{"id":283746,"date":"2023-05-13T03:54:31","date_gmt":"2023-05-13T03:54:31","guid":{"rendered":"\/forum\/forums\/topic\/structural-analysis-issues-on-a-cable-stayed-bridge\/"},"modified":"2023-06-12T09:34:45","modified_gmt":"2023-06-12T09:34:45","slug":"structural-analysis-issues-on-a-cable-stayed-bridge","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/structural-analysis-issues-on-a-cable-stayed-bridge\/","title":{"rendered":"Structural Analysis Issues on A Cable-Stayed Bridge"},"content":{"rendered":"<p>I am trying to conduct a static analysis and modal analysis on a simplified cable-stayed structure as shown below. The bridge deck and the two pylons are modeled as beam elements, while the stay cables are modeled as Link element with prestressing which are assigned using APDL commands.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/05\/13-05-2023-1683944271-mceclip0.png\" width=\"942\" height=\"396\"><\/p>\n<p>For the static structural analysis, I have tried running the analysis without using large deflection and with large deflection. The analysis ran well without large deflection. However the analysis diverged when ran with large deflection turned on. Trying to run the analysis with large deflection yielded the following error messages.<\/p>\n<div id=\"paraDiv\" style=\"display: inline\">\n<p id=\"paragraphData\" class=\"paragraphText\" style=\"font-size: 12px;display: inline\"><span>&nbsp;*** ERROR ***&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CP =&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8.828&nbsp;&nbsp; TIME= 10:42:04<\/span><br \/><span>&nbsp;The value of UX at node 228 is 152664947.&nbsp; It is greater than the&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;current limit of 1000000 (which can be reset on the NCNV command).&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;This generally indicates rigid body motion as a result of an&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;unconstrained model.&nbsp; Verify that your model is properly constrained.&nbsp;&nbsp; <\/span><\/p>\n<p><span>&nbsp;*** ERROR ***&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CP =&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8.828&nbsp;&nbsp; TIME= 10:42:04<\/span><br \/><span>&nbsp;*** MESSAGE CONTINUATION &#8212;- DIAGNOSTIC INFORMATION ***&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;If one or more parts of the model are held together only by contact&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;verify that the contact surfaces are closed.&nbsp; You can check contact&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;status in the SOLUTION module for the converged solutions using&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;CNCHECK.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><\/p>\n<p><span>&nbsp;*** ERROR ***&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CP =&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8.828&nbsp;&nbsp; TIME= 10:42:04<\/span><br \/><span>&nbsp;*** MESSAGE CONTINUATION &#8212;- DIAGNOSTIC INFORMATION ***&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;Rigid body motion can also occur when net section yielding has&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;occurred resulting in large displacements for small increments of load&nbsp; <\/span><br \/><span>&nbsp;or when buckling has occurred.&nbsp; You can plot the time history curve&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;for node 228 in the UX direction to check for stiffness (slope of the&nbsp;&nbsp; <\/span><br \/><span>&nbsp;curve) approaching zero.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><\/p>\n<p><span>&nbsp;*** WARNING ***&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CP =&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8.859&nbsp;&nbsp; TIME= 10:42:04<\/span><br \/><span>&nbsp;The unconverged solution (identified as time 1 substep 999999) is&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;output for analysis debug purposes.&nbsp; Results should not be used for&nbsp;&nbsp;&nbsp;&nbsp; <\/span><br \/><span>&nbsp;any other purpose.<\/span><\/p>\n<p class=\"paragraphText\" style=\"font-size: 12px;display: inline\">&nbsp;<\/p>\n<\/div>\n<p>Apart from that, I also have tried doing modal analysis using the results from static analysis without large deflection turned on. The analysis was finished properly, but the some of the resulting mode shapes were abnormal like the ones shown below of which the pylons detached from each other. The program also released a warning message saying that &#8220;the model dimensions were determined to be very large&#8221;.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/05\/13-05-2023-1683944348-mceclip1.png\" width=\"912\" height=\"383\"><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/05\/13-05-2023-1683944437-mceclip2.png\" width=\"921\" height=\"390\"><\/p>\n<p>In short, my goal is to get the static analysis running with large deflection turned on and for the modal analysis to give sensible results. Any help would be greatly appreciated.<\/p>\n","protected":false},"template":"","class_list":["post-283746","topic","type-topic","status-closed","hentry","topic-tag-Modal_Analysis-1","topic-tag-bridge","topic-tag-static-structural"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["261660","88","240"],"_bbp_author_ip":["23.39.172.22"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["1245"],"_bbp_status":["publish"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["283746"],"_bbp_forum_id":["27791"],"_bbp_engagement":["88","240","261660"],"_bbp_voice_count":["3"],"_bbp_reply_count":["11"],"_bbp_last_reply_id":["288161"],"_bbp_last_active_id":["288161"],"_bbp_last_active_time":["2023-06-12 09:34:22"]},"test":"35020306mahasiswa-itb-ac-id"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/283746","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\/283746\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=283746"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}