Bridges

Cover of Evaluation and Strengthening of Existing Bridges to Carry Increased Vehicle Weights
Evaluation and Strengthening of Existing Bridges to Carry Increased Vehicle Weights
  • Publication no: ABC-AAI405-14
  • Published: 22 October 2014

Detailed investigation and live-load evaluation was undertaken for several 1930s reinforced concrete bridges followed by strengthening where required.

New approaches were adopted to improve the accuracy of capacity evaluation, and to optimise strengthening works. These include:

  • statistical methods to assess the characteristic strength of a group of reinforcing bars
  • utilising international code recommendations for the evaluation of longitudinal shear capacity
  • post-tensioning of multiple, simply supported spans in a single operation.

In a number of cases the evaluations identified deficiencies, including longitudinal shear failures in reinforced concrete beams, and flexural-shear deficiencies, which were confirmed by detailed investigations on site. Where deficiencies were identified these were proactively managed through the period from identification until strengthening measures were complete.

Strengthening solutions were detailed such that future concrete deterioration would not compromise the integrity of the strengthening works.

These evaluations and strengthening works have enabled NZ Transport Agency to increase the allowable load-carrying capacity of its bridge stock by realistic evaluation of existing capacity, and through implementation of cost-effective strengthening solutions.