Masonry partition wall
A non-loadbearing interior concrete masonry partition spanning from the floor to a braced head, or cantilevered from the floor, under its out-of-plane seismic force as a nonstructural component (ASCE 7-22 13.3 and 13.5) or the 5 psf minimum of ASCE 7-22 4.3.4. Reinforced or unreinforced, TMS 402-22 strength or allowable stress design (the switch in the toolbar), with the slip (deflection) head that lets the structure above deflect. US and metric units.
Edition. ASCE 7-22 4.3.4, 13.1.4, 13.3.1, 13.5.8 and Table 13.5-1 were read in the library copy. TMS 402-22 is not on hand: the wall uses the shared masonry library (402-16 text with the 402-22 numbering where confirmed). MDG-2022 Example 11.3-1 is on hand and verifies the unreinforced allowable stress case.
Inputs of the partition #
- Wall: height; braced at the head (simple span) or cantilevered; thickness; reinforced or unreinforced; grouting (fully, at the bars only, or none); f′m; mortar (it sets the modulus of rupture and the allowable tension); bar, spacing and grade (bars at the centre); the wall weight with its grout.
- Lateral loads: the minimum horizontal load of 4.3.4 (5 psf, applied to walls over 6 ft) as a live load; the dead load that acts with it, which ASCE 7 does not state: 0.6D in allowable stress and 0.9D in strength design as MDG-2022 Example 11.3-1 reasons (prefilled), the combination factor, or none.
- Seismic: the seismic design category (exempt in SDC A, and in SDC B with Ip = 1.0, 13.1.4); SDS; Ip; supported above grade plane or at or below it; the height z of the upper attachment and the roof height h (the upper attachment is the conservative reading of z for a wall attached at two levels); Hf by Eq. 13.3-5 or 13.3-4 with Ta; Rμ = 1.3 when the system is not specified, or from R, Ω0 and Ie (Eq. 13.3-6). CAR and Rpo come from Table 13.5-1 by the wall: reinforced masonry partition 1.0 / 1.5; all other partitions 2.2 (at or below grade) or 2.8 (above) / 1.5; cantilever interior walls 1.8 or 2.2 / 1.5. The vertical effect 0.2 SDS acts on the wall weight.
- Head (slip joint): the gap; the deflection of the structure above (your analysis); the angle leg length, the minimum engagement (1-1/2 in. prefilled, your choice), the clip spacing, length and thickness and Fy.
Auto-design (editor toolbar) varies the wall thickness, bar size and spacing and the head clip thickness and spacing. Objective: the thinnest wall, then the least steel and clips. Height, loads, seismic data, f′m, wall weight and the head gap are kept.
Checks performed #
| Check | Basis |
|---|---|
| Seismic force | Fp = 0.4 SDS Ip Wp (Hf/Rμ)(CAR/Rpo), 0.3 to 1.6 SDS Ip Wp (Eqs. 13.3-1 to 13.3-3), uniform on the wall |
| Bracing of partitions over 6 ft | A braced head is required (13.5.8.1); a masonry partition cannot meet the exception (10 lb per ft of height) |
| Flexure, reinforced | Strength: stress block, φ of Table 9.1.4, moment magnifier ψ = 1/(1 − Pu/Pe) with 0.75 In uncracked or Icr cracked (9.3.5.4.3); allowable stress: cracked transformed section (8.3) |
| Flexure, unreinforced | Net tension M/Sn − P/An at a bed joint, at most φ fr (Table 9.1.9.2, φ = 0.60) or the allowable tension of Table 8.2.4.2 |
| Shear | Reinforced: 9.3.3.1.2 or 8.3.5 with Mu/(Vu dv) = 1; unreinforced: on the webs (three 3/4 in. webs per unit) and, in allowable stress, sliding on the bed joint against 15 psi (MDG-2022 Example 11.3-1) |
| Head gap and engagement | Gap ≥ the deflection above; angle overlap at the full gap ≥ the minimum engagement |
| Clip angle | Reaction w H/2 per clip on a lever arm of the gap plus half the overlap; Mn = Fy Z of the leg (AISC 360-22 F11.1), φ = 0.90 or Ω = 1.67 |
The drawing is the wall section with the floor, the structure above, the head angles, the gap and the bar.
Limitations #
- One foot of a solid wall; openings, intersecting walls and wall ends are not covered.
- The angle's attachment to the structure, the base of the wall (dowels or friction), the wall's in-plane forces and its in-plane drift accommodation (13.3.2) are not designed.
- The allowable stress method does not magnify the moment for P-delta (the wall carries only its own weight).
- The sliding stress limit of 15 psi is the MDG's conservative choice; the full Table 8.2.6.2 value is to be confirmed against the code text.
Verification examples #
Verification status: 16 values compared in 2 examples (1 published, 1 hand calculations from the cited equations): 16 within tolerance, 0 recorded deviations. Thin: only 1 published example. Code basis: not yet recorded for this module.
Published: MDG-2022 Example 11.3-1 (section properties, flexural and axial stresses, net tension against the 12 psi allowable, shear on the webs and the bed joint). Hand calculations: the seismic force of the default wall and its slip head.