    # Thread: Verification of modal analysis Results

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## Re: Verification of modal analysis Results Originally Posted by length zero Mech
When u use directional X=2 it means that you have doubled seismic force in that direction
Hi Z.G
X ,y and Z are only vectors not values
it is like i, j, K in vectors
X means the program will put the mass in X- direction
and Y and Z same Things  Reply With Quote

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## Re: Verification of modal analysis Results

Edward and Length zero
Which you are right?
where is the scale factor of seismic loads. Please can you show in jpg. screenshot? I'm so confused. thanks  Reply With Quote

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## Re: Verification of modal analysis Results

If u need to define seismic regarding to EC - i can helep, and you dont need scale factor
If u need to perform via UBC - mecheil can help you
Regards
Z.G. ( Lengh Zero)  Reply With Quote

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## Re: Verification of modal analysis Results

Mechil
In EC i use this values to determine direction of seismic excitation,
And if i want to use 120% of seismicX loads and 35% of seismic Y loads, you must put X=1.2 and Y=0.35, ( this mean in this case you have apply 1.2SX+0.35SY - in one case)
i MEAN SO : Put 1 on X and read Base shear And for example 100kN, Go again and put in x=2 and you will get base shear 200nK, and i mean this you can use to scaling forces by seismic excitation, And maybe this is an SCALE FACTOR to EC, ahhah
Regards
Z.G.  Reply With Quote

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## Re: Verification of modal analysis Results Originally Posted by troy_the.best Edward and Length zero
Which you are right?
where is the scale factor of seismic loads. Please can you show in jpg. screenshot? I'm so confused. thanks
Hi troy,
see follow this steps to show meaning of x,y,z directions byspectrum analysis by ubc code
2-select : analysis type
3-one form will open and you will see seismic ubc x .....
(these cases you defined before)
4-select seismic ubc _x and under the window click on parameters
5-you will get new window click on direction
6-u will get new window contains X Y and Z
when you type 1 in X this means the program will generate seismic forces in x direction
when you type 0 in x and 1=y and 1=z this means the program will generatw forces in y directiona+z direction and so on

usually we will put for seismic_x we put x=1 y=0 z=0
for seismic_y we put x=0 ;y=1; z=0
and if you would like to generate one seismic load to consider x+y we put in this case
x=1 ;y=1
hoping this clear  Reply With Quote

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## Re: Verification of modal analysis Results

Edward,

yes you are righ but It means when we say the same things.

direction in robot=scale factor in etabs

isnt it?

best regards  Reply With Quote

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## Re: Verification of modal analysis Results Originally Posted by troy_the.best Edward,

yes you are righ but It means when we say the same things.

direction in robot=scale factor in etabs

isnt it?

best regards
See falconado, Now I try one other thing
Forget now scale factor ok
run the seismic analysis ok.
get the base shear from dynamic analysis say 1000 KN ok and say the name of case is Seismic_x
calcultae the static base shear say 500 KN.
now go to combinations and make a new case say Comb1 and use the case: seismic_x multiply into combination scale = 500/1000 = 0.5
Now you get the same idea of scale factor
but when you start design do not use Seismic_x but use Comb1
Hoping this is good  Reply With Quote

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## Re: Verification of modal analysis Results Originally Posted by length zero Mechil
In EC i use this values to determine direction of seismic excitation,
And if i want to use 120% of seismicX loads and 35% of seismic Y loads, you must put X=1.2 and Y=0.35, ( this mean in this case you have apply 1.2SX+0.35SY - in one case)
i MEAN SO : Put 1 on X and read Base shear And for example 100kN, Go again and put in x=2 and you will get base shear 200nK, and i mean this you can use to scaling forces by seismic excitation, And maybe this is an SCALE FACTOR to EC, ahhah
Regards
Z.G.
But believe me x,y,z is a only a direction vector in masses by using ubc
x=1 means but forces of masses from newton equations in x-direction
x=2 same thing
but yuor concept is valid only when you apply x=1 and y=2
this means you have a vector force F=1i +2j
then the program will prepare a new unit vector
hoping you get my point  Reply With Quote

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## Re: Verification of modal analysis Results Originally Posted by mecheil.edward.hanna But believe me x,y,z is a only a direction vector in masses by using ubc
x=1 means but forces of masses from newton equations in x-direction
x=2 same thing
but yuor concept is valid only when you apply x=1 and y=2
this means you have a vector force F=1i +2j
then the program will prepare a new unit vector
hoping you get my point
edward,

I understood what he meant. Please do not be attached to the term. x = i, y = j say. all misunderstood anything. sonuçte F = 1 i + 2 j is the mean resultant force vector. that can not scale well. How well do you scale factor logging. (If you're changing coefficients in the combination?) jpeg screenshot please attaching menu.

Thank you again for interest on.  Reply With Quote

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## Re: Verification of modal analysis Results

Hi Troy
Hi Z.G
this file show u step by step seismic load by ubc
But still scale factor without solution by robot
as I told before we can generate a new combination and multiply the seismic load by the required scale factor
Hoping it will be useful
http://www.4shared.com/file/QoEHcxiR/ToTroyAndZG.html  Reply With Quote

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