Repairing Yielded Reinforcement

[Respawn]

How is yielded rebar repaired after a seismic event? This question pertains to rebar found in the yielding zone of a beam. Does anyone have any references regarding this?

 

[RabitPete]

Demolish and recommend rebuilding in the area which is not prone to seismic events big enough to cause yielding.

 

[Agent666]

In recent NZ major seismic events in 2010/2011, most ductile concrete structures were subsequently demolished because they were deemed impractical or uneconomic to repair, and where the lateral system wasn't significantly damaged often the cost of the fitout and non structural repairs made repair uneconomic leading to demolition.

Basically apart from two significant collapses leading to significant loss of life, most concrete structures achieved the intent of the code, being no collapse and life safety.

There are ways of measuring the residual capacity remaining in the bars in a hinge region. So if your hinge resulted in distributed yielding as opposed to one crack you may be able to prove sufficient capacity remains by reinstating the concrete damage. The exact name of the process eludes me as haven't seen it done for nearly ten years. Basically they expose the bars and they measure insitu how far along the stress strain curve you're at to get an idea of the remaining low cycle fatigue potential.

https://engineervsheep.com

 

[Agent666]

Lookup Leeb hardness method.

https://engineervsheep.com

 

[HTURKAK]

You may compare the general situation and global response of the bldg . with the following pictures;

If the question pertains to rebar found in the yielding zone of the say; 10% beams , the beams and cracks could be repaired with repair mortars , plaster etc..

The limited yielding of the beam rebar is not the end of the game.. still residual strength could be available..

 

[Respawn]

@HTURKAK What do you mean by 10% beams?

 

[HTURKAK]

Remember sway mechanism .. if some of the beams develop plastic hinge , the structure still has potential strength ..Try to evaluate performance level after a seismic event..

The following pic. from SEISMIC DESIGN HANDBOOK , explains the sequence of plastic formation;