Certification of Temporary Structures – Mobile Stages

Working in the field of entertainment engineering and temporary structures, I'm often asked of the specific requirements of obtaining approval and certifications, acc. to local legislation in Denmark. 

As the matter concerns a lot of my clients, which includes a wide range of end users, structure owners, designers and manufactures, I've decided to publish this post in a planned series of guides/posts, primary covering the area of temporary structures, secondary some of my other areas of work.

The posts will be kept short, which is quite difficult, compiling all relevant information of design, standards, legislation, and calculation into something actually worth sharing. Some posts will be in Danish, others in English, depending on the intended recipients. Beginning with the demands of documentation for the certification of the industries popular mobile stages.

For the non-industry reader; the term 'mobile stage' covers a range of structures in variety of sizes and shapes, typically relying on different means of hydraulics or mechanically aided movement, to transform it from its collapsed state for transportation - often in the shape of a trailer - to its erected state of being a temporary stage or platform, etc.

A brief resume on the legislative background.

In Denmark, the Danish Government passed an Executive Order, due to the industries different approaches to the areas of both structural calculation of tents and temporary structures and the concern of public safety - trying to streamline the standards used.

Most significantly a certification process was introduces, enabling the owner of a certified structure to raise the structure anywhere in Denmark, without the hassle of obtaining a permit from local authorities - a process, which can take weeks, sometimes months, and depending on the specific municipality be extremely demanding and costly.

The certification of temporary strutures is governed by the Executive Order no. 880/2014 Certification scheme for transportable tents and structures. and the Danish Building Regulation (BR18) as stated in this official English translation of the Executive Order No. 1615

The certification process

The main process of certification is quite straight forward - get an accreditted company to cross check the documentation and inspect the specific structure; pay a fee for the service, and if everything checks out - get certified for a period of up to 5 years.

A simple and fast process if you have the right documentation and a structurally sound structure. As to the choice of an accredited inspection company; currently only two companies are offering the certification in Denmark; Teknologisk Institut and Midtconsult.

Trying to help ensure, all of the right calculations and documents to obtain a certification is provided, I've compiled a short checklist and started to drafta list of Danish / English / French / German / Spanish explanations - to aid with the correspondence across the main languages spoken in the EU.

Pls. do note, the provided list is not exhaustive, and is only provided to ease some of the process to request/provide the relevant documents and calculations. Requirements for a specific structure may alter from the list below.

The documents needed - mobile stages

1 ) Classification of reaction to fire in accordance with EN 13501-1 for the canopy cover, the sheeting applied to floor, roof, etc.

2) Drawings showing rigging point placement and applicable load, pls. do provide all rigging loads stated on drawings as SWL (Safe working loads) in an effort to prevent end users browsing the documentation from applying non-safe loads.

3) Drawings - as a minimum, Plan and cross section

4) Assembly instructions, preferably in Danish.

5) Maintenance instructions

6) Static report in its entirety - By experience the one sole reason, why some certification process' can get really expensive and not least be delayed, is due to the lack of prober static calculations. This also includes a tendency of some manufacturers to provide a limited report, usually with no or little relevant structural or mechanical information, or even as I've experienced recently a client met with a demand of paying a vast amount for a copy - the amount asked for, was more than twice the cost of re-doing the entire documentation.

I understand the fear of design/product rip-offs, but most static reports rarely contain information not already disclosed, either by the competitors employment of former employees, the hiring of same freelance consular/ engineering services, basic re-engineering, public records like the DiBt Zullassung, or by simply performing a search online.

Most manufacturers are, when reasoned upon, by sharing details of the legislative demands, willing to provide the information needed. Why you should reach out and if not answered, ask again. Eventually you can either hire someone else to draft it, or find another supplier for future investments. Not getting sufficient disclosure of a structures structural performance could lead to unintended use and increase the risk of structural failure.

The content of the static calculations

As prior mentioned, the content of a static calculation seems to involve a lot of interpretation. As of my experience having aided to document an extensive amount of temporary structures, in the case of the certification of a mobile stage and other temporary structures, it should at least include:

(In an effort to limit the length of this post, the more formal demands of BR18 and SBi 223 has been left out).

A)  A list of the standards used

Relevant standards in acc. to the Eurocode such as EN 1990, EN 1991-1-1, EN 1991-1-4, EN 1993-1-1, EN 1999-1-1, EN 13814, EN 13782, etc. - pls. note EN 13814 is NOT a mandatory standard in Denmark. Structural calculations are usually not valid in Denmark, unless they are calculated either in accordance with the relevant Eurocode, including the associated Danish national annex, or using similar partial and reduction factors, load combinations, etc. Do note all of Danish national annexes to the Eurocode are provided in English free of charge.

 B) Load assumptions:

• Self-weight a factor of at least 1,1 should be multiplied to the self-weight, if your model does not contain weldments, fasteners, minor brackets, etc.
• Wind Loads Do provide wind pressure (kN), peak and basis winds (m/s) for all 4 terrain classes; I, II, III, and IV, unless the structures intended usage is limited to a specific terrain class. And do provide the information in accordance with the official guidance for wind calculations on temporary structures and tents, The guide is also published in English.
•  Snow Load - The calculations can be performed without snow loads, as long as it states either a reference to EN 13782:2015 §7.4.3 or simply states the structure isn’t designed to carry the load, decreasing the span of months the structure is usable.
•  Permissible live load on deck/floor Do note the risk of the calculations of horisontal loads being lower than the demands of the Danish national annex DS/EN 1991-1-1 DK-NA Table 6.12
• Permissible suspended loads
• Other relevant loads/scenarios with/without side structures, PA wings, etc.

C) A list of the applied load cases and not least the proof of load cases.

Load cases should preferably be in acc. to the Danish national annexes or comparable.

D) Stability calculations

Do remember to provide calculations for any possible scenario of lift, sliding and overturning. And do include information regarding any specific amount of required ballast.

E) Information on the forces applied to supports

Easing the process of controlling baseplate sizes and not least assuring the right decision is made upon the need of geotechnical surveys, when planning to erect the structure.

F) An appendix

Containing datasheets of the canopy, special sheeting, etc.

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I hope the above can provide some aid and hopefully ease the process of certification.