2. Size
unit:mm
3：Geometric features of all cross-section
1):Calculation of effective width bf´, obtaining minimum value of the following three ones: (1): Simple supported beam span’s l/3, l/3=27660/3=9220mm;
unit:mm
Fig1. End of prestressed beam Fig.2 anchor position in the end Fig.3 cable position in mid-span
In order to be convenient for construction,three steel cables anchor end of beam,which fits principle of homogeneous disperse and requirement of tension.It will offer much preshear force by bending more depth of N1 and N2 in end of beam. The all shown Fig1 and Fig2.
3):Location and angle of steel cable from other sections.
(1)Bending shape、angleθ and radius of bending.
Obtain interpolate curve between straight lines.In order to make preapplied force be
perpendicular to anchor bearing plate,bending angle of N1, N2, N3 are 。

80=θ. Radius of each steel cable is: ;450001mm R N = mm 300002=N R ; mm 150003=N R .
(2)calculating location of steel stable control points.
unit:mm
Figure4
unit:mm
3)Requirement for non-prestressed reinforcement(location and area of rebar section)
To satisfied with the ultimate limit state, the number of non-prestressed reinforcement are: After deciding the reinforcement number, non- prestressed reinforcement is decided according to the normal cross-section’s ultimate limit state.
Assume the distance from prestressed and non-prestressed reinforcement’s resultant force point
to the cross-section bottom is a=80mm,so mm a h 1720801800h 0=-=-= Assume first kind of T shape beam, according to )
2/('00x h x b f M f cd d -≤γ, we can get the depth of
compressive zone x
1.0×5554.8×106
=22.4×2200X(1720-X/2) x= 67mm<mm h f 228'= So,As=(f cd b f́ - f pd A p )/f sd =384mm
2
Select 2Φ18mm HRB440 As=509mm 2
,lay out one line,space is 264mm. as = 45mm,shown following Figure.
unit:mm
unit:mm
The area moment na S of area above a--a to n n x x - gravity axis ：
3
81098.1)2/1201802.573(120200)
3/1201802.573(120)2001800(21
)2/1802.573(1801800mm
S na ⨯=--⨯⨯+--⨯⨯-⨯+-⨯⨯=
With the same theory, area moment from different calculation point are shown in Table:
List of area moment
Type of section The first stage
（x=573) The second stage
（x=597)
The third stage
（x=556)
Position of
a-a
x 0-x 0
b-b
a-a
x 0-x 0
b-b
a-a
x 0-x 0
b-b。