Structural Grounding

[muazmi02]

As per NFPA780, Article 3-12.13, Down Conductors (Bare Copper Wire, 50 mm sq) coursed in Reinforcement Concrete Columns shall be connected with the reinforcing steel re-bars at its upper and lower extremities. This down conductor is further coursed to the grounding ring (having several grounding rods) outside the building in order to effectively ground the concrete structure of the building. This process is done in concrete structure buildings having steel re-bars.

We have a project in which concrete structure building have epoxy coated steel re-bars and if we chip the epoxy coating of these steel re-bars at upper and lower level of structural columns to connect down conductor within the columns, it will not have a continuous grounding system as compared to the steel re-bars without epoxy coating. Therefore, it will defeat the purpose of structural grounding in the case of Lightning Strike or otherwise. Kindly inform me with some code reference that how can we effectively do the structural grounding for the concrete building having epoxy coated Re-inforcement bars.

Thanking you all....

 

[bphgravity]

This is the second question on the NFPA 780 that references a section number I am not familair with...

The section in question can be found in the last three editions of the NFPA 780 in Section 4.9.13 - Down Conductors and Structural Cloumns.

The purpose of this section is to ensure interconnection (bonding) of the paralleled vertical paths through the strucutral columns. This reduces the potential of sideflash and the inductive effect. Additional bonding of the metal bodies may be required per Section 4.21. Analysis of the steel placement and its relation to the LPS conductors will be needed to determine if additional bonding connections will be needed or if isolation and intentional non-connnection is preferable.

(The LPS does not serve to "ground" the structure, nor does any other electrical system. The LPS and electrical systems are requried to be grounded, and in some cases, the structure serves as the source of gorund.)