Impact of Research

Projects 1, 2, 3, 7, 11, 13, 21, 29, 36, 43

An order of magnitude reduction in seismic stresses in piping systems -- demonstrated by CREST and CREST-IRS programs in conjunction with the DST's PIPESTRESS computer program in analyzing realistic piping systems provided by Duke Power Company and Framatome Technologies. Validation of CREST and CREST-IRS.

It will allow:

• Determination of operability.
• A major planned reduction of snubbers and supports in many plants.
• Elimination of bad snubbers and supports instead of replacing them.
• Reduction of the number of snubbers and supports when a section of piping is replaced.
• Qualification of piping systems for higher-than-the-design basis earthquake input when necessary.
• Increased lead shielding on piping systems.
  
  

Projects 4, 9, 15

Reduction in seismic stresses in piping and supports due to incorporation of ductile (elasto-plastic) support behavior.

The research has resulted in:

• Development of a simple equation for calculating reduction in piping and support responses.
• A method to determine operability of piping supports.
  
  

Projects 5, 10, 14, 19, 20, 27, 28, 37, 38, 44

Implementation of improved cyclic plasticity models including ratchetting phenomenon in the ANSYS program and reconciliation of experimental and analytical results.

Ongoing progress in the research has led or will lead to:

• Efficient, numerable simulations of inelastic dynamic behavior of piping systems up to the failure.
• Rationalization of design methods.
• Increased allowable stresses.
• Basis for changes in the ASME code to account for ratchetting-related failures.
  
  

Projects 6, 8

Closed-form equation for evaluating instructure spectra and response of coupled components (piping systems) and buildings.

Equations can be used for quick evaluation of:

• Instructure (floor) response spectra and in-equipment (for example, incabinet) response spectra.
• Response of coupled components and buildings.
  
  

Projects 12, 17, 25, 35

Evaluation of realistic incabinet response spectra using detailed finite element analysis of several typical cabinets, and reconciliation of analytical and experimental results.

Completed and ongoing research will lead to:

• Development of simplified methods for generating incabinet amplification factors.
• Reduction in unknown conservatism.
• An efficient tool for qualification of relays and other mounted equipment.
• Significant reduction in qualification cost.
  
  

Projects 16, 24, 32, 40

High cycle fatigue in welded nozzles and pipe-vessel junctions.  A number of high cycle fatigue failures of nuclear plant components are being investigated.  Fatigue test data of welded components are analyzed using finite element analyses to review the ASME Code fatigue design methods.  The ongoing research will lead to:

• Identification of locations of welded joints susceptible to fatigue failure.
• Development of new insight about i and K_e  factors in the ASME Code.
• Understanding of the root causes of weld crack initiation.
• Development of a long-term solution to the problem.
• Development of a procedure to monitor cracks.
  
  

Projects 18, 26, 33, 34, 41

Design of temporary structures for earthquake loading.

This research is developing:

• Simple design methods for unanchored structures.
• Computer program to numerically simulate behavior of unanchored structures that cannot be designed using simple methods.
• Experiments to illustrate seismic behavior of unanchored structures.
  
  

Projects 22, 30, 39. 45

Determination of stress indices for equations (9)-(11) of Section NB-3600 of the ASME Code using the finite element method and comparison of analytical and experimental results.

Ongoing research will provide:

• Guidelines for using the finite element method for calculating stress indices.
• Illustration of  using  inelastic analysis in obtaining B-indices.
• Experimental justification for using finite element analysis.
  
  

Projects 23, 31

Evaluation of stresses in buried pipes.

This research will allow:

• Determination of parameters that significantly influence the buried pipe response.
• Improvement in the existing simple equations to reduce unknown conservatism.
  

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