Shear assessment of prestressed concrete bridges

The shear capacity of existing concrete structures is often unable to meet current standards requirements. This can be due to inadequacies in shear design provisions at the time of the original design, deterioration of materials, increased load requirements and higher demand in shear capacity owing to flexural strengthening. However, assessment methods are often conservative, and the actual strength may be sufficient to sustain the specified load. This paper describes the results of an experimental investigation into the shear capacity of prestressed concrete bridge beams post-tensioned transversely to form a deck. It is shown that the ultimate shear capacity of these structures can be significantly greater than suggested by the relevant standards. Analytical models based on the upper-bound theorem of plasticity theory are successfully applied, resulting in realistic predictions. Use of the proposed methodology would allow significant savings, as the cost associated with replacing or strengthening the structure can be avoided or minimised, encouraging a sustainable approach.