Steel lintel
A steel lintel over an opening in a masonry wall: a single angle, two angles back to back, a W, channel or rectangular HSS, or one of those with a plate under it. It carries the wall above, either as the full height or as the 45 degree arching triangle, plus any uniform and point loads you enter. The calculation checks flexure, shear, deflection and bearing on the masonry, and gives torsion as an advisory.
Inputs of the steel lintel #
Lintel. Single angle (veneer or cavity wall), double angle (solid wall; a double angle record with the long legs back to back has them vertical), W, channel or rectangular HSS, or a shape with a plate. For a single angle, pick which leg is vertical. The toe of the vertical leg is in compression under gravity load, which is how the checks read it.
Opening and bearing. The clear span and the bearing length N at each end. The span used is clear span + N, the distance between the bearing centres (BIA TN 31B, TEK 17-1D). The minimum bearing length is prefilled at 4 in. (TMS 402, TEK 17-1D; BIA says 3 in.).
Lateral restraint. Your call, not the program's. Continuous means the masonry restrains the lintel along its length, so a single angle is designed about its geometric axis (F10). At the ends only, or at the ends and midspan, an equal-leg angle takes F10.2 with Sc = 0.8 S. An unequal-leg angle without continuous restraint is NOT FEASIBLE here: F10 sends it to principal axis design with H2, which this calculation does not do.
Load eccentricity e. The distance from the shear center to the load. For a single angle under a wythe, take it from the vertical leg's centerline to the centre of the wythe. It drives the horizontal leg check and the torsion advisory.
Wall above and arching. The wall weight per square foot of face and the masonry height above the lintel. Arching is the engineer's assumption, on by default as the usual case: the lintel then carries the wall within the 45 degree triangle on the span. The program checks two of TEK 17-1D's conditions, the height (half the span plus 8 in.) and running bond; it lists the others for you to confirm: end bearing, no control joints beside the lintel, no openings in the triangle, room for the thrust beside the opening, and cured masonry.
Other loads. Uniform loads and point loads, each at a height above the lintel. With arching, a uniform load at or above the apex goes to the masonry beside the opening. One below it is applied in full, or its part within the triangle dispersed at 45 degrees (TEK 17-1D Figure 4 gives both, so you choose). A point load outside the triangle goes to the masonry beside the opening. One inside is dispersed at 2 vertical : 1 horizontal (TMS 402), 60 degrees (BIA) or not at all.
Deflection limits. Clear span / 600 and 0.3 in. under dead plus live load, prefilled from TMS 402 and BIA TN 31B. Set either to 0 to leave it out.
Auto-design varies the shape of the lintel's family, lightest first. The vertical leg, grade and plate are kept.
Checks performed #
| Check | Basis |
|---|---|
| Flexure, single angle | AISC 360-22 F10: yielding 1.5 My, lateral-torsional buckling without continuous restraint (F10.2(2)), leg local buckling with the toe in compression (F10.3) |
| Flexure, double angle | F9.1(c), F9.2(b) with the negative B, F9.4(b) with F10.3 |
| Flexure, W, channel, HSS | F2, F7 through the shared steel library |
| Flexure, with a plate | The built-up section's elastic strength, top and bottom fiber, the top times the base shape's Mn / My (at most 1). A hand reading on the safe side: no plastic strength is taken |
| Shear | G3 for angles (kv = 1.2), G2 and G4 for the rest |
| Deflection | Service D + L against your limits, TMS 402 and BIA TN 31B prefilled |
| Bearing length and strength | TMS 402 9.1.8, Bn = 0.8 f'm Abr, phi 0.60; ASD 0.33 f'm (TMS 402-13 8.1.5: the 2022 text is not on disk) |
| Horizontal leg | A strip of the leg in bending, per inch of lintel, F11.1 |
| Plate weld | Shear flow V Q / I against two lines of intermittent E70 fillet weld, J2.4; minimum size Table J2.4 |
| Arching height and bond | NCMA TEK 17-1D |
| Torsion (advisory) | Rotation under service load and the movement of the top of the section against BIA's 1/16 in.; St. Venant shear stress beside the bending stress for H3.3 |
| Angle size (advisory) | BIA TN 31B: 1/4 in. and a 3-1/2 in. leg under nominal 4 in. brick |
Limitations #
Gravity load only, on one simple span. Not covered: wind on the wall, the masonry jambs and their thrust, web local yielding and crippling at the bearing, shelf angle anchors, flashing, corrosion protection, control joints, and the lintel under wet masonry during construction.
Torsion is an advisory. It counts St. Venant torsion with the ends held against rotation and no warping; the masonry above often helps and the calculation does not rely on that. For a W or channel with a real eccentricity, run the steel beam with torsion calculation. Bearing stress is taken as uniform over the bearing width, although BIA notes a rotating angle bears harder at its toe.
The flexure of a shape with a plate is a hand reading: AISC 360-22 has no chapter for a shape with a plate on one flange under these limit states, so the program keeps to first yield.
Verification examples #
Verification status: 21 values compared in 13 examples (11 published, 2 hand calculations from the cited equations): 21 within tolerance, 0 recorded deviations. Code basis: partial. Only some provisions were read in the target edition; the rest rests on older editions, examples or summaries.
No free source prints a worked example of a whole steel lintel: published verification of this type is thin, and this section says what it rests on.
| Source | What is compared | Published | ILX |
|---|---|---|---|
| AISC Design Examples v16.0, F.11A | L4X4X1/4, 6 ft, braced at the ends: LRFD and ASD | 3.69, 2.46 kip-ft | 3.69, 2.46 |
| AISC Design Examples v16.0, F.11B | The same, braced at midspan too | 3.98, 2.65 kip-ft | 3.98, 2.65 |
| AISC Design Examples v16.0, F.1-1A | W18X50, 35 ft, continuously braced | 379, 252 kip-ft | through the steel library |
| BIA TN 31B Table 1 | The table's load read back: at a load where L/600 governs, the deflection is span / 600; where moment governs, the required moment is the printed resisting moment | 4 and 2 rows | within tolerance |
| BIA TN 31B Table 3 | Bearing area arithmetic | 3,500 lb | 3,500 lb |
BIA's table is on the 1980 allowable stress method (Fb = 22 ksi). It confirms the load path, deflection and section properties, not the strength. The arching triangle moment W L / 6, the double angle, the built-up section, the horizontal leg, the plate weld and the dispersions are hand calculations from the cited equations, named as such in the test files. F.11B reuses F.11A's leg local buckling value with Sc = 0.8 S at a midspan brace; the program follows the example there.