Civil Engineering Reference
In-Depth Information
Figure 8.9
A church in Bendigo, Victoria, with buttresses that appear like wings along the outside of the walls to
resist the outward pressure of the roof from spreading the walls
of the rafters are unable to drop, and so the load is transferred vertically into the outside
wall and into the ridge beam, which transfers it to the post supporting the beam and
down through the floor to the earth below (see Figure 8.10). Tying the bottom of the
rafters together will negate the lateral pressure thereby preventing the destructive
spreading motion (see Figure 8.11).
Figure 8.10
Rafters supported by a load bearing
central ridge beam held up by posts, and by
pitching beams on posts at the outside walls
Figure 8.11
Rafters supported only at the external
walls with the addition of a ceiling joist to prevent
spreading of the bottom of the rafters
