{"id":1809,"date":"2023-03-09T20:33:50","date_gmt":"2023-03-10T04:33:50","guid":{"rendered":"https:\/\/gantovnik.com\/bio-tips\/?p=1809"},"modified":"2024-05-14T12:34:23","modified_gmt":"2024-05-14T19:34:23","slug":"342-gravity-loading-in-nastran-grav-card","status":"publish","type":"post","link":"https:\/\/gantovnik.com\/bio-tips\/2023\/03\/342-gravity-loading-in-nastran-grav-card\/","title":{"rendered":"#342 Gravity loading in Nastran (GRAV card)"},"content":{"rendered":"<p>Inertia loading: 1G GRAV load (down)<\/p>\n<p>Description: Used to define gravity vectors to determine gravity loading for the structural model.<\/p>\n<pre class=\"brush: python; title: ; notranslate\" title=\"\">\r\n$2345678$2345678$2345678$2345678$2345678$2345678$2345678$2345678\r\n$1111111$0222222$3333333$4444444$5555555$6666666$7777777$8888888\r\n$GRAV   SID     CID     G       N1      N2      N3   \r\nGRAV    200     0       386.4   0.0     0.0     -1.0   \r\n<\/pre>\n<p>SID = load id.<br \/>\nCID = coordinate system id. A CID=0 references the basic coordinate system. If CID=-1, the gravity vector components are in the local displacement coordinate system of the grid points.<br \/>\nG = gravity vector scale factor.<br \/>\nN1, N2, N3 = gravity vector components measured in coordinate system defined by CID.<\/p>\n<p>Nastran does allow a global change in Mass units with the parameter WTMASS. This is typically used when using English units so the user can enter concentrated masses, densities, etc with weight units since this is easier to think in terms of weight than actual English mass units. NASTRAN will then multiple the assembled structural mass matrix by the value on the PARAM WTMASS card hence converting the weight to mass. The relationship of mass to weight is: weight= mass*gravity. So to convert weight to mass is 1\/gravity. Applicable WTMASS values would be:<\/p>\n<p>PARAM, WTMASS, value<br \/>\n1\/32.2[ft\/s^2]=0.031056<br \/>\n1\/386.4[in\/s^2]=0.002588<\/p>\n<p>This parameter is used when material density is input in weight instead of mass units.<br \/>\nrho_m = (1\/g)*rho_w<br \/>\nrho_m = mass or mass density<br \/>\nrho_w = weight or weight density<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Inertia loading: 1G GRAV load (down) Description: Used to define gravity vectors to determine gravity loading for the structural model. $2345678$2345678$2345678$2345678$2345678$2345678$2345678$2345678 $1111111$0222222$3333333$4444444$5555555$6666666$7777777$8888888 $GRAV SID CID G N1 N2 N3 GRAV 200 0 386.4 0.0 0.0 -1.0 SID = load id. CID = coordinate system id. A CID=0 references the basic coordinate system. If CID=-1, the [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","_lmt_disableupdate":"yes","_lmt_disable":"","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[22],"tags":[80,42],"class_list":["post-1809","post","type-post","status-publish","format-standard","hentry","category-nastran","tag-grav","tag-nastran"],"modified_by":"gantovnik","jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p8bH0k-tb","jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":690,"url":"https:\/\/gantovnik.com\/bio-tips\/2020\/09\/122-wtmass-parameter\/","url_meta":{"origin":1809,"position":0},"title":"#122: WTMASS Parameter in Nastran","author":"gantovnik","date":"2020-09-28","format":false,"excerpt":"#121: WTMASS