{"id":31889,"date":"2026-04-27T11:56:05","date_gmt":"2026-04-27T11:56:05","guid":{"rendered":"https:\/\/protasoftware.com\/technical-manuals\/pre-analysis\/seismic-analysis-to-eurocode-8\/"},"modified":"2026-06-19T12:37:57","modified_gmt":"2026-06-19T12:37:57","slug":"seismic-analysis-to-eurocode-8","status":"publish","type":"wiki","link":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/","title":{"rendered":"Seismic Analysis To Eurocode 8"},"content":{"rendered":"<div>\n <b><span><span class=\"colour\">Prota<\/span><\/span><\/b><span class=\"colour\">Structure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been implemented :<br \/>\n <\/span><span class=\"colour\"><br \/><\/span><span class=\"colour\"><br \/>\n<\/span><\/div>\n<div><span class=\"colour\"><br \/>\n<\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">MS EN 1998-1 : 2015 (Malaysia National Annex)<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">SS EN 1998-1 : 2013 (Singapore National Annex)<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n<\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n<\/span><\/div>\n<div>\n<p class=\"MsoNormal sty__4p8xk0__cls\" style=\"font-size: 16px;letter-spacing: 0.1px\"><span class=\"sty__xjicyd__cls\">Go to&nbsp;<b class=\"sty__8r8g38__cls\">Building Analysis<\/b>&nbsp;dialog &gt;&nbsp;<b class=\"sty__f4w2hj__cls\">Pre-analysis&nbsp;<\/b>tab :&nbsp;<br class=\"sty__lkj91j__cls\" \/><\/span><\/p>\n<ol class=\"sty__4iof5m__cls\" style=\"font-size: 16px;letter-spacing: 0.1px\">\n<li class=\"sty__h68izl__cls sty__6d5qa8__cls\" style=\"list-style-type: disc\"><span class=\"sty__c67qmf__cls\">Click on&nbsp;<b class=\"sty__pbesn9__cls\">Settings Center&nbsp;<\/b>&gt;&nbsp;<a target=\"_blank\" href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/project-settings-ps-2022#Template:~:text=member%20labels%C2%A0templates.-,Codes,-This%20page%20controls\" class=\"sty__wblbsy__cls\" style=\"cursor: pointer\" rel=\"noopener noreferrer\">Code<\/a>&nbsp;section will be shown &gt; Pick&nbsp;<b class=\"sty__xaw5ej__cls\">Earthquake Code&nbsp;&nbsp;<\/b>&nbsp;<br class=\"sty__ut3lyt__cls\" \/><\/span><\/li>\n<li class=\"sty__nizzq3__cls sty__wmrzzb__cls\" style=\"list-style-type: disc\"><b class=\"sty__2cxeda__cls\"><span class=\"sty__6rnhi4__cls sty__52ho09__cls\" style=\"font-weight: 400\">Click&nbsp;<\/span>Seismic Parameter&nbsp;<\/b><span class=\"colour sty__wskv74__cls sty__gc3izr__cls\">to access the Seismic Parameters &amp; Settings<\/span><\/li>\n<\/ol>\n<\/div>\n<div>\n <b><span class=\"colour\">Malaysia NA&nbsp;<br \/><\/span><\/b><\/div>\n<div><b><span class=\"colour\"><img decoding=\"async\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png\" style=\"max-width: 100%;height: auto;padding: 0\" \/><br \/><\/span><\/b><b><span class=\"colour\"><br \/><\/span><\/b><\/div>\n<div><b><span class=\"colour\"><br \/><\/span><\/b><\/div>\n<div><b><span class=\"colour\">Singapore NA&nbsp;<\/span><\/b><br \/>\n<\/div>\n<div>\n<p> <img decoding=\"async\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-f80b5e63ce5dd4eccc4799b08313d4b2.png\" style=\"max-width: 100%;padding: 0px;height: auto\" data-zdeskdocid=\"img_6298058021706645\" class=\"docsimage\" data-zdeskdocselectedclass=\"original\" \/>\n<\/div>\n<div>\n<div>\n  \n <\/div>\n<div><span class=\"KB_New_Editor_Highlights\" style=\"margin: 10px 0px;position: relative;padding: 10px 10px 10px 40px\"><\/p>\n<div><img decoding=\"async\" alt=\"Info\" data-image=\"contentStyle\" style=\"position: absolute;left: 12px;top: 14px;width: 15px;max-width: 100%\" data-type=\"non-resize\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-db572d1aef0ece78223b48d1c4e22d0c.png\" \/>\n   <\/div>\n<div>\n    <span class=\"colour\">Click the<br \/>\n<\/span><span><i><span class=\"size\" style=\"font-size: 18px\"><span class=\"colour\"><b>i&nbsp;&nbsp;<\/b><\/span><\/span><\/i><\/span><span class=\"colour\">icon for more information and guidance on the parameter.<br \/>\n    <br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div><span class=\"colour sty__3hnba7__cls sty__bnlhwc__cls\" style=\"font-size: 16px;letter-spacing: 0.1px\">Please ensure to also read this article<\/span><span class=\"sty__sw37we__cls\" style=\"font-size: 16px;letter-spacing: 0.1px\">&nbsp;<\/span><a class=\"sty__i245fj__cls sty__qivteo__cls\" target=\"_blank\" href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/seismic-load-basic-guide\" style=\"cursor: pointer;font-size: 13px;letter-spacing: 0.1px\" rel=\"noopener noreferrer\"><span class=\"size sty__hchi09__cls sty__bepkkm__cls\" style=\"font-size: 16px\">Seismic Load &#8211; Basic Guide<\/span><\/a><span class=\"sty__9s7p67__cls\" style=\"font-size: 16px;letter-spacing: 0.1px\">.&nbsp;<\/span>\n   <\/div>\n<p><\/span><\/div>\n<h1 id=\"Parameters\" class=\"toc_anchors\"><span><span class=\"colour\">Parameters<\/span><\/span><span class=\"colour\"><br \/><\/span><\/h1>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><span><span class=\"colour\">The following are explanation of key inputs in \u201c<\/span><b><span class=\"colour\">Parameters<\/span><\/b><span class=\"colour\">\u201d tab :<\/span><\/span><span class=\"colour\"><br \/>\n  <\/span><span class=\"colour\"><br \/><\/span><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__phvd6c__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Spectrum Angle<\/span><\/b><span><span class=\"colour\">&nbsp;: Is the angle of the applied seismic forces with respect to the orientation of the structure on plan view; measured anti-clockwise from global horizontal.&nbsp;<\/span><span><span class=\"colour\">&nbsp;<\/span><\/span><span class=\"colour\">For example, if a rectangular building is modelled at a rotated angle, then the spectrum angle should be changed accordingly.<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__3xsgg9__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Seismic Zone :&nbsp;&nbsp;<\/span><\/b><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li class=\"sty__3xsgg9__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><span class=\"colour\">Singapore NA :&nbsp; Not applicable &amp; hence hidden<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li class=\"sty__3xsgg9__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><span class=\"colour\">Malaysia NA : User to select <\/span><b><span class=\"colour\">Zone<\/span><\/b><span class=\"colour\"> and <\/span><b><span class=\"colour\">City or Town &gt;&nbsp; Agr&nbsp;<\/span><\/b><span class=\"colour\">will automatically update.<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__owygiy__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Peak Reference Ground Acceleration (Agr)<\/span><\/b><span class=\"colour\">&nbsp; :&nbsp; Default values according to NA or City selected.&nbsp; This value can be changed.