TM-5-5420-279-10
OVERBRIDGING
Sect/
Contents
Page
Para
INTRODUCTION .............................................................................................................C-1
OVERBRIDGES ..............................................................................................................C-1
C.2.1 General .....................................................................................................................C-1
BANK PREPARATION ....................................................................................................C-1
C.3.2 Access from both side of an existing Bridge ............................................................C-1
C.3.3 Access from one side of an existing bridge only. .....................................................C-2
C.1.1.1
This section provides the information needed to construct the DSB over an existing
bridge, which has been damaged or has a low military load class capability.
General
C.2.1.1
Overbridges are constructed over existing bridges that are not strong enough to
carry the expected traffic weight.
C.2.1.2
The overbridge uses the existing bridges abutments as bearing points.
C.2.1.3
It is essential that the overbridge does not come into contact with the existing bridge
span while traffic is crossing.
C.2.1.4
It is important to ensure that the existing span is capable of supporting any weight,
which may be applied to it during the construction of the overbridge.
BANK PREPARATION
NOTE
9.8ft (3 meters) is the maximum the DSB system can build up or downhill. Bank
conditions other than flat and level will not give an approach angle of 1 in 9.
C.3.1.1
For all overbridges, the amount of bank preparation is determined using the
following procedures. This is to ensure that the overbridge does not come into
contact with the existing bridge underneath.
Access from both sides of an existing Bridge
C.3.2.1
Bank Height = Overbridge Deflection + h = 35.4in (900mm) + h (Bank Height = DSB
Overbridge Deflection + h = 35.4in (900mm) + h) see Figure C. 2.
