{"id":2971,"date":"2018-09-17T12:56:15","date_gmt":"2018-09-17T12:56:15","guid":{"rendered":"http:\/\/buildsoftsupport.com\/?post_type=ht_kb&#038;p=2971"},"modified":"2025-10-09T16:06:03","modified_gmt":"2025-10-09T16:06:03","slug":"how-to-do-the-elastic-analysis-for-concrete","status":"publish","type":"ht_kb","link":"https:\/\/support.buildsoft.eu\/fr\/knowledge-base\/how-to-do-the-elastic-analysis-for-concrete\/","title":{"rendered":"How to do the elastic analysis for concrete"},"content":{"rendered":"<h2>Theoretical background<\/h2>\n<p>According to Eurocode\u00a0<a href=\"http:\/\/buildsoftsupport.com\/knowledge-base\/what-is-the-difference-between-a-1st-and-a-2nd-order-calculation\/\">2nd order effects<\/a> (EN 1992-1-1 \u00a75.1.4 (1)P) and imperfections (EN 1992-1-1 \u00a75.2 (2)P) must be taken into account.<\/p>\n<ul>\n<li style=\"text-align: left;\">For the 2nd order effects (EN 1992-1-1 \u00a75.8.5), you\n<ul>\n<li style=\"text-align: left;\">either do the calculation according to the general method based on a non-linear 2nd order calculation (see EN 1992-1-1 \u00a75.8.2 (2)P, \u00a75.8.5 (1), \u00a75.8.6 and \u00a75.7).<\/li>\n<li style=\"text-align: left;\">either use one the two simplified methodes:\n<ul>\n<li style=\"text-align: left;\">method based on nominal stiffness (see EN 1992-1-1 \u00a75.8.7): not implemented in Diamonds<\/li>\n<li style=\"text-align: left;\">method based on nominal curvature (see EN 1992-1-1 \u00a75.8.8)<br \/>\nIn this method the 2nd\u00a0order effects are taking into account by increasing the 1st order bending moment M<sub>Ed<\/sub> with a nominal second order moment equal to e<sub>2<\/sub>\u00a0x N<sub>Ed<\/sub>.<\/p>\n<p style=\"text-align: center;\">M<sub>Ed.reinforcement<\/sub> = M<sub>Ed<\/sub> + e<sub>2<\/sub> x N<sub>Ed<\/sub><\/p>\n<p>e<sub>2<\/sub>\u00a0[mm] is function of the effective length (syn. buckling length).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n    \t\t<div class=\"hts-messages hts-messages--info   hts-messages--withicon \" id=\"\" style=\"\">\r\n    \t\t\t    \t\t\t    \t\t\t\t<p>\r\n    \t\t\t\t\tAlthough Eurocode 2 allows the use of a 2nd order calculation, it is not used often. Most engineers use the method of nominal curvature (= Case 1, see below).     \t\t\t\t<\/p>\r\n    \t\t\t    \t\t\t\r\n    \t\t<\/div><!-- \/.ht-shortcodes-messages -->\r\n    \t\t\n<ul>\n<li>The imperfections can be represented by an inclination \u03b8<sub>i<\/sub>. The inclination\u00a0\u03b8<sub>i<\/sub> may be taken into account (EN 1992-1-1 \u00a75.2 (7)):\n<ul>\n<li>either by translating the inclination\u00a0\u03b8<sub>i<\/sub> to equivalent horizontal forces (= &lsquo;Global imperfections&rsquo; in Diamonds)<\/li>\n<li>either by translating the inclination\u00a0\u03b8<sub>i<\/sub>\u00a0to an accidendental eccentricity e<sub>i<\/sub><br \/>\nIn this method the imperfections are taking into account by increasing the 1st order bending moment M<sub>Ed<\/sub>\u00a0with an additonal moment equal to e<sub>i<\/sub>\u00a0x N<sub>Ed<\/sub>.<\/p>\n<p style=\"text-align: center;\">M<sub>Ed.reinforcement<\/sub> = M<sub>Ed<\/sub> + e<sub>i<\/sub>\u00a0x N<sub>Ed<\/sub><\/p>\n<p>The default value for e<sub>i<\/sub> is set to 20mm in acccordance to EN 1992-1-1 \u00a76.1(4). But this is a minimum value. You should check if a higher value might apply to your model (using EN 1992-1-1 equ. 5.2)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>So if you would use <strong>the simplyfied method for both the 2nd order effects and the imperfections<\/strong>, you will end up with the following bending moment:<\/p>\n<p style=\"text-align: center;\">M<sub>Ed.reinforcement<\/sub>\u00a0= M<sub>Ed<\/sub>\u00a0+ e<sub>2<\/sub>\u00a0x N<sub>Ed<\/sub> + e<sub>i<\/sub>\u00a0x N<sub>Ed<\/sub> = M<sub>Ed<\/sub> + N<sub>Ed<\/sub> x (e<sub>2<\/sub>\u00a0+ e<sub>i<\/sub>)<\/p>\n<h2>How is the theory implemented in Diamonds?