multi support seismic excitation 1

[lsms]

Hi, would you please tell me how to define different acceleration time histories at different supports of a bridge model? I have sap2000 vergion 10.
Sap defines only built in ground acceleration,

can i:
1.integrate the accelaration twice to get displacement history
2. assign joint displacement=1
3. in the anlysis case, apply the function resulted in 1. as the load is the one defined in 2
??
Please help me
yasmeen

 

[lsms]

Please help me in this regard.

 

[masomenos]

You can create time history function and analysis case in which the time history case is applied to an acceleration instead of a displacement or force. You will need to scale the acceleration in the TH analysis case to some percentage of G using current units. For example, if your units are mm and you wanted to specify .2 G, you would scale the TH analysis case to 2000 (mm) or use 6.43 for .2 G if your units are Kip-ft and so on.

Also, if you have displacement data, you could assign joint displacements under a separate static load case to your restraint points, then define a time history function with multipliers to those static joint displacements as a function of time, and define an analysis case using that time history function with the load case which you used to assign the restraint joint displacements.

You could assign the joint displacement to equal 1 and define your TH function to multiply that as a function of time.