✨Introduction of the NIAZIT Joist ✨
NIAZIT Joist (An Appropriate Alternative to Open-Web Steel Joists – Kromit)
In the NIAZIT roof system, since the dead load of the roof is lower than that of the Kromit roof system, it can be easily substituted without the need for recalculating the existing structural system (however, if the NIAZIT roof dead load is applied in the structural calculations, the structure will naturally become more economical).
The performance behavior of the complete truss system of the NIAZIT joist compared to Kromit joists has been fully explained in dedicated articles, as well as in detailed comparisons between NIAZIT and Kromit systems. In NIAZIT joists, the components are designed in such a way that their structural behavior—especially under seismic loading—demonstrates more optimized performance.
Furthermore, the special design of this type of joist eliminates the need for U-bars and negative moment reinforcement in the roof system.
The installation and execution guidelines for the NIAZIT roof system are similar to those of other steel joist systems and can be implemented easily on site.
Components of the NIAZIT Joist
A) Top Chord
Instead of using an angle section (L), a tee section (T), with or without reinforcement, is used for the top chord. This member acts as the compression member of the joist (compression chord).
B) Web Members (Middle Chord)
The diagonal and vertical web members are made of plain or deformed reinforcing bars. Instead of a continuous zigzag form, discontinuous vertical and inclined elements are used, which are welded to the top and bottom chords. The vertical elements function as compression members, while the inclined elements function as tension members (vertical web members in compression and inclined web members in tension).
C) Bottom Chord
Formed from a steel flat bar (PL) or ST37 steel plate.
D) Reinforcement Elements (Shear Connectors)
These are considered reinforced sections and are applied based on critical conditions identified in the joist structural calculations.
E) Assembly Rebar
The assembly rebar is a non-load-bearing member used to facilitate joist installation in reinforced concrete frames during concreting. In steel frames, since the bottom chord of the joists is tack-welded to the steel beams during installation, the use of assembly rebar is not required.
General Configuration of the NIAZIT Joist
تیرچه نیازیت مورد استفاده در اسکلت بتنی
تیرچه نیازیت مورد استفاده در اسکلت فلزی
Connection of the Joist to the Main Beam
A) Support on Steel Structures:
The end of the joist shall be welded to the support using a nominal weld. The minimum length of this weld shall be 5 cm, and its minimum weld size shall be 3 mm. The top chord does not require welding.
A) Support on Steel Structures:
The end of the joist shall be welded to the support using a nominal weld. The minimum length of this weld shall be 5 cm, and its minimum weld size shall be 3 mm. The top chord does not require welding.
Specifications of the NIAZIT Roof System
برش عرضی سقف نیازیت
The figure opposite illustrates the location of composite section formation in the NIAZIT joist, where the shear force transfer (shear stud action) is provided.
Dead Load Table for NIAZIT Roof
| Type of materials | DL (kg/m2) | Type of materials | DL (kg/m2) |
| Web Concrete | 0 | Slab Concrete + Joist Weight + Triangular Concrete | 165 |
| Polystyrene Block (EPS) | 5 | Plaster and Finish Coat | 50 |
| Levelling Lightweight Aggregate | 37 | Levelling Lightweight Aggregate | 21 |
| SUM = 320 (kg/m2) | |||