&nbsp;<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Ductility Level<\/span><\/b><span class=\"colour\">&nbsp;:&nbsp; <b>DCL<\/b> \/ <b>DCM<\/b> \/<b> DCH<\/b>&nbsp; &gt;&nbsp;User to choose (for low seismic zone, choose DCL)<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__vigkp8__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Importance Factor<\/span><\/b><span class=\"colour\">&nbsp;:&nbsp; User to select<\/span><\/li>\n<li class=\"sty__n46ftr__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><span class=\"font\"><b><span class=\"colour\">Behavior<\/span><\/b><\/span><b><span class=\"colour\">&nbsp;Factor (q)<\/span><\/b><span class=\"colour\">&nbsp;and&nbsp;<\/span><b><span class=\"colour\">Overstrength Factor (\u03b1u\/\u03b11)&nbsp;<\/span><\/b><span class=\"colour\">are automatically fetched from tables in the seismic code.<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__v10xfp__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Prevailing Failure Mode Coefficient (kw)<\/span><\/b><span><span class=\"colour\">&nbsp;:<\/span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">Factor associated with the prevailing failure mode in structural system with walls. Automatically fixed according to NA chosen.&nbsp;&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol><span class=\"colour\"><br \/>\n   <\/span><span class=\"colour\"><br \/>\n  <\/span><\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol><span class=\"colour\"><br \/>\n   <\/span><span class=\"colour\"><br \/>\n  <\/span><\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__36tijr__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Soil Parameters : <\/span><\/b><span class=\"colour\">Options <\/span><span class=\"font\"><span class=\"colour\">available<\/span><\/span><span class=\"colour\">&nbsp;will depend on NA chosen.&nbsp;<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li class=\"sty__36tijr__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Soil Deposit Depth <\/span><\/b><span class=\"colour\">(applicable only to Malaysia NA) : User to choose<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li class=\"sty__36tijr__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Ground Type<\/span><\/b><span><span class=\"colour\">&nbsp;: User to select and all other fields, example&nbsp;<\/span><b><span class=\"colour\">Tb<\/span><\/b><span class=\"colour\">, <\/span><b><span class=\"colour\">Tc<\/span><\/b><span class=\"colour\">,&nbsp;&amp; <\/span><b><span class=\"colour\">Td<\/span><\/b><span class=\"colour\">&nbsp;will be automatically updated.<\/span><\/span><\/li>\n<\/ol>\n<\/ol>\n<div><span class=\"KB_New_Editor_Highlights\" style=\"margin: 10px 0px;position: relative;padding: 10px 10px 10px 40px\"><\/p>\n<div><img decoding=\"async\" alt=\"Info\" data-image=\"contentStyle\" style=\"position: absolute;left: 12px;top: 14px;width: 15px;max-width: 100%\" data-type=\"non-resize\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-db572d1aef0ece78223b48d1c4e22d0c.png\" \/>\n     <\/div>\n<div>\n      <b><span class=\"size\" style=\"font-size: 16px\"><span class=\"colour\">Ductility Level&nbsp; <\/span><\/span><\/b><span class=\"colour\"><br \/>\n      <br \/>\n     <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n     <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n      EC8 stipulates upper limits of axial compression ratios (normalised axial force) for ductile walls &amp; columns for DCM and DCH, but no restriction for DCL.<br \/><\/span><\/div>\n<div>\n<div><span class=\"colour\">For example, in the ductile design of shear walls in <b>DCM <\/b>and <b>DCH<\/b>, according to&nbsp;<\/span><span>EN 1998-1:2004,&nbsp;<\/span><span>Clause 5.4.3.4.1(2) for DCM and Clause 5.5.3.4.1(2) for DCH, the normalized design axial force&nbsp;shall not exceed a specified percentage of the theoretical axial concrete capacity (excluding reinforcement), as shown below:<\/span><\/div>\n<div><img decoding=\"async\" alt=\"\" src=\"https:\/\/desk.zoho.com\/DocsDisplay?zgId=672206093&amp;mode=inline&amp;blockId=mjtuu4b5295545f1a4d55aa7402a7aebd69b2\" style=\"padding: 0px;max-width: 100%\" \/><\/div>\n<div><span class=\"colour\">This means that only <\/span><b><span class=\"colour\">35% (DCH)<\/span><\/b><span class=\"colour\"> &amp; <\/span><b><span class=\"colour\">40% (DCM)<\/span><\/b><span class=\"colour\"> axial capacity of the shear walls can be utilized based on concrete area only, ignoring any reinforcement.<\/span><\/div>\n<\/div>\n<div><span class=\"colour\">For columns, the axial load ratio limits are <b>0.65 for DCM <\/b>and <b>0.55 for DCH<\/b>, as specified in EN 1998-1:2004, Clause 5.4.3.2.1(3) for DCM and 5.5.3.2.1(3) for DCH.<\/span><\/div>\n<div><span class=\"colour\">This directly results in&nbsp;<br \/>\n      <\/span><b><span class=\"colour\">DCL<\/span><\/b><span class=\"colour\">&nbsp;being the most practical and efficient design choice for low seismic zones&nbsp; :<\/span><\/div>\n<div><span class=\"colour\"><br \/>\n     <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n      <\/span><\/div>\n<li style=\"list-style-type: disc\"><font color=\"#000000\">EuroCode 8 does not specify an upper PGA (Peak Ground Acceleration) limit for use of <b>DCM<\/b>, rather it sets a limit below which seismic design provision can be ignored for low seismicity region, i.e. where&nbsp;<b>DCL<\/b> can be adopted.&nbsp;<br \/><\/font><\/li>\n<li style=\"list-style-type: disc\"><font color=\"#000000\">Cases where ground design acceleration is not greater than <b>0.10g <\/b>may be considered as low seismicity, allowing the use of simplified <b>DCL<\/b> design method.&nbsp;<\/font><\/li>\n<li style=\"list-style-type: disc\"><span class=\"colour\">The main reason <b>DCL<\/b>&nbsp;design is more economical for low seismic zone is the reduction in design seismic load allowed for DCM &amp; DCH is too small to compensate for the drastic reduction in the column &amp; wall axial capacity limits.&nbsp;<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n      <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">Further, for DCM &amp; DCH, there are additional rigorous &amp; onerous design &amp; detailing requirements, e.g. higher minimum steel requirements.&nbsp;<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<li style=\"list-style-type: disc\"><span class=\"colour\">To summarize, for low seismic zones, <\/span><span class=\"colour\"><b>DCL<\/b> is recommended as it is more practical and economical.