The actual shear capacity of existing concrete structures is often unable to meet
current standard requirements. This may be attributable to increased load
requirements, inadequate shear provisions in the original design or increased
demand in shear capacity owing to flexural strengthening. However, available
methods of assessment are often conservative, and the actual strength may be
sufficient to sustain the specified assessment load. Therefore, it is important that
realistic assessment methods are employed.
This research comprises an investigation into the shear capacity of prestressed
concrete bridges and into the feasibility of a novel strengthening approach, both
through comprehensive laboratory experimentation and theoretical analyses. The
laboratory testing indicates that the shear capacity of prestressed concrete bridges,
post-tensioned transversely to form a deck, can be significantly greater than
suggested by the relevant standards. The strengthening method proposed, namely
deep embedment of steel or fibre-reinforced polymer (FRP) bars, is found to be
feasible and very effective for reinforced concrete (RC) and prestressed concrete
(PSC) beams of any size.
Analytical models based on the upper-bound theorem of plasticity theory are
successfully developed and applied, resulting in much more realistic predictions
than those from current standards and codes when assessing shear capacity. For
the strengthened beams, in addition to an upper-bound model, a strengthening
design method based on a truss analogy is developed, which can be directly
implemented into codes of practice.
The analytical methods permit the assessment of existing longitudinally and
laterally prestressed concrete bridges for shear capacity in a rational manner, and
then to determine the capacity of a practical shear strengthening system if the
bridge turns out to actually be understrength. Use of the proposed methodology will
allow significant savings, as the costs associated with replacing or strengthening
the structure can be avoided or minimised, encouraging a sustainable approach.
|Date of Award
|1 Nov 2009
|Tim Ibell (Supervisor) & Antony Darby (Supervisor)
- prestressed concrete