Prefabricated Library Stack System

[jcoffey]

A question has come up about existing floor load capacity in a library. It was designed and built in the early 1970's, and I have the drawings (architectural and structural) which show it as three stories, basically reinforced concrete on spread footings. The problem is that the middle floor is part of a 'prefabricated library stack' system in which the floor is supported by metal posts that also support the library stack shelves and are supported at grade below. The supported floor is only shown on the architectural drawings and about all it says is that the floor is '3" steel', which doesn't sound right. The upper floor is post-tensioned concrete and designed for 125 psf, so I might expect the intermediate floor system was similarly designed, but there is little to go by on the drawings. It appears that the entire mid-level is some sort of proprietary stack/floor system. Does anyone know anything about these systems or have a reference as to where I can find out more? I've seen them before in libraries, and the concept makes sense as these stack posts are generally on 3' to 5' centers and could be easily used to support a floor above as well as the book shelves. Any help would be appreciated.