Civil Engineering Reference
In-Depth Information
Fig. 5.15 Strengthening of vertical wooden rods:
1. original wooden rods; 2. strengthening tension rods; 3. cracks on the shear surface of original clamps.
When rectification is carried out, the hauling ropes and pull-back ropes must be run
synchronously with intermissions. The rectification can only be continued when rectified
quantity and structural state are normal. During the application, perpendicularity of the
frame and variation of the joints must be observed and recorded. Generally, the overcor-
rection should not exceed 20 mm, and the rectified frame should be vertical and stable for
acceptance.
After rectification, some work such as repairing and fixing connective joints, masoning
walls, and repairing roofs should be done. Then the rectification tools can be removed, with
every column axis of the wood frame vertical and in the same vertical plane.
When the rectification is for two-story frame buildings, additional towing points, pull-
back ropes and stretching instruments should be installed in accordance with the building
situation. If the frame has double-direction inclination, one direction should be rectified to
conform to design requirements before the other direction is rectified.
5.4
Retrofitting of Wooden Columns
When buildings show settlement due to deformation or corrosion and damage at the
bottom of columns, the wooden columns must be propped vertically before strengthening.
The wooden columns embedded in walls should generally be strengthened after masonry
removal. Before strengthening, beams and trusses upon the columns should be supported
temporarily.
It is feasible to adopt methods such as jointing columns or installing plinths to strengthen
the wooden columns corroded at the bottom.
Use bricks or concrete to build plinths. The cut-down sections of columns should be per-
pendicular to the axial lines of the columns. At the joints of the columns and the plinths,
prevention against corrosion and humidity should be carried out. Temporary supports can-
not be removed unless the concrete strength of the plinth is above 50% of the design strength.
The joint surface between the column and the plinth should be smooth and coupled tightly.
Specification, dimension, disposition and embedded depth of the anchoring steel compo-
nents should conform to the design requirements. Eyelets, connecting steel components and
wooden columns should be drilled through with bolts tied up.
When columns are jointed with timber, it is feasible to adopt flat-bottom connection or
splicing-tenon methods.
