{"id":1964,"date":"2025-11-07T11:59:02","date_gmt":"2025-11-07T10:59:02","guid":{"rendered":"https:\/\/www.invator.se\/projekt\/non-destructive-testing-and-condition-assessment-of-the-alno-bridge\/"},"modified":"2026-04-10T11:34:47","modified_gmt":"2026-04-10T09:34:47","slug":"non-destructive-testing-and-condition-assessment-of-the-alno-bridge","status":"publish","type":"projekt","link":"https:\/\/www.invator.se\/en\/projekt\/non-destructive-testing-and-condition-assessment-of-the-alno-bridge\/","title":{"rendered":"Non-destructive testing and condition assessment of the Aln\u00f6 Bridge"},"content":{"rendered":"\n<p><strong>Problem<\/strong><br\/>Aln\u00f6bron, located in Sundsvall, is a cantilever bridge in prestressed concrete completed in 1964. During previous condition surveys, signs of corrosion were detected in the tension cables and casing, especially in spans 6-8. Chloride levels of up to 6% were measured in the grout, which together with small cover layers (0-20 mm) indicated a significant risk of continued degradation.  <br\/><br\/>The purpose of the assignment was to determine the condition of the tension reinforcement, assess the impact on the load-bearing capacity of the structure and provide recommendations for long-term sustainability. The project was conducted as a collaboration between Norconsult AB and Invator Sverige AB. <\/p>\n\n<p><\/p>\n\n<figure class=\"gb-block-image gb-block-image-76be5d7c\"><img loading=\"lazy\" decoding=\"async\" width=\"2000\" height=\"1125\" class=\"gb-image gb-image-76be5d7c\" src=\"https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Skador_Invator.jpg\" alt=\"\" title=\"Skador_Invator\" srcset=\"https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Skador_Invator.jpg 2000w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Skador_Invator-300x169.jpg 300w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Skador_Invator-1024x576.jpg 1024w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Skador_Invator-768x432.jpg 768w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Skador_Invator-1536x864.jpg 1536w\" sizes=\"auto, (max-width: 2000px) 100vw, 2000px\" \/>\n<figcaption class=\"gb-headline gb-headline-a56f30df gb-headline-text\"><em>Bridge joint, internal crack and exposed tie rod.<\/em><\/figcaption>\n<\/figure>\n\n<p><\/p>\n\n<p><strong>Solution<\/strong><br\/>To enable an accurate condition assessment, a combined methodology was implemented using both non-destructive and destructive testing. The work began with an extensive drone inspection, carried out by Invator AB, where approximately 10,000 high-resolution images were taken and then compiled into a detailed 3D model. The model allowed for a comprehensive mapping of damage such as corrosion precipitation, cracking and splitting.  <\/p>\n\n<figure class=\"wp-block-embed is-type-video is-provider-vimeo wp-block-embed-vimeo wp-embed-aspect-18-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"3D model of the Aln\u00f6 Bridge - Invator\" src=\"https:\/\/player.vimeo.com\/video\/1134525558?dnt=1&amp;app_id=122963\" width=\"1200\" height=\"579\" frameborder=\"0\" allow=\"autoplay; fullscreen; picture-in-picture; clipboard-write; encrypted-media; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\"><\/iframe>\n<\/div><\/figure>\n\n<p><em>3D animation of Aln\u00f6 bridge for effective external condition assessment<\/em> (<em><strong>Video 2 min 47 sec<\/strong><\/em>).<\/p>\n\n<p><br\/>The fieldwork followed the methodology in Statens Vegvesen&#8217;s &#8220;Post-Tensioned Concrete Bridges &#8211; Inspection Manual 718&#8221;, adapted from Invators&#8217; experience from similar projects. The inspection was carried out in several steps: <\/p>\n\n<ul class=\"wp-block-list\">\n<li>Planning and mapping: Identification of critical sections and planning of measurement points based on previous damage observations.<\/li>\n\n\n\n<li>Location of tension rods: Georadar (GPR) was used to map the location, depth and cover of tension rods.<\/li>\n\n\n\n<li>Ultrasound tomography (MIRA): Performed to detect cavities and inadequate grouting in the feed tubes.<\/li>\n\n\n\n<li>Impact Echo (IE): Used as a verification method to identify delaminations and internal damage.<\/li>\n\n\n\n<li>Verification by core drill and videoscope:** Performed on selected points for visual assessment of corrosion status.<\/li>\n\n\n\n<li>After the surveys, opened areas were restored with adhesive slurry and high-performance repair mortar<\/li>\n<\/ul>\n\n<p>The study also included recommendations for the re-injection of empty casings and the introduction of cathodic protection according to EN ISO 12696.