Essential Rammed Earth Construction by Tim Krahn

Author:Tim Krahn
Language: eng
Format: epub
Publisher: New Society Publishers
Published: 2018-11-19T16:00:00+00:00

Fig. 5.16: Elevation view of allowable opening geometry in the long exterior wall between shear walls.

Table 5.1: Shear strength for embedded bolts in raw rammed earth

Bolt Diameter

Shear Strength

16mm (⅝”)

1.26 kN (283 Ibf)

20 mm (¾”)

1.82 kN (409 Ibf)

24mm (1”)

3.08 kN (692 Ibf)

Other fixings — in particular, embedded bolts or threaded rod — may be necessary to connect non-rammed earth elements such as roof and floor components to the walls. For raw rammed earth, we can take shear capacities for embedded steel bolts from the New Zealand standard. Table 5.1 summarizes the factored capacities of various diameters of bolts.

The required bolt embedment depth is three-quarters the width of the wall element, with a 200 mm (8″) minimum. For walls too thin to allow 200 mm (8″) embedment, reduce the shear capacity of the bolt by the embedded length in mm divided by 200 mm. For example, a 200 mm (8″) wall would have an embedment depth of 150 mm (6″). So, our reduction in shear strength for a 16 mm (⁵⁄₈″) bolt would be 150/200 = 0.75. Applying the reduction factor to the shear strength yields 0.75 × 1.26 kN = 0.945 kN (212 lbf). The NZ 4297 bolt embedment shear strength values for raw rammed earth assumes that the head of the bolt is embedded in the wall, with a 3 mm (¹⁄₈″) 50 mm × 50 mm (2″ × 2″) square or 3 mm (¹⁄₈″) × 55 mm diameter (2¼″) round washer in place as well.

The minimum edge distance between the bolt and the edge or end of the wall, measured from the center of the bolt, is equal to the minimum embedment depth. The NZ 4297 standard assumes a minimum compressive strength of 0.5 MPa for raw rammed earth, and advises a minimum wall thickness of 250 mm (10″); however, there is a note stating that 280 mm (11¼″) may be necessary to meet minimum thermal requirements without additional insulation. This is well within the range of strengths and geometries we have been working within in our empirical design guidelines.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.