Puente de Ting Kau

Infrastructure Development: The Team Ko Bridge Project

Overview of the Team Ko Bridge

• The Team Ko Bridge and its access viaducts were crucial infrastructure projects in Hong Kong during the 1980s and 1990s, designed to connect rapidly developing areas with urban centers.

• The bridge spans 1,177 meters across the Wrangler Channel, linking the peninsula of Tim Ko with Lantau Island and the new Chek Lap Kok Airport.

Design and Construction Details

• The project was awarded to a consortium led by 5 O Contractors in August 1994, based on a unique design from Stuttgart-based engineers.

• The bridge features two central and two lateral decks supported by cables anchored in three slender towers, designed to withstand extreme typhoon winds.

Engineering Challenges

• To ensure stability against high winds (up to 95 m/s), additional lateral support was provided through struts beneath the deck and cross cables.

• A technical office was established on-site for coordinating construction activities and ensuring effective communication between builders and designers throughout the project.

Construction Phases

• Excavation work commenced in February 1995, involving significant earth-moving operations under challenging conditions near busy highways.

• Foundation piles for access viaducts were manually excavated at steep slopes using traditional methods; this included teamwork among local workers.

Safety Measures and Techniques

• Strict safety measures were implemented during large excavations adjacent to traffic routes, including protective nets to safeguard vehicles below.

• Different solutions were developed for constructing foundations at each tower location due to varying geological challenges; blasting was used where necessary.

Innovative Solutions for Foundations

• An artificial island was created for the central tower's foundation by replacing dredged mud with sand, enhancing stability against potential ship impacts.

Construction of a Major Infrastructure Project

Execution of Pilotage and Construction

• The project involved the execution of pilotage and construction using provisional metallic actions, with 52 piles excavated at a diameter of 25 meters and an average length of 27 meters. Prefabricated reinforcement was placed inside the pile before being concreted.

• After completing the pilotage, fill material was excavated within a highlighted area measuring 35 x 40 meters, which would later be used for the enclosure. The heads of the piles were subsequently demolished.

• For constructing the enclosure, 1,300 tons of reinforcement were installed, consisting of 12 layers at the bottom and 9 at the top. A supporting metal structure was necessary due to the weight of these bars.

• The pouring operation for 5,800 cubic meters of concrete was executed in one continuous maritime operation lasting 75 hours without interruptions. This required transporting concrete using four barges and a total of 820 mixer trucks.

• To manage the large volume of fresh concrete, ice water was utilized along with a cooling tube system spanning 700 meters to control temperature during curing. By sunset on day three, this massive continuous pouring operation concluded successfully.

Foundation Work

• Dredging and rock blasting were performed for the foundation of the south tower located in an area where the coast sharply slopes into water. A semicircular sheet pile enclosure measuring 29 meters in diameter was constructed.

• Ninety-five H-section concrete sheet piles were positioned in a trench previously excavated by blasting to a depth reaching up to 22 meters. Strict alignment and verticality checks were conducted by divers working in the trench.

• Once concreted, both the trench and space between sheet piles were sealed with submerged concrete totaling three thousand cubic meters. Following cleaning and refinement processes on rock surfaces, five thousand cubic meters more mass concrete were poured above water level.

Tower Construction Techniques

• Waiting reinforcements for towers were placed as foundational work progressed; thus preparing for subsequent phases despite tight construction timelines necessitating rapid decisions regarding construction methods.

• Sliding formwork techniques allowed continuous pouring into metal molds that ascended via hydraulic jacks controlled from a central panel. High-strength concrete advanced at a rate of four meters per day during this process.

• Towers featured rectangular sections capped with two semicircular sides composed of three segments differing in size separated by transition slabs where sliding formwork was replaced with conventional curved forms for easier placement.

Final Structural Elements

• Transition slabs reached heights up to eight meters and were poured in batches while maintaining continuous operations around-the-clock throughout tower construction phases.