<\/p>\n\n<p><\/p>\n\n<figure class=\"gb-block-image gb-block-image-8db770ae\"><img loading=\"lazy\" decoding=\"async\" width=\"2000\" height=\"1125\" class=\"gb-image gb-image-8db770ae\" src=\"https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Interior-Alnobron_Invator.jpg\" alt=\"\" title=\"Interio\u0308r-Alno\u0308bron_Invator\" srcset=\"https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Interior-Alnobron_Invator.jpg 2000w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Interior-Alnobron_Invator-300x169.jpg 300w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Interior-Alnobron_Invator-1024x576.jpg 1024w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Interior-Alnobron_Invator-768x432.jpg 768w, https:\/\/www.invator.se\/wp-content\/uploads\/2025\/11\/Interior-Alnobron_Invator-1536x864.jpg 1536w\" sizes=\"auto, (max-width: 2000px) 100vw, 2000px\" \/>\n<figcaption class=\"gb-headline gb-headline-054cbbdc gb-headline-text\"><em>Interior of Aln\u00f6bron.<\/em><\/figcaption>\n<\/figure>\n\n<p><\/p>\n\n<p><strong>Results<\/strong><br\/>The inspection showed that some tension rods had signs of corrosion and insufficient grouting but that the vast majority performed well.  <br\/><br\/>The most vulnerable areas were found on the outside of the girder between supports 6-8, where the lining pipes were partially missing filling and corrosion damage was noted. The detailed 3D model provided a clear overview of the condition of the entire bridge and enabled an effective condition assessment of the exterior of the bridge. <br\/><br\/>The results of the condition assessment are the basis for recommended repair measures, where possibly re-injection and cathodic protection can be measures to restore and preserve the structure&#8217;s future corrosion protection. However, none of this has been performed at this time (winter 2025). The project contributed new knowledge on how advanced non-destructive testing and photogrammetric drone technology can be combined for a comprehensive assessment of prestressed concrete structures.  <\/p>\n\n<p><\/p>\n\n<p><strong>Equipment<\/strong><\/p>\n\n<ul class=\"wp-block-list\">\n<li>Georadar (GPR, Proceq) &#8211; localization of prestressing struts and cover layers<\/li>\n\n\n\n<li>Ultrasound tomography (MIRA) &#8211; mapping grouting deficiencies<\/li>\n\n\n\n<li>Impact Echo (Proceq) &#8211; verification of voids and delaminations<\/li>\n\n\n\n<li>Core drilling equipment &#8211; sampling and visual inspection<\/li>\n\n\n\n<li>Videoscope &#8211; internal inspection of casing<\/li>\n\n\n\n<li>Drones &#8211; photogrammetric collection and 3D modeling<\/li>\n\n\n\n<li>Coating and chloride analysis measuring instruments<\/li>\n<\/ul>\n\n<p><strong>Standards and references<\/strong><\/p>\n\n<ul class=\"wp-block-list\">\n<li>Norwegian Public Roads Administration Inspection Manual 718 &#8211; Methodology for post-tensioned concrete bridges  <\/li>\n\n\n\n<li>EN 12696 &#8211; Cathodic protection of concrete reinforcement  <\/li>\n\n\n\n<li>EN 446, 447, 934-4 &#8211; Grouting procedure and material requirements  <\/li>\n\n\n\n<li>EN 1504-9 &#8211; Principles and methods for concrete repair  <\/li>\n\n\n\n<li>AMA Civil Engineering 20 (BED.141) &#8211; Concrete cutting and repair work  <\/li>\n\n\n\n<li>Swedish Transport Administration TRVINFRA-00213 &#8211; Inspection of bridges and bridge-like structures  <\/li>\n<\/ul>\n\n<p><strong>Other<\/strong><\/p>\n\n<ul class=\"wp-block-list\">\n<li>The project was carried out in close collaboration between Invator AB, Norconsult AB and the Swedish Transport Administration.<\/li>\n\n\n\n<li>The effort helped to identify critical structural elements and establish a methodological basis for future maintenance strategies.<\/li>\n\n\n\n<li>Drone technology combined with non-destructive testing has proven to be a very effective method to minimize traffic impact while obtaining high data quality when inspecting complex concrete bridges.<\/li>\n<\/ul>\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>In the condition assessment of the Aln\u00f6 Bridge, Invator and Norconsult combined advanced drone technology with non-destructive testing to identify corrosion and grouting deficiencies. The results showed localized damage in the range 6-8, while the majority of the tension reinforcement was intact &#8211; an important basis for future repairs. <\/p>\n","protected":false},"featured_media":1735,"template":"","meta":{"_acf_changed":false},"bransch":[19],"class_list":["post-1964","projekt","type-projekt","status-publish","has-post-thumbnail","hentry","bransch-construction"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.invator.se\/en\/wp-json\/wp\/v2\/projekt\/1964","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.invator.se\/en\/wp-json\/wp\/v2\/projekt"}],"about":[{"href":"https:\/\/www.invator.se\/en\/wp-json\/wp\/v2\/types\/projekt"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.invator.se\/en\/wp-json\/wp\/v2\/media\/1735"}],"wp:attachment":[{"href":"https:\/\/www.invator.se\/en\/wp-json\/wp\/v2\/media?parent=1964"}],"wp:term":[{"taxonomy":"bransch","embeddable":true,"href":"https:\/\/www.invator.se\/en\/wp-json\/wp\/v2\/bransch?post=1964"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}