3 Westgate Street, Southery.

PE38 0PA. United Kingdom.

studio@anthony-johnson-engineering.co.uk:

Telephone

01945 660504

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Structural Design:

A client was in the process of extending his property with a bespoke Brick and timber single storey extension. Having produced preliminary drawings and specifications and obtained both Planning and Building regulations approval, he felt that a Vaulted Ceiling would be more in keeping with the property than a trussed roof. I was engaged to design a steel beam over a series of bi-fold doors, allowing for a ridge beam to run the full length of the extension, thereby supporting rafters and a series of velux windows set into the roof.

In designing this new roof, I had to consider the entire structure, including rafters, ridge beam, steel post to the ridge beam and steel beam over the bi-fold doors. I first analyzed loading on the roof to Eurocodes, taking into account snow loading and drifted snow loading, wind on the dominant face of the building and Dead (permanent) loads from self weight. The roof, even with the load from concrete tiles would be subject to Uplift, so wall ties running the length of the wall were necessary.

Designing the timber members to the roof meant considering deflection in the members first- the finishes were brittle and included glass!. They were then checked to Eurocode 5 to make sure they could take the design load.

The steelwork beam and post was again designed for deflection and checked for the Ultimate Limit State. This time, I wanted to make sure the bi-fold doors continued to work even when the weather had turned poor during the winter!

Although not a complicated design, it’s important to note the need to consider deflection of structural members as the critical design factor in this project. I could have quite easily used smaller structural members but deflection in excess of span/360 would have meant redecorating within 5 years and doors and velux roof lights that were forever sticking!

richardanthonyj