{"id":7147,"date":"2019-08-13T09:03:43","date_gmt":"2019-08-13T05:33:43","guid":{"rendered":"https:\/\/niazit-ceiling.com\/?page_id=7147"},"modified":"2026-01-20T21:06:20","modified_gmt":"2026-01-20T17:36:20","slug":"faq","status":"publish","type":"page","link":"https:\/\/niazit-ceiling.com\/en\/faq\/","title":{"rendered":"FAQ Page"},"content":{"rendered":"\t\t
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\u2728NIAZIT Steel Joist FAQ\u2728<\/h1>\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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Innovative solution for safe, lightweight, and cost-effective structures<\/h2>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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If you are looking for a system that simultaneously ensures construction speed, economic efficiency, and structural safety, NIAZIT Steel Joist is a smart choice for your project.<\/p>

This technology is patented and, with its modern design, reduces concrete consumption, lightens the roof structure, and allows spanning of long openings.<\/p>

In this section, we answer the most important questions that may arise for the client, contractor, supervising engineer, structural designer, and architect; from technical and code analyses to costs and execution methods.<\/p>

If you have more specialized questions, the NIAZIT technical team is ready to provide free consultation and recommend the best solutions for your construction projects.<\/p>

By choosing NIAZIT, experience higher safety, faster execution, and lower costs.<\/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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<\/path><\/svg><\/span><\/path><\/svg><\/span>between Open-Web Joist and Joist without Concrete in Web (Non-Concrete Web Joist)<\/span><\/path><\/svg><\/div>

In European standards, an open-web joist refers to joists whose web is not filled with concrete.<\/p>

In Iran, an open-web joist refers to joists whose web is encased in concrete, forming a T-shaped section, with only the lower flange remaining outside the concrete.<\/p>

The joist without concrete in the web (NIAZIT) functions like European open-web joists; concrete does not penetrate the web, and structural performance relies on the steel system.<\/p><\/div>\n\t\t\t\t\t<\/div>

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<\/path><\/svg><\/span><\/path><\/svg><\/span>Difference between SJI 200-2015 and SJI 100-2020 Standards<\/span><\/path><\/svg><\/div>

In the international SJI standards, joists without concrete in the web are analyzed in two scenarios:<\/p>

Composite<\/strong><\/p>

In this scenario, the joist works in combination with the topping concrete, and the composite behavior of the slab is considered.<\/p>

\ud83d\udd39 Reference: SJI 200-2015<\/p>

Non-Composite<\/strong><\/p>

The joist alone carries the slab loads; concrete does not contribute structurally.<\/p>

\ud83d\udd39 Reference: SJI 100-2020<\/p>

\u00a0<\/p><\/div>\n\t\t\t\t\t<\/div>

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<\/path><\/svg><\/span><\/path><\/svg><\/span> Is NIAZIT Joist officially certified?<\/span><\/path><\/svg><\/div>

Yes. NIAZIT joist has been tested by the Road, Housing & Urban Development Research Center and received official technical approval.<\/p>

The system holds patent number 98813, valid until 1415 (Iranian calendar).<\/p><\/div>\n\t\t\t\t\t<\/div>

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<\/path><\/svg><\/span><\/path><\/svg><\/span>Which publications and standards cover joists?<\/span><\/path><\/svg><\/div>

  • Standard 543 and its updates 82, 94, 151: Guidelines for designing and executing joist and block slabs<\/p><\/li>

  • National Standard ISIRI 1-2909: Joist truss and joist for joist-block slabs \u2013 specifications and testing<\/p><\/li>

  • National Standard ISIRI 12977: Open-web joist \u2013 specifications and testing (specific to Chromit joists)<\/p><\/li><\/ul><\/div>\n\t\t\t\t\t<\/div>

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    <\/path><\/svg><\/span><\/path><\/svg><\/span>Is using joists with ceramic footing allowed?<\/span><\/path><\/svg><\/div>

    No. According to ISIRI 1-2909, trussed joists with ceramic footing are prohibited; only concrete-footed trussed joists are allowed.<\/p><\/div>\n\t\t\t\t\t<\/div>

