Civil Engineering Reference
In-Depth Information
The compressive height
x
is given as follows:
f
y
0
A
s
0
−
f
y
0
A
s
0
−
f
ay
A
a
=
f
cm
0
b
0
x
(3
.
53)
The bearing capacity can be computed by:
M
u
=
f
cm
bx
h
0
−
h
0
−
+
f
y
A
s
(
h
0
−
x
2
b
2
a
s
)+0
.
9
f
ay
A
a
(3
.
54)
where,
f
ay
is the factored compressive strength of sticked plate,
A
a
is the section area of the
plate,
b
1
is the width of the plate.
steel plate
steel plate
Fig. 3.32
Retrofit scheme of beam stuck with steel plates in compression region.
5. Construction provisions
Construction of members retrofitted by sticking steel plates shall comply with the following
requirements:
a. The strength grade of concrete pasted with the plates should not be less than C15;
b. Range of the steel plates thickness shall be 2
∼
4 mm. They should be stratified and
pasted when the computed thickness is larger than 4 mm.
c. If retrofitted in the compressive region, the width of the steel plate may not be larger
than 1/3 of the beam height.
d. 200
t
(
t
refers to the thickness of plates) or 600 mm, whichever is greater, shall be
taken as the anchorage length in a tensile region. For the compressive region, the anchorage
length is the greater one of 160
t
and 480 mm. Additional anchorage measures such as
using bolts may be taken in earthquake resistant structures, long-span constructions and
structures likely to bear cyclic reverse loads.
e. Steel plate surface should be plastered with M15 cement mortar, the thickness of which
should not be less than 20 mm for beams and 15 mm for slabs.
f. To retrofit the tensile regions in supports of continuous beams exposed to negative
moment, different methods could be chosen based on whether there are some obstacles such
as column:
a) If not, steel plates could be pasted on top surface (Fig. 3.33).
b) For obstacles on the top surfaces but not the sides of beam, steel plates should be
pasted on the sides of upper parts in beams (Fig. 3.34).
stick plate
crack
Fig. 3.33
Retrofit of continuous beam with steel plates on top surface.
