Many times beams are necessary for efficient analyses. Or beams in connections with solids (e.g. solid frame nodes). According to ANSYS the BEAM188 is both very accurate and efficient as beam elements. However, the "Common sections" are actually non-existing! (Except the simple solid ones and the circular pipe). All real life sections have fillets that affects the sections properties significantly. For the hollow section 200x100x10 mm the 2. Moment of area is 13.7% too high when the fillets are not considered (R=25 mm). It is possible to maintain both the cross section area (for weight) and the 2. Moment of area Iy (strong direction) with adjustments of the wall thicknesses. But then, in the transverse direction (Iz), the value becomes 24 % too low! So one may wonder why these "common sections" are there at all. Of course we have user integrated sections where you fill in cross section values from beam tables. But it is a cumbersome task to keep track of the cross section orientations in a more complicated framework. Then there are the User defined cross sections, where you make a cross section drawing. This works fine in APDL (after some initial work) because you can make your own cross section library (SEC-files). In Workbench it is more tricky to make cross sections based on your own drawings, but it is possible - within the Design Modeler (DM) - model, where you are working. However, it seems very difficult to benefit from drawings that are made in earlier jobs. There is a possibility to export the cross sections as js-scripts. But for the hollow section (mentioned above), it became solid when the js-script was imported in a later job! (The inner sketch lines were ignored). (And No!, DM cannot use the SEC-files from APDL). The easiest way would have been to use the user integrated types, with beam table values or user integrated values, and then ANSYS should let the user assign one of the "common types" as a graphical illustration to the geometry for each line body to keep track of the orientation. There could have been some rough graphical sizing based on, say the cross section area (as in frame statics software). The alternative is to have better library facilities in DM. Well, I may have missed possibilities and facilities. Only recently I found that it was possible to make a DM cross section from an IGES file ("Solution" on Customer Portal, updated 22. Oct. 2015 - but reuse in later jobs is still complicated). Are there anybody else out there with information, opinions or updates on this topic? Hilsen (Best Regards) Roar Andreassen Førstelektor (Associate Professor) Høgskolen i Narvik Tlf. +47 76966115, mob. +47 90199753

On Dec 11, 2015, at 2:27 AM, Andreassen Roar wrote: > According to ANSYS the BEAM188 is both very accurate and efficient > as beam elements. However, the "Common sections" are actually non- > existing! (Except the simple solid ones and the circular pipe). All > real life sections have fillets that affects the sections > properties significantly. Likewise, the tabulated section properties in the AISC manual are considered minimum values for design. The presence of fillets may or may not be included. What is included are allowances for fabrication such as the wear on rolling forms, since the dimensions of a section change size as the tool wears. Sometimes fillets are included, sometimes not: no fillets are included in the tabular data for rolled angle sections. Anyone who uses the tabular sections will also note that design values for flange and web thickness for channels and I- sections are not the same as the nominal values in fractional inches. > It is possible to maintain both the cross section area (for weight) > and the 2. Moment of area Iy (strong direction) with adjustments of > the wall thicknesses. But then, in the transverse direction (Iz), > the value becomes 24 % too low! Absolutely bang on! The effect gets magnified when the mass of the structure is important, for example in seismic analysis, where frequencies and inertial loads depend directly on the correct mass. Mass inaccuracies are not so pronounced in machined items (depending on how many liberties are taken in modeling, but the mass, as modeled, for structures fabricated from rolled or wrought products can be way off because of parasitic (non-structural) weight from overgauge and local stiffening or brackets for handling, from small (or large) items which add weight but have no structural purpose and from poorly guessed lumped masses. My practice for seismic analysis is to increase the material densities by about 20%, based on measure shipping weights for large welded structures and pressure vessels. There's just about that much difference between the modeled portion of the system and the rest of the stuff that's carried. > So one may wonder why these "common sections" are there at all. Of > course we have user integrated sections where you fill in cross > section values from beam tables. But it is a cumbersome task to > keep track of the cross section orientations in a more complicated > framework. Not so hard. Just make a file of design properties for common beam sections or pipes and call them in with an APDL macro function using the standard AISC designation (like WF10x30)to search through an array of structural properties for real constant input. Personally, I think that the effort of writing and trouble shooting such a macro is more trouble than simply entering properties manually, but that's true of most macros and doing the macro has recreational value. Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen. .......................................| John Sedgwick, Spotsylvania 1864) http://www.skypoint.com/members/chrisw/

