Civil Engineering Reference
In-Depth Information
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Fig. 5.4
Strengthening of beam with bottom-bracing steel tension rods:
1. wooden beam; 2. brace rod; 3. steel tension rod.
Before strengthening, it is necessary to check whether the ends of the beam are corroded
or moth-eaten. The steel tension rod can only be fixed well if it is of good material quality.
Make samples of the steel items, tension rods, and brace rod according to design demands
and actual dimensions of strengthening members. Checking must be conducted before ap-
plication. Temporarily support and fix each component during application. Do not fix the
bracing rods until the trial assembly reaches the design requirements. Then pull the tension
rods tight. The steel rods should be pulled tightly and straight, and be fastened firmly and
the interfaces of beams and bracing rods or steel items should be inosculated. New bottom
bracing should be added within the same vertical plane to the beam axis.
3. Strengthening with flat steel hoops
Strengthening with flat steel hoop is suitable for wooden beams subjected to longitudinal
splitting damage
(Fig. 5.5)
.
The flat steel hoop should be in accurate dimension and uniform configuration, and ad-
hered to the beam. The lofting should be in full size, while the bolts need to be fastened
and fixed individually with no loosing of the steel hoops. It must be noted that there should
be a gap after the bayonet bolt closes. Only in this way can the bolt be fastened tightly and
adhered to the beam well. The cracks on the beam should be stuffed.
4. Strengthening with double clamps
When double clamps are used for strengthening, the lofting and fabrication should be in
accordance with design requirements and real dimensions. The clamping boards should be
parallel and symmetrical, with correct angles and positions of bolts. The interface between
both ends of clamping boards and beams (or columns) should be inosculated.
5. Strengthening beam-column joints with bolster
In this case
(shown in Fig. 5.6)
,
tenons at joints should be reset first, and then wooden
wedges driven in to achieve fixation. The holes on the bolsters and columns should be drilled
through at one time. Fastened to columns by the bolts, the bolsters should be attached to
the beams and columns closely.
