Load: Time Forcing Functions

Function

Assign time forcing functions for time history analyses.

Call

Model > Load > Time History Analysis Data > Time Forcing Function

incomplete beta

<Time Forcing Function>

<Enter new or additional time forcing functions>

Click  when the time forcing function is of random type or a walking load. Click  when the time forcing function is sinusoidal.
 

<Modify previously entered time forcing functions>

Select a time forcing function from the list in the dialog box and click .
 

<Delete previously entered time forcing functions>

Select a time forcing function from the list in the dialog box and click .

Data entry method by clicking
 

<Add/Modify/Show Time Forcing Function>

Function Name

Enter the name of the time forcing function, which will be used for applying time history loads in Dynamic Nodal Loads , Ground Acceleration, or Time Varying Static Loads. In the case of a walking load or earthquake data, the name may be automatically selected.
 

Time Function Data Type

Select a type of Time Function Data. When assigning dynamic nodal load, only Force or Moment accelerations can by used for time forcing functions.
 

Normalized Accel.

Values obtained by dividing time history acceleration by the gravitational acceleration.

Acceleration

Time history acceleration.

Force

Force acceleration.

Moment

Moment acceleration.

Normal

Force or Moment is selected to enter the time history loads as dynamic nodal loads in the Dynamic Nodal Loads function.

Normalized Accel. or Acceleration is selected to enter the time history loads as ground accelerations in the Ground Acceleration function.

Normal is selected to enter the time history loads as time dependent static loads in the Time Varying Static Loads function.
 

Scaling

Scale Factor

Specify a multiplier for Time History Data.
Maximum Value

Specify the maximum spectrum value.
 

Gravity

Display the applied acceleration of gravity, which may be revised in Project Setting.
 

Graph Options

Specify whether or not to generate a Graph in Log Scale.
 

Description

Enter a brief description of Time History Function.

For convenience, MIDAS/GTS supports the following 3 data entry methods:
 

1. Save and retrieve frequently used time history loads in and from files, respectively.

2. Access the built-in time history loads from the database.

3. The user directly enters the time function data.

1. Save and retrieve frequently used time history loads in and from files

Enter the time history loads by reading previously created files. The data are saved with '.sgs' or '.thd' extension and are written according to the following formats.
 

'fn.sgs' file type
 

'fn.thd' file type
 

 2. Access the built-in time forcing functions from the MIDAS/Civil database

Create time history loads by reading earthquake records from the database.

There are 32 types of built-in seismic accelerations in the database.

<Generate Earthquake Acceleration Record>

3. Enter directly the time forcing functions in the entry fields in the Add/Modify/Show Time History Functions dialog box

The user directly enters the time and the time forcing function values in the entry fields to the left of the dialog box

Data entry method by clicking

<Add/Modify/Show Time Forcing Function>

Function Name

Enter the name of the time forcing function, which will be used for applying time history loads in Dynamic Nodal Loads, Ground Acceleration or Time Varying Static Loads.
 

Time Function Data Type

Assign the type of data to be entered.
 

Normalized Accel

Values obtained by dividing the time history acceleration by the gravitational acceleration.

Acceleration

Time history acceleration
Force

Load (force)
Moment 

When Force or Moment is assigned, the time forcing function is used to enter the Dynamic Nodal Loads.

When Normalized Accel. or Acceleration is assigned, it is used to enter the Ground Acceleration

When Normal is assigned, a static load is defined to vary with time as a time history load in Time Varying Static Loads.
 

Parameters constituting the Sinusoidal Functions

A, C are constants, f is the frequency of excitation, D is the Damping Factor, PA is the Phase Angle.

When the time forcing function is entered in the form of a harmonic function, specify the parameters required in the Sinusoidal Function. Click Redraw Graph to display the graph of the forcing function to the right and click   to save the time forcing function.