{"id":7473,"date":"2024-12-16T22:00:57","date_gmt":"2024-12-16T18:30:57","guid":{"rendered":"https:\/\/niazit-ceiling.com\/en\/?p=7473"},"modified":"2026-02-12T13:29:11","modified_gmt":"2026-02-12T09:59:11","slug":"evolution-of-steel-joist","status":"publish","type":"post","link":"https:\/\/niazit-ceiling.com\/en\/evolution-of-steel-joist\/","title":{"rendered":"Evolution of Open Web Steel Joists"},"content":{"rendered":"\t\t
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\u00a0\u2728Evolution of NIAZIT Open Web Steel Joists (OWSJ) \u2728\u00a0<\/h1>

Preface<\/h2>

In structural engineering literature, the term Open Web Steel Joist (OWSJ)<\/strong> in Europe, North America, and many other regions refers to steel joists whose web is completely free of concrete<\/strong>, meaning no concrete is placed within the web zone. The structural behavior of such joists is generally classified into two categories:<\/p>

  1. Non-Composite Action<\/strong>, where the joist alone resists dead and live loads.<\/p><\/li>

  2. Composite Action<\/strong>, where the joist works integrally with a concrete slab.<\/p><\/li><\/ol>

    In contrast, in Iran, the term \u201copen web joist\u201d has been incorrectly used for joists whose web is filled with concrete<\/strong>, resulting in a T-shaped reinforced concrete section<\/strong>. From an engineering standpoint, these joists are considered closed-web systems<\/strong>. This conceptual misunderstanding has led to frequent confusion between NIAZIT steel joists<\/strong> and conventional Iranian steel joists with concrete-filled webs, despite their fundamentally different structural behavior, design philosophy, and code background.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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    Historical Development of Open Web Steel Joists in Europe and North America<\/h2>

    In European and American structural systems, open web steel joists have long been recognized as primary load-carrying members in floors and roofs. These joists are typically designed without concrete in the web and may function either independently or compositely with a concrete slab, depending on the floor system.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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    Types of Open Web Steel Joists<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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    1. Non-Composite Open Web Steel Joists<\/h3>

    These joists are designed as steel truss systems and are capable of carrying dead and live loads without any contribution from concrete<\/strong>. They are commonly used as both primary and secondary structural members.<\/p>

    Typical examples include:<\/p>

    • K-Series<\/strong><\/p><\/li>

    • LH-Series<\/strong><\/p><\/li>

    • DLH-Series<\/strong><\/p><\/li><\/ul>

      Their design and verification are governed by SJI Standard 100-2020<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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      2. Composite Open Web Steel Joists<\/h3>

      Composite joists are a subset of OWSJ systems in which the top chord<\/strong> participates in composite action with the concrete slab through:<\/p>

      • shear studs, or<\/p><\/li>

      • direct embedment of the top chord within the slab.<\/p><\/li><\/ul>

        This system provides increased floor stiffness, reduced structural weight, and higher load-bearing capacity compared to non-composite joists.<\/p>

        A well-known example is the CJ-Series<\/strong>, designed in accordance with SJI Standard 200-2015<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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        In most metal deck and steel deck floor systems<\/strong> in Europe and North America, open web steel joists are widely used in place of secondary steel beams, resulting in optimized steel consumption and faster construction.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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        Development of Steel Joists in Iran<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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        1. Steel Joists with Concrete-Filled Webs (Commonly Known as Cormit)<\/h3>

        Steel joists were first introduced to the Iranian engineering community in 1977<\/strong> and entered the construction market in 1979<\/strong>. By 1983<\/strong>, this system became widely known as the \u201copen web joist\u201d and later under the commercial name Cormit Joist<\/strong>.<\/p>

        In this system, the web is filled with concrete, forming a T-shaped reinforced concrete section<\/strong> similar to traditional joist\u2013block floors. From a structural perspective, this system is classified as a closed-web joist<\/strong>, despite its misleading terminology.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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        2. Truss Joists without Concrete in the Web<\/h3>

        In 2001<\/strong>, a truss-type steel joist with a fully concrete-free web<\/strong> was introduced in Iran, closely resembling European OWSJ systems. In this design, the top chord consisted of reinforcing bars, and the joist behavior aligned with true open web steel joists.<\/p>

        This system was registered under Patent No. 27734<\/strong>, and its load tests were officially approved by the Building and Housing Research Center of Iran<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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        3. Multi-System Structural Joist (NIAZIT)<\/h3>

        In 2019<\/strong>, with the aim of optimizing previous generations of concrete-free joists, a new system titled \u201cStructural Joist Applicable to Various Floor Systems\u201d<\/strong> was introduced under Patent No. 98813<\/strong> and commercialized as NIAZIT Joist<\/strong>.<\/p>

        The optimized design of the top chord and the modular arrangement of truss components enable:<\/p>

        • compatibility with various floor systems,<\/p><\/li>

        • application in both steel and reinforced concrete frames, and<\/p><\/li>

        • improved structural and economic performance compared to domestic and international counterparts.<\/p><\/li><\/ul>

          From a design philosophy and performance standpoint, the NIAZIT joist represents one of the most optimized open web steel joist systems developed in Iran.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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          4. Composite Joist with Integrated Shear Studs and Bolted Connections (CAMO)<\/h3>

          In 2021<\/strong>, an advanced generation of NIAZIT joists was introduced under the title Composite Joist with Integrated Shear Studs and Weld-Free Connections<\/strong>, registered as Patent No. 105559<\/strong> and marketed as CAMO Joist<\/strong>.<\/p>

          This system was internationally registered in August 2022<\/strong> under WIPO No. WO2022172065<\/strong>.<\/p>

          Key distinguishing features include:<\/p>

          • complete elimination of welding in primary connections,<\/p><\/li>

          • use of industrial bolted connections,<\/p><\/li>

          • integrated shear studs within the joist web, and<\/p><\/li>

          • fully controllable and code-compliant composite behavior.<\/p><\/li><\/ul>

            These characteristics place the CAMO joist among the most advanced composite steel joist systems, even when compared with conventional European and North American OWSJ solutions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

            \u00a0\u2728Evolution of NIAZIT Open Web Steel Joists (OWSJ) \u2728\u00a0 Preface In structural engineering literature, the term Open Web Steel Joist (OWSJ) in Europe, North America, and [\u2026]<\/span><\/p>\n","protected":false},"author":1,"featured_media":3452,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[33],"tags":[],"class_list":["post-7473","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/posts\/7473","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/comments?post=7473"}],"version-history":[{"count":0,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/posts\/7473\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/media\/3452"}],"wp:attachment":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/media?parent=7473"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/categories?post=7473"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/tags?post=7473"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}