In January 2000 the PCI Journal described the Bang Na Expressway as the longest bridge in the world, ahead of the 38 km Lake Pontchartrain Causeway in Louisiana. Longer viaducts have since been built, among them the 164.8 km Danyang–Kunshan Grand Bridge in China, which opened in 2011, so the title no longer stands. What has lasted is the method.

The elevated expressway runs for about 55 km above Highway 34 in Bangkok, with a deck area of about 1.9 million m². The owner was Thailand’s Expressway and Rapid Transit Authority; Bilfinger + Berger and Ch. Karnchang built it as a joint venture. Jean Muller International designed the columns and superstructure; the paper credits Asian Engineering Consultants with the alignment and foundations. The contract was signed in June 1995 and allowed 3½ years, with construction starting while design was still under way. One condition shaped everything else: traffic on the highway below had to keep flowing at 80 km/h.

55 km
Length
1.9 M m²
Deck area
≈40,000
Precast segments
≈1,800
Segments cast per month
11
Launching girders
Constraint 1 — The road
Traffic kept at 80 km/h
The contract required traffic on Highway 34 to flow without interruption, and the PCI paper records that interrupting it for construction operations was not permitted. The deck passes about 14 m above the road. That left erection to equipment running on the structure itself rather than working from the ground.
Constraint 2 — The column
An H that lets the girder through
The columns stand in the open drainage area of the median, where an H-shaped column takes the least from the free-flow channel. With no cross-beam above the girder, an underslung girder can move through the column’s upper arms, which simplifies launching. Jean Muller International designed the H column, the underslung truss and the mainline segments as one integrated approach.
Constraint 3 — The girders
Eleven launching girders
Five underslung girders erected the mainline and six overhead trusses erected the ramps. Measured in square metres of deck erected, the paper reports the D6 underslung-girder operation at about twice the rate of the D2/D3 overhead-truss operation, and about 2,100 m of mainline deck and 2,500 m of ramp deck erected each month. The segments were match cast and post-tensioned in place with dry joints and external tendons.
Constraint 4 — The yard
One yard for every front
About 40,000 segments of different types were cast at a yard at Bang Bo of about 650,000 m². Typical D6 mainline segments weighed about 85 t; D6 pier segments weighed about 100 t. The paper reports approximately 1,800 segments a month, with storage for about seven weeks of production.
Four-phase schematic of the Bang Na Expressway: the deck about 14 m above Highway 34 with traffic required to flow at 80 km/h; an H-shaped column in the median with an underslung girder passing between its upper arms; five underslung and six overhead launching girders; and one casting yard of about 65 hectares feeding the erection fronts at about 1,800 segments a month, with typical mainline segments of about 85 t and pier segments of about 100 t
The four conditions behind the method. Conceptual schematic, not to scale; the full yard-to-front haul plan is not detailed in the source and is not shown.
Source: Brockmann & Rogenhofer, PCI Journal, January–February 2000. Diagram: EE&HL Network, 2026.

At this scale the erection method is also a logistics contract: casting rate, delivery and girder cycle have to stay locked together on every front.

The PCI article explains that segments were delivered at grade or onto the erected deck and then handled by crane or transport chassis, but the full yard-to-front haul plan is not detailed, and nor is how cycle times were managed, so that part of the picture is not covered here. What it does show is a structure and a method designed together, with column, girder and segment by one designer, around a traffic condition fixed in the contract.

That is the commercial pattern worth noting. A method that only works if casting rate, delivery windows and girder cycle stay locked together carries a commercial dependency as well as a technical one: when one of the three drifts, several fronts that draw on the same yard can be affected. This is an editorial reading; the PCI article does not discuss how that risk was allocated.

For the techniques involved, see What Is Match-Casting? and What Is a Launching Gantry?. For the wider pattern at viaduct scale, see the insight When the Erection Method Becomes the Project. For the sector context, see Erection Engineering in Bridge Construction.

Related case studies: Millau Viaduct · Oléron Viaduct · Woronora River Bridge · Sidu River Bridge · Skarnsund Bridge

Core concepts: What is erection engineering? · What is heavy lift engineering?

The elevated concrete deck of the Bang Na Expressway on single piers, running alongside a ground-level highway in Thailand
The elevated Bang Na Expressway running alongside the Bang Na–Bang Pakong road, March 2008. Optimised for web display.
Photo: Miniwildebeest, via Wikimedia Commons; public domain.

Sources: PCI Journal — Brockmann, C. and Rogenhofer, H., “Bang Na Expressway, Bangkok, Thailand — World’s Longest Bridge and Largest Precasting Operation”, January–February 2000, pp. 26–38 (length, deck area, contract, traffic condition, H columns, girders, segments, yard, record claim); Wikipedia — Bang Na Expressway — joint venture, opening date; Wikipedia — Danyang–Kunshan Grand Bridge — length and 2011 record. Span counts and the cycle time per span are not stated in the PCI article and are not given here. The “longest bridge in the world” description is the article’s own, as of January 2000.

Frequently Asked Questions

No. The PCI Journal described it in January 2000 as the longest bridge in the world, ahead of the 38 km Lake Pontchartrain Causeway. Longer viaducts have since been built; the Danyang–Kunshan Grand Bridge in China, at 164.8 km, opened in 2011.

The deck was erected span by span from launching girders running on the structure itself, so no erection work needed the highway closed. The contract required traffic to flow without interruption at 80 km/h. Five underslung girders built the mainline and six overhead trusses built the ramps.

In span-by-span construction a whole span is assembled from precast segments held by a launching girder and post-tensioned, and the girder then advances to the next span. At Bang Na the segments were match cast and joined with dry joints and external tendons.

The PCI article gives two reasons: an H-shaped column takes up the least of the free-flow channel in the median of Highway 34, and with no cross-beam above the girder an underslung girder can move through the column’s upper arms, which simplifies launching.

Jean Muller International designed the columns and superstructure, and the PCI paper credits Asian Engineering Consultants with the alignment and foundations. A joint venture of Bilfinger + Berger and Ch. Karnchang built it for Thailand’s Expressway and Rapid Transit Authority, under a contract signed in June 1995.