<\/h2>\n<p>Depending on the selected options during the elastic analysis <img decoding=\"async\" loading=\"lazy\" class=\"img_inline alignnone size-full wp-image-1292\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2017\/06\/KnopRekenmachine.png\" alt=\"\" width=\"29\" height=\"29\" \/>, you will have to (un)check some options in the Buckling parameters window<img decoding=\"async\" loading=\"lazy\" class=\"img_inline alignnone size-full wp-image-2122\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png\" alt=\"\" width=\"37\" height=\"36\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png 37w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters-35x35.png 35w\" sizes=\"(max-width: 37px) 100vw, 37px\" \/>. An overview:<\/p>\n<p><strong>Case 1: assume you do a 1st order calculation [Recommended and most often used option]<\/strong><\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"45%\"><img decoding=\"async\" loading=\"lazy\" class=\"size-large wp-image-4331 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik3.png\" alt=\"\" width=\"579\" height=\"330\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik3.png 579w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik3-300x171.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik3-50x28.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik3-60x34.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik3-35x20.png 35w\" sizes=\"(max-width: 579px) 100vw, 579px\" \/><\/td>\n<td>\u21d2<\/td>\n<td>Then:<\/p>\n<ul>\n<li>e<sub>i<\/sub>\u00a0= 20mm\u00a0because global\u00a0imperfections\u00a0have NOT BEEN taken into account yet<\/li>\n<li>e<sub>2<\/sub>\u00a0\u2260 0 because 2nd order effects have\u00a0NOT BEEN taken into account yet<\/li>\n<\/ul>\n<p>So, in the window\u00a0<img decoding=\"async\" loading=\"lazy\" class=\"img_inline alignnone size-full wp-image-2122\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png\" alt=\"\" width=\"37\" height=\"36\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png 37w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters-35x35.png 35w\" sizes=\"(max-width: 37px) 100vw, 37px\" \/>you must:<\/p>\n<ol>\n<li>check the option\u00a0\u2018Verify buckling with an additional eccentricity&rsquo;<\/li>\n<li>set <a href=\"http:\/\/buildsoftsupport.com\/knowledge-base\/how-to-set-the-buckling-lengths\/\">the buckling lengths<\/a> to a meaningful value, because\u00a0e<sub>2<\/sub>\u00a0= ft(buckling lengths).<\/li>\n<li>set the accidental eccentricity\u00a0e<sub>i<\/sub>\u00a0to 20mm<\/li>\n<\/ol>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"wp-image-4363 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik9.png\" alt=\"\" width=\"501\" height=\"117\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik9.png 643w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik9-300x70.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik9-50x12.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik9-60x14.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik9-35x8.png 35w\" sizes=\"(max-width: 501px) 100vw, 501px\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Case 2: assume you do a 1st order calculation\u00a0 + global imperfections<\/strong><\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"45%\"><img decoding=\"async\" loading=\"lazy\" class=\"size-large wp-image-4332 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik4.png\" alt=\"\" width=\"577\" height=\"330\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik4.png 577w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik4-300x172.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik4-50x29.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik4-60x34.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik4-35x20.png 35w\" sizes=\"(max-width: 577px) 100vw, 577px\" \/><\/td>\n<td style=\"text-align: center;\">\u21d2<\/td>\n<td>Then:<\/p>\n<ul>\n<li>e<sub>i<\/sub>\u00a0= 0 because global\u00a0imperfections\u00a0have been taken into account<\/li>\n<li>e<sub>2<\/sub> \u2260 0 because 2nd order effects have NOT BEEN taken into account yet<\/li>\n<\/ul>\n<p>So, in the window\u00a0<img decoding=\"async\" loading=\"lazy\" class=\"img_inline alignnone size-full wp-image-2122\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png\" alt=\"\" width=\"37\" height=\"36\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png 