Design of building for storage of archival materials (construction type vs deflections)

[Karlos80]

Hi All,

I am currently designing a large redevelopment of existing warehouse into a high-quality archive storage facility.The scope of work includes the construction of new intermediate floors within the existing one story warehouse to increase the vertical space of the warehouse area. The floor will support a mobile shelving system for storing archives. All will be designed to meet the requirements of PD 5454 (guide to storage of archival materials). The critical design factor for sizing the frame /slab is the deflection limits required for mobile shelving (L/1000 and maximum 5 mm). The maximum span is 9300mm between columns. There is limited headroom in the existing building. 4hrs fire rating is also required.

Initially I was looking at insitu frame but calculating accurately deflections in RC beams and long term behavior is very difficult due to non-linear behavior, cracked section vs uncracked section, shrinkage, etc.
Steel option could be also considered ,but will require more columns to break the span and could be a issues with constructability inside the existing building (lifting etc).

I wonder if you have experience in designing similar structures with a such requirements (deflections, etc)

Regards
Karol

 

[rapt]

L/1000 and 5mm deflection will be difficult to achieve with a suspended RC structure. It might be possible with a PT structure (preferably bonded!) but would still need significant depth of beams for the spans you have and the loading. Reasonable long term deflection estimates can be achieved for concrete members as long as you can control the material properties and use the right calculation methods (not code deemed to comply depths or simplified code methods) or use software that does the deflection calculation properly.