Hey everybody!
I have a question I would like to share and ask you.
We have a soil layer with medium gravel which has a depth of 38 m. We want to build a multi storey framed building safely with a fundamental period of 1.7 sec.Do you think it will be safe?
Vs is given as 750 m/s in the question.
It is also asking the natural period of the layer with 38 m but I cannot find any formula anywhere so I am a bit desperate.
Can you help me please?
All I can suggest is that gravel is inherently unstable. When building on unstable soil in California, we drive piling until we reach bedrock. Perhaps another tutor will have a formula for you. Another factor in the stability of a building in a quake is what KIND of framing? Wood? Steel? There's a difference.
http://www.gharexpert.com/articles/Earthquake-2082/Earthquake-Resistant...
I cannot open the page through this link. Should I register or sth?
Ooops! You're right. I'll find another one for you. Give me a minute.
http://en.wikipedia.org/wiki/Earthquake_engineering
http://www.earthquake.usgs.gov/learn/publications/saferstructures
I hope these help.
Thank you so much. I will check them out.
Actually I got the formula and found the answer. Now, I just need to know about the safety when ground's period is greater, equal and lower than the structure's period. Can we say that it is too dangerous if the periods are equal?
I can't help with this. The sites I found aren't very helpful either. Maybe someone else can help. Or keep looking on line and see if you can find opinions as to what is too dangerous.
Of course, I'd be happy to help you!
To determine if it will be safe to build a multi-storey framed building on a soil layer with medium gravel, we need to calculate the natural period of the soil layer and compare it to the desired fundamental period of 1.7 seconds.
To calculate the natural period of the soil layer, we need to use the formula for the period of an SDOF (Single Degree of Freedom) system:
T = 2π√(m/k)
where:
T is the period of the system,
m is the mass of the system, and
k is the stiffness of the system.
In this case, the soil layer can be considered as a mass-spring system, where the mass is the mass of the soil and the stiffness is the shear modulus of the soil.
To calculate the mass of the soil layer, we need to know the volume of the soil and its density. Let's assume that the soil layer has a uniform cross-sectional area throughout its depth:
Volume = cross-sectional area x depth
= A x d
where:
A is the cross-sectional area of the soil layer and
d is the depth of the soil layer.
Next, we need to calculate the mass of the soil by multiplying the volume by the density:
m = ρ x Volume
where:
ρ is the density of the soil.
Finally, to calculate the stiffness of the soil layer, we need to know the shear modulus (G) of the soil. In your question, the shear wave velocity (Vs) is given as 750 m/s. The shear modulus can be calculated using the following equation:
G = ρ x Vs^2
Once we have the mass and stiffness of the soil layer, we can substitute these values into the formula for the period to calculate the natural period of the layer with 38 m.
I hope this helps! Let me know if you have any further questions.