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Prolyte Campus: Truss loading in theory and practice01/08/2017
German event technology magazine Production Partner wrote an interesting article about Prolyte Campus events. "Truss loading in theory and practice" is the title of a Prolye Campus seminar offered by Truss manufacturer Prolyte at the location of its central warehouse in Emsdetten.
Prolyte Campus Seminar
Starting in early 2011 with the learning initiative “Prolyte Campus”, Prolyte Group has been supporting users at various international seminars, dealing with topics such as rigging, handling of trusses, hoists and stage constructions ever since.
Dipl.-Ing. Matthias Moeller, Senior Technical Advisor at Prolyte, chairman of the DTHG committee for rigging and flying structures and representative of the IGVW, lectures several seminars for Prolyte, in this case: "Truss loading in theory and practice".
After some general information on the course, the legal basis for the use of a truss system was clarified. For understanding of the design principles and the load-bearing capacity of trusses, the basic principles of normal force, shear force and bending moment were explained by the lecturer and how these forces are in play in a truss. The difference between loading trusses within the tolerances of elastic deformation (deflection with return to the original shape after relief) and when plastic deformation occurs due to severe overloading (permanent deformation, like bending or breaking) are explained.
Further explanations describe the different static systems, such as single point load and multi point load, as well as the load types CPL (center point load), UDL (uniformly distributed load) and cantilever loading.
It was clearly pointed out, however, that even the experienced user can only be able to estimate the loads of a single truss span with multi point loads as a simple static system due to the static data provided by the respective manufacturer of the trusses. The stress calculation of trusses loaded with multiple point loads and more elaborate truss constructions should in principle only be made by experienced and professionally qualified engineers.
A further agenda of the seminar was devoted to changes in technical building regulations. In the course of European harmonization, the building regulations of the member countries were adapted here and the construction regulations in Europe were harmonized across Europe. The Eurocode 9 "Calculation and dimensioning of aluminum constructions" also has an impact on the calculation bases for the stress calculation of trusses. After a transitional period, which has now elapsed, all truss producers in Europe must therefore take these rules into account.
Damage pictures: TrussBusters
After so much dry theory, it was time for a change. The afternoon was one of the highlights of the day for many participants. Under the work title “TrussBusters” the manufacturer performs overload tests directly on a truss structure, to give the user an idea of how these situations might work out in practice. It’s often a huge eye-opener.
Matthias Moeller demonstrated this with obvious joy and started as a warmup with the demonstration of the system-dependent lack of lateral rigidity in a ladder beam. More spectacular was the attempt to raise a 2-ton block as a CPL by means of a ProLyft motor on a 12 metre square 30-series truss. With the help of the data from a load measuring cell, the participants were able to observe how the truss was able to absorb overloading over the maximum value specified by the statics in the area of elastic deformation.
Only when clearly exceeded did the plastic deformation of the upper main chords occur. In a second test with a 4-meter truss, despite deliberate weakening by bending the braces and dynamics of the engine, it was not possible to break the it.
Of course, for safety reasons, these experiments took place in a controlled environment, directly discarding the truss. An imitation without appropriate knowledge is expressly warned, in other words – don’t try this at home!
Do not mix!
At the end of the seminar, the participants met once more in the lecture room, Matthias Moeller explained the damage patterns observed in the experiments that were just held and reported from his practice as an expert on experiences in the evaluation of truss failure.
He also took a position on combining different truss system from different manufacturers. Although the idea is sometimes that some products are compatible with each other, and given the "weaker statics", this is permissible, by connecting two non-related items you are legally creating a new product, and thereby become liable for that product. So, do not mix!
The seminar was an event which is recommended to every practitioner in dealing with trusses. It is to be hoped that other manufacturers will also take an example and accompany their customers as informative and entertaining - even after the purchase.
Source: Production partner