Applies To Product(s): AutoPIPE, Version(s): all Area: Modeling Original Author: Bentley Technical Support Group Dec 2014, AutoPIPE V8i 09.06.01.10 Problem: How do I model Flex / Braided hose: Solution: Most flexible hoses fall into one of two categories, see the following for categories and suggested modeling approach: 1.Short stubby flex hosing between end connection. Usually very stiff but does allow a little bit of flexing between connection points. Modeling The flexible piping between the end connection is short enough where the user should consider its stiffness properties. Therefore, contact the manufacture of the flexible joint assembly and request all the values required by the Flexible Joint dialog in AutoPIPE. This info should include, overall length, stiffness in all 6 directions, weight, and pressure area. Due to the construction, the hose material or outside braiding may be strong enough to withstand axial expansion. If true, then insert a tie/link support connecting the 2 end points of the Flexible Joint. Be sure to configure the support with the proper stiffness and gap to represent the amount of moment before the axial expansion would be restrained. Conclusion: model using one flexible joints with appropriate stiffness values, weight, and Pressure Area. In addition, insert a support between Flexible Joint end points to restrain axial extension. Again, be sure to enter the appropriate stiffness and gap settings. 2. Lengths of flexible hose with end connection but due to their length no forces or moments are transferred Modeling Flex hoses are typically so flexible that it is like a break in the pipe with no transfer of forces or moments. Therefore recommend using a 1 or more flexible Joints back-to-back with low stiffnesses in all degrees of freedom; unless the the manufacturer can provide some stiffness values. D ue to possible instability issues during analysis, may need to provide a small non-zero value, e.g. 1 lb/in. How to deal with pressure thrust for this type of flexible hose? assuming that the hose material or braiding will be strong enough to withstand the pressure thrust generated and will not be transferred down the pipe to supporting structure, recommend Pressure Area would be set to 0.00. Therefore no Tie/Link support would be required like that used for the short hose mentioned above. Conclusion, model using one or multiple flexible joints with appropriate stiffness values, weight, and Pressure Area = 0.00 Notes: 1. Remember that AutoPIPE cannot handle large deformation and forces/moments are based on original un-deformed geometry. 2. One could use Beam elements to represent a flexible hose, In this modeling approach enter non-standard section properties instead of stiffness. See Also Flexible Joint - Modeling Approaches, Tips, Techniques Bentley AutoPIPE
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