Ben Drake, Associate at Peter Dann Consulting Engineers gives a structural engineer’s perspective on designing an integrated superstructure from individual modular parts, with adequate strength, stability, connectivity and buildability.
Peter Dann have over 25 years’ experience in the structural design of offsite construction projects, in almost all types – panelised and volumetric modular, from single to multi-storey, in the residential, commercial and education sectors. In cutting our teeth in the early years, we have developed a very detailed understanding of the principles of design and procurement of offsite construction projects. We recently finished work on the volumetric modular Marriott Hotel at Luton Airport.
Here, seven storeys of volumetric modular steel framed modules, containing 250 hotel bedrooms, are supported by a traditionally constructed steel substructure up to first floor/podium level. The modular superstructure is self-stable i.e. no traditionally constructed cores (these are also modular). Therefore, this eightstorey building pushes the boundaries of structural viability for this type of structural system. Module installation was completed at a rate of one floor per week, with construction onsite progressing from one to eight storeys in under two months.
Hotel construction lends itself perfectly to offsite techniques. Of course, there is the obvious ‘stackability’ aspect, with load-bearing walls or columns able to nicely line up from floor-to-floor and room-to-room. As well as structural benefits, the repetitive stacked nature of the modules generally means that M&E risers also line up down the building. This opens up the option of ‘plug-and-play’ modular M&E units, which can be ‘dropped’ down the riser voids from the top of site-installed modules, significantly reducing site installation and commissioning time for M&E elements, not to mention providing useful locations for structural connections.
Volumetric modular construction is also generally easier when the supporting traditional podium structure is at first floor level or above. This worked well for the Luton Airport project, as the ground floor entry lobby and general amenities area was able to be relatively open plan, with fit-out occurring concurrently with module installation above.
In contrast to traditional construction, a key element of any successful offsite project is very early client decision making. This does not mean there is no flexibility from project to project of a similar product (this is elaborated on below), it just means that if there are changes, the client needs to have a clear idea of these very early during supply chain engagement and certainly before design freeze. Once again, this suits hotel construction. Hotels generally have a very detailed understanding of their brand requirements – usually right down to toilet pans and taps – and are thus able to provide very detailed specifications in early design stages. This in turn provides much more quality and cost certainty, and allows all consultants to commence and finish detailed design significantly earlier than for traditional projects.
To continue reading this article, visit: Offsite Magazine Issue 12