Empirical masonry design
A masonry wall proportioned by the empirical rules of TMS 402-16 Appendix A rather than by analysis: the limits on where the method applies (seismic design category, risk category, wind speed and building height), lateral support (l/t or h/t), the allowable compressive stress on the gross area, minimum thicknesses, foundation walls, shear wall length and the ties of non-composite walls. US and metric units.
Edition: TMS 402-22 has no empirical design. The TMS cross reference list (2016 to 2022, on hand) marks Appendix A "Deleted"; the 402-22 contents have Appendices C and D only. This calculation follows TMS 402-16 Appendix A (pp. C-203 to C-219, on hand), the edition IBC 2021 adopts. Where your governing code adopts TMS 402-22 (IBC 2024, to be confirmed against its text) a wall cannot be designed this way: choose that edition in the input and the calculation says NOT FEASIBLE; engineer the wall with the masonry wall or unreinforced masonry wall types.
Inputs of the empirical wall #
- Building and limits: the code edition adopted; the seismic design category; the risk category; the basic wind speed and building height (Table A.1.1); whether the wall is exterior, interior load-bearing, or a shear wall of the lateral-force-resisting system; whether the building is enclosed (interior walls); for SDC C, whether the prescriptive reinforcement of 7.4.3.1 is provided; whether the masonry sits on wood; whether it resists soil, fluid or other horizontal loads.
- Wall: the construction (the rows of Table A.4.2: solid or grouted clay and concrete masonry, hollow clay or concrete units, non-composite multiwythe walls, stone); for concrete units, whether they meet the normalized web area of A.1.1.3 or are grouted solid; the unit strength on the gross area (net strength × percent solid); the mortar; the nominal thickness (the sum of the wythes for a non-composite wall, with the loaded wythe entered separately); load-bearing or not; the number of stories; a wall supported top and bottom, a cantilever wall or a foundation wall; the height between lateral supports, the length between cross walls or pilasters, a parapet, and one opening with its strip WS.
- Gravity loads: dead and live load on the wall per foot, the wall weight, and the eccentricity of the resultant.
- Foundation walls: unbalanced backfill, the length between perpendicular walls, and the site conditions of A.6.3.1 (b), (c), (d), (f) as one confirmation.
- Ties and shear walls: tie spacing for non-composite walls; for shear walls the long dimension of the building, the cumulative length in the weakest plane, the number of planes, the diaphragm and its length-to-width ratio.
Auto-design varies the nominal thickness and the unit strength. Objective: the thinnest wall, then the weakest units. Everything else is kept.
Checks performed #
| Check | Basis |
|---|---|
| Edition adopted, SDC, risk category, wood support, other horizontal loads, wind and height | A.1.2.2 to A.1.2.6, Table A.1.1; Table CC-A.1.1; TMS 402-22 deleted the appendix |
| SDC C reinforcement, CMU web area | Table CC-A.1.1 (7.4.3.1), A.1.1.3 |
| Building height 35 ft (shear walls) | A.2 |
| Compressive stress on the gross area | A.4.1, Table A.4.2 interpolated (note 1); the loaded wythe of a non-composite wall (note 2) |
| Resultant in the middle third | A.1.2.1 |
| l/t or h/t, with openings | A.5.1, Table A.5.1, √(WT/WS), WS ≥ 3t, opening span |
| Cantilever walls | A.5.2 |
| Minimum thickness, parapets | A.6.2 |
| Foundation walls | A.6.3.1, Table A.6.3.1 |
| Shear walls | A.3.1.1, A.3.1.2, Table A.3.1 |
| Wythe ties | A.7.3.1 |
Twelve-inch hollow concrete masonry falls under both "greater than 8 and up to 12 in." and "12 in. and greater" in Table A.4.2; the lower values are used (to confirm against the code text). Rubble stone has one printed value, used for both mortars. The drawing is the wall elevation with its supports, parapet and opening.
Limitations #
- Anchorage (A.8), solid units under joist bearing (A.8.3.6), roofs without thrust (A.3.2), headers (A.7.2), stone bonding (A.7.4), change in thickness (A.6.2.7), chases and lintels (A.9), foundation piers (A.6.4) and running bond (4.5) are listed as notes to follow on the drawings, not checked.
- Partition walls are not designed by Appendix A (A.1.1.1): use the masonry partition type.
- One opening per wall strip; for several openings enter the virtual opening that encompasses them (A.5.1).
Verification examples #
Verification status: 12 values compared in 11 examples (8 published, 3 hand calculations from the cited equations): 12 within tolerance, 0 recorded deviations. Code basis: not yet recorded for this module.
Published values: rows of TMS 402-16 Tables A.4.2, A.5.1 and A.6.3.1 and the shear wall length of Commentary Figure CC-A.3-1. The interpolation of Table A.4.2, the reduction for an opening and the parapet thickness are hand calculations from the same provisions. There is no TMS 402-22 example: the 2022 edition has no empirical design.