huangyhg

capacity of a precast concrete joist
is there a way to determine the capacity of an existing precast joist, which i do not know who manufactured it?
thanks
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this is what i would try, before calculating anything:
1. get as much detail information on the joist as possible, all the dimensions, the span and spacing, are ends visible so you can see the reinforcing bar or stran?
2. try to find out when the structure was built. that gives an indication of what codes it was designed under, what companies might have manufactured it etc.
3. send a note outlining all you know about the joist, with a sketch of the details, to all the precasters within a reasonable trucking distance of the site, to see if they may have any information. if the structure is a bridge, check with the highway department that has juristiction.
4. if all that fails, then you have to get your slide ruler out (sorry, that was just for effect), your calculator or computer. all you can do is make some reasonable assumptions of loading and materials and see if the section will support them. the tough part is trying to find out what the reinforcing is. you may have to do some probing or non distructive testing.
this is the path i would take, hope it is some help.
very similiar thread running with proprietory open web steel joists when you don't know the manufacturer. reinforced concrete, post tensioned/pretensioned the worst. destructive and non-destructive testing to verify as-built condition is about the only way if the manufacturer can't be found or no longer exists. load testing and measured deflection is another possibility on a statisically significant sample. we have a saying 'if we can't see it we can't comment'. as well we don't rely on the original design drawings either.
thanks all for your help.
i have reduced the dead loads from tie column tie beam and block wall to light gage steel framing with plywood and stocco wall type.

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