    \n\t\t\t\t\t
    <\/path><\/svg><\/span><\/path><\/svg><\/span>Do Iranian standards cover NIAZIT joists?<\/span><\/path><\/svg><\/div>

    No. Current Iranian standards only cover joists with concrete-filled webs forming T-sections.<\/p><\/div>\n\t\t\t\t\t<\/div>

    \n\t\t\t\t\t
    <\/path><\/svg><\/span><\/path><\/svg><\/span>Are other manufacturers allowed to produce NIAZIT joists?<\/span><\/path><\/svg><\/div>

    No. Due to patent and technical approval, production without official licensing is illegal.<\/p>

    \u26a0\ufe0f Important Legal Notes<\/strong><\/p>

    Any modification of the joist by other manufacturers is illegal and invalid.<\/p><\/div>\n\t\t\t\t\t<\/div>

    \n\t\t\t\t\t
    <\/path><\/svg><\/span><\/path><\/svg><\/span>Is \u201cNIAZIT\u201d a brand or a joist type?<\/span><\/path><\/svg><\/div>

    \u201cNIAZIT\u201d is a registered brand name but is also commonly used in the market to refer to joists without concrete in the web.<\/p><\/div>\n\t\t\t\t\t<\/div>

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    <\/path><\/svg><\/span><\/path><\/svg><\/span>What is a composite joist?<\/span><\/path><\/svg><\/div>

    A composite joist is a system where steel and concrete simultaneously share the bending and shear loads.<\/p><\/div>\n\t\t\t\t\t<\/div>

    \n\t\t\t\t\t
    <\/path><\/svg><\/span><\/path><\/svg><\/span>Are Chromit joists and joists without concrete in the web considered composite?<\/span><\/path><\/svg><\/div>

    Both create a composite section during concrete pouring, but their analysis, design assumptions, and structural behavior differ significantly.<\/p><\/div>\n\t\t\t\t\t<\/div>

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    <\/path><\/svg><\/span><\/path><\/svg><\/span>Does \u201cComposite Chromit\u201d exist?<\/span><\/path><\/svg><\/div>

    It is a colloquial and market term in Iran, used outside the ISIRI 12977 standard and Publication 543.<\/p><\/div>\n\t\t\t\t\t<\/div>

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    <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the maximum span of joists?<\/span><\/path><\/svg><\/div>

    Open-Web Joist (Chromit):<\/p>

    According to Publication 543 \u2013 Clauses 2-3-1, 6: Spans over 7\u20138 m should be double.
    ISIRI 12977 \u2013 Clause 4-4: Joists longer than 7.5 m must have continuous male plate along their length.
    Top flange: symmetric double flange; bottom flange: male plate for spans over 6.5 m.<\/p>

    \u00a0
    NIAZIT Joist (Non-Concrete Web):<\/p>

    Top flange is selected as a beam from the start.
    Bottom web is calculated according to required section.
    Long spans up to 16 m can be executed as single joists without doubling.<\/p><\/div>\n\t\t\t\t\t<\/div>

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    <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the center-to-center spacing of NIAZIT joists?<\/span><\/path><\/svg><\/div>

    Depending on usage, span length, and load, spacing ranges from 50 to 75 cm.
    Doubling is not required.
    If spacing increases, appropriate measures for the topping slab must be applied.<\/p><\/div>\n\t\t\t\t\t<\/div>

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    <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the thickness of the topping concrete in NIAZIT slabs?<\/span><\/path><\/svg><\/div>
    • Short spans: 5 cm<\/li>
    • Long spans: 6 cm<\/li>
    • Minimum concrete grade: C20<\/li><\/ul><\/div>\n\t\t\t\t\t<\/div>
      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>How does the slab perform in earthquakes without concrete in the web?<\/span><\/path><\/svg><\/div>

      Open-Web Joist (Chromit):<\/p>

      Part of shear resisted by concrete web, rest by zigzag reinforcement.
      Issues: improper vibration, cracking, web failure, rebar unable to carry full shear.
      Result: web failure (8\u201312 cm), shear system collapse, deflection, increased risk of slab collapse.<\/p>

      \u00a0
      NIAZIT Joist (Non-Concrete Web):<\/p>

      Middle members act independently, without concrete dependency.
      Elastic and recoverable behavior after earthquake.
      High seismic resistance; joists return to original position.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the height of NIAZIT joists?<\/span><\/path><\/svg><\/div>

