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Section 2109 Empirical Design of Adobe Masonry
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Empirically designed adobe masonry shall conform to the requirements of Appendix A of TMS 402, except where otherwise noted in this section.
The use of empirical design of adobe masonry shall be limited as noted in Section A.1.2 of TMS 402. In buildings that exceed one or more of the limitations of Section A.1.2 of TMS 402, masonry shall be designed in accordance with the engineered design provisions of Section 2101.2 or the foundation wall provisions of Section 1807.1.5.
Section A.1.2.2 of TMS 402 shall be modified as follows:
- A.1.2.2 — Wind. Empirical requirements shall not apply to the design or construction of masonry for buildings, parts of buildings, or other structures to be located in areas where Vasd as determined in accordance with Section 1609.3.1 of the International Building Code exceeds 110 mph.
Adobe construction shall comply with this section and shall be subject to the requirements of this code for Type V construction, Appendix A of TMS 402, and this section.
Adobe units shall have an average modulus of rupture of 50 psi (345 kPa) when tested in accordance with the following procedure. Five samples shall be tested and individual units shall not have a modulus of rupture of less than 35 psi (241 kPa).
A cured unit shall be simply supported by 2-inch-diameter (51 mm) cylindrical supports located 2 inches (51 mm) in from each end and extending the full width of the unit.
A 2-inch-diameter (51 mm) cylinder shall be placed at midspan parallel to the supports.
A vertical load shall be applied to the cylinder at the rate of 500 pounds per minute (37 N/s) until failure occurs.
The modulus of rupture shall be determined by the equation:
f r = 3 PLs /2 Sw (St 2)
(Equation 21-2)
| where, for the purposes of this section only: | ||
| Sw | = | Width of the test specimen measured parallel to the loading cylinder, inches (mm). |
| fr | = | Modulus of rupture, psi (MPa). |
| Ls | = | Distance between supports, inches (mm). |
| St | = | Thickness of the test specimen measured parallel to the direction of load, inches (mm). |
| P | = | The applied load at failure, pounds (N). |
Adobe units shall have a moisture content not exceeding 4 percent by weight.
Adobe units shall not contain more than three shrinkage cracks and any single shrinkage crack shall not exceed 3 inches (76 mm) in length or 1/8 inch (3.2 mm) in width.
Stabilized adobe shall comply with Section 2109.2.1 for unstabilized adobe in addition to Sections 2109.2.2.1 and 2109.2.2.2.
Soil used for stabilized adobe units shall be chemically compatible with the stabilizing material.
A 4-inch (102 mm) cube, cut from a stabilized adobe unit dried to a constant weight in a ventilated oven at 212°F to 239°F (100°C to 115°C), shall not absorb more than 21/2 percent moisture by weight when placed on a constantly water-saturated, porous surface for seven days. Not fewer than five specimens shall be tested and each specimen shall be cut from a separate unit.
The allowable compressive stress based on gross cross-sectional area of adobe shall not exceed 30 psi (207 kPa).
Bolt values shall not exceed those set forth in Table 2109.2.3.1.
ALLOWABLE SHEAR ON BOLTS IN ADOBE MASONRY
| DIAMETER OF BOLTS (inches) | MINIMUM EMBEDMENT (inches) | SHEAR (pounds) |
| 1/2 | — | — |
| 5/8 | 12 | 200 |
| 3/4 | 15 | 300 |
| 7/8 | 18 | 400 |
| 1 | 21 | 500 |
| 11/8 | 24 | 600 |
For SI: 1 inch = 25.4 mm, 1 pound = 4.448 N.
Adobe construction shall be limited to buildings not exceeding one story, except that two-story construction is allowed where designed by a registered design professional.
Mortar for adobe units shall be in accordance with Section 2103.2.1, or be composed of adobe soil of the same composition and stabilization as the adobe brick units. Unstabilized adobe soil mortar is permitted in conjunction with unstabilized adobe brick units.
Adobe units shall be laid with full head and bed joints and in full running bond.
Parapet walls constructed of adobe units shall be waterproofed.
The minimum thickness of exterior walls in one-story buildings shall be 10 inches (254 mm). The walls shall be laterally supported at intervals not exceeding 24 feet (7315 mm). The minimum thickness of interior load-bearing walls shall be 8 inches (203 mm). The unsupported height of any wall constructed of adobe units shall not exceed 10 times the thickness of such wall.
Foundations for adobe construction shall be in accordance with Sections 2109.2.4.5.1 and 2109.2.4.5.2.
Walls and partitions constructed of adobe units shall be supported by foundations or footings that extend not less than 6 inches (152 mm) above adjacent ground surfaces and are constructed of solid masonry (excluding adobe) or concrete. Footings and foundations shall comply with Chapter 18.
Stabilized adobe units shall be used in adobe walls for the first 4 inches (102 mm) above the finished first-floor elevation.
Adobe units shall not be used for isolated piers or columns in a load-bearing capacity. Walls less than 24 inches (610 mm) in length shall be considered to be isolated piers or columns.
Exterior walls and interior load-bearing walls constructed of adobe units shall have a continuous tie beam at the level of the floor or roof bearing and meeting the following requirements.
Wood tie beams shall be solid or built up of lumber having a nominal thickness of not less than 1 inch (25 mm), and shall have a depth of not less than 6 inches (152 mm) and a width of not less than 10 inches (254 mm). Joints in wood tie beams shall be spliced not less than 6 inches (152 mm). Splices shall not be allowed within 12 inches (305 mm) of an opening. Wood used in tie beams shall be approved naturally decay-resistant or preservative-treated wood.
Exterior walls constructed of unstabilized adobe units shall have their exterior surface covered with not fewer than two coats of Portland cement plaster having a minimum thickness of 3/4 inch (19.1 mm) and conforming to ASTM C926. Lathing shall comply with ASTM C1063. Fasteners shall be spaced at 16 inches (406 mm) on center maximum. Exposed wood surfaces shall be treated with an approved wood preservative or other protective coating prior to lath application.
Lintels shall be considered to be structural members and shall be designed in accordance with the applicable provisions of Chapter 16.
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Adobe units shall have an average modulus of rupture of 50 psi (345 kPa) when tested in accordance with the following procedure. Five samples shall ...
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