Full-Span Precasting for Light-Rail Transit and High-Speed Railway Bridges

Full-span precasting of light-rail transit bridges

Numerous major bridges have been built for high-speed railway projects. The 113 km Beijing-Tianjin route in China includes 100 km of bridges (88%), the 1318 km Beijing-Shanghai route includes 1140 km of bridges (86%), the 904 km Harbin-Dalian route includes 663 km of bridges (73%), and the 995 km Wuhan-Guangzhou route includes 402 km of bridges (41%). More than 35.000 spans for high-speed railway bridges have been built in China, and large investments in high-speed railway infrastructure have also been made in Europe, Japan, Korea, and Taiwan.

The cost of track infrastructure and systems diminishes the share of the supporting structures of the total cost of the project. The cost of embankments with transition wedges at abutments and box culverts, the disruption of traffic in case of track geometry defects or settlement, and restraints on the vertical alignment all favor the use of long prestressed concrete bridges, while control of train-induced vibrations necessitates short spans. The combination of long bridges and short spans makes for hundreds of spans, justifying the investment needed to set up large precasting facilities and to provide special means of transport and placement. Full-span precasting of high-speed railway bridges accelerates construction, minimizes labor, improves quality, and further increases the competitiveness of prestressed concrete bridges over embankments.

Several recent light-rail transit projects include miles of prestressed concrete elevated guideway. The light-rail transit spans are short to facilitate control of train-induced resonant vibrations; thus the large number of spans lends itself to full-span precasting in this application as well.

Many high-speed railway bridges and some light-rail transit bridges have been built with full-length precast concrete beams transported into place and erected span by span. Single-cell and twin prestressed concrete box girders are well suited for dual-track bridges, while single-track U beams offer the additional advantages of noise reduction, train containment in case of derailment, optimum integration with the environment, and easier handling because of the lighter weight.

Full-span precasting offers rapid construction; repetitive, high-quality casting processes in factory-like conditions; and year-round erection in almost any weather conditions. The maximum span length depends on the capacity of the erection equipment. In large-scale projects where this construction method is used, it is common to build custom equipment for the length and weight of the beams to be handled. Ground transport of single-track, light-rail transit U beams and delivery of light-rail transit and high-speed railway beams on the completed deck are rarely used for spans longer than 30 to 35 m due to the cost of the erection equipment and the loads applied to the deck. Minimal gradients on bridges and access routes are also important for beam delivery on the deck.

Full-Span Precasting for Light-Rail Transit and High-Speed Railway Bridges (2014, PCI Journal) explores design and construction of railway bridges by full-span precasting. The eManual Full-Span Precasting of High-Speed Railway Bridges (2016, BridgeTech) and the bestseller Bridge Construction Equipment (2013, ICE Publishing) further expand the discussion of the topic. These publications are indispensable sources of information and guidance for bridge owners, designers and construction professionals interested in the design and construction of prestressed concrete railway bridges.