall which show the assembly details for roof trusses, and you can see more information on fabricating the ENDUROTRUSS® system (including the posters) at https://enduroframe.atlassian.net/wiki/spaces/IM/pages/24510800#ENDUROTRUSSRoofingSystemInstallationManual-6.6ENDUROTRUSS%C2%AEFramingSystemstiffeningandre-inforcement .

Images of the tests carried out in the BlueScope NATA accredited laboratory are below.Note the ENDUROTRUSS® installation manual provides good shots which clarify the truss construction which you can see at https://enduroframe.atlassian.net/wiki/spaces/IM/pages/24510800 .