{"id":248095,"date":"2023-01-31T04:40:57","date_gmt":"2023-01-31T04:40:57","guid":{"rendered":"\/forum\/forums\/topic\/applying-base-acceleration-in-ls-dyna\/"},"modified":"2023-04-07T00:26:56","modified_gmt":"2023-04-07T00:26:56","slug":"applying-base-acceleration-in-ls-dyna","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/applying-base-acceleration-in-ls-dyna\/","title":{"rendered":"Applying Base Acceleration in LS-Dyna"},"content":{"rendered":"

Hello everyone, <\/span><\/p>\n

I am a student working in structural dynamics using LS-Dyna and I am a novice in this software. As a starting point, I wanted to do a simple problem, which is modeling a cantilever beam as a single degree-of-freedom (SDOF) system. My plan was to verify the numerical displacement results from the free-end SDOF using available analytical procedures from dynamics book.<\/span><\/p>\n

So far, I have modeled a single element steel beam with a square section of 6 inches by 6 inches and a length of 60 inches. The relevant keyword cards, such as *MAT_ELASTIC, *ELEMENT_BEAM, and *SECTION_BEAM, have been used to assign the material properties and geometries. I have fixed the origin node of the beam using *BOUNDARY_SPC_SET, while the other end has been left free. A snippet of my model is attached here (with the beam prism option disabled):<\/span><\/p>\n

\"A<\/span><\/p>\n

After modeling the beam in PrePost, I was intending to subject the beam’s base to an axial ground motion (perpendicular to the cross-section of the beam, or a ground motion toward the x-direction of the beam) at the origin\/far end shown here. Despite searching in various resources such as the internet, LS-Dyna manual, forums, and other instructions, I failed to find the suitable keyword card I need to apply for this. I tried to apply the *BOUNDARY_PRESCRIBED_MOTION card, but it resulted in the beam flying (not respecting the applied fixed boundary condition). I also used the *LOAD_BODY_X card, but the results obtained did not align with my analytical calculations as you can see below:<\/span><\/p>\n

\"Displacement<\/p>\n

Suspecting my model I have done two other analysis with the model but both of them matches accurately (only had 0.05% error). <\/span><\/p>\n

 <\/p>\n

Hence, I would really appreciate any help or direction on what I am getting wrong here. Thanks in advance.<\/span><\/p>\n","protected":false},"template":"","class_list":["post-248095","topic","type-topic","status-closed","hentry","topic-tag-1d-beam","topic-tag-explicit-dynamics","topic-tag-ls-dyna","topic-tag-structural-dynamics"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["273386","178077"],"_bbp_author_ip":["23.192.164.18"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["2304"],"_bbp_status":["publish"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["248095"],"_bbp_forum_id":["27814"],"_bbp_engagement":["178077","273386"],"_bbp_voice_count":["2"],"_bbp_reply_count":["4"],"_bbp_last_reply_id":["278277"],"_bbp_last_active_id":["278277"],"_bbp_last_active_time":["2023-04-07 00:26:40"]},"test":"tonmoymailinator-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/248095","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/248095\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=248095"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}