      According to SJI 200-2015, joist height is determined based on span-to-depth ratio and architectural slab thickness.
      Typically 20\u201335 cm for standard spans.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>How is corrosion protection applied in NIAZIT joists?<\/span><\/path><\/svg><\/div>

      Parts not in contact with concrete \u2192 anti-corrosion coating
      Parts embedded in concrete \u2192 no coating needed
      According to SJI, coating non-concrete-exposed members prevents corrosion.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>How are thermal reinforcement bars arranged in NIAZIT slabs?<\/span><\/path><\/svg><\/div>

      Purpose: prevent temperature-induced cracks
      Minimum bar: #6
      Spacing: 25 cm, ~2 cm below slab surface
      According to SJI, thermal bars only need to be perpendicular to joists.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>Why is negative moment reinforcement not used in NIAZIT slabs?<\/span><\/path><\/svg><\/div>

      According to SJI 200-2015, negative moment reinforcement is not required in joists without concrete in the web.
      Reason: hinged end connection, top flange not attached to girder, or double-end shear connector in concrete frame.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span> What is the function of end shear connectors and are angles allowed?<\/span><\/path><\/svg><\/div>

      Controls tensile and compressive forces at joist ends
      According to SJI: designed with engineering software and shear analysis
      Strap or angle can be used; angle preferred for larger polar moment of inertia<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>What type of reinforcement is used in the web of NIAZIT joists?<\/span><\/path><\/svg><\/div>

      Plain bar (AI): better weldability, lower tensile strength
      Deformed bar (AII): higher tensile strength, lower weldability
      According to SJI: actual bar tensile strength considered in calculations<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>Is splicing allowed in steel joists?<\/span><\/path><\/svg><\/div>

      Yes, according to:
      ISIRI 12977 Clause 5-2-5-5
      Publication 543 Clause 2-2-2-5, Part 5
      Connecting two profiles by splice at any flange location is permitted.
      For tensile members: butt weld splice with minimum resistance 1.14Fy \u00d7 A (A = total spliced section).
      Example: For bottom flange 4.2 cm\u00b2 (12\u00d74 mm strap), #10 rebar can be used as equivalent in splice.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the function of rib or mid-span lateral tie? Is it mandatory?<\/span><\/path><\/svg><\/div>

      Rib \/ mid-span tie:
      Provides lateral support for joists
      Reduces sinusoidal vibrations and slab deflection
      Increases overall slab stiffness
      According to ISIRI 12977 and Publication 543, technically necessary and recommended.<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>What is joist camber effect and does it occur in NIAZIT slabs?<\/span><\/path><\/svg><\/div>

      Joist camber: seen when plaster\/concrete applied directly, mid-rebar curvature, improper seating
      Result: gradual deflection of joist
      In NIAZIT slabs: special design and proper connection, deflection controlled within code limits, practically no camber effect.<\/p><\/div>\n\t\t\t\t\t<\/div>

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      <\/path><\/svg><\/span><\/path><\/svg><\/span> How does the NIAZIT system perform under fire?<\/span><\/path><\/svg><\/div>

      Performance similar to steel frame fire protection
      If polystyrene (EPS) used as formwork: suspended ceiling with 5 cm gap below mandatory
      Implementation responsibility lies with owner and supervising engineer<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>Is it logical to use polystyrene blocks between joists?<\/span><\/path><\/svg><\/div>

      Yes, for ease of installation, labor reduction, and accessibility
      Technical requirements: minimum density 12 (Std. 11108)
      Fire requirement: flame spread \u2264 15 mm in 20 sec
      Non-compliance: plaster cracking, EPS deterioration
      Suspended ceiling mandatory for fire safety<\/p><\/div>\n\t\t\t\t\t<\/div>

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      <\/path><\/svg><\/span><\/path><\/svg><\/span>How to model NIAZIT slabs in ETABS?<\/span><\/path><\/svg><\/div>

      ETABS has Steel Joist Design option for joists without concrete in the web.
      Training limitation: joists can be modeled like standard steel joists, replacing dead load DL = 320 kg\/m\u00b2<\/p><\/div>\n\t\t\t\t\t<\/div>

