The Chacao Bridge, which connects Chiloé Island and mainland Chile via the Chacao Strait, is a suspension bridge with three towers and two main spans, making it the longest multi-span suspension bridge in the world with a total length of 2.75 kilometers. When completed, it will be the longest suspension bridge in South America.

The bridge deck of the Chacao Bridge is a streamlined steel box girder with a height of 3.27 meters and a width of 23.824 meters, providing a four-lane roadway, and the PPWS method was applied to the main cable. The three main towers consist of an inverted Y-shaped central tower with a height of 158.9 meters and two portal-shaped side towers with a height of 128 meters. In particular, the central tower was designed with four legs to increase the longitudinal stiffness of the bridge. The foundations of the towers were designed as bored piles, one of which is located on the reef in the center of the strait, while the other tower foundations are located on the shore.

BAND is providing construction engineering consulting services for the erection of the bridge deck.

Construction engineering is the task of establishing complex erection planning and geometry control of structures that require special equipment, such as suspension bridges and cable-stayed bridges, temporary structure design, and equipment operation plans, and providing solutions to problems that may arise at the construction sites. It can be defined as site design enables safer construction.

The work scope of steel deck erection construction engineering, which BANDI was in charge of, is largely divided into erection planning of steel deck, design of temporary structure, and planning of erection equipment.

The deck erection of Chacao Bridge was planned using a lifting gantry. Most of the segments were applied with the direct lifting method, but some segments at the beginning of the bridge and near the tower were not accessible by barge, so the swing method was chosen.

The length of one deck segment was determined to be 20m, the same as the hanger spacing, and the new segment was planned to be temporarily connected to the already lifted deck segment using steel pt-bar. For the deck segments near the beginning and end of the bridge and the deck segments near the tower, permanent hangers were not planned, so temporary hangers for the steel deck were proposed.

Since the Chacao Bridge has three main towers and two main spans, five key segments for deck closures out of total of 124 steel deck segments were planned. According to the steel deck installation plan, two key segments are located near the north tower, two near the central tower, and one near the south tower. The installation of these key segments requires the setback of the steel deck, and a plan was developed to minimize the forces required for the setback process.

Design of Temporary Structure For Construction

To construct a suspension bridge deck, it is necessary to establish a design methodology for various temporary members such as temporary connections between decks, temporary lugs, temporary hangers, and clamps. The temporary members are attached to the permanent members, and the damage to the permanent members caused by these temporary members is verified through detailed FEM analysis.