IBC Concerns for Structural Engineers

[vtgeotech]

I posted this thread in the general Civil Forum, but I believe this forum is more appropriate.

I have a question for all the structural engineers out there who have to design with the IBC code. I am a geotech and our company consults on the east coast, where siesmicity is not at the forfront of everyones mind.

I am putting together a presentation for an audience of structural engineers, and my question is, what would you, as a engineer, like to know about the site classes that a geotech could provide insight for? I could go on about the theory and why the IBC does what it does, but I would imagine that eye would start to glaze over in the middle of the presentation.

Thanks for any advice you may have. Hopefully, this can start a good discussion on a relatively new topic.

 

[JAE]

I sorta brought this up in the thread: thread256-115114

As a structural engineer, if you really want to know what I would love to see in a geotechnical report concerning site class would be:

1. A brief description of the types of soils found in the top 100 feet (100 ft. per IBC req'mt for site class).

2. A description of how you "know" what these types of soils are - from a special boring, from nearby 100 ft borings, from general knowledge of the local geostrata in the area, etc.

3. A statement that says, "The site class for this building, in accordance with IBC Table whatever, is X"

I really don't care what the shear wave etcs. are or blowcounts or whatever.

I also get a bit frustrated when I don't get the site class in the geotechnical report and have to call to get it from the geotechnical engineer. While seismic loads are not real big in much of the country, the IBC and the site class do make it much more a part of structural design than it used to be. Much more than people suspect. It should be just as typical an item in a report as the max. bearing pressure.

 

[jjeng2]

Most important is that the site class is identified. We need to know what it is to do the IBC seismic calcs and I hate having to classify a site based on other data in the soils report. I feel I am taking on unescessary liability and if Im not sure, I have to use the more conservative value.

 

[JStephen]

I'm an ME, and have only occasional use for IBC- but one thing I've noticed is that quite often, seismic data is given based on older UBC, which is different. So how do the older UBC's relate to current IBC in this regard?

 

[JAE]

Both the UBC and the IBC are model codes that can be adopted by governing entities such as cities, states, counties, our countries.

The code to use is that which has been legally adopted by the entity in which the project resides. The both the UBC and the IBC series of codes have continued to modify the seismic provisions over time. But the general concepts are all based on the same things - just slightly different magnitides and different parameters that determine the seismic demand.