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CivilFEM for ANSYS includes a large library of beam sections based on standard sections from all over the world Peter Barrett CAE Associates > On Dec 11, 2015, at 5:37 PM, Christopher Wright <chrisw@skypoint.com> wrote: > > >> On Dec 11, 2015, at 2:27 AM, Andreassen Roar wrote: >> >> According to ANSYS the BEAM188 is both very accurate and efficient as beam elements. However, the "Common sections" are actually non-existing! (Except the simple solid ones and the circular pipe). All real life sections have fillets that affects the sections properties significantly. > Likewise, the tabulated section properties in the AISC manual are considered minimum values for design. The presence of fillets may or may not be included. What is included are allowances for fabrication such as the wear on rolling forms, since the dimensions of a section change size as the tool wears.. Sometimes fillets are included, sometimes not: no fillets are included in the tabular data for rolled angle sections. Anyone who uses the tabular sections will also note that design values for flange and web thickness for channels and I-sections are not the same as the nominal values in fractional inches. > >> It is possible to maintain both the cross section area (for weight) and the 2. Moment of area Iy (strong direction) with adjustments of the wall thicknesses. But then, in the transverse direction (Iz), the value becomes 24 % too low! > Absolutely bang on! The effect gets magnified when the mass of the structure is important, for example in seismic analysis, where frequencies and inertial loads depend directly on the correct mass. Mass inaccuracies are not so pronounced in machined items (depending on how many liberties are taken in modeling, but the mass, as modeled, for structures fabricated from rolled or wrought products can be way off because of parasitic (non-structural) weight from overgauge and local stiffening or brackets for handling, from small (or large) items which add weight but have no structural purpose and from poorly guessed lumped masses. My practice for seismic analysis is to increase the material densities by about 20%, based on measure shipping weights for large welded structures and pressure vessels. There's just about that much difference between the modeled portion of the system and the rest of the stuff that's carried. > >> So one may wonder why these "common sections" are there at all. Of course we have user integrated sections where you fill in cross section values from beam tables. But it is a cumbersome task to keep track of the cross section orientations in a more complicated framework. > Not so hard. Just make a file of design properties for common beam sections or pipes and call them in with an APDL macro function using the standard AISC designation (like WF10x30)to search through an array of structural properties for real constant input. Personally, I think that the effort of writing and trouble shooting such a macro is more trouble than simply entering properties manually, but that's true of most macros and doing the macro has recreational value. > > > Christopher Wright P.E. |"They couldn't hit an elephant at > chrisw@skypoint.com | this distance" (last words of Gen. > .......................................| John Sedgwick, Spotsylvania 1864) > http://www.skypoint.com/members/chrisw/ > > > > > _______________________________________________ > Xansys-temp mailing list > Xansys-temp@xansystest.info > http://xansystest.info/mailman/listinfo/xansys-temp_xansystest.info > If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode. > > Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This email and any attachments may contain privileged or confidential information of Computer Aided Engineering Associates. This e-mail is intended solely for the use of the individual or entity to which it is addressed. If you are not the intended recipient of this e-mail, you are hereby notified that any copying, distribution, dissemination or action taken in relation to the contents of this e-mail and any of its attachments is strictly prohibited and may be unlawful. If you have received this e-mail in error, please notify the sender immediately and permanently delete the original e-mail and destroy any copies or printouts of this e-mail as well as any attachments.