Dynamic Analysis

Modal Analysis

Modal analysis is a technique of dynamic analysis of structures. Its objective is the estimation of dynamic properties such as frequencies and natural modes during free vibration as well as damping. AutoPIPE adds nodes to distribute mass and applies Finite Element techniques to accurately calculate natural modes of vibration and associated mass.

The modal analysis is the basis of Auto PIPE the other dynamic analyses: Response Spectrum, Time History or Harmonic Analysis.

During the audits carried out by the NUPIC and by the nuclear clients, it has been verified that the vibration modes and the mass distribution of the AutoPIPE is very precise and therefore it has always passed the verifications against more than 100 dynamic benchmarks.

AutoPIPE distribute mass over multiple nodes to calculate natural modal shapes

AutoPIPE calculates the optimal distance between nodes for the frequency that we indicate and divides each element into up to 10 elements, being able to increase the number of nodes in the system up to 100,000.

Seismic Response Spectra

Response Spectra

AutoPIPE can apply up to 50 seismic response spectra or 10 force spectra to a piping model. The response spectrum analyses that can be performed with AutoPIPE are:

  • Simple Spectra: in this analysis, the same spectrum is applied to the entire system or a response spectrum for each direction.
  • Multiple Response Spectra: In case the piping system is supported in several levels or in several structures, one spectrum can be applied per level or structure, as many as necessary up to the limitation of 50.
  • SAM and Multiple Response Spectra: Up to 10 Seismic Anchor Movements (S.A.M.) can be applied per analysis.
  • • Certain analyses are carried out with Force Spectra. AutoPIPE allows up to 10 force spectra to be applied in one calculation.

SAM and Multiple Response Spectra

EIn case the piping system is supported by two or more structures, an analysis with the seismic anchor motion (SAM) must be additionally performed and combined with the multiple spectrum analysis.

The SAM is a static analysis based on the deformations caused by the movement of the supports. It is very important to do it whenever the pipes are supported since the structures will have different natural modes of vibration and therefore will move in a non-solidarity way.

Multiple Spectral Analysis of a Combined Pipe and steel structure System

Time History Analysis

AutoPIPE puede calcular en una única ejecución varios casos por Time History, como:

  • Surge.
  • Triggering of safety valves.
  • Slug Flow.
  • Pump stop.
  • Pump start.
  • Turbine trip.
  • Seismic analysis by Ground Motion.

AutoPIPE integrates a Fluid Transients calculator that generates force profiles for integration by Time History. This generator is very useful for rapid valve closure phenomena, such as the tripping of a turbine, the closure of a HIPPS system, or any system where a block valve quickly closes the pipe.

Safety Valve Discharge

AutoPIPE integrates the ASME B31.1 formulas and prepares the force profile for the valve and discharge. Forces in discharge pipe direction changes, whether open or closed discharge, can be calculated using AutoPIPE's fluid transient calculation.

These histograms are integrated using the Time History analysis method.

Safety Valve Trip Force Calculation Dialog.

Harmonic Analysis

AutoPIPE can apply up to 10 Harmonic loads in a calculation. These loads can be:

  • Harmonic imposed acceleration
  • Harmonic imposed acceleration in g
  • Harmonic imposed force
  • Harmonic imposed displacement
  • Harmonic imposed speed

Harmonic loads can be generated by:

  • Vibration from rotating equipment.
  • Pulsating flow from reciprocating compressor or pumps.
  • Harmonic imposed forces.
  • Orifice plate or control valve vortices.

The AutoPIPE has a bi-directional interface with the Bentley PULS program that performs the acoustic calculation of piping systems, including reciprocating compressors and exports the harmonic forces to AutoPIPE.