Criteria and guidance for the design of integral bridges

Abstract

The design and implementation of integral and semi-integral bridges has grown in prominence in New Zealand practice over the last two decades, and bridge designers in the country refer to the New Zealand Transport Agency (NZTA) Bridge Manual for design guidance. However, several issues related to the design and construction of integral bridges were identified as requiring either further investigation or clearer guidance for local design practice. These included non-seismic effects such as concrete creep, shrinkage and temperature, seismic effects and geotechnical issues including soil–structure interaction. Particularly, it was noted that there are no well-established earthquake design procedures for bridges with integral abutments and that the topic of soil–structure interaction required further guidance. NZTA research report 577, published in November 2015, was developed to sit alongside the Bridge Manual and provide local engineers with the necessary guidance for the design of integral bridges, including a description of the issues that need consideration to ensure excellent long-term performance. Report 577 also contains details of a review of the performance of numerous existing integral bridges in both New Zealand and California that have been subject to strong seismic events. This paper discusses the key issues for consideration in the design of integral bridges in non-seismic and seismic regions and the key recommendations for addressing these issues, and also provides examples of documented performance of some integral bridges in New Zealand.