loud bang heard during occupancy

huangyhg

"loud bang" heard during occupancy
i was called to one a job today because a client heard a 鈥渓oud bang鈥?during occupancy of the building (which took place this weekend).  this happened once on thursday and again on saturday in the same general area.  during the site visit (which included a close inspection of the connections and suspended slab) i could see no sign of distress in the building.  in talking to the people who heard the noise they said it sounded like someone 鈥渉it the steel with a hammer鈥?
construction:
bay 24鈥?0鈥?by 28鈥?0鈥?br />secondary beams w16x26 24鈥?0鈥?long spaced 8鈥?0鈥?o.c.
girders w24x55 with 28 studs 28鈥?0鈥?long
slab construction
6鈥?slab placed atop 2鈥?20 ga. composite decking reinforced with 6x6 w2.1xw2.1 wwf.
the facility is a car dealership and they were basically moving cars around on the suspended floor when they heard the noise.
i have some theories on what it could possibly be but i am wondering if anyone has any ideas on what may have caused this noise.
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steelpe,
rcraine has it... sounds like a "banging bolts" occurence.  
thank you rcrain and jkstruct.  that is what my initial thought was.  i have read the papers and questions in msc.  it just looks like there is really no way to prove this is what is happening?  i just want to make sure this isn鈥檛 something i am overlooking.
i also suspect it is "banging bolts".
what type of connections are they using for the gravity beams? bearing or slip critical? were the beam and the connection parts primed or masked off? what type of bolts (tc or regular) were used and were they partially of fully torqued?
jike
for the w16x26 they are using single sided angle connections. this was not my preferred connection but they worked for the light loads and made erection much easier.
the bolts are designed to be in bearing.
  
they applied 4 bolts per connection.  
all connections are bolted 鈥?bolted.

the angles were attached to the girder in the shop.  
i believe that the surface between the girder and the angle is unpainted.  the surface between the secondary beam and the angle is painted.
i believed they used t.c. bolts that are fully torqued by evidence of shear spline removal.
as for the girder, they are double angle connections with 7 bolts in double shear (14 bolts to the column).
the typical cause for banging bolts are bolts that were designed as bearing bolts, but tightened as slip critical bolts onto an prepared fraying surface (i.e. painted surface).  your secondary beams are probably sliding into bearing and creating that noise.
er..that should read "onto an unprepared.."
sounds like bolt banging to me.  not really much you can do except document it and forward it on to the incompetent erector.  there's no excuses for bolt banging.  typically its due to drift pins being left in too long while the connection bolts are tightened.
banging sounds means may be web of beam is banging on bolt shanks. this additional impact load is considered or connection can break? it鈥檚 may also fall into fatigue criteria?