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Steel Designers' Manual - 6th Edition (2003)
856 Bearings and joints
(1) concrete bridges: 0900 BST ± 1 hour each day,
(2) steel bridges: at about 0400 to 0600 BST each day during the summer, and at
any time on ‘average’ days during the winter.
Further guidance on bridge temperatures is given in Reference 10.
Frequently bearings are incorporated into the structure using a bedding layer
above and below the unit, typically of 25 mm thickness, which allows some tolerance
in fixing of the bearing and will also permit final adjustment of the levels of
the structure above during construction.The form of the bedding may be ‘dry pack’,
trowelable or pourable material. Epoxy resin, sand/cement, sand/epoxy, or
sand/polyester compounds are commonly used.The same material may also be used
for filling the spaces around fixing devices once final positioning has been carried
out.
28.2.4 Assemblies of bearings
28.2.4.1 General
The selection and use of bearings of various types has been discussed in terms of
the individual units. The behaviour of the structure or substructure as a whole will
now be considered, and the use of the four principal forms of bearing to control
movement illustrated.
28.2.4.2 Structures straight in plan
As an example, the movement of a typical bridge deck will be considered in the
horizontal plane, although the principles involved can equally be applied in other
directions.
The four forms of bearing commonly available are given in section 28.2.3.3.
Consider the bridge deck shown in plan in Fig. 28.8.
The deck vertical loading arises from dead and live loads, from which maximum
and minimum values of bearing loads can be derived at each position. Longitudinal
loading on the deck will arise from wind loads, braking and traction of vehicles,
and also from the manner in which the chosen restraint system accommodates
Fig. 28.8 Straight bridge deck