&nbsp;<\/span><\/li>\n<\/ol>\n<p><\/span><\/p>\n<h2 id=\"Quasi-Permanent_Factors\" class=\"toc_anchors\"><span class=\"colour\">Quasi-Permanent Factors&nbsp;<\/span><span class=\"colour\"><br \/><\/span><\/h2>\n<div><span class=\"colour\">Quasi-permanent load coefficients are implemented for EuroCode are namely:<\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div>\n<ol>\n<li style=\"list-style-type: decimal\"><span class=\"colour\">Quasi-permanent Coefficient for Live Loads (\u03a8<\/span><span class=\"size\" style=\"font-size: 10px\"><span class=\"colour\">2<\/span><\/span><span class=\"colour\">, Q)<br \/><\/span><\/li>\n<li style=\"list-style-type: decimal\"><span class=\"colour\">Quasi-permanent Coefficient for Roof Live Loads (\u03a8<\/span><span class=\"size\" style=\"font-size: 10px\"><span class=\"colour\">2<\/span><\/span><span class=\"colour\">, Qr)<br \/><\/span><\/li>\n<li style=\"list-style-type: decimal\"><span class=\"colour\">Quasi-permanent Coefficient for Snow Loads (\u03a8<\/span><span class=\"size\" style=\"font-size: 10px\"><span class=\"colour\">2<\/span><\/span><span class=\"colour\">, Qs)<\/span><\/li>\n<\/ol>\n<div><span class=\"colour\">These factors can be changed in<b> Settings Center<\/b> &gt; <a target=\"_blank\" href=\"http:\/\/Nationally Determined Parameters (NDPs)\" rel=\"noopener noreferrer\">Nationally Determined Parameter (NDP)<\/a><b> <\/b>&#8211; a shown below&nbsp;<br \/><\/span><\/div>\n<div><span class=\"colour\"><br \/><\/span><\/div>\n<div><span class=\"colour\"><img decoding=\"async\" data-zdeskdocselectedclass=\"best\" class=\"docsimage\" data-zdeskdocid=\"img_5809081103060835\" style=\"max-width: 100%;padding: 0px;width: 725.5px;height: auto\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-702105db7c6bf9e7f78c0357fb8cb9b6.png\" \/><br \/><\/span><\/div>\n<div><span class=\"colour\"><br \/><\/span><\/div>\n<div><span class=\"colour\">These factors are used for the following purposes in ProtaStructure:<\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div>\n<ol>\n<li style=\"list-style-type: decimal\"><span class=\"colour\">Calculating the seismic mass to be used in earthquake analysis.<br \/><\/span><\/li>\n<li style=\"list-style-type: decimal\"><span class=\"colour\">Creating load combinations for seismic actions.<br \/><\/span><\/li>\n<\/ol>\n<h3 id=\"Seismic_Mass_Calculation\" class=\"toc_anchors\"><span class=\"colour\">Seismic Mass Calculation<br \/><\/span><\/h3>\n<div><span class=\"colour\">In the seismic analysis, the mass associated with permanent loads should be combined with that associated with variable loads.<\/span><\/div>\n<div class=\" align-center\" style=\"text-align: center\"><img decoding=\"async\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-ae36016d1cc92b9ed52524cd3753a0dd.png\" style=\"padding: 0px;max-width: 100%;width: 295px;height: auto\" data-zdeskdocid=\"img_8454537486683\" class=\"docsimage\" data-zdeskdocselectedclass=\"best\" \/><\/div>\n<div><span class=\"colour\">Where:<br \/><\/span><\/div>\n<div><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">G<\/span><sub><span class=\"colour\">k,j<\/span><\/sub><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is the<br \/>\ncharacteristic value of the j<\/span><sup><span class=\"colour\">th<\/span><\/sup><span class=\"colour\"> permanent load<\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><span lang=\"EN-US\"><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">Q<\/span><sub><span class=\"colour\">k,i<\/span><\/sub><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is the characteristic<br \/>\nvalue of the i<\/span><sup><span class=\"colour\">th<\/span><\/sup><span class=\"colour\"> variable load<\/span><\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><span lang=\"EN-US\"><span lang=\"EN-US\"><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">g<\/span><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is the acceleration due to gravity<\/span><\/span><\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">\u03a8<\/span><sub><span class=\"colour\">E,i<\/span><\/sub><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is the<br \/>\nmass combination factor for the mass corresponding to the i<\/span><sup><span class=\"colour\">th<\/span><\/sup><span class=\"colour\"><br \/>\nvariable action for the&nbsp;<\/span><\/span><span style=\"text-indent: 35.4pt\"><span class=\"colour\">seismic<br \/>\ndesign situation.<\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><span class=\"colour\"><br \/><\/span><\/div>\n<div><span lang=\"EN-US\" style=\"font-size: 11pt;line-height: 110%\"><span class=\"size\" style=\"font-size: 16px;line-height: normal\"><span class=\"colour\">For<br \/>\nbuildings<\/span><\/span><span class=\"colour\">, <\/span><\/span><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">\u03a8<\/span><sub><span class=\"colour\">E,i <\/span><\/sub><\/span><\/i><span lang=\"EN-US\" style=\"font-size: 11pt;line-height: 110%\"><span class=\"colour\">&nbsp;<\/span><span class=\"size\" style=\"font-size: 16px;line-height: normal\"><span class=\"colour\">is derived from the following relation:<\/span><\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div class=\" align-center\" style=\"text-align: center\"><img decoding=\"async\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-a21fde4300d732de75fae17c2e0b7742.png\" style=\"padding: 0px;max-width: 100%;width: 156px;height: auto\" data-zdeskdocid=\"img_2738191696630605\" class=\"docsimage\" data-zdeskdocselectedclass=\"best\" \/><span class=\"colour\"><br \/><\/span><\/div>\n<div><span lang=\"EN-US\" style=\"font-size: 11pt;line-height: 110%\"><span class=\"size\" style=\"font-size: 16px;line-height: normal\"><i style=\"font-size: 15px\"><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">\u03a8<\/span><sub><span class=\"colour\">2,i <\/span><\/sub><\/span><\/i><\/span><span lang=\"EN-US\" style=\"font-size: 15px\"><span class=\"size\" style=\"font-size: 16px;line-height: normal\"><span class=\"colour\">&nbsp;is associated with the quasi-permanent values<br \/>\nfor variable loads, as given in EC0, depending on the categories of loads.<br \/>\nThese values are considered automatically by ProtaStructure depending on the<br \/>\nselected Eurocode National Annex.<\/span><\/span><\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><span class=\"colour\"><br \/><\/span><\/div>\n<div><span style=\"font-size: 19.2px\"><span class=\"size\" style=\"font-size: 18px;line-height: normal\"><span class=\"colour\">\u03c6&nbsp;<\/span><\/span><\/span><font color=\"#111111\"><span style=\"font-size: 16px\"><span class=\"colour\">accounts for the probability of the simultaneous presence of variable loads during the seismic event. These values are again considered automatically by ProtaStructure depending on the selected Eurocode National Annex.<\/span><\/span><\/font><span class=\"colour\"><br \/><\/span><\/div>\n<div><span class=\"colour\"><br \/><\/span><\/div>\n<div><font color=\"#111111\"><span style=\"font-size: 16px\"><span class=\"colour\">Simultaneous presence factors&nbsp;\u03a6<\/span><\/span><\/font><span style=\"font-size: 16px\"><span class=\"colour\">&nbsp;c<\/span><\/span><font color=\"#111111\"><span style=\"font-size: 16px\"><span class=\"colour\">an be specified for each storey in ProtaStructure using the <a target=\"_blank\" href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/storey-related-controls-and-settings#Remove_Storey:~:text=be%20decreased%20accordingly.-,Edit%20Storey,-Use%20the%20%22Edit\" rel=\"noopener noreferrer\">Edit Storey<\/a>&nbsp;command (as shown below).