• Circular foundations measuring seventeen meters in diameter supported transition piers linking access structures to cable-stayed bridges; these foundations utilized climbing forms providing additional weight through granular fill contained by annular walls.

• Two sixty-meter high piers alongside others built using sliding formwork contributed significantly to structural integrity; remaining seventeen piers varied from thirteen to fifty-meter heights constructed using conventional climbing forms over four-meter increments.

Construction Process of the Twin Moon Highway Bridge

Construction Stages and Techniques

• The construction involved a four-stage process for pouring concrete, with maximum spans reaching 22 meters.

• Granular material was used to fill the struts, acting as counterweights to prevent overturning of cantilevers on the single-span deck.

• Six metal heads housing cable anchorage were manufactured in China, weighing up to 200 tons and measuring 31 meters in height.

• A total of 360 longitudinal beams and 530 transverse beams were fabricated for the mixed structure deck of the cable-stayed bridge.

• Special holes were drilled in beam connections during assembly to ensure correct geometry and secure bolted joints.

Heavy Lifting Preparations

• Preparations at each tower's base included installing heavy load lifting systems for raising metal heads and starter panels.

• In March 1997, metal heads arrived by barge from China, marking a significant milestone in the project timeline.

• Precise positioning of metal heads at the tower base was crucial before lifting commenced using specialized equipment.

• Limited space required additional movements before elevating components into their designated positions within the tower structure.

Record-Breaking Lifts

• May 1997 marked a record achievement with unprecedented lifting of two central tower heads weighing 200 tons each to a height of 200 meters.

Installation Challenges

• The first panels delivered were complex assemblies for Tim Ko's tower, requiring careful handling due to limited space at night when unloading from barges.

• A "space launcher," a metallic structure standing 20 meters tall, facilitated slow transport of these panels into position for elevation.

Final Assembly Steps

• Panels were secured into temporary hinges on the tower after being lifted; this process took about three hours per panel installation.

• Subsequent months saw installation of starter panels on central towers following familiar procedures established earlier in construction.

• Cross cables for stabilization were installed between lower transition slabs and vertical supports, enhancing structural integrity against wind forces.

Construction of the Bridge: Key Insights

Cable Installation and Structure

• The cable layout for the bridge deck consists of a maximum of 58 strands, each made up of 7 galvanized wires. Each strand was installed individually between passive anchors at the deck level and active anchors at the top of the tower using a special hoisting device.

• The protective casings have an external helical protrusion that minimizes vibration caused by wind and rain. Tensioning of each strand was performed using a specific method within the metal heads of the towers.

Prefabricated Elements and Assembly

• Typical prefabricated panels measured 18.8 meters in width and 13.5 meters in length, which were crucial for constructing the bridge's structure.

• New pairs of panels were connected to previously completed ones using high-strength plates and bolts, with cross beams joining them at cable anchors.

Construction Efficiency

• The initial assembly experience allowed for significant efficiency improvements, reducing construction cycles to as little as four days per segment.

• In one cycle, two new pairs of girders were installed along with 24 prefabricated concrete panels, preparing cranes for subsequent lifts.

Project Milestones

• Over four months, 75 pairs of panels were erected across three towers simultaneously, extending constructed deck length by 1000 meters. December 1997 marked peak activity with substantial material usage: 2,680 tons of steel and over 11,200 square meters mounted in one month.

Stability Measures During Construction

• As cantilevers increased in length, provisional cables anchored to foundations were added to prevent excessive movement and deformation due to strong winds.

Record Achievements

• Before connecting lateral decks, central tower cantilevers reached a record length of 556 meters in free cantilever execution.

• Longitudinal stabilization cables running from the top of the central tower to near lateral towers provided necessary stability during both construction phases and service operations; these are noted as the longest tension cables ever installed on a bridge (465 meters).

Finalization and Opening Ceremony

• After three years since excavation began, final adjustments led to connecting central tower decks with a special closure panel. This culminated in witnessing intense collaborative efforts from constructors and clients.