Steel Lintel (Angle, T-Lintel or PFC+Plate)

How it calculates

The Steel Lintel calculator designs angle, T-lintel, and PFC+plate steel lintels to AS 4100:2020, using limit state (LRFD) design. It models the lintel as a beam with multiple supports and loads, then checks section capacity, member capacity, shear, combined shear-moment interaction, and deflection against serviceability limits.

Section types and properties

Three lintel types are supported, each with distinct section property calculations:

• Single angle - effective section properties are calculated for bending about the geometric axis, assuming the angle is restrained from lateral deflection and rotation at its supports
• T-lintel - treated as a T-section loaded equally on each of its two flanges, with capacities derived from the combined geometry
• PFC+plate - a parallel flange channel with a welded flat plate; composite section properties are computed from the combined PFC and plate geometry

For all types, moments are calculated about the principal axes per AS 4100:2020 Cl. 5.7 (indicated by axes '11' and '22'). Net areas equal gross area minus maximum allowable holes.

Moment capacity checks (AS 4100:2020 Cl. 5.1, 5.3, 5.6, 8.4)

The bending demand M* is compared to the effective moment capacity phiM_gov. Section moment capacity M_s is calculated from the reduced section modulus (accounting for yielding and local buckling). Member moment capacity M_b incorporates lateral-torsional buckling using the reference buckling moment and moment modification factors for the unbraced length L_L between lateral restraints. For biaxial bending, the combined check per Cl. 8.4 is applied.

utilization = M / (phi × M_gov) ≤ 1.0*

Shear capacity (AS 4100:2020 Cl. 5.11) and interaction (Cl. 5.12)

Web shear capacity phi × V_v is based on web yield and shear buckling. Where bending moment and shear are both significant, a shear-moment interaction check is applied per Cl. 5.12.

utilization (MV) = interaction ratio ≤ 1.0

Flange loading checks

For distributed loads and point loads applied at an eccentricity from the web (e_DL and e_PL), separate flange shear capacity and flange moment capacity checks are performed per AS 4100:2020 Cl. 5.11 and Cl. 5.3/5.6. T-lintels carrying masonry loads typically require these checks.

Deflection analysis

Short-term deflection (delta_s), long-term deflection (delta_l), and imposed-load deflection (delta_Q) are each compared to their respective span/limit criteria. The governing load case for each deflection type is identified.

Assumptions

Beam is uniform cross-section, net areas equal gross area with maximum allowed holes, bearing limit states are not checked, and all distributed loads are applied at the same eccentricity. For T-lintels, loads are assumed equally distributed to each flange.