<\/span><\/span><\/font><\/div>\n<div><\/div>\n<div><img decoding=\"async\" data-zdeskdocselectedclass=\"best\" class=\"docsimage\" data-zdeskdocid=\"img_8061936615940848\" style=\"max-width: 100%;padding: 0px;width: 806px;height: auto\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-77b9a06402b4b9215c67c2a88cb91a39.png\" \/><\/div>\n<div><\/div>\n<h3 id=\"Seismic_Combinations\" class=\"toc_anchors\"><span class=\"colour\">Seismic Combinations<\/span><span class=\"colour\"><br \/><\/span><\/h3>\n<div><span class=\"colour\">ProtaStructure uses equations 6.10 and 9.10 for ULS combinations. The seismic combinations are generated using the following formula:<\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div class=\" align-center\" style=\"text-align: center\"><img decoding=\"async\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-7e4113694f75282d93ed65142c72ad75.png\" style=\"padding: 0px;max-width: 100%;width: 373.5px;height: auto\" data-zdeskdocid=\"img_6889956067938683\" class=\"docsimage\" data-zdeskdocselectedclass=\"best\" \/><span class=\"colour\"><br \/><\/span><\/div>\n<div><span class=\"colour\">Where:<\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">G<\/span><sub><span class=\"colour\">k,j<\/span><\/sub><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is<br \/>\nthe permanent loads<\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div>\n<div><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">P<\/span><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&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; is the prestressing<br \/>\naction, whenever applicable<\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><span lang=\"EN-US\"><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">A<\/span><sub><span class=\"colour\">Ed<\/span><\/sub><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is<br \/>\nthe design value of the seismic action. <\/span><\/span><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">A<\/span><sub><span class=\"colour\">Ed<\/span><\/sub><span class=\"colour\"> <\/span><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">includes the importance factor \u03b3<\/span><sub><span class=\"colour\">1<\/span><\/sub><\/span><\/span><span class=\"colour\"><br \/><\/span><\/div>\n<div><span lang=\"EN-US\"><span lang=\"EN-US\"><i><span lang=\"EN-US\" style=\"font-size: 12pt;line-height: 110%\"><span class=\"colour\">\u03a8<\/span><sub><span class=\"colour\">2,i<\/span><\/sub><span class=\"colour\"> .Q<\/span><sub><span class=\"colour\">k,i<\/span><\/sub><\/span><\/i><span lang=\"EN-US\"><span class=\"colour\">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is<br \/>\nthe characteristic value of the i<\/span><sup><span class=\"colour\">th<\/span><\/sup><span class=\"colour\"> variable load<\/span><\/span><\/span><\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div>\n<div>\n<div>\n<div>\n<div>\n<h1 id=\"Analysis\" class=\"toc_anchors\"><span class=\"colour\">Analysis<br \/><\/span><\/h1>\n<\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><span><span class=\"colour\">The following are explanation of key inputs in \u201c<\/span><b><span class=\"colour\">Analysis<\/span><\/b><span class=\"colour\">\u201d tab :<\/span><\/span><span class=\"colour\"><br \/>\n  <\/span><span class=\"colour\"><br \/><\/span><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__ua42rv__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Apply Accidental Eccentricity (5%)<\/span><\/b><span><span class=\"colour\">&nbsp;:<\/span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">Check to apply<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Damping Ratio<\/span><\/b><span class=\"colour\">&nbsp;: User input according to building type. Generally, 0.05 (5%) for concrete structure and 0.02 (2%) for steel structure.&nbsp;<\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__ppz2le__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Number of&nbsp; Horizontal Modes&nbsp;<\/span><\/b><span><span class=\"colour\">:<\/span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">User input (recommended value = 15)<br \/><\/span><\/span><\/li>\n<li style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\" class=\"sty__ppz2le__cls\"><b><span class=\"colour\">Number of&nbsp; Vertical&nbsp; Modes&nbsp;<\/span><\/b><span class=\"colour\">:<\/span><span class=\"colour\">&nbsp;&nbsp;<\/span><span class=\"colour\">User input (recommended value = 15)<\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<p><span class=\"KB_New_Editor_Highlights\" style=\"margin: 10px 0px;position: relative;padding: 10px 10px 10px 40px\"><\/p>\n<div><img decoding=\"async\" alt=\"Notes\" data-image=\"contentStyle\" style=\"position: absolute;left: 12px;top: 14px;width: 15px;max-width: 100%\" data-type=\"non-resize\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-07fe3bac599025b89f070e8f243432e0.png\" \/><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n     ProtaStructure will check the number of modes automatically &amp; issue a warning during analysis if cumulative mass participation is not satisfied.<\/span><span class=\"colour\"><br \/>\n     <br \/>\n    <\/span><\/div>\n<p><\/span><\/p>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\"><b>Use user-defined periods in equivalent static analysis (Tx &amp; Ty) : <\/b>User to decide &amp; input&nbsp;<b><br \/><\/b><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n<\/span><\/div>\n<\/div>\n<div><span class=\"colour\"><br \/>\n<\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Structural Usage or Type<\/span><\/b><span class=\"colour\">&nbsp;:&nbsp;User to select.&nbsp;<br \/><\/span><\/li>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Interstorey Drift Limit<\/span><\/b><span class=\"colour\">&nbsp;:&nbsp; User to select.&nbsp;<\/span><\/li>\n<\/ol>\n<div>\n<h1 id=\"Structural_Irregularity\" class=\"toc_anchors\"><span class=\"colour\">Structural Irregularity<br \/><\/span><\/h1>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><span><span class=\"colour\">The following are the list of irregularities checks in \u201c<\/span><b><span class=\"colour\">Structural Irregularities<\/span><\/b><span class=\"colour\">\u201d tab :<\/span><\/span><span class=\"colour\"><br \/>\n  <br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<p class=\"MsoNormal\" style=\"margin: 0.5em 0px;padding: 0px\"><b><u><span><span class=\"colour\">Irregularities in Plan<\/span><\/span><\/u><\/b><span class=\"colour\"><br \/><\/span><\/p>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  The following criteria for regularity in plan is with reference to Clause 4.2.3.2 of EN 1998-1 : 2004 :&nbsp;<br \/>\n  <br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__mg6hd4__cls align-left\" style=\"list-style-type: disc\"><span class=\"font\"><b><span class=\"colour\">Non symmetrical Distribution of Stiffness in Plan&nbsp;<\/span><\/b><\/span><span class=\"colour\">: User to evaluate &amp; check if exist<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__mg6hd4__cls\" style=\"list-style-type: disc\"><b><span class=\"colour\">Non symmetrical Distribution of Mass in Plan&nbsp;<\/span><\/b><span class=\"colour\">: User to evaluate &amp; check if exist<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__mg6hd4__cls\" style=\"list-style-type: disc\"><b><span class=\"colour\">Non compact Plan Shape&nbsp;<\/span><\/b><span class=\"colour\">: User to evaluate &amp; check if exist<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__mg6hd4__cls align-left\" style=\"list-style-type: disc\"><span class=\"font\"><b><span class=\"colour\">Plan