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earthquakes

Posted: Sun Oct 21, 2007 10:35 am
by jayjay
im doing a project on how different foundations stand up to earthquakes but i dont know exactly how i will carry this experiment out please help me if you can all advice is needed :?

Posted: Sun Oct 21, 2007 1:15 pm
by SGelman
You can try looking that this experiment to see if you get any ideas:
http://www.sciencebuddies.org/mentoring ... ?from=Home

Another way to test your question is to build your own miniature buildings. Depending on how in-depth you go, building could get a little pricey, but if you keep it basic there shouldn't be a problem. Decide on a certain number of foundations to test [maybe 3 or so] and try simulating an earthquake.
Hope this helps!


-Susan

Posted: Mon Oct 22, 2007 11:02 am
by Craig_Bridge
Please provide your hypothesis to enable us to better understand what you are trying to test.

Smaller buildings typically have burried soil born footings. Tall buildings typically have structural members driven down to bedrock. These are very different types of foundations.

The most common type of earth quake building failures for footing style foundations are separation of the building from the foundation and not a foundation failure. There are cases of soil plastisity during earthquakes where non-uniform soils or uneven building loads will cause one corner or side to sink and render the building unusable; however, these typically aren't catestrophic building colapses unless there is some other structural failure mechanism.

Posted: Mon Oct 22, 2007 1:13 pm
by wildfirefox
...and to chime in with Craig's info:

Here in California, new earthquake foundations and structural (the building's frames) are designed to withstand certain levels of tremors, depending on the size of the buildings. I hope someone in the geology and structural engineering areas can support me on this. I'm still a tad behind on the last study I've done:

Imagine the earthquake is not like a baking pan that gets shaken side-to-side. Rather, imaging the earthquake area is on a jello surface, that actually moves in a wave pattern (similar to the ocean's wave). The movement is actually up-and-down, as well as side-to-side movement at the same time. To minimize the damages:

Small houses/single story building:

1. The foundation has to be re-enforced with rebars as the special mixture of concrete is poured over them. This allows the concrete foundation to buckles and flexes with the 20 feet of very compacted amended soil during the rough grading processes (a process that the earth moving company performed to remove old soils and replace with better soils to prevent the building from sinking).

2. For the larger buildings, rather than 20 feet of amended soils, it may be up to 50 feet. On top of that, the foundation is re-enforced with rebars, and there are two (not one) foundations. The bottom foundation is used to move with the soil when there's an earthquake. In between foundations, there may be high tension spring coils/columns to minimize any movement of the bottom foundation to the building itself. Just like how your car is built. Wheels touch the ground and bounce with it. The springs and shocks attaching to the wheels prevent the bouncing-rattling-rolling movements from shaking you too badly so you can drink your sodas without spilling it.

You get my pictures? :wink: There's a massive research on a city in Japan that can withstand up to a 9.0 earth quake. You heard me right. It's called the "Neo-Tokyo" project. That was my old researches based on, and studies of California Building Industrial Association engineered structures as well.

Posted: Mon Oct 22, 2007 1:58 pm
by tdaly
jayjay,

I have done miniaturized research in seismic engineering (I've done this kind of project before), so I would be more than happy to help you as you develop your project. However, in order to be of the most help to you, I need to know a few things:

1. What grade are you in?
2. What is the question you are trying to answer?
3. What is your hypothesis? (What do YOU think will happen?)

Once you've answered these questions in as much detail as possible, we can help you design your experiment and analyze its results.

I would also do some reading about earthquakes in general. Try looking at the chapter on earthquakes in a science text book (once I know what grade you are in I can provide more details). Also be sure to understand the difference kinds of seismic waves (P-waves, S-waves, Q-waves, L-waves, etc.) and the type of movement they produce. If you have questions about this or need some help in doing research, feel free to ask.

Looking forward to your question and hypothesis!

Posted: Mon Oct 22, 2007 3:59 pm
by Craig_Bridge
Since we don't know the hypothesis, we are ahead of the researcher, but I've got to point out something that just doesn't make sense:
This allows the concrete foundation to buckles and flexes with the 20 feet of very compacted amended soil during the rough grading processes (a process that the earth moving company performed to remove old soils and replace with better soils to prevent the building from sinking).

Even in California where some local building codes are very strange, I can understand 20 cm of soil replacement under footings for hydrology considerations, even 20 inches in extreme cases, but replacing and compacting a 20 foot thickness of soil would be VERY expensive for even 4 story residences and would require a lot of engineering design, simulation, and testing during construction. Maybe if the site was a landfill so there were other reasons for soil replacement, otherwise, pile driving would be a more cost effective way of putting a high load on a poor soil.

Posted: Mon Oct 22, 2007 4:18 pm
by wildfirefox
Quite true on us being ahead of the researcher. Talking about the carriage is before the horse.

As for the soil amending, it's not odd at all actually. Here's an example of the extreme soil amendment:

Construction project for a 1200 units residential site near a river called Lytle Creek, developed by the company called Lytle Creek, LLC, which being controlled by two master developers by the names of Pulte and Lennar. The developing areas were at the foothills of the San Bernardino County mountains, where the soil was sandy-loam. The areas used to be cultivated for growing grapes for wine-making. City's engineers required the site to be cut down a minimum of 10 feet, imported tons of soil from the remote hillsides to backfill the cut, and compact the site according to specs. Let's just say that the residential areas went from low $400 during planning phases to the high $800 when the first home was sold. :roll: Talking about killing the home buyers with astronomical fees.

Nam