What is the minimum number of column bond/grounds required for a rectangular steel frame building using steel as downleads?

In the context of lightning protection systems, the minimum number of column bonds or grounds required for a rectangular steel frame building utilizing steel for downleads is determined by the standard practices for grounding. Each steel column should ideally be bonded to a ground to ensure proper conductivity and to provide an effective pathway for lightning energy to safely dissipate into the ground.

Having at least two grounds is essential to improve system redundancy and to reduce resistance, which ensures safety and effective operation. Two column bonds help mitigate the risk of potential differences in the system, considering that lightning can strike various parts of the structure. Effective grounding minimizes the chance of damage and enhances the protection offered to the entire building by providing multiple pathways for lightning to follow.

Higher numbers of grounds may enhance safety, but for a rectangular frame building, the basic requirement establishes that two are the minimum necessary for functional grounding and bonding to align with safety standards.