Dimension Ratio is Greater than 4 :&nbsp;<\/span><\/b><\/span><span class=\"colour\">User to evaluate &amp; check if exist<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__h9m0x6__cls\" style=\"list-style-type: disc\"><b><span class=\"colour\">Torsionally Flexible Plan :&nbsp;<\/span><\/b><span class=\"colour\">User to evaluate &amp; choose the following option<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__h9m0x6__cls\" style=\"list-style-type: disc\"><b><span class=\"colour\">Detect Automatically Based on Lateral Drifts&nbsp;<\/span><\/b><span class=\"colour\">(i.e. if lateral drifts exceeds limit, then model is torsionally flexible)<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__h9m0x6__cls\" style=\"list-style-type: disc\"><b><span class=\"colour\">Detect Automatically Based on Eigenvalue Results <\/span><\/b><span class=\"colour\">(i.e. if torsion is the first mode, then model is torsionally flexible)<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__h9m0x6__cls\" style=\"list-style-type: disc\"><b><span class=\"colour\">User Defined&nbsp;<\/span><\/b><\/li>\n<\/ol>\n<\/ol>\n<p class=\"MsoNormal\" style=\"margin: 0.5em 0px;padding: 0px\"><b><u><span class=\"colour\">Irregularities in Elevation<\/span><\/u><\/b><span class=\"colour\"><br \/><\/span><\/p>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  The following criteria for regularity in elevation is with reference to Clause 4.2.3.3 of EN 1998-1 : 2004 :&nbsp;<br \/>\n  <\/span><span class=\"colour\"><br \/><\/span><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__eyfd6g__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><span class=\"font\"><b><span class=\"colour\">Discontinuous<\/span><\/b><\/span><b><span class=\"colour\">&nbsp;Vertical Load Resisting Elements<\/span><\/b><span class=\"colour\"> :&nbsp;User to evaluate &amp; check if exist<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__toigtt__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Non uniform InterStorey Stiffness Distribution (Soft Storey)<\/span><\/b><span><span class=\"colour\">&nbsp;: Automatically Detected or User Defined<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__ykygnd__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Non uniform InterStorey Mass Distribution<\/span><\/b><span><span class=\"colour\">&nbsp;: Automatically Detected or User Defined<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__loqtl1__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><span class=\"font\"><b><span class=\"colour\">Non uniform InterStorey Strength Distribution (Weak Storey) :&nbsp;<\/span><\/b><\/span><span class=\"colour\">&nbsp;Automatically Detected or User Defined<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<li class=\"sty__mfcjs6__cls\" style=\"margin: 0px;padding: 0px;list-style-type: disc;line-height: 1.7\"><b><span class=\"colour\">Building with Setbacks<\/span><\/b><span><span class=\"colour\">&nbsp;:&nbsp;<\/span><\/span><span class=\"colour\">User to evaluate &amp; check if exist<\/span><\/li>\n<\/ol>\n<\/div>\n<div>\n<div><span class=\"KB_New_Editor_Highlights\" style=\"margin: 10px 0px;position: relative;padding: 10px 10px 10px 40px\"><\/p>\n<div><img decoding=\"async\" alt=\"Info\" data-image=\"contentStyle\" style=\"position: absolute;left: 12px;top: 14px;width: 15px;max-width: 100%\" data-type=\"non-resize\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-db572d1aef0ece78223b48d1c4e22d0c.png\" \/>\n   <\/div>\n<div>\n    <b><span class=\"size\" style=\"font-size: 16px\"><span class=\"colour\">Guidance on structural regularity with reference to EN1998-1-2004&nbsp; Clause 4.2.3<\/span><\/span><\/b><span class=\"colour\"><br \/>\n    <br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n    Structural regularity will affect the structural model, analysis method and q (behavior factor), as shown in below table :<br \/>\n    <br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<div class=\"target_moving\" id=\"target_mov_img_30715521531643986\"><span class=\"colour\"><br \/>\n     <\/span><img decoding=\"async\" alt=\"\" src=\"https:\/\/desk.zoho.com\/DocsDisplay?zgId=672206093&amp;mode=inline&amp;blockId=n3kdq2f5368b35f7643d3a25e6412507f2606\" class=\"docsimage currimg\" data-zdeskdocid=\"img_30715521531643986\" data-zdeskdocselectedclass=\"best\" style=\"padding: 0px;max-width: 100%;width: 486px;height: auto\" \/><span class=\"colour\"><br \/>\n     <br \/>\n    <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n    <\/span><b><u><span class=\"colour\">Regularity in plan<\/span><\/u><span class=\"colour\"> :<\/span><\/b><span class=\"colour\"><br \/>\n    <\/span><span><span class=\"colour\">&nbsp;criteria are given in Sect. 4.2.3.2 of EC8.<\/span><\/span><span class=\"colour\"><br \/>\n    <br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">When the building is irregular in plan, a spatial (3D) model should be used.<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">Regularity in plan may enhance the&nbsp;<\/span><i><span class=\"colour\">q&nbsp;<\/span><\/i><span class=\"colour\">value via Overstrength Factor : refer to 5.2.2.2.(5) for concrete buildings, 6.3.2(3) for steel buildings, &amp; 7.3.2(3) for composite steel-concrete buildings. <br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">Overstrength factor is only applicable for DCM &amp; DCH (not DCL). The program provides code recommended values for users to choose.&nbsp;<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n    <\/span><b><u><span class=\"colour\">Regularity in Elevation<\/span><\/u><\/b><span class=\"colour\"><br \/>\n    <\/span><span><span class=\"colour\"> : criteria given in Sect. 4.2.3.3 of EC8<\/span><\/span><span class=\"colour\"><br \/>\n    <br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">&nbsp;When building is irregular in elevation, the modal response spectrum analysis must be used (not equivalent static \/ lateral force method). <br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n    <\/span><\/div>\n<li style=\"list-style-type: disc\"><span class=\"colour\">&nbsp;The program will warn user if this condition is violated.<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n    <\/span><span><span class=\"colour\">If model is <\/span><\/span><span class=\"colour\"><br \/>\n    <\/span><b><span class=\"colour\">irregular in plan or elevation<\/span><\/b><span class=\"colour\"><br \/>\n    <\/span><span><span class=\"colour\">, the behavior factor is automatically multiplied by <\/span><\/span><span class=\"colour\"><br \/>\n    <\/span><b><span class=\"colour\">0.8 (reduced by 20%), <\/span><\/b><span class=\"colour\">i<br \/>\n    <\/span><span><span class=\"colour\">n accordance to Cl 4.2.3.1 (7).&nbsp;<\/span><\/span><span class=\"colour\"><br \/>\n    <br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n    <\/span><span><span class=\"colour\">After any enhancement or reduction, a minimum value of&nbsp;<\/span><i><span class=\"colour\">q<\/span><\/i><span class=\"colour\">&nbsp;= 1.5 will be used for all building type, in accordance to Cl 5.2.2.2 Equation 5.1.