Effects of temperature-related creep in concrete bridges
Creep analysis plays a vital role in structural design and analysis,
especially for the design of sequentially constructed bridge
structures. The theory of uniform creep is widely applied in
practice and elastic thermal analysis is processed independently.
If the effects of temperature on the rate of creep are considered,
however, the traditional way of analysis may lead to unsafe results
even if the extreme temperature difference has already been considered.
The thermal-creep computer analysis is usually done in the form of a
force method and the principles of applied mechanics are clear.
But the algorithm of the force method for structural analysis is
complicated, especially for sequentially constructed bridge structures
when the change of structural system and boundary conditions must be
taken into account.
This work is mainly based on thermal creep theory developed by
England. When applied to the structural analysis, however, the
displacement method is used for its convenience in sequential
analysis. The work concentrates on effects of construction
sequence on thermal-creep behaviour in comparison with the structure
completed in one stage. Both termal creep and uniform creep
analyses are included. The time-dependent analysis is studied in
detail, the steady-state analysis is also emphasized in order to find
safe bounds for total thermal creep effects. A method analogous
to the displacement method is employed in the steady-state
analysis. The creep analysis is programmed using FORTRAN 90.
Bridge structures are exposed to daily and seasonal variations of
temperature. This work simulates a structure under long-term
natural temperature variations, which is based on theories of heat
transfer and approximate variations of shade temperature, to find
the range of structural response by time-dependent analysis. The
cyclic steady-state analysis is then applied in comparison with
time-dependent analysis. If the duration is long enough, the
results of the time-dependent analysis agree with steady-state analysis
very well. It is concluded that the appropriate steady-state
analysis can give a safe, although sometimes conservative, range for
sequentially built structures
[Cambridge University | CUED | Structures
Group | Geotechnical
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