Welcome to this June 2022 issue of the Institution of Civil Engineers’ journal Bridge Engineering. In this journal we aim to publish a mix of practice and research papers, which we hope will be of interest to all bridge engineers.
In the editorials of the two general issues last year, Jones (2021) and Giaccio (2021) separately mentioned efforts bridge engineers are taking to reduce equivalent carbon emissions in order to address the climate crisis and to make progress towards net zero. These included calculating the carbon of new works but also the efforts that need to be taken, where possible, to avoid demolishing and reconstruction when existing infrastructure can be upgraded for incorporation in the new works. Other measures are to maximise offsite construction, which has long been recognised as a way to minimise waste, reduce the risk of delays or re-working on the critical path, and minimise disruption to existing infrastructure. Significant advances in the use of improved cranage and the increasing use of building information modelling and digital twins in recent years have helped these advances. This journal is always keen to highlight innovative bridge projects that advance design and construction techniques that contribute to reduced carbon emissions. We would welcome papers describing case studies that illustrate any innovations that reduce the environmental impact of bridge structures.
This issue of Bridge Engineering includes five technical papers that cover a range of topics from the design and construction of a new prestressed concrete bridge to advanced remote inspection techniques.
In the first paper, Sandberg et al. (2022a) describe the design of the new River Dee Bridge constructed as part of the Aberdeen Western Peripheral Route (Aberdeen, UK). This is a 270 m long concrete box girder bridge that was built using the balanced cantilever construction method. This paper focuses on the complex design challenges, particularly associated with the tight geometrical constraints imposed by environmental and aesthetic considerations on the foundations and the superstructure. The post-tensioned tendon design, which was particularly challenging for this relatively narrow and shallow box section, is also discussed. The second paper, also by Sandberg et al. (2022b), is a companion paper to the first one that describes the complex construction by the balanced cantilever method. This second paper describes the importance of managing the construction sequence and its impact on both the design and the programme. Monitoring and managing the loads in the temporary works were crucial to ensuring the stability of the structure. The issues associated with the temporary jacking system and the monitoring adopted are also considered.
The third paper by Proske et al. (2022) deals with the application of the latest advanced calculation methods for the seismic analysis of bridges. The authors note that many older bridges are not adequately designed for earthquakes. To enable structural verification, new methods such as conditional spectra and conditional mean spectra have been developed to estimate seismic hazards more accurately. To quantify the advantage of the methods for regions with low and moderate seismic hazards, the seismic internal forces of four existing Swiss bridges were determined and compared based on conditional mean spectra and uniform hazard spectra. The examples chosen were two reinforced concrete and two steel bridges, one of which was used for road traffic and one for railway traffic. The results for the different bridge types demonstrated the validity of the new methods. The authors point out that the practical application in a design office would be very time-consuming with currently available software. Nevertheless, the results show that the differences at component level can be significant.
The next paper considers remote methods of bridge inspection. Yinhuai et al. (2022) describe a systematic approach to verify the dimensions of complex bridges using a combination of three-dimensional (3D) point clouds obtained by both terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) surveys. The authors use the Xinglinpu Bridge in China as a case study; this is a cable-stayed steel bridge that was built in preparation for the Beijing 2020 Winter Olympics. Existing methods for dimensional verification of complex bridges rely on manual inspection and contact-type measurement devices, which can be time consuming and costly. The paper suggests a systematic procedure for the verification of dimensions using remote laser scanning techniques (TLS and UAV). The potential and limitations of 3D laser scanning for assessing the dimensions of complex bridges are discussed.
The final paper by Zhang et al. (2022) describes the monitoring and controls conducted during the replacement process of the cables on a cable-stayed bridge. It uses the Rainbow Bridge in China as a case study. The cable force and deck levels were monitored, and the distribution of cable forces was adjusted to make them closer to their design values and to increase their safety reserve. An impressive degree of accuracy was achieved with the difference between the measured and the design cable force being less than 2%. Owners of ageing cable-stayed bridges that need cable replacements will be interested in the techniques described in this paper.
I hope you find these papers interesting and useful. Comments on the content of any of the papers are always welcome. Details on how to contribute your comments can be found at the end of each paper. Also, there are many fascinating bridge-related projects being constructed around the world, so if you are involved with one of these projects then please consider submitting a paper to this journal.
