earthquake loads 1

[rachanapillai]

I have the response spectrum function for my model and now I want to input these details into etabs so that it can perform the earthquake analysis.How can i do this

 

[slickdeals]

Do you have any colleagues at work who know to use etabs? It seems a little dangerous that you are setting off on a path of designing buildings subject to seismic forces.

If you the spectrum, you will need to define the RS cases. Remember that you have to do a static analysis and then scale the base shears from dynamic analysis to 85% of the static values. Also remember that you will need to capture 90% of the modal mass for the analysis to be valid.

 

[ge0san]

slickdeals,
Would it be needed to do the static analysis first and, after that, to scale the spectrum cases to reach 85% of the static base shear force? If, from analysis, you get >90% horizontal vibrating mass accelerated, then you will get the base shear force = >90%*mass*acceleration. This is more than 85%. So, the problem reduces to requesting sufficient number of eigenmodes to be found by the program, so the influence of the higher modes is considered in analysis. The number of modes I usually request is [3*sqrt(number of floors)]. But, to be overconservative, one can request [3*(number of floors)], which means [(translation+translation+rotation)*(number of lumped masses at story levels)].

 

[jenofstructures]

to input your response spectrum you must go to "define" then go to "define response spectrum function" then have input on it

after that go to "response spectrum cases"

we you already had these input answered try to run the analysis first and then check the summary for the ETABS analysis on this

scaling factor also must be considered on the dynamics. in our case we do it by SF= Ig / R
where:
I = Importance factor
g = gravitational force
R= response modulus
I don't now what others used when it comes to these


@ geOsan, i do the 3*the number of floors for the modes. I didn't know of the 3*SQRT of number of floors thanks for sharing this

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