[Univ of Cambridge] [Dept of Engineering]

Effects of temperature-related creep in concrete bridges constructed sequentially

  Qing Xu


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 Group]

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