Seismosoft | Earthquake Engineering Solutions

Dear Sir,

i need a clear understanding about plastic hinge modelling. i have modelled
a cantilever RC bridge pier subject to axial and lateral load, i wanted to
simulate the real behavior of damaged specimen wherein plastic deformation
occurs at shear zone (plastic hinge formation at shear zone) under
experimental test QSL.

First i need to a suggestion that which approach is best for modelling the
plastic hinge either introducing spring or introducing infrmFBPH in only
plastic hinge length (i-e 8" as per experimental data) while the rest of
element remain elastic, to get real simulation of damaged specimen /
optimized capacity of damaged pier.

Second, please also let me know if in either case i allow spring or follow
distributed plasticity, how to account for the stiffness degradation under
static time history analysis, either stiffness degradation is carried out
by software on auto or it has to be introduced by the user.

Last but not the least, meanwhile if a user define spring having two
coincide nodes which allowing shear deformation under modified stiffness,
then applying jacketing to that zone, either the effect of jacket in the
same will be accounted in analysis results?

Please suggest?

Hello,
1. The selection between lumped plasticity (infrmDBPH) and distributed plasticity (infrmFBPH, but also infrmFB & infrmDB) is a subject that cannot be fully analyzed in one forum post. Both approaches have advantages and disadvantages, the main points are the following:
-distributed plasticity is generally more stable numerically
-distributed plasticity models are more accurate (usually the blind prediction contests are won by programs that employ distributed plasticity)
-lumped plasticity is generally faster, especially in dynamic time-history analysis

2. In both cases, the stiffness degradation is accounted for by the hysteretic models in the plastic hinges.
3. If you apply jacketing, this should be reflected by the shape of the hysteretic models in your spring.

Finally, note that this is a forum for support on the use of our programs, and not a general purpose support on earthquake engineering and nonlinear analysis. Thus, for further guidance you should better discuss such issues with your supervisor.
Seismosoft Support