Jacking Stresses for C-I-P bridge structures

[VoyageofDiscovery]

The Contractor has poured a bridge and the minimum concrete strengths are not being attained. With self weight included, stresses are at capacity for this initial stage, and it appears this bridge will need to be load rated.

Do we include self weight for the jacking condition calculations?

Thanks

VOD

 

[VoyageofDiscovery]

My post should have read, "As designed, with self weight included, stresses are at capacity for this initial stage"

VOD

 

[Ingenuity]

VOD,

When you state "stresses are at capacity" I guess you mean calculated flexural compressive and/or tensile stresses are greater than code-specified allowable stresses based upon the actual concrete strengths to date.

If so, when calculating the flexural stresses at TRANSFER, the self weight and other applicable loads present, need to be considered.

Just because the stresses exceed code-specified allowable values does NOT mean that the strength capacity is exceeded.

What concrete stresses are exceeded?

 

[Ingenuity]

VOD,

Having re-read your post, maybe you are talking about the stresses at the PT anchorages - bursting and spalling stresses due the jacking loads. If so, then you need consider only the PT jacking forces but theses areas are very non-linear areas and always contains confinement reinforcement to take care of the tensile stresses. You usually need to consider the effects of multiple anchorages and the stages that these anchorage are stressed during the jacking operation.

 

[VoyageofDiscovery]

Thanks for your reply,

That's exactly what I thought with regard to flexural stresses, I was just seeing if there was another angle I could approach this from. Fortunately for the Contractor, the concrete finally reached the design transfer strength. We wait for the 28 day strength.

Regards

VOD