{"id":464,"date":"2023-09-21T05:42:52","date_gmt":"2023-09-21T05:42:52","guid":{"rendered":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/?page_id=464"},"modified":"2023-12-30T01:50:00","modified_gmt":"2023-12-30T01:50:00","slug":"basic-truss-method-of-joints","status":"publish","type":"page","link":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/basic-truss-method-of-joints\/","title":{"rendered":"BASIC TRUSS&#8211;method of joints"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">This 3 member (piece) truss is made from the 2 angled legs and the connecting member (the thin black thread). It&#8217;s part of the 8 truss bridge kit.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"768\" src=\"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-content\/uploads\/2023\/09\/basic-truss-3-1024x768.jpg\" alt=\"\" class=\"wp-image-465\" srcset=\"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-content\/uploads\/2023\/09\/basic-truss-3-1024x768.jpg 1024w, https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-content\/uploads\/2023\/09\/basic-truss-3-300x225.jpg 300w, https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-content\/uploads\/2023\/09\/basic-truss-3-768x576.jpg 768w, https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-content\/uploads\/2023\/09\/basic-truss-3-1536x1152.jpg 1536w, https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-content\/uploads\/2023\/09\/basic-truss-3-2048x1536.jpg 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"3 member truss\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/NcMfWo7piFo?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">First we need to understand the geometry of the truss.<\/p>\n\n\n\n<figure class=\"wp-block-video\"><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"basic truss---mateo\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/LYtkedYw1OQ?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Now to find the External forces acting on the truss.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"> First the reactions a A and C. We use the sum of the forces in the Y direction and the sum of the moments about point A.<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"truss bridge---external forces\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/fnlK_cexYgw?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">I&#8217;ve been told by engineers who know, that when computing the external forces, we DO NOT include the weight of the truss. So instead of 11.9 pounds for the &#8220;load&#8221; I should have used just the weight of the 2 bricks- 9.4 pounds.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"> That means that when you Sum the forces in the Y direction- the sum of the 2 reactions is not 11.9 but 9.4 pounds.Next we use the Sum of the moments about point A- and use 9.4 instead of 11.9,  and get 4.7 pounds for the reaction @ C and when substituting back into the earlier formula, we get 4.7 for the reaction @A.  This makes sense seeing as that the truss is symmetric so there should be 4.7 pounds in the reactions at both A and C.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"> Now for the Internal forces. We use the Free Body diagram   FBD.<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"truss bridge model  free body diagram\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/j_PFPg-XRNo?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">By convention, when analyzing the forces using the FBD, we always assume the forces are pulling aweay from the joint- so the arrows point away from joint A<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"truss bridge model--equilibrium equations\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/yB5mmJzA9sg?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Using the sum of the forces in the X (horizontal) direction, we get an equation with 2 unknowns. The diagonal force AB can be broken down into its vertical and horizontal components.<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"truss bridge model-free body diagram--sum of forces in Y direction\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/iqtGl0tCbSQ?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Now we use the sum of the forces in the Y (vertical ) direction to compute the value of Fab.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But the reaction @A is not 5.95 but 4.7 lbs. so when we substitute 4.7 into the equation for sum of Y forces we get    Fab= negative 6.89<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"truss bridge model- sum of forces in the X direction\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/ivXL_deUvoM?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Now we have to change Fab from  8.72 to 6.89. When we substitute 6.89 into the formula, we get<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Fac (the thread)= 5.02pounds of tension. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is what the goal was from the beginning.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>This 3 member (piece) truss is made from the 2 angled legs and the connecting member (the thin black thread). It&#8217;s part of the 8 truss bridge kit. First we need to understand the geometry of the truss. Now to find the External forces acting on the truss. First the<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-464","page","type-page","status-publish","hentry"],"aioseo_notices":[],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/pages\/464","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/comments?post=464"}],"version-history":[{"count":4,"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/pages\/464\/revisions"}],"predecessor-version":[{"id":538,"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/pages\/464\/revisions\/538"}],"wp:attachment":[{"href":"https:\/\/cloudliftdesigns.com\/hammerheadcranes\/wp-json\/wp\/v2\/media?parent=464"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}