construction safety

huangyhg

construction safety
i have a client that has an existing one-story store that was originally designed for a second floor.  they want to put on the second floor now, but want to keep the first floor store operational during the construction.  is there any osha regulations that prohibits keeping the store open below?  the existing roof is a concrete slab, and the building frame is structural steel (building is about 50,000 sf).
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there is no cut and dry answer i know of. i can think of no specification that specifically states an existing structure must be closed for construction, but this is an answer for a structural engineer and will require serious thought and analysis to determine if the space below can remain occupied and what must be taken into cosideration. hopefully you have available the original drawings and specifications, as well as the as built set of drawings such that you may see what really went into the building. a building that may have been originally designed for additional levels, may not have been constructed in a way to make expansion feasible, structurally or financially.
additionally, construction loading can vary significantly from the loads expected as the permanent building loads. shoring of the roof slab may be necessary to actively construct the next level, and this shoring would need to bear in the occupied space. all of these issues would need to be evaluated and investigated before any construction is mobilized. asce standard 37-02 covers loads during construction, and while it does not specifically speak to the closure of the occupied levels, it does speak to the loadings and load cases to consider when deciding if the structure is suffiecent to handle the loads of new construction.
please ask further questions if needed.
daniel
zulk,
while i haven't done it myself, i know of a commercial building in my home town that did just what you are talking about.  most of the work was done without ever shutting down the store operations on the first floor.  however, depending on the type of construction, some lifts might have to be done with the store closed, so think about after hours or on weekends.  if the schedule is worked out ahead of time the contractors can allow for the overtime in their bids.  
it really should not be a problem. you have the advantage of a concrete roof slab to build on.  the building i noted above had a wood roof deck.