Thursday, May 1, 2014

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Time History Analysis in Staad Pro.V8i for Structures under Seismic Accelerations

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Analysis of a structure, applying data over increment time steps as a function of:
  • Acceleration
  • Force
  • Moment, or
  • Displacement
It provides the response of a structure over time during and after the application of a load.
The Time History Response of a structure is simply the response (motion or force) of the structure evaluated as a function of time including inertial effects.
Stage One
  • Time History Function Definition
  • Time Step
  • Function Definition
  • Analysis Parameters
Time Step
  1. Time Increments or Δt used for analysis.
  2. Output time-step size should be small enough to provide sufficient resolution for analysis.
  3. The required resolution is dependent upon the characteristics of applied loading and such structural properties as the natural periods.
  4. The sufficiency of resolution may be determined by decreasing the time-step size until it is small enough to not affect results.
Arrival Time is the time at which a load assignment begins
Can be positive, negative, or zero
Begins at time zero, by default
Portion of the input which occurs before time zero is ignored for negative arrival time
eg: an arrival time of -5 will neglect the first 5sec of the input function.
Scale Factor
When load type is set to Accel, the scale factor should be specified to produce the acceleration desired in the current units  when multiplied with function.
If function is in the current units, the scale factor should be set to 1.0.
eg: if time-history data is in cm/sec/sec, and current units are ft/sec/sec, then a scale factor of
1ft / 30.48cm = 0.0328 should be used.


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