Questions tagged [seismic]

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1answer
50 views

What is the frequncy range of seismic vibrations?

I'm working on a structure which needs to sustain common seismic vibrations due to earthquakes. So I want to do some modal analysis to find natural frequencies of the structure and make sure they are ...
1
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1answer
31 views

Wind load vs Earthquake load and R factor

I read somewhere that if for instance for a building earthquake forces are expected to be much higher than wind loads, we can increase the R (response modification factor) value, so that we bring down ...
0
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0answers
15 views

Minimum nominal cross section for a masonry column that supports only a roof for a structure in Seismic Design Cat B?

Minimum nominal cross section for a masonry column that supports only a roof for a structure in Seismic Design Cat B? Trying to find this referenced in IBC and no luck.
0
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0answers
116 views

Seismic Design Changes between ASCE and UBC Code?

what is the difference between the seismic design between ASCE and UBC code? from load combinations to loads applied to the history between the sudden shift or change in the code. and which one of the ...
0
votes
1answer
60 views

Slab Stiffness Modifiers applied in Vertical Elements design but not in Slab design?

Why in the design of vertical elements (columns and walls) for a structure against lateral loads (such as seismic and wind) we use a slab (or shell) with a stiffness modifiers (such as 0.25 according ...
0
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0answers
20 views

Wave train 200 m/s meaning

I ran a 60 m seismic line. Energization with hammer. 12 (10 hz vertical 5 m spaced) geophones and 5 shots (15 m spaced). Record length 0.5 s. Thanks to a borehole near a estrata of gravelly silt man-...
1
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2answers
93 views

How to distribute moment from Lateral Load Method (Static Analysis IBC for example) to Each shear wall individually?

I have used the Equivalent Lateral Load Method from the IBC code to distribute forces and moments on each storey (level) but what I need to know is how to distribute the moment on each shear wall. ...
1
vote
1answer
422 views

How to handle modal combination in response spectrum analysis for member forces for member with more than 1 element?

My textbook says for mode combination, the peak value $r$ of each response quantity is determined by combining the peak values $r_n$ of the modal contributions to the same response quantity. From ...
4
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2answers
849 views

Generating a Blank Seismic Tripartite Graph

I am performing a calculation in which I need to plot a generated response spectrum to a seismic tripartite graph. However, I am having a heck of a time finding a blank tripartite graph online. A ...
1
vote
1answer
226 views

Why is it useful to scale seismic ground motion data

I am learning by myself structural dynamics but confused about the concept of scaled ground motion data. I can't get the reason why the acceleration data should be scaled. I mean, isn't it better to ...
4
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2answers
663 views

Accidental Torsion and Equivalent Static Load for an irregular structure

Important note: I am writing a structural FEM software from scratch, so I won't able to use existing commercial FEM package. I would need to know how all the important quantities are calculated from ...
4
votes
1answer
3k views

How to calculate the relative contribution of each mode in seismic dynamic mode analysis?

In structural dynamic mode analysis, one would have to carry out modal analysis in order to get different modes that contribute to the response of the seismic ( or wind) force. Here is a nice summary. ...
6
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1answer
620 views

How to derive Equivalent Static Load for irregular structure modeled with FEM?

Building codes such as the Uniform Building Code (UBC) or International Building Code (IBC) require the determination of Equivalent Static Lateral Forces in order to compute $P-\Delta$ effect and to ...
12
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3answers
4k views

How can large bridges be made resistant to earthquakes?

How can large bridges, with spans on the order of 1 km, be made resistant to earthquakes? I'm no expert on quakes, but there are at least two kinds of shaking: lateral and vertical. The vertical ...
5
votes
1answer
151 views

What drives improvements in seismic safety?

I get the impression that a lot of old buildings fail to meet modern earthquake safety norms, and need to be rebuilt or retrofitted. But what has changed in the last few decades that would make a ...
11
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2answers
4k views

Why are tremors of an earthquake felt more on upper floors?

Why are tremors of an earthquake felt most on the upper floors of a building in comparison to lower floors? Does this have something to do with a third class lever?