“There is no longer any point in using old glass dimensioning tables.”
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Expert interview on DIN 18008

Sebastian Rücker recently gave an interview with the journal “glasspezial”, published by the Radeberg company Thiele AG. The managing director of glasfaktor Ingenieure GmbH in Dresden was asked about his experience with the new DIN 18008 glass dimensioning standard.

An expert explains the pros and cons

Engineer Sebastian Rücker and his colleagues at glasfaktor Ingenieure GmbH specialize in statics, structural design planning and engineering support during the fulfilment of façade and glass construction projects. As a result, because of his profession he deals with the new DIN 18008 glass dimensioning standard on a daily basis and faces a large number of user questions from his customers.

INTERVIEW                                                                           Engineer Sebastian Rücker answers some frequently asked questions about DIN 18008

Working as a partner with Thiele Glas, you are happy to provide both our staff and our customers with advice. In spring of this year, you passed on your knowledge about DIN 18008 twice, during the architects’ and planners’ day and at a staff training course, answering participants’ questions. Thank you very much! We are all the more delighted that you have agreed to sum up some of the most frequent questions for the “glasspezial” editing team.

The previously valid Technical Regulations TRLV, TRPV and TRAV contained extensive rules on how to use glazing. Why was a new glass dimensioning standard even introduced?

The main reason for introducing a new standard was to adapt the dimensioning concept for glass construction to the concept of semi-probabilistic evidence rooted in the Eurocode and already applied to other construction materials. The old rules are not based on this safety concept. The identification of glazing with partial load and resistance safety factors is now much fairer on glass, a brittle material.

What is the most important conclusion from DIN 18008 for our consultants and customers?

For work on projects, it is all the more important, with immediate effect, for an expert to be involved in dimensioning glass at the earliest possible juncture. The new DIN 18008 standard has made glass dimensioning so complex that it is impossible to reliably undertake glass dimensioning without expert knowledge of engineering and without precise information on the situation in which the panes are fitted. Only using a software solution to find the dimensions for glass does not guarantee the right thickness.

What happens if you can’t apply a regulation?

In the case of glazing which deviates greatly from the DIN standard, an individual application must be made to the highest regional building authorities. In the field of glass drilling, for example, an application of this kind is required for drilling countersunk and blind holes.

Can old glazing tables still be used in glass dimensioning?

There is no longer any point in using old glass dimensioning tables. It’s definitely not advisable.

What about the duty to produce supporting documents in theory and practice?

Many companies carrying out work still do not realise that they need to produce supporting documents when fitting structural glazing. Depending on the project, the use of glazing requires you to gather statics documents and sometimes other verification (such as proof that glazing used as a safety barrier is shockproof) and show them to the test engineer or building inspection authorities. If you don't consider this necessary you run the risk of installing glazing with the wrong dimensioning. The consequences can be really expensive, even years later.

One interesting question that the learners on the course asked was “What are the general pros and cons of DIN 18008?”

The new standard covers a considerably wider range of rules. This offers the advantage of greater planning confidence for various tasks requiring approval where the dimensioning and design previously depended on the project / region / person processing a request. This also reduces the need to seek approval. The new standard also includes a dimensioning concept which is far more precisely and individually adapted to the specific material characteristics of glass. Unfortunately, however, in some fields the standard was written without taking established practice into account. In terms of the amount of statics calculations and supporting documents required, the standard-writers have created a “bureaucratic monster” which cannot be applied in practice without additional regulations or the granting of special dispensation. In my view, the greatest disadvantage of the new standard is that it does away with the “four-metre rule”. This was a special dispensation for shop windows and door glazing. It allowed specialist companies to take on responsibility for stable, fit-for-purpose vertical glazing fitted less than 4 m over circulation areas. Due to the low safety risk for public spaces, it was not necessary to provide building supervisory authorities with supporting documents. According to the new regulations, statics documentation in line with DIN 18008 must be shown to the statics inspector for all door glazing, including fully glazed doors and shower doors. The abolition of the four-metre rule has proven particularly problematic in the case of small, narrow panes of double glazing. It is often impossible to produce documents because of temperature and pressure effects! Here, I hope there will be a retroactive change so that the pros end up outweighing the cons.