Retrofitting Design of Wood Structures - Retrofitting Design of Building Structures - page 156

When flat-bottom butt connection is adopted, the compressive surface cut down should
be perpendicular to the axis of the column, smooth, and tightly coupled. And clamps should
be connected to the column and fixed reliably.
When splicing-tenon (Fig. 5.16) is adopted, both upper and lower compressive surfaces
should be tightly coupled after being fixed with bolts. Vertical interface should be at the
location of the axis of column.

1

3

2

1

Fig. 5.16 Splicing-tenon method:
1. compressive surface; 2. bolts; 3. vertical interface.

5.5 Retrofitting of Other Wooden Components

Generally speaking, temporary supports must be installed before wooden purlins, stairs,
and ceilings are strengthened.

5.5.1 Strengthening of Wooden Purlins

(1) Strengthening of attached purlins
Selecting of purlins should consider design and condition of buildings. When attached
purlins are supported by brick walls, holes chiseled on brick walls should be uniform and
close to the original damaged purlins, while the ends of attached purlins embedded in the
brick walls should be treated to prevent corrosion and be tightened by wooden wedges. The
attached purlins should be adhered to the substrate of the roof above and tightened by
wooden wedges if the adherence is not steady; holes on the walls should be filled and the
support lengths of purlins should conform to design requirements.
When attached purlins are supported by roof trusses, the depth of groove should not be
larger than 1/3 of the height of the purlin if its ends are grooved; if the attached purlins are
supported by bolsters, the connections between the bolsters and the upper chords of roof
trusses should be fixed reliably, and the support length should conform to design require-
ments.
In areas that are prone to earthquakes, typhoons or strong winds, attached purlins should
be anchored to roof trusses or walls reliably to conform to relevant specifications.
(2) Replacing purlins with bracketing beams
When purlins deform severely due to insucient section areas, it is feasible to adopt this
strengthening method. A round or rectangle timber is installed under the purlin. As a result,
the timber and the strengthened purlin compose a kingpost truss, as the purlin becomes one
member of the truss (Fig. 5.17) .
(3) Strengthening with round tension rods
First, drill one φ 17 hole transversely 10 cm away from each end of the purlin that needs
strengthening. Then, install the precast units, including two φ 8 steel loops, one φ 12 rebar,
two φ 16 bolts, two 50 mm

× ×

50 mm 6 mm steel angles and nuts, as shown in Fig. 5.18.