Seohaedaegyo Bridge, a landmark of Dangjin

Landmark bridges found in metropolitan cities across the globe including the Harbour Bridge of Sidney, Australia, the Golden Gate Bridge of San Francisco, USA, as well as Gwanandaegyo Bridge of Busan and Incheondaegyo Bridge of Incheon are famous for the rigorous construction work that took years to complete. Seohaedaegyo Bridge, which took 7 years to build (Nov. 1993 ~ Nov. 2000), is a 353km bridge, the construction of which was considered the most challenging part of the Seohaean Expressway construction project. It is now considered a landmark of Dangjin.

Seohaedaegyo Bridge, incorporating the latest construction technologies

The construction of Seohaedaegyo Bridge took around 2.2 million man-days over the course of 7 years. A wide range of the latest construction technologies and methods were employed to build the bridge, and it helped further advance the level of domestic construction technology and contributed to the stimulation of the local economy in the West Coast Era.

Seohaedaegyo Bridge, referred to as the “stage for advanced construction methods,” is a complex bridge incorporating three different bridge types that was built using the latest construction technologies and methods. The cable-stayed bridge, which is the key part of Seohaedaegyo that required the application of frontier technology, was erected using a heavy lifting technique that had not been applied in Korea. The adoption of new construction methods, guaranteeing safety and constructability, helped achieve remarkable progress in the bridge construction technology.

A cable-stayed bridge consists of cables installed centering on two tall towers to support the bridge deck. 990m of Seohaedaegyo Bridge is in the form of a cable-stayed bridge, and being 470m wide and 62m tall, container ships in the 50,000 DWT class or higher can pass through underneath. As the longest cable-stayed bridge (470m) found in Korea, it is the first bridge to have a steel composite structure incorporated into the floor plate, which is known for being cost-effective and allowing efficient maintenance and management. The latest seismic and wind-resistant designs were applied to erect the main towers (height: 180m~182m) and ensure their safety, in addition to employing special construction methods to reduce the construction period (252 days). An elevator and moving car for inspections as well as a gondola were installed after the construction work was complete in order to perform maintenance and management.

A PSM bridge built using the precast segment construction method is cost-effective and ensures construction accuracy (takes 12 days to build a 60m bridge) because the standard segments (upper part of the bridge) are manufactured in a factory and transported to the construction site for assembly. Also, the upper part and lower part of the bridge are built simultaneously, which helps shorten the construction period. PSM bridges that are higher than 46m are erected using high-strength concrete so as to enhance stability, especially during an earthquake. In the case of PSM bridges, quality control is relatively easy and it is highly economical to build. For this reason, it was built to make up the longest section (5,820m) of Seohaedaegyo Bridge.

A free cantilever method (FCM) bridge is built with the bridge piers and the upper structure integrated into an all-in-one structure. A mold is used for the upper part of the bridge to maintain a horizontal balance, and a series of 4m-long bridge decks are connected together. A 500m section of Seohaedaegyo Bridge was built as an FCM bridge, and it was designed to allow ships in the 20,000 DWT class to pass through underneath.

Standing tall on the sea of Dangjin

The 180m and 182m tall bridge towers face each other in a north-south direction, with cables hanging from them, and they add an aesthetic value as a beautiful decoration to the otherwise simple Seohaedaegyo Bridge. It presents a breathtaking night view of the offshore area of the tranquil and peaceful Hanjinpogu Port in Songak-eup, Dangjin, and its exquisite beauty can be admired from the observatory of Sapgyoho Tourist Park located in Yunjeong-ri, Sinpyeong-myeon, Dangjin.

Seohaedaegyo Bridge has turned Haengdamdo, a small island off the coast Sinpyeong-myeon, Dangjin, into a popular travel destination and a tourist attraction along Seohaean Expressway. Haengdamdo Service Area fulfills its function as an expressway service area, and it even contains the Seohaedaegyo Bridge PR Center, which you should visit while stopping here for a short break. The PR center has models use to test the construction methods and technologies to ensure safety of the bridge prior to its construction and presents videos and models showing that the bridge has been built based on safety design and construction methods incorporating a variety of frontier technologies. A model of the cable-stayed bridge built using the latest construction techniques that is only display at the PR center was actually used in the earthquake and wind tunnel tests prior to the bridge construction.