<\/span><\/span><br \/>\n    \n   <\/div>\n<p><\/span><\/div>\n<h1 id=\"Settings\" class=\"toc_anchors\"><span class=\"size\" style=\"font-size: 32px;line-height: normal\"><span class=\"colour\">Settings<\/span><\/span><span class=\"colour\"><br \/><\/span><\/h1>\n<div><span class=\"colour\"><br \/>\n <\/span><\/div>\n<div style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<p class=\"MsoNormal\" style=\"margin: 0px;line-height: 1.7;letter-spacing: 0.1px\"><span><span class=\"colour\">The following are explanation of key inputs in \u201c<\/span><b><span class=\"colour\">Settings<\/span><\/b><span class=\"colour\">\u201d tab :<\/span><\/span><span class=\"colour\"><br \/><\/span><\/p>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><b style=\"font-size: 15px;letter-spacing: normal\"><u><span class=\"colour\">Post Analysis Checks<\/span><\/u><\/b><span class=\"colour\"><br \/>\n   <br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Check Relative InterStorey Drift&nbsp;<\/span><\/b><span class=\"colour\">(Cl 4.4.3.2)<\/span><b><span class=\"colour\">&nbsp;:<\/span><\/b><span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">Tick to perform check.&nbsp;<\/span><\/span><span class=\"colour\">This is seismic drift check (unrelated to the regular horizontal drift check for wind \/ NHL)<br \/><\/span><\/li>\n<li style=\"list-style-type: disc\"><span class=\"colour\"><b>Use user-defined interstorey drift ratio limit<\/b> : User to decide and input value<\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b style=\"letter-spacing: 0.1px\"><span class=\"colour\">Check Building Height<\/span><\/b><span style=\"letter-spacing: 0.1px\"><span class=\"colour\">&nbsp;:<\/span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">User to decide&nbsp;<\/span><\/span><span class=\"colour\">&nbsp;<br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Check Wall-Frame Interaction<\/span><\/b><span><span class=\"colour\">&nbsp;: User to decide&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Check Second Order Effect<\/span><\/b><span><span class=\"colour\">&nbsp;: User to decide.&nbsp; <\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<ol>\n<li style=\"list-style-type: disc\"><span><span class=\"colour\">If checked program will check &amp; warn if second order effects need to be taken into account in accordance with clause 4.4.2.2.&nbsp; This check is based on the inter-storey drift (lateral deflection) of the building.&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<li style=\"list-style-type: disc\"><span><span class=\"colour\">If limit is exceeded, warning message will be given &quot;<\/span><b><span class=\"colour\">Dir 1 \/ 2 : Stiffness of load bearing System must be increased<\/span><\/b><span class=\"colour\">&quot;.&nbsp; <\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<li style=\"list-style-type: disc\"><span class=\"colour\">For details refer to the&nbsp;<\/span><b><span class=\"colour\">Post Analysis Checks Report : Second Order Effects Requirement Check<\/span><\/b><\/li>\n<li style=\"list-style-type: disc\"><span><span class=\"colour\">This means the model must be evaluated using Second Order Analysis.&nbsp; ProtaStructure performs only 1st Order Analysis and hence, will not take additional steps.&nbsp; User must decide further action.&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<li style=\"list-style-type: disc\"><span style=\"letter-spacing: 0.1px\"><span class=\"colour\">To pass this check without running 2nd order analysis, the stiffness of the model in the specified direction must be increased.&nbsp; This can achieved by :&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<ol>\n<li style=\"list-style-type: lower-alpha\"><span class=\"colour\">Increase the size of the columns &amp; walls<br \/><\/span><\/li>\n<li style=\"list-style-type: lower-alpha\"><span class=\"colour\">Increase the number of columns and walls.&nbsp; Walls at perimeter of the building, with major axis aligned with the weaker direction specified is the most effective.&nbsp; These perimeter will also increase the torsional stiffness &amp; improve the torsional flexibility irregularity check.<br \/><\/span><\/li>\n<li style=\"list-style-type: lower-alpha\"><span class=\"colour\">Combination of the above.&nbsp;<\/span><\/li>\n<\/ol>\n<\/ol>\n<\/ol>\n<div>\n   <b style=\"font-size: 15px;letter-spacing: normal\"><u><span class=\"colour\">Post Analysis Design Checks<\/span><\/u><\/b><span class=\"colour\"><br \/>\n   <\/span><span class=\"colour\"><br \/><\/span><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Check Strong Column \u2013 Weak Beam<\/span><\/b><span><span class=\"colour\">&nbsp;:<\/span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">User to decide&nbsp;<\/span><\/span><span class=\"colour\">&nbsp;<\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Perform Joint Shear Check<\/span><\/b><span><span class=\"colour\">&nbsp;:<\/span><span><span class=\"colour\">&nbsp;&nbsp;<\/span><\/span><span class=\"colour\">User to decide&nbsp;&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Check Minimum Member Dimensions<\/span><\/b><span><span class=\"colour\">&nbsp;: User to decide<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b style=\"font-size: 15px;letter-spacing: normal\"><span class=\"colour\">Check Building Overturning<\/span><\/b><span class=\"size\" style=\"font-size: 15px\"><span class=\"colour\">&nbsp;: User to decide<br \/><\/span><\/span><\/li>\n<li style=\"list-style-type: disc\"><span class=\"size\" style=\"font-size: 15px\"><span class=\"colour\"><b>Include Basements in overturning check <\/b>:&nbsp; User to decide. Note :&nbsp;<span style=\"font-size: 16px;letter-spacing: normal\">&quot;<\/span><b style=\"font-size: 16px;letter-spacing: normal\">No. of Rigid Basement<\/b><span style=\"font-size: 16px;letter-spacing: normal\">&quot;<\/span>&nbsp;is set in&nbsp;<a target=\"_blank\" href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/storey-related-controls-and-settings#Remove_Storey:~:text=be%20decreased%20accordingly.-,Edit%20Storey,-Use%20the%20%22Edit\" style=\"font-size: 16px;letter-spacing: normal\" rel=\"noopener noreferrer\">Edit Storey<\/a><span style=\"font-size: 16px;letter-spacing: normal\">&nbsp;menu.&nbsp;<\/span><\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n   <\/span><b style=\"font-size: 15px;letter-spacing: normal\"><u><span class=\"colour\">Response Spectrum Analysis<\/span><\/u><\/b><span class=\"colour\"><br \/>\n   <br \/>\n  <\/span><\/div>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Check Cumulative Effective Mass Participation<\/span><\/b><span><span class=\"colour\">&nbsp;:&nbsp;<\/span><span><span class=\"colour\">&nbsp;User to decide<\/span><\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b><span class=\"colour\">Compare RSA Results with Equivalent Static Load<\/span><\/b><span><span class=\"colour\">&nbsp;: User to decide&nbsp;<br \/><\/span><\/span><\/li>\n<li style=\"list-style-type: disc\"><span><span class=\"colour\"><b>Use User-defined RSA Scale Factor<\/b> : User to decide&nbsp;<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: disc\"><b style=\"font-size: 15px;letter-spacing: normal\"><span class=\"size\" style=\"font-size: 16px;line-height: normal\"><span class=\"colour\">Results Sign Method for RSA<\/span><\/span><span class=\"colour\"> :&nbsp;&nbsp;<\/span><\/b><span class=\"size\" style=\"font-size: 15px\"><span class=\"colour\">Use &quot;Signs of dominant mode&quot; or &quot;Absolute Value&quot;.