Development length of rebar 1

[BAGW]

Hi,

Do the rebar development length in high seismic areas for foundations be calculated per the seismic chapter (ACI 318) or just the standard development lengths be used for foundations?

The foundations are not detailed as any SFRS, so I dont see any requirement for using seismic chapter for calculation development lengths.

Any comments?

 

[HTURKAK]

It would be better to look ACI 318 Clauses 18.13—Foundations..

Clause 18.13.2.2

.. Longitudinal reinforcement of columns and structural walls resisting forces induced by earthquake shall extend into
the footing, mat , or the pilecap, and shall be fully developed for tension at the interface..


Clause 18.13.2.4 Columns or boundary elements of special structural walls that have an edge within one-half the footing
depth from an edge of the footing shall have transverse reinforcement in accordance with 18.7.5.2 through 18.7.5.4
provided below the top of the footing. This reinforcement shall extend into the footing, mat, or pile cap a length equal
to the development length..

 

[BAGW]

Yeah but that has nothing to got to do with the reinforcement mat in the footings.. the reinf mat in the footings or longitudinal bars in the piers/piles need not be developed per ACI seismic requirements..

 

[KootK]

If the foundation elements are not detailed to be part of the SFRS, I believe that the standard development lengths are sufficient. My recollection is that the longer development lengths are required only when cyclic, inelastic rebar straining is expected.

 

[driftLimiter]

Yea the longer development lengths are needed where need ductile post-elastic deformation. But you could make an argument on certain foundation elements that you might seismic bar splices on, for example foundation ties, shear transfer from LFRS baseplates directly into concrete grade beam. Elements like these obviously carry a direct seismic load, a little extra laps add comfort that the tension will be resolved even after cycling the loads.