Retrofitting Design of Masonry Structures - Retrofitting Design of Building Structures - page 131

where ρ av , volume ratio of reinforcement (%). And when the section area of single-limb
batten plate is A av 1 , and the spacing is s :

ρ av = 2 A av 1 ( a + b )
abs

f a , design value of tensile strength of batten plates;
σ a , the stress of tension limb of section steel, which can be calculated by Eq. (4.6); and
the rest of the symbols are in accordance with the above mentioned.
The height of compression zone x can be calculated by Eq. (4.5).

4.5 Retrofitting of Wall between Windows

The wall between windows is a weak area of masonry structure where cracks or bearing
capacity inadequacy usually occurs during an earthquake, vertical loads, uneven settlement
and thermal stress. Methods for retrofitting a wall between windows are similar with those
for retrofitting the brick wall and brick column, such as setting buttress columns, packing
mat reinforcement covers, augmenting section area and outer packing section steels, etc.
The detailed retrofitting design methods should be in accordance with the rules outlined in
Sections 4.3 and 4.4.
Setting reinforced concrete columns on both sides of original walls could be more effective
and economical, and the window apertures can be reduced properly.
When using the method of outer packing rolled angles to retrofit the wall between windows,
packing only rolled angles on four corners is not enough. It cannot restrict the middle section
of the wall effectively or achieve an expected effect; for the case that the width of the wall is
too large compared with its thickness. Therefore, when a wall's ratio of width to thickness
is larger than 2.5, a flat iron may be extended vertically on each side of the wall's middle
section and tied by the screw bolts, as in Fig. 4.11. After that, a mortar-covering layer
should be plastered, which can avoid the rustiness of rolled angles and, meanwhile, achieve
the decorative functions of buildings.

φ 25 bolt

−60×6

1

1

−60×6 L 75×6

φ 25 bolt

620 620

plastering thick 40

−60×6

1240

L 75×6

1-1

Fig. 4.11 Outer packing rolled angles method for retrofitting wall between windows.

The bearing capacity of a wall between windows retrofitted by rolled angles may be
calculated by the same method as that for brick columns retrofitted by outer packing rolled
angle.