&nbsp; Refer this article :<\/span>&nbsp;<\/span><a href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/results-sign-method-for-response-spectrum-analysis\" target=\"_blank\" style=\"letter-spacing: normal;font-size: 13px\" rel=\"noopener noreferrer\"><span class=\"size\" style=\"font-size: 16px\">Results Sign Method for Response Spectrum Analysis<\/span><\/a><\/li>\n<\/ol>\n<\/div>\n<\/div>\n<div>\n<div><span class=\"KB_New_Editor_Highlights\" style=\"margin: 10px 0px;position: relative;padding: 10px 10px 10px 40px\"><\/p>\n<div><img decoding=\"async\" alt=\"Alert\" data-image=\"contentStyle\" style=\"position: absolute;left: 12px;top: 14px;width: 15px;max-width: 100%\" data-type=\"non-resize\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-32fe1f850587f656e78efec728188464.png\" \/>\n   <\/div>\n<div>\n    <span class=\"colour\">The above checks includes requirements from other seismic code, eg. UBC. If the check is not specified in or relevant to EC8, it will not be done, even if ticked.&nbsp; We recommend you simply leave all the options checked.&nbsp;<\/span><\/div>\n<p><\/span><\/div>\n<div>\n<h1 id=\"Important_Notes__Scope__Limitations_\" class=\"toc_anchors\"><span><span class=\"colour\">Important Notes \/ Scope \/ Limitations :<\/span><\/span><span class=\"colour\"><br \/><\/span><\/h1>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: square\"><span><span class=\"colour\">Refer to \u201c<\/span><b><span class=\"colour\">Post-analysis Checks Report<\/span><\/b><span class=\"colour\">\u201d in \u201cReports\u201d tab for seismic analysis results &amp; clause compliance.<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li class=\"sty__w5ajxg__cls\" style=\"list-style-type: disc\"><span><span class=\"colour sty__hfnbel__cls\">In&nbsp;<b>Reports<\/b>&nbsp;tab, click on &quot;<b>Strong Column Check<\/b>s&quot; &amp; &quot;<b>Joint Shear Checks<\/b>&quot; to perform the check and generate the report.&nbsp;<\/span><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: square\"><span><span class=\"colour\">Elastic and design spectra are automatically calculated.<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: square\"><span style=\"letter-spacing: 0.1px\"><span class=\"colour\">Applicability of Equivalent Static Method is automatically checked.<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: square\"><span style=\"letter-spacing: 0.1px\"><span class=\"colour\">Overstrength factors are automatically applied to design forces.<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: square\"><span><span class=\"colour\">If there is a basement in the building, a two-stage approach is used to analyze the building. Basement and superstructure is analyzed separately in different load cases and the results are combined for the design. All these are done automatically (user input is not required).<\/span><span class=\"colour\"><br \/><\/span><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol style=\"font-size: 16px;letter-spacing: 0.1px\">\n<div><span class=\"colour\"><br \/>\n   <\/span><\/div>\n<li style=\"list-style-type: square\"><span><span class=\"colour\">Results for cracked and uncracked section analysis can be combined in same design combination (if desired)<\/span><\/span><span class=\"colour\"><br \/><\/span><\/li>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<\/ol>\n<div><span class=\"colour\"><br \/>\n  <\/span><\/div>\n<ol>\n<div><span class=\"colour\" style=\"font-size: 16px;letter-spacing: 0.1px\"><br \/>\n   <\/span><\/div>\n<li style=\"font-size: 16px;letter-spacing: 0.1px;list-style-type: square\"><span class=\"colour\">If model is irregular in plan or elevation, the behavior factor is is automatically multiplied by 0.8 (reduced by 20%) in accordance to Cl 4.2.3.1 (7).&nbsp;<\/span><\/li>\n<li style=\"font-size: 16px;letter-spacing: 0.1px;list-style-type: square\"><span style=\"letter-spacing: 0.1px\">The program will check &amp; warn if second order effects need to be taken into account in accordance with clause 4.4.2.2.&nbsp; However, the program will take no further action. User to decide further action, example to run p-delta analysis.&nbsp;<\/span><\/li>\n<li style=\"font-size: 16px;letter-spacing: 0.1px;list-style-type: square\"><span class=\"colour\">CQC (Complete Quadratic Combination) method is used to combine modal responses. This method is superior and preferable, compared to SRSS since SRSS is a special case of CQC.<\/span><\/li>\n<li class=\" align-left\" style=\"list-style-type: square;text-align: left\"><font color=\"#000000\"><span style=\"font-size: 16px;letter-spacing: 0.1px\">ProtaStructure will automatically calculate the tension shift and apply bending moment and shear&nbsp;<\/span><\/font>force envelope<span class=\"font\"><span style=\"font-size: 16px;line-height: normal\" class=\"size\"><span class=\"colour\"><span class=\"highlight\">s in shear wall design, according to the procedure outlined in <b>Eurocode 8 &#8211; 5.4.2.4<\/b>.&nbsp; For details refer to :&nbsp;<a href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/eurocode-8-shearwall-moment-shear-design-envelope\" target=\"_blank\" rel=\"noopener noreferrer\"><u>Eurocode 8 (Seismic code) &#8211; Shearwall Moment &amp; Shear Design Envelope<\/u><\/a><\/span><\/span><\/span><\/span><\/li>\n<\/ol>\n<p class=\"MsoNormal\" style=\"margin: 0px;line-height: 1.7;letter-spacing: 0.1px\">\n<div>\n   <span class=\"KB_New_Editor_Highlights\" style=\"margin: 10px 0px;position: relative;padding: 10px 10px 10px 40px\"><img decoding=\"async\" alt=\"Info\" data-image=\"contentStyle\" style=\"position: absolute;left: 12px;top: 14px;width: 15px;max-width: 100%\" data-type=\"non-resize\" src=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-db572d1aef0ece78223b48d1c4e22d0c.png\" \/><span class=\"highlight\"><span class=\"size\" style=\"font-size: 15px\"><span class=\"colour\">Please read this article<\/span>&nbsp;<\/span><\/span><a href=\"https:\/\/support.protasoftware.com\/portal\/en\/kb\/articles\/seismic-load-basic-guide\" target=\"_blank\" style=\"letter-spacing: normal;font-size: 13px\" rel=\"noopener noreferrer\"><span class=\"size\" style=\"font-size: 16px\">Seismic Load &#8211; Basic Guide<\/span><\/a><span class=\"highlight\"><span class=\"size\" style=\"font-size: 15px\"><span class=\"size\" style=\"font-size: 16px\">&nbsp;<\/span>&nbsp;<span class=\"colour\">on how to generate seismic load combination and check the results.