37w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters-35x35.png 35w\" sizes=\"(max-width: 37px) 100vw, 37px\" \/>you must:<\/p>\n<ol>\n<li>check the option\u00a0\u2018Verify buckling with an additional eccentricity&rsquo;<\/li>\n<li>set <a href=\"http:\/\/buildsoftsupport.com\/knowledge-base\/how-to-set-the-buckling-lengths\/\">the buckling lengths<\/a> to a meaningful value, because\u00a0e<sub>2<\/sub>\u00a0= ft(buckling lengths)<\/li>\n<li>set the accidental eccentricity\u00a0e<sub>i<\/sub>\u00a0to 0mm<\/li>\n<\/ol>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"wp-image-4336 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik8.png\" alt=\"\" width=\"500\" height=\"116\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik8.png 646w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik8-300x70.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik8-50x12.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik8-60x14.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik8-35x8.png 35w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Case 3: assume you do a 2nd order calculation + global imperfections<\/strong><\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"45%\"><img decoding=\"async\" loading=\"lazy\" class=\"size-full wp-image-4329 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik1.png\" alt=\"\" width=\"582\" height=\"331\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik1.png 582w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik1-300x171.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik1-50x28.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik1-60x34.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik1-35x20.png 35w\" sizes=\"(max-width: 582px) 100vw, 582px\" \/><\/td>\n<td>\u21d2<\/td>\n<td>Then:<\/p>\n<ul>\n<li>e<sub>i<\/sub> = 0 because global imperfections\u00a0have been taken into account<\/li>\n<li>e<sub>2<\/sub> = 0 because 2nd order effects have already been taken into account<\/li>\n<\/ul>\n<p>So, in the window\u00a0<img decoding=\"async\" loading=\"lazy\" class=\"img_inline alignnone size-full wp-image-2122\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png\" alt=\"\" width=\"37\" height=\"36\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png 37w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters-35x35.png 35w\" sizes=\"(max-width: 37px) 100vw, 37px\" \/>you must:<\/p>\n<ol>\n<li>uncheck the option \u2018Verify buckling with an additional eccentricity&rsquo;.<\/li>\n<li>it is not necessary to calculate the buckling lengths, because only\u00a0e<sub>2<\/sub>\u00a0= ft(buckling lengths), and e<sub>2 <\/sub>=0 because the option \u2018Verify buckling with an additional eccentricity&rsquo; is unchecked.<\/li>\n<li>The entered value for the accidental eccentricity\u00a0e<sub>i<\/sub> is\u00a0irelevant because the\u00a0option \u2018Verify buckling with an additional eccentricity&rsquo; is unchecked.<\/li>\n<\/ol>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"wp-image-4333 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik5.png\" alt=\"\" width=\"503\" height=\"120\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik5.png 646w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik5-300x72.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik5-50x12.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik5-60x14.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik5-35x8.png 35w\" sizes=\"(max-width: 503px) 100vw, 503px\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Case 4: assume you do a 2nd order calculation <\/strong><\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"45%\"><img decoding=\"async\" loading=\"lazy\" class=\"size-large wp-image-4330 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/betonknik2.png\" alt=\"\" width=\"581\" height=\"328\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik2.png 581w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik2-300x169.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik2-50x28.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik2-60x34.