Civil Engineering Reference
In-Depth Information
Slicing design
Steel load plate
Stainless steel
PTFE
Molded neoprene or
natural rubber
Steel base plate
Steel load plate
Multidirectional
(a)
(b)
Concave plate with woven PTFE
Stainless steel convex plate
(c)
Figure 8.16
High-load multirotational bearings. (a) Disk bearing. (b) Pot bearing. (c) Spherical
bearing.
with consideration given to designing for the resulting force and deflection
envelopes. Note also that during bridge erection, bearing points may be tem-
porarily blocked (partially fixed), so the construction cases may not have
guided or nonguided (free) bearing points. This may be a consideration if
significant thermal movements are anticipated at partially erected structural
conditions.
Compared to I-shape girder, a steel box girder is stiff and difficult to adjust
in the field. NCHRP Report 12-79 (White et al. 2012) advises to detail tub
girders for no-load fit or steel DL fit (with consideration given to possible
temporary shoring or hold cranes; if sufficient shoring or temporary support
is provided, detailing for no-load it may be more appropriate). It should be
noted that almost all structural analyses are based on the assumption that
the structure is under initial no-load (undeformed, unstrained) geometry.
The stresses and forces in the system are based on the deformations from
this configuration, including any lack-of-fit effects (White et al. 2012).
8.2.2.3 Description of the noncomposite bridge models
A two-span noncomposite, single steel box girder bridge as shown in
Figure 8.17 is used in this chapter as an example to illustrate different
modeling methods. The total span length of this bridge is 97 m (320′).
A lateral-bracing system is installed at the top-flange level in the open-top
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