Parameter Global mass matrix scaling factor. The terms of the global mass matrix are multiplied by the value of WTMASS when they are generated. This parameter is used when material density is input in weight instead of mass units. It does not affect loads generated by GRAV or\u2026","rel":"","context":"In &quot;nastran&quot;","block_context":{"text":"nastran","link":"https:\/\/gantovnik.com\/bio-tips\/category\/nastran\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":10486,"url":"https:\/\/gantovnik.com\/bio-tips\/2025\/09\/464-difference-between-cbush-and-cbush1d-in-hypermesh\/","url_meta":{"origin":1809,"position":1},"title":"#464 Difference Between CBUSH and CBUSH1D in HyperMesh","author":"gantovnik","date":"2025-09-30","format":false,"excerpt":"When working with connectors in HyperMesh \/ Nastran, you will often see two element types: CBUSH and CBUSH1D. While they sound similar, they serve slightly different purposes. CBUSH (General-Purpose Bushing Element) Type: 2-node element, each node has 6 DOF (12 total). Flexibility: Allows stiffness definition in all 6 directions (translation\u2026","rel":"","context":"In &quot;HyperMesh&quot;","block_context":{"text":"HyperMesh","link":"https:\/\/gantovnik.com\/bio-tips\/category\/hypermesh\/"},"img":{"alt_text":"Generated image","src":"https:\/\/sdmntpraustraliaeast.oaiusercontent.com\/files\/00000000-ebfc-61fa-8b58-b37a4b4c018b\/raw?se=2025-09-30T21%3A33%3A03Z&sp=r&sv=2024-08-04&sr=b&scid=fa3459b1-8b6d-5d9f-afff-30ef6a559619&skoid=8cb40e9f-389f-4cf6-afaa-e5bd4c7fd98c&sktid=a48cca56-e6da-484e-a814-9c849652bcb3&skt=2025-09-29T23%3A21%3A56Z&ske=2025-09-30T23%3A21%3A56Z&sks=b&skv=2024-08-04&sig=zsfkgTujIKv1NO97C10CMa7N1D5tSM2AO403bHULAqg%3D","width":350,"height":200,"srcset":"https:\/\/sdmntpraustraliaeast.oaiusercontent.com\/files\/00000000-ebfc-61fa-8b58-b37a4b4c018b\/raw?se=2025-09-30T21%3A33%3A03Z&sp=r&sv=2024-08-04&sr=b&scid=fa3459b1-8b6d-5d9f-afff-30ef6a559619&skoid=8cb40e9f-389f-4cf6-afaa-e5bd4c7fd98c&sktid=a48cca56-e6da-484e-a814-9c849652bcb3&skt=2025-09-29T23%3A21%3A56Z&ske=2025-09-30T23%3A21%3A56Z&sks=b&skv=2024-08-04&sig=zsfkgTujIKv1NO97C10CMa7N1D5tSM2AO403bHULAqg%3D 1x, https:\/\/sdmntpraustraliaeast.oaiusercontent.com\/files\/00000000-ebfc-61fa-8b58-b37a4b4c018b\/raw?se=2025-09-30T21%3A33%3A03Z&sp=r&sv=2024-08-04&sr=b&scid=fa3459b1-8b6d-5d9f-afff-30ef6a559619&skoid=8cb40e9f-389f-4cf6-afaa-e5bd4c7fd98c&sktid=a48cca56-e6da-484e-a814-9c849652bcb3&skt=2025-09-29T23%3A21%3A56Z&ske=2025-09-30T23%3A21%3A56Z&sks=b&skv=2024-08-04&sig=zsfkgTujIKv1NO97C10CMa7N1D5tSM2AO403bHULAqg%3D 1.5x, https:\/\/sdmntpraustraliaeast.oaiusercontent.com\/files\/00000000-ebfc-61fa-8b58-b37a4b4c018b\/raw?se=2025-09-30T21%3A33%3A03Z&sp=r&sv=2024-08-04&sr=b&scid=fa3459b1-8b6d-5d9f-afff-30ef6a559619&skoid=8cb40e9f-389f-4cf6-afaa-e5bd4c7fd98c&sktid=a48cca56-e6da-484e-a814-9c849652bcb3&skt=2025-09-29T23%3A21%3A56Z&ske=2025-09-30T23%3A21%3A56Z&sks=b&skv=2024-08-04&sig=zsfkgTujIKv1NO97C10CMa7N1D5tSM2AO403bHULAqg%3D 2x"},"classes":[]},{"id":1489,"url":"https:\/\/gantovnik.com\/bio-tips\/2022\/06\/210-parametric-curve-in-3d-2-2-2-2-2-2-2-2-2-2-2-2-2-3-2-2-2-2-2-2-2-2-2-3-2-2-2-2-2-2-2-2\/","url_meta":{"origin":1809,"position":2},"title":"#284 Coordinate Systems in Nastran","author":"gantovnik","date":"2022-06-09","format":false,"excerpt":"In Nastran The stress and strain of the