November 6, 2014
Thank you for the response and I agree with the interpretation that "vertical" applies to the orientation of the member. The commentary for the California existing building code explicitly states this as well (i.e. applies to vertical elements of the gravity load carrying system such as columns and load bearing walls).
I also noticed that the wording changed from "vertical load-carrying components" to "vertical gravity load-carrying component" between the 2003 IEBC and the 2006 IEBC. Unfortunately, the commentary for the 2006 IEBC does not provide insight into the reason for the change; however, it seems to me the intent was to separate "vertical" from "load" and, thus, the adjective "vertical" does not directly qualify the term "load". Furthermore, as you said, it does not make sense to say "vertical gravity" since all gravity loads are vertical.
Thank you again for the input.
April 27, 2015
I had researched this a year or two ago and I spoke to the gentleman who authored this section. He said that the intent was the the word "vertical" applies to the member (walls or columns) and not the direction of the load. If you think about it, there's no need to use the word "vertical" if the woprd was referring to gravity loads. That would be redundant. He was a little surprised that it could be misinterpreted.
What that means is that an entire roof can be destroyed but it would not be classified as substantial structural damage if vertical members were not damaged.
November 6, 2014
The second of two criteria for Substantial Structural Damage (defined in Chapter 2) of IEBC 2015 reads as follows:
"2. The capacity of any vertical gravity load-carrying component, or any group of such components, that supports more than 30 percent of the total area of the structure's floor(s) and roof(s) has been reduced more than 20 percent from its predamage condition..."
I have encountered varying opinions from collegues and local building officials regarding the interpretation of "vertical gravity load-carrying component." Is this intended to apply to all components that support vertical load, or only those components that are oriented vertically? To put it another way, should damaged horizontally oriented components (i.e., beams, joists, roof trusses. etc.) be considered when determining the "30 percent" threshold (assuming the vertical components supporting them are not damaged), or does the supported area only apply if the vertically oriented components (i.e., columns, load bearing walls, etc.) are damaged?
At the risk of being redundant, I propose the following simple example: a 10,000 SF, one-story buidling incurrs damage to the roof deck and trusses/joists; however, the columns and load bearing walls are not damaged. Thus, although more than 30 percent of the roof area is damaged, only the horizontally oriented elements are damaged. Should this be considered "subsatial structural damage to gravity load carrying components" per 606.2.3?
Thank you for your responses.
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