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/betonknik2-35x20.png 35w\" sizes=\"(max-width: 581px) 100vw, 581px\" \/><\/td>\n<td>\u21d2<\/td>\n<td>Then:<\/p>\n<ul>\n<li>e<sub>i<\/sub> = 20mm because global imperfections\u00a0have NOT BEEN taken into account yet<\/li>\n<li>e<sub>2<\/sub>\u00a0= 0 because 2nd order effects have already been taken into account<\/li>\n<\/ul>\n<p>So, in the window\u00a0<img decoding=\"async\" loading=\"lazy\" class=\"img_inline alignnone size-full wp-image-2122\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png\" alt=\"\" width=\"37\" height=\"36\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters.png 37w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2017\/12\/KnopKnikParameters-35x35.png 35w\" sizes=\"(max-width: 37px) 100vw, 37px\" \/>you must:<\/p>\n<ol>\n<li>check the option\u00a0\u2018Verify buckling with an additional eccentricity&rsquo;<\/li>\n<li>set the buckling lengths in both directions to a small value (1cm for example, but not 0!), so that e<sub>2<\/sub>\u00a0= 0. Otherwise the\u00a02nd order effect, will be taken into account twice!<\/li>\n<li>set the accidental eccentricity\u00a0e<sub>i<\/sub> to 20mm<\/li>\n<\/ol>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"wp-image-4352 aligncenter\" src=\"http:\/\/buildsoftsupport.com\/wp-content\/uploads\/2018\/09\/knikbeton7.png\" alt=\"\" width=\"502\" height=\"118\" srcset=\"https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/knikbeton7.png 642w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/knikbeton7-300x71.png 300w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/knikbeton7-50x12.png 50w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/knikbeton7-60x14.png 60w, https:\/\/support.buildsoft.eu\/wp-content\/uploads\/2018\/09\/knikbeton7-35x8.png 35w\" sizes=\"(max-width: 502px) 100vw, 502px\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Notes:<\/p>\n<ul>\n<li>If your model contains multiple independent structures (for example: isolated columns), and you want to take global imperfections into account: make one Diamonds-file for each structure. Because Diamonds only remember the worst direction of the global imperfection, not the enveloppe. That direction can be the worst for structure 1, be not necessarily for structure 2.<\/li>\n<li>In Diamonds the reinforcement pattern \u00ab\u00a0Optimal\u00a0\u00bb is the default. However, this doesn&rsquo;t always results in the most economic reinforcement. <a href=\"https:\/\/support.buildsoft.eu\/knowledge-base\/what-is-the-difference-between-the-reinforcement-patterns-and-why-is-one-more-economic-than-another\/\" target=\"_blank\" rel=\"noopener\">Read more about it.<\/a><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Theoretical background According to Eurocode\u00a02nd order effects (EN 1992-1-1 \u00a75.1.4 (1)P) and imperfections (EN 1992-1-1 \u00a75.2 (2)P) must be taken into account. For the 2nd order effects (EN 1992-1-1 \u00a75.8.5), you either do the calculation according to the general method based on a non-linear 2nd order calculation (see EN 1992-1-1&#8230;<\/p>\n","protected":false},"author":3,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":[],"ht-kb-category":[62],"ht-kb-tag":[263,260,658,261,918,259,657],"_links":{"self":[{"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/ht-kb\/2971"}],"collection":[{"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/ht-kb"}],"about":[{"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/types\/ht_kb"}],"author":[{"embeddable":true,"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/comments?post=2971"}],"version-history":[{"count":2,"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/ht-kb\/2971\/revisions"}],"predecessor-version":[{"id":18686,"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/ht-kb\/2971\/revisions\/18686"}],"wp:attachment":[{"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/media?parent=2971"}],"wp:term":[{"taxonomy":"ht_kb_category","embeddable":true,"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/ht-kb-category?post=2971"},{"taxonomy":"ht_kb_tag","embeddable":true,"href":"https:\/\/support.buildsoft.eu\/fr\/wp-json\/wp\/v2\/ht-kb-tag?post=2971"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}