Bygningsreglementets vejledning om konstruktionsforhold for transportable konstruktioner – Structural Guidance for Transportable Structures
The Bygningsreglementets vejledning om konstruktionsforhold for transportable konstruktioner is an official guidance document issued by Social- og Boligstyrelsen in Denmark. It provides the regulatory framework for the design, execution, operation, and maintenance of transportable structures in accordance with the Building Regulations 2018 (BR18), specifically Chapter 15. The document was originally published in July 2016 and underwent a significant revision on August 27, 2024, to clarify technical assessments for consequence classes and wind load monitoring.
The scope of this guidance covers a wide range of temporary and mobile structures, including skurvogne (sheds/cabins), pavilloner (pavilions), telte (tents), scener (stages), tribuner (stands/grandstands), and gangbroer (pedestrian bridges). It establishes the criteria for classifying these structures into Konstruktionsklasser (KK1 to KK4) based on their complexity, consequence class (CC1 to CC3+), and industry experience. The guidelines integrate European standards, primarily the Eurocodes (EN 1990 and EN 1991) with Danish National Annexes, ensuring that transportable structures meet the same safety levels as permanent buildings unless specific monitoring or risk-reduction measures are implemented.
The documentation details specific load requirements for wind, snow, and rhythmic human movements. It also provides technical specifications for geotechnical investigations, foundation stability, and various anchoring methods such as jordankre (earth anchors) and ballastankre (ballast weights). Technical parameters for soil bearing capacity and anchor pull-out tests are defined to maintain structural integrity across different Danish terrain types.
Classification of Transportable Constructions
Transportable structures requiring a building permit must be placed in a Konstruktionsklasse (KK) as per BR18 §10. This classification determines the level of technical documentation and independent control required for the project.
- Konsekvensklasse (CC): Expresses the risk to human life and economic consequences of a structural failure. Structures are categorized from CC1 (Low) to CC3+ (Extra High).
- Complexity: Defined as simple or complex based on how loads are transferred to the foundation. Complex examples include tents with large deformations or structures relying on active/passive soil pressure.
- Experience: Categorized as traditional (standard materials and methods) or untraditional (vibration-sensitive structures like long-span gangways).
- Classification Table: Simple traditional structures in CC2 fall into KK2, while complex or untraditional structures in the same consequence class are elevated to KK3.
Wind and Snow Load Requirements
Loads on transportable structures follow DS/EN 1991 (Eurocode 1). The guidance allows for reduced wind and snow load calculations if specific monitoring and action plans are established to mitigate risks during extreme weather.
- Vindlast (Wind Load): Calculated based on a 50-year return period. If wind speeds are monitored using calibrated anemometers or weather services like DMI, partial safety factors can be reduced from 1.5 to 1.2.
- Monitoring Methods: Wind speed can be tracked as 10-minute averages or peak values (gusts). Monitoring allows for threshold-based actions such as closing tent openings or evacuating stands.
- Snelast (Snow Load): For short-term installations in summer, snow loads can be omitted. For winter use, heating systems must maintain the tent fabric at a minimum of 2°C to prevent snow accumulation.
- Terrain Categories: Wind loads vary across four categories, ranging from Category I (open water/lakes) to Category IV (dense urban areas with buildings over 15 meters high).
Foundation and Anchoring Systems
Foundations must ensure stability against vertical loads, horizontal shifts, and uplift. All transportable structures must be documented in a geostatisk dokumentation (geostatic report) to verify anchor strength.
- Jordbundsforhold (Soil Conditions): Bearing capacity in Denmark varies by season; topsoil layers in spring may have a 50% reduction in bearing capacity compared to late summer.
- Simple Earth Anchors: Must have a minimum embedment depth of 80 cm in the ground. The pull-out capacity is calculated based on anchor length and diameter (e.g., d_min = 0.025 * l' + 0.5).
- Ballastankre: When using buried ballast, the calculated weight must be multiplied by 0.9 to account for buoyancy or installation variations.
- Testing: Pull-out tests (prøvetrækning) must be performed on-site. The characteristic breaking load is reduced by a factor of v = 1.6 for safety calculations.
Frequently Asked Questions
What is the minimum embedment depth for simple earth anchors?
Simple earth anchors must be driven to a minimum depth of 80 cm into the ground, with a total length typically around 1.0 meter.
How much does soil bearing capacity reduce during the spring thaw?
The bearing capacity of upper soil layers in Denmark can be reduced by approximately 50% during the thaw period and the month following it.
Can the partial safety factor for wind load be reduced?
Yes, if wind speed is monitored on-site using both weather services and local anemometers, the partial safety factor (gamma_Q,1) can be reduced from 1.5 to 1.2.
What are the requirements for preventing snow accumulation on tents?
Tents used in winter must either be designed for full snow loads or utilize a heating system capable of keeping the outer fabric at a minimum temperature of 2°C throughout the snowfall.
Which consequence class (CC) do most large party tents fall into?
Large party tents are typically placed in consequence class CC2, as failures rarely result in more than 5 fatalities due to the light nature of the materials compared to concrete or steel.
When is a transportable structure considered 'complex'?
A structure is complex if the distribution of forces is non-linear or relies on large deformations, such as tent constructions where equilibrium is only reached after significant movement.