&nbsp;<\/span><\/span><\/span><\/span><\/div>\n<div><\/div>\n<\/p>\n<\/div>\n<\/div>\n<div>\n \n<\/div>\n<div><\/div>\n<\/div>\n<div><\/div>\n","protected":false},"excerpt":{"rendered":"<p>ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been implemented : MS EN 1998-1&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"template":"","meta":{"_whitepaper_youtube_videos":"","_whitepaper_youtube_url":"","_whitepaper_youtube_thumbnail":"","footnotes":""},"categories":[158],"whitepaper_topic":[],"whitepaper_product":[],"whitepaper_type":[],"class_list":["post-31889","wiki","type-wiki","status-publish","hentry","category-pre-analysis"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.9 (Yoast SEO v27.9) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Seismic Analysis To Eurocode 8 - Prota Software<\/title>\n<meta name=\"description\" content=\"ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Prota Software\" \/>\n<meta property=\"og:description\" content=\"ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been\" \/>\n<meta property=\"og:url\" content=\"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/\" \/>\n<meta property=\"og:site_name\" content=\"Prota Software\" \/>\n<meta property=\"article:modified_time\" content=\"2026-06-19T12:37:57+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:title\" content=\"Prota Software\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"12 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/\",\"url\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/\",\"name\":\"Seismic Analysis To Eurocode 8 - Prota Software\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/protasoftware.com\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/protasoftware.com\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png\",\"datePublished\":\"2026-04-27T11:56:05+00:00\",\"dateModified\":\"2026-06-19T12:37:57+00:00\",\"description\":\"ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/#primaryimage\",\"url\":\"https:\\\/\\\/protasoftware.com\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png\",\"contentUrl\":\"https:\\\/\\\/protasoftware.com\\\/wp-content\\\/uploads\\\/2026\\\/04\\\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png\",\"width\":1474,\"height\":1077},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/seismic-analysis-to-eurocode-8\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/protasoftware.com\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Wiki\",\"item\":\"https:\\\/\\\/protasoftware.com\\\/wiki\\\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Seismic Analysis To Eurocode 8\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/protasoftware.com\\\/#website\",\"url\":\"https:\\\/\\\/protasoftware.com\\\/\",\"name\":\"Prota Software\",\"description\":\"\",\"publisher\":{\"@id\":\"https:\\\/\\\/protasoftware.com\\\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/protasoftware.com\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/protasoftware.com\\\/#organization\",\"name\":\"Prota Software\",\"url\":\"https:\\\/\\\/protasoftware.com\\\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/protasoftware.com\\\/#\\\/schema\\\/logo\\\/image\\\/\",\"url\":\"https:\\\/\\\/protasoftware.com\\\/wp-content\\\/uploads\\\/2026\\\/07\\\/prota-logo.png\",\"contentUrl\":\"https:\\\/\\\/protasoftware.com\\\/wp-content\\\/uploads\\\/2026\\\/07\\\/prota-logo.png\",\"width\":1200,\"height\":340,\"caption\":\"Prota Software\"},\"image\":{\"@id\":\"https:\\\/\\\/protasoftware.com\\\/#\\\/schema\\\/logo\\\/image\\\/\"}}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Seismic Analysis To Eurocode 8 - Prota Software","description":"ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/","og_locale":"en_US","og_type":"article","og_title":"Prota Software","og_description":"ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been","og_url":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/","og_site_name":"Prota Software","article_modified_time":"2026-06-19T12:37:57+00:00","og_image":[{"url":"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png","type":"","width":"","height":""}],"twitter_card":"summary_large_image","twitter_title":"Prota Software","twitter_misc":{"Est. reading time":"12 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/","url":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/","name":"Seismic Analysis To Eurocode 8 - Prota Software","isPartOf":{"@id":"https:\/\/protasoftware.com\/#website"},"primaryImageOfPage":{"@id":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/#primaryimage"},"image":{"@id":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/#primaryimage"},"thumbnailUrl":"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png","datePublished":"2026-04-27T11:56:05+00:00","dateModified":"2026-06-19T12:37:57+00:00","description":"ProtaStructure can now calculate seismic loads in accordance EuroCode 8.&nbsp; Country specific requirements of the following National Annex have been","breadcrumb":{"@id":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/#primaryimage","url":"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png","contentUrl":"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/04\/prota-doc-00f93caadf9c18a538ecc838de0e6700.png","width":1474,"height":1077},{"@type":"BreadcrumbList","@id":"https:\/\/protasoftware.com\/wiki\/seismic-analysis-to-eurocode-8\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/protasoftware.com\/"},{"@type":"ListItem","position":2,"name":"Wiki","item":"https:\/\/protasoftware.com\/wiki\/"},{"@type":"ListItem","position":3,"name":"Seismic Analysis To Eurocode 8"}]},{"@type":"WebSite","@id":"https:\/\/protasoftware.com\/#website","url":"https:\/\/protasoftware.com\/","name":"Prota Software","description":"","publisher":{"@id":"https:\/\/protasoftware.com\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/protasoftware.com\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/protasoftware.com\/#organization","name":"Prota Software","url":"https:\/\/protasoftware.com\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/protasoftware.com\/#\/schema\/logo\/image\/","url":"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/07\/prota-logo.png","contentUrl":"https:\/\/protasoftware.com\/wp-content\/uploads\/2026\/07\/prota-logo.png","width":1200,"height":340,"caption":"Prota Software"},"image":{"@id":"https:\/\/protasoftware.com\/#\/schema\/logo\/image\/"}}]}},"_links":{"self":[{"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/wiki\/31889","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/types\/wiki"}],"author":[{"embeddable":true,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":1,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/wiki\/31889\/revisions"}],"predecessor-version":[{"id":36207,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/wiki\/31889\/revisions\/36207"}],"wp:attachment":[{"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/media?parent=31889"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/categories?post=31889"},{"taxonomy":"whitepaper_topic","embeddable":true,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/whitepaper_topic?post=31889"},{"taxonomy":"whitepaper_product","embeddable":true,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/whitepaper_product?post=31889"},{"taxonomy":"whitepaper_type","embeddable":true,"href":"https:\/\/protasoftware.com\/wp-json\/wp\/v2\/whitepaper_type?post=31889"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}