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      <\/path><\/svg><\/span><\/path><\/svg><\/span>What type of welding is allowed for joists? Is CO\u2082 welding permitted?<\/span><\/path><\/svg><\/div>

      Concrete-bottom joists:
      Std. 1-2909, Clause 1-3 \u2192 CO\u2082 only allowed for top rebar
      Std. 1-2909, Clause 9-1 \u2192 certified welder required
      CO\u2082 welding must be in closed, wind-free environment<\/p>

      Steel joists (Chromit & NIAZIT):
      Std. 12977 Cl. 8-1, Pub. 543 Cl. 2-2-2-5 Part 4, SJI 200-2015 Cl. 3.3
      Electrode welding mandatory, CO\u2082 not permitted<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>How is NIAZIT slab stiffness ensured?<\/span><\/path><\/svg><\/div>

      Slab diaphragm stiffness depends on: structural system type, dimensions, lateral load elements, frame rigidity, slab thickness\/type, number of stories
      Displacement control per Iranian Code 2800
      According to Pub. 543 Appendix 2, Part 11-B and 10th Building Code (2022), defined for composite beams, no recalculation required<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span> Is NIAZIT slab really more economical and lighter?<\/span><\/path><\/svg><\/div>

      Short spans (\u22645 m) and low-rise buildings \u2192 conventional block joists common
      Other cases: reduced concrete, no negative\/udca bars, long spans, fewer columns, smaller beams\/columns\/foundation
      Result \u2192 economical, lighter, cost-effective<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span> Is NIAZIT joist heavier than Chromit?<\/span><\/path><\/svg><\/div>

      No. Removing web concrete \u2192 reduced dead load
      Top flange: composite performance like Chromit
      Bottom flange: tensile force carried by steel
      Result: NIAZIT joist lighter than Chromit<\/p><\/div>\n\t\t\t\t\t<\/div>

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      <\/path><\/svg><\/span><\/path><\/svg><\/span>How to perform accurate cost comparison between slabs?<\/span><\/path><\/svg><\/div>

      \u00a0Three main factors:
      1\ufe0f\u20e3 Dead load \u2192 reduces beam\/column\/foundation size
      2\ufe0f\u20e3 Materials \u2192 joist, formwork, concrete, rebar, shoring, accessories
      3\ufe0f\u20e3 Labor cost
      Sum of three \u2192 real criterion for slab system selection<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the price difference among NIAZIT products?<\/span><\/path><\/svg><\/div>

      Main difference: type of formwork and installation cost
      Not in the NIAZIT joist itself<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>Is NIAZIT truss priced by kg or meter?<\/span><\/path><\/svg><\/div>

      Pricing: based on plan & m\u00b2
      By kg \u2192 low transparency, weight tolerance, scale differences
      Transparent method: final cost per m\u00b2<\/p><\/div>\n\t\t\t\t\t<\/div>

      \n\t\t\t\t\t
      <\/path><\/svg><\/span><\/path><\/svg><\/span>What is the delivery time for NIAZIT products?<\/span><\/path><\/svg><\/div>

      • Depending on order volume: 3\u201310 working days<\/p><\/li>

      • Production capacity: >5000 m\u00b2\/day, facility >2000 m\u00b2<\/p><\/li><\/ul>

        \u00a0<\/p>

        • Includes: manufacturing, assembly, anti-corrosion, full product preparation<\/p><\/li><\/ul><\/div>\n\t\t\t\t\t<\/div><\/div>\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":"

          \u2728NIAZIT Steel Joist FAQ\u2728 Innovative solution for safe, lightweight, and cost-effective structures If you are looking for a system that simultaneously ensures construction speed, economic efficiency, [\u2026]<\/span><\/p>\n","protected":false},"author":1,"featured_media":3140,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-7147","page","type-page","status-publish","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/pages\/7147","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/types\/page"}],"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=7147"}],"version-history":[{"count":0,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/pages\/7147\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/media\/3140"}],"wp:attachment":[{"href":"https:\/\/niazit-ceiling.com\/en\/wp-json\/wp\/v2\/media?parent=7147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}