Problem:

How to evaluate DLF values consider by AutoPIPE during the dynamic analysis.

Solution:

Some dynamic loads can be considered with an equivalent static approach like Blast, Relief, etc.  However, in a piping system acted upon by time varying (dynamic) loads, the internal forces and moments are generally greater than those produced under the static application of the same magnitude load.  This amplification (difference between max dynamic and static displacement) is often expressed as the dynamic load factor, DLF, and is defined as the maximum ratio of the dynamic deflection at any time to the deflection which would have resulted from the static application of the load. 

The Static Equivalent approach simulates dynamic events with Static Load times the DLF (Static Earthquake).  A piping system’s DLF will range between 1 and 2 depend on the type of load (speed of application) and response of the system (stiffness).  This is true only for an instantaneously applied load and so is a maximum conservative value. 

Therefore, the DLF does not get applied to the dynamic analysis.  If an equivalent static approach is used to represent a dynamic load, the DLF could be multiplied by the static response to make an assumption about what the dynamic response would be.  In AutoPIPE, we have to ability to apply these loads dynamically, so we recommend doing so.

See Also

Dynamic "Time History" Analysis

Bentley AutoPIPE