Civil Engineering Reference
In-Depth Information
When the ends of stairs are strengthened by splints, it is feasible to fabricate full-scale
mould boards according to the dimensions of design and actual components, number the
members individually, and manufacture strengthening components according to the mould
boards.
5.5.3
Strengthening of Wooden Ceilings
Strengthening of wooden ceilings generally includes hanging ceiling on wooden purlins
with wooden sag rods and using wooden grid to bear ceilings and installing insulating layer
in cold areas.
Temporary support should be installed before wooden ceilings are strengthened.
The wooden sag rods splitting at ends should be replaced, while the number of wooden
sag rods should be increased if there are not enough. The ends of each wooden sag rod
should be pinned firmly by no less than two nails. When clamps are used in strengthening
the damaged major wooden grid of ceiling (joist), it is feasible to fabricate full-scale mould
boards according to the dimensions of design and actual components, and then manufacture
strengthening components specifically for the mould boards. Nails (if any) should conform
to relevant specifications.
5.6
Seismic Retrofitting of Wood Structure Buildings
5.6.1
Basic Principles of Seismic Strengthening
When wood structure buildings do not satisfy requirements after seismic assessment, seis-
mic strengthening is required. Wood structures can better resist earthquakes. As long as the
wooden components are free from decay, severe fracture, pull-out of tenons or inclination,
and have connections to enclosure walls, damages of wood structure would be slight under
earthquake action, even in high seismic intensity regions. Therefore, the key for seismic
strengthening of wood structure buildings is their bearing systems, so the seismic capacities
of wood frames should be enhanced. When conducting seismic strengthening, it is feasible
to lighten roof weight, reinforce wood frames, strengthen and add braces, strengthen con-
nections between wooden components or between enclosure walls and wooden components,
install new seismic brick walls, and eliminate inadequate construction details.
When wood structure buildings are undergoing seismic strengthening, seismic checking
calculations are not necessary. Section dimensions of the newly installed components for
the seismic strengthening of wood structural buildings can be calculated from a static load.
However, connections between the new and the original components need to be enhanced.
Feasible methods and measures for seismic strengthening are adopted according to the actual
situation.
Wood structure buildings, especially old wood frame buildings, which show decay, cor-
rosion, erosion, deformation and cracks in separate positions such as beams, columns, roof
trusses and purlins, should be strengthened.
5.6.2
Scopes and Methods of Strengthening
(1) Strengthening of wooden components such as beams, columns, roof trusses and purlins,
etc.
a. To prevent horizontal displacement of roof skew beams or herringbone roof trusses in
earthquake, it is feasible to strengthen them with steel tension rods
(Fig. 5.19)
.
