Multiple Support Excitation

 

 

In a structure with multiple supports, different time history functions in terms of ground acceleration can be applied to different supports.  

In cases of long-span bridges (suspension bridge or cable stayed bridge), when the distance between the supports of a substructure is large, arrival time of seismic excitation varies. This effect can be considered using the "Multiple Support Excitation" function.

 

 

 

From the Main Menu select Load > Seismic > Time History Analysis Data > Multiple Support Excitation

 

 

Time History Load Case Name

Select a time history analysis load case entered in "Time History Load Cases". Click to define the relevant function if the load case has not been previously defined.

  Options

Time history load case of ground acceleration is applied to selected support nodes, or a previously defined time history load for specific support nodes is changed or removed.

Add/Replace: First data entry is added, and previously defined values are updated.

Delete: Values entered are deleted.  

Function for Direction-X

Enter the ground acceleration in GCS X-direction.

Function Name: Select the ground acceleration to be used from the list

Scale Factor: Scale factor for the ground acceleration

Arrival Time: "Delay" time for the ground acceleration. Enter the delay time when the seismic excitation arrives at the structure some time after the time history analysis is initiated.   

Function for Direction-Y

Enter the ground acceleration in GCS Y-direction.

Function Name: Select the ground acceleration to be used from the list

Scale Factor: Scale factor for the ground acceleration

Arrival Time: "Delay" time for the ground acceleration  

Function for Direction-Z

Enter the ground acceleration in GCS Z-direction.

Function Name: Select the ground acceleration to be used from the list

Scale Factor: Scale factor for the ground acceleration

Arrival Time: "Delay" time for the ground acceleration    

Angle of Horizontal Ground Acc.

Rotational angle about GCS Z-axis signifying the direction of the horizontal component of the ground acceleration. Sign convention is (+) in the counter-clockwise direction and (-) in the clockwise direction, with reference to the X-axis.