The Third line of The Metropolitan Expressway の変更点

追加された行はこの色です。
削除された行はこの色です。
The Third line of The Metropolitan Expressway へ行く。
The Third line of The Metropolitan Expressway の差分を削除
*The Third line of The Metropolitan Expressway [#q6ab2e4c]

**1.Field of application [#d6fae10b]

>The third line of the metropolitan expressway, Tokyo.&br;

**2.Circumstances of Repair [#aba595e9]

>Fatigue cracks were found in the sole plate welds at the girder support locations in 1986 after 15 years of  service.&br;

**3.Types of structure [#qb95c75d]
>The outline of the bridge structure is as follows.
-Span length : 2＠41.2m+3＠31.2m+5＠27.7m (10 spans)
-Structure : Simple composite I-beam girder bridge
-Deck : Light-weight concrete deck (21.0 cm thickness)
-Structural steel : SM 58
&br;
&br;

>Plan and elevation views were shown in [[figure 1>#fig1]]. The number of the girders, which are 1.6m deep, is five. The kind of the support is the bearing plate support as shown in [[figure 2>#fig2]].&br;
&br;
&br;
CENTER:&aname(fig1);&attachref(new_pa11.gif);&br;
&br;
CENTER:Fig.1 Plan and elevation views.&br;
&br;
&br;
CENTER:&aname(fig2);&attachref(new_pa12.jpg);&br;
&br;
CENTER:Fig.2 Bearing plate support structure.&br;
&br;
&br;

**4.Details of loading [#w78cd699]
>Fluctuating loads due to expressway live load.

**5.Description of damage [#j3219100]
>Fatigue cracks were found in the sole plate welds at the girder supports.&br;

>Most of the cracks initiated from the weld in front of sole plate. After penetrating through the girder bottom flange, some cracks, which initiated from the welds in front of the sole plate, propagated at an angle in the girder web.&br;

>Causes of fatigue cracks were thought as follows:
-Stress concentration due to the lost of the support function.
-Stress concentration due to sudden change of the section.

**6.Repair method applied [#g612bdce]
>Emergency repair &br;
>24.5mm diameter stop holes were drilled at the crack tips and the high strength bolts of M22 were fastened there.&br;
&br;
&br;
>Permanent repair &br;
>270 by 16 by 230mm plates were installed by bolts on the girder both web sides. These plates were groove weld connected to the girder bottom flanges ([[Fig.3(a)>#fig3]]).&br;
&br;

>The plates of 12mm thickness by 250mm length were installed by bolts on the bottom face of the girder bottom flange. These plates were fillet weld connected to the front side of the original sole plate ([[Fig.3(b>#fig3]])).&br;
&br;
>The effect of repair is under investigation.&br;
&br;
&br;
CENTER:&aname(fig3);&attachref(new_pa13.jpg);&br;
&br;
CENTER:Fig.3 Permanent repair.&br;
&br;
&br;