Prestressed Girder Failures

[dison]

I am trying to develop a list of all the potential ways/reasons a prestressed concrete girder could fail.

For example:

inadequate concrete strength
inadequate flexural capacity
overload
uneven bearing support
loss of prestress force due to corrosion of strands
loss of prestress force due to inadequate bond to concrete
sustaining lateral impact damage
inadequate anchorage of strands
etc.

Please respond with any and all potential ways of failure, even very site specific reasons.

Also, descriptions of personal experiences with inspection or investigation of prestressed concrete failures would be great to pass along - even stories that someone else has told you would be very helpful. ~dison

 

[ishvaaag]

bad design
lateral buckling
shear failure

I suggest you a methodical way of making your checklist grow: examine diverse specifications and PC texts and state the lack of compliance with specific articles as the source of failure.

 

[Ingenuity]

dison,

Types of potential failures in addition to yours:

1.web crushing
2.flexural shear
3.web shear
4.transfer of prestress
5.flexural-torsional buckling during erection
6.dapped/notch failure - see Pittsburgh Airport parking strcuture!


some will argue that excessive camber or deflection is "failure", but i think you are referring to actual structural strength limit state NOT serviceability criteria.

some reasons...

1.inadequate design
2.inadequate details
3.inadequate supervision of construction
4.inadequate erection techniques

A really great text that i read often is "Design and Construction Failures - Lessons in Forensic Investigation " by Dov Kaminetzky. It features real failures of many structures with many materials - including precast pretensioned.

HTH

 

[RiBeneke]

Expanding some of the above :

Bursting or pull-in of anchorages due to voids in the concrete (honeycomb). Voids can be partly (not entirely) due to too much or badly designed bursting reinforcement.

Bursting at anchorages due to insufficient bursting reinforcement.

The 2 cases above can be complicated when bursting reinforcement is often a split design responsibility between the structure designer and the prestressing specialist or subcontractor.

Undetected wedge slip at anchorages before grouting.

Girders falling over sideways in the contractor's precasting yard. It is not unknown for the girders to be hoisted upright, patched and sent as though nothing had happened.

Precast girders that are temporarily braced (eg deck not yet cast) slipping off their bearings. This latter case happened years ago here, and was presumed to have been caused by the vibration of trains passing below. One of the beams fell onto a train.

 

[dison]

Thanks! Comments so far have been great.

A few other questions to add:

What are the major causes of loss of prestress forces over time (creep or strand slip beyond the predicted losses)?

In your opinion, what is the shortest practical span length for which prestressed concrete is practical? economical?

If anyone has personal experiences with failures or preventing failures in prestressed structures, I would appreciate hearing about them here.

Ingenuity:

Seriviceability failures should be included in this list as well. I will have to check on the book you suggested - it sounds like a great source of failure info on structures of all kinds. ~dison

 

[7of9]

Hi RiBeneke,

Are there any reports/articles on the failure linked to the vibration of the passing trains?

 

[RiBeneke]

I would have to try to find something in old construction magazines. Can't do it right now, I'm afraid.