This edition of Bridge Engineering is the second of two themed issues devoted to arch bridges. Arch bridges come in many different types ranging from traditional masonry structures to more recent long-span bridges constructed from steel or concrete. There is a continuing need to innovate in the design of new structures as well as the maintenance of existing structures – a need that is equally applicable to arch bridges even though many have been in existence for many years. Consequently, there is an extensive range of potential topics relating to arch bridges and the response to the call for abstracts in April 2010 for this special edition was excellent. Therefore, it was decided to produce two themed issues.
The first issue was devoted to the more traditional arch bridge form (Daly and Cole, 2012) and concentrated on the assessment and maintenance of masonry arch bridges. This second issue considers more recent developments in the use of the arch structural form together with innovative methods of reconstruction of older arch bridges. The eight papers contain an interesting mix of design, analysis, testing and construction methods from seven different countries.
The first paper in this second issue describes an innovative method for rapidly constructing a concrete arch bridge that can either be used to replace a masonry arch or as part of a new development. Long et al. (2013) describe how the method of using precast concrete voussoirs interconnected via polymeric reinforcement and a concrete screed was developed. The method utilises the benefits of factory production, simple delivery on a lorry and a straightforward lift into position when the concrete voussoirs assume the desired shape of the arch under gravity. Extensive model and full-scale tests were carried out to validate the system and traditional masonry arch analysis methods can be used for design and assessment. The structure contains no reinforcement which reduces future maintenance requirements.
The second paper describes how a skew arch constructed of discrete interlocking concrete voussoirs was constructed to replace the previous reinforced concrete arch on the site. Redpath (2013) explains how the chosen solution not only provided the most economic initial capital outlay but also offered the most durable solution because of the absence of steel reinforcement. The innovative use of 3D modelling allowed the discrete voussoir blocks to be precast and then erected on site by conventional site resources to produce an economic structure with a pleasing traditional appearance.
The next five papers deal with various aspects of modern arch bridges. Sarmiento–Comesías et al. (2013) provide a state-of-the-art review of spatial arch bridges, i.e. a bridge where ‘vertical deck loads produce bending moments and shear forces not contained in the arch plane due to their geometrical and structural configuration’. The authors note that even though there have been six international conferences on arch bridges in recent years, this type of bridge has not been considered, although over 80 have been designed. The paper provides a comprehensive flowchart that aids the classification of the design aspects of this type of bridge and is a welcome addition to the knowledge base. The authors propose further research that would help to establish design criteria for what are often described as ‘landmark’ bridges.
Foglar and Lubas (2013) describe the design and construction of four network arch bridges in the Czech Republic. This type of bridge is defined as a tied arch ‘with inclined hangers where some hangers cross other hangers at least twice’. The tie consists of a longitudinally prestressed concrete slab. This structural form provides high stiffness, low live load deflection and a low construction depth which has been verified by load tests and monitoring during construction and in service. The bridges described by the authors were an effective solution to providing a grade-separated interchange.
The next paper (Pircher et al., 2013) provides further insight into the behaviour of network arch bridges for which there is little codified information, this time considering examples constructed in Norway. The behaviour of the network of inclined hangers is similar to a truss where axial loads predominate. The paper discusses the stability of such bridges and notes, in particular, the importance of considering local modes of failure and the effect of material imperfections.
The hangers in a through arch bridge are important elements because they suspend the bridge deck from the arch ribs. Jiang et al. (2013) describe a method for the design of vertical hangers that improves the resilience and robustness of this type of structure. Importantly, the method proposed allows the structure to maintain some load carrying capacity in the event that one or more of the hangers are damaged.
Gao and Chen (2013) describe laboratory tests carried out on two 6 m span model arches constructed with concrete-filled steel tubular (CFST) ribs with corrugated steel webs (CSW). The authors noted that previous analytical and experimental work with CFST-CSW structures concentrated on bending and compression behaviour. The authors have found no literature available that discusses the in-plane behaviour of CFST-CSW arch ribs. The authors present a number of important design principles for this type of structure that were derived from the results of the model testing and numerical analyses that were carried out.
The final paper in this special edition describes the design and construction of the new Mizen Head footbridge (Ruane et al., 2013). This 50 m reinforced concrete through arch footbridge is situated in a spectacular coastal location in County Cork, Ireland. The paper describes the investigation techniques that were applied to the original bridge that had been constructed in 1909 and the evaluation of strengthening/replacement options. The chosen solution cleverly used the existing bridge as falsework for the new construction which replicated the form of the original bridge. The project was the overall winner of the 2012 Irish Concrete Society awards.
This collection of fourteen papers and one article contained in the two issues of this special edition illustrate some of the innovative work that is taking place to design and maintain arch bridges of both traditional and modern appearance.