elements are given in the element coordinate system. In Patran, you can select different coordinate systems in coordinate transformation in plot options under [Action\/Create, Object\/Fringe].","rel":"","context":"In &quot;HyperMesh&quot;","block_context":{"text":"HyperMesh","link":"https:\/\/gantovnik.com\/bio-tips\/category\/hypermesh\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":666,"url":"https:\/\/gantovnik.com\/bio-tips\/2020\/09\/112-msc-nastran-sol-106\/","url_meta":{"origin":1809,"position":3},"title":"#112 MSC Nastran SOL 106","author":"gantovnik","date":"2020-09-28","format":false,"excerpt":"#112 MSC Nastran SOL 106 MSC Nastran SOL 106 The nonlinear effects in structures occur due to nonlinear material behavior and large deformations. Geometric nonlinearity becomes relevant when the structure is subjected to large displacement and rotation. Geometric nonlinearity effects are prominent in two aspects: geometric stiffening due to initial\u2026","rel":"","context":"In &quot;nastran&quot;","block_context":{"text":"nastran","link":"https:\/\/gantovnik.com\/bio-tips\/category\/nastran\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":651,"url":"https:\/\/gantovnik.com\/bio-tips\/2020\/09\/106-nonlinear-buckling-sol106\/","url_meta":{"origin":1809,"position":4},"title":"#106: Nonlinear Buckling in MSC Nastran (SOL106)","author":"gantovnik","date":"2020-09-25","format":false,"excerpt":"#106: Nonlinear Buckling (SOL106) 1) Linear buckling of Euler column. For clamped-free boundary conditions the critical load is: Pcrit = (pi**2)*E*I\/(4*(L**2)), where, E = 10.5E6, I = 8.333-5, L=10 means Pcrit = 21.59 2) Nonlinear buckling with PARAM,BUCKLE,2 In f06 result file search for following message (right after eigenvalue table).\u2026","rel":"","context":"In &quot;buckling&quot;","block_context":{"text":"buckling","link":"https:\/\/gantovnik.com\/bio-tips\/category\/buckling\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":660,"url":"https:\/\/gantovnik.com\/bio-tips\/2020\/09\/109-how-to-output-the-stiffness-matrices-in-nastran\/","url_meta":{"origin":1809,"position":5},"title":"#109: How to output the stiffness matrices in Nastran?","author":"gantovnik","date":"2020-09-28","format":false,"excerpt":"#109: How to output the stiffness matrices in Nastran? PARAM,EXTOUT,DMIGPCH The matrices will be printed in punch file *.pnch KAAX = boundary stiffness matrix PAX = boundary load matrix","rel":"","context":"In &quot;nastran&quot;","block_context":{"text":"nastran","link":"https:\/\/gantovnik.com\/bio-tips\/category\/nastran\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"_links":{"self":[{"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/posts\/1809","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/comments?post=1809"}],"version-history":[{"count":2,"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/posts\/1809\/revisions"}],"predecessor-version":[{"id":2187,"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/posts\/1809\/revisions\/2187"}],"wp:attachment":[{"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/media?parent=1809"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/categories?post=1809"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gantovnik.com\/bio-tips\/wp-json\/wp\/v2\/tags?post=1809"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}