Post tensioned concrete plastic hinge
Post tensioned concrete plastic hinge
(OP)
I am currently trying to perform either a pushover analysis or non-linear time history of a bridge with precast post tensioned piers. Plastic hinges will form at the base of the piers under high seismic loads, and I am trying to determine the properties of this hinge.
There is plenty of guidance out there for determining the properties for a normally reinforced concrete plastic hinge, however, I've had trouble with a post tensioned structures. The plastic hinge will develop at the joint between the bottom segment of the pier and the pilecap. This is effectively zero length, so the normal procedure of assuming a hinge length does not apply. Can anyone give me any guidance as to how to proceed?
There is plenty of guidance out there for determining the properties for a normally reinforced concrete plastic hinge, however, I've had trouble with a post tensioned structures. The plastic hinge will develop at the joint between the bottom segment of the pier and the pilecap. This is effectively zero length, so the normal procedure of assuming a hinge length does not apply. Can anyone give me any guidance as to how to proceed?





RE: Post tensioned concrete plastic hinge
What above is where the section is allowed at much to fail on the tensile sides at any time. Other thing is for the cases where the strength of the concrete has been overpowered by the shakeout, and the degradation of the section that has crushed/spalled concrete needs be represented, on which I have not guide to give.
RE: Post tensioned concrete plastic hinge
Once i figure this out, the next level of sophistication would be to figure out the axial force/ moment/displacement interaction relationship.
RE: Post tensioned concrete plastic hinge
Respect the length of the "plastic hinge" the compatibility of deformation analyses will give you the height along the pier by what by the standing moments all or part of the passive or active rebar may have yielded. I recently read some literature about plastic hinges in shear walls in buildings and think to remember 1 to 3 stories tall plastification under Earthquake might be used in the model.
1 to 1 or 2 to 1 to the width of the pier maybe also sound reasonable, I think, yet the compatibility of deformations if feasible to follow apeace with the progression of the anlysis will give you more information of the actual behaviour, since all stresses in every concrete and steel component and separately given and charted as output.
RE: Post tensioned concrete plastic hinge
RE: Post tensioned concrete plastic hinge
dik: You make a good point about the applicability of plastic hinges to my structure. One thing i would like to establish is the exact amount of ductility in my section. My understanding is that precast, post tensioned piers tend to have significantly less ductility than a normal reinforced section. I am anticpating that by quantifying the exact moment rotation relationship of the member I will get an answer to the question.
RE: Post tensioned concrete plastic hinge