Lightning Protection (Structural Steel + Grounding Rods?) 1

[mbk2k3]

I am using the CSA-B72-M87 Installation code for lightning protection systems.
It is closely related to NFPA 780.

My building is a standard industrial facility, with the framework comprising of structural steel that is connected to the ground grid via bolted/welded connections.

According to the CSA standard:

8.6 Use of Reinforcing Steel
Reinforcing steel in an exterior wall, in a column, or in a reinforced concrete post that complies with CSA Standard CAN3-A23.3, may be used as a down conductor or ring conductor if the electrical continuity of the bars equivalent to No. 2 AWG is ensured.

According to NFPA 780:

4.16 Structural Steel Systems.
4.16.1 General. The structural steel framework of a structure shall be permitted to be utilized as the main conductor of a lightning protection system if it is electrically continuous or is made electrically continuous.

So my question is this:
If I have air terminals and copper down conductors, do they need to be connected to a grounding rod directly? Or can i simply connect them to the structural steel closest to grade level (at the bottom of the building?)

 

[bikenut44]

I am not a certified lightning designer, but I have seen UL master labeled systems connected to the building steel only at the top of the structure and then a ground loop outside tied to the building steel at the base.

 

[7anoter4]

First of all, the new NFPA-780 2011 Edition it is a bit changed:
4.16.1 General. The metal framework of a structure shall be
permitted to be utilized as the main conductor of a lightning
protection system if it is equal to or greater than 4.8mm(3⁄16 in.)
in thickness and is electrically continuous, or it is made electrically
continuous by methods specified in 4.16.3.
4.16.3 Connections to Framework. Conductors shall be connected
to areas of the structural metal framework that have
been cleaned to base metal, by use of bonding plates having a
surface contact area of not less than 5200 mm2 (8 in.2) or by
welding or brazing.
Second: the main conductor has to terminate at a grounding electrode [concrete-encased or else]:
4.13.1.1 Each down conductor shall terminate at a grounding electrode dedicated
to the lightning protection system.
In my opinion, a grounding electrode has to be provided. If it is an existing building
no basement structure could be employed as concrete-encased electrode.
4.13.3 Concrete-Encased Electrodes. Concrete-encased electrodes shall be used only
in new construction.
So grounding electrodes like ground rods, plate electrodes or ground plate electrode or else
has to be provided.
If it is a new construction a concrete-encased electrode could be used.