PICK, SLEW AND VERTICAL LOWERING

A Total Solution in Temporary Steel Structure

Dino Spaleta
Chief Project Officer

“The synergy of our people, built upon technical engineering expertise and high-end facilities accompanied with high-quality steel structure fabrication, has once again flagged our credentials as a total solutions provider. On this complex project, precision engineering and accuracy of works were the critical success factors. From planning to execution, we had complete trust in our team in terms of capability and due diligence.”

“The synergy of our people, built upon technical engineering expertise and high-end facilities accompanied with high-quality steel structure fabrication, has once again flagged our credentials as a total solutions provider. On this complex project, precision engineering and accuracy of works were the critical success factors. From planning to execution, we had complete trust in our team in terms of capability and due diligence.”

Yuen Long Bridge Manoeuvre

Yuen Long Station Property Development (YLTL No.510) involved a series of residential developments. Sanfield and MTR, the co-developers, wished to extend the transportation network by linking the old town to a newly developed area in Yuen Long. A passenger bridge and a vehicle bridge were designed to connect the residential site to the existing MTR station.

To alleviate potential disruptions to the daily operations of public transport adjacent to the site, a slew & lowering erection method was adopted. The biggest challenge was to complete a rapid and safe installation in an extremely congested construction site––not once, but twice for the two permanent bridges respectively. The rotation and lowering of the two bridges were carefully carried out above high voltage (750V DC) overhead cables, without inducing any impact on the operation of light rail, transit trail and access to YL MTR station.

Goldwave was commissioned to material supply, fabricate, offsite trial, build and erect a full set of temporary turntable steel structures to facilitate a specialised bridge rotation over a live rail line, including lowering and final installation and anchoring. To ensure maximum safety, the heavy-duty turntable frame and platform were anchored on top of a reinforced concrete podium. Our experience in precision engineering made it possible to meet a stringent specification based upon a complex structural and mechanical/hydraulic steelwork design, which was meticulously merged with the reinforced concrete structure. Together with world-renowned Freyssinet, our strategic partner, the bridge installation time durations were significantly reduced due to safe and efficient working conditions that were carefully planned and executed by our project teams.

Project Summary

Passenger Bridge (length)

46 m

Vehicle Bridge (length)

52 m

Turntable Rotary Frame (diameter)

21 m

Main Frame Steelwork (weight)

1,250 t

Counterweight

1,800 t

Stakeholders

Sanfield (Management) Limited

MTR Corporation Limited (MTRCL)

Award

Gold Medal, Award for Best Method Statement by Occupational Safety & Health Council

Project Types

Heavy Lifting ; Steel Bridge and Tower

CHALLENGES

“Is Bridge Rotation Feasible?”

During the tender consultation stage, we were asked to explore the technical concept of bridge rotation. The idea was at the conceptual stage and required an extensive study before reaching consensus and then manufacturing and construction. To transform from a mechanical (hydraulic/electric) rotation to a vertical hydraulic lowering system, our expert engineering team proposed a convincing steel structure solution. For ease of installation, steel billets were adopted to act as counterweights for this technically demanding operation. Larger billets were used for the skid shoes and these were deployed to minimise distortion to the skidding system.

The 16-meter-long curved rail track components required the largest size machining equipment in its class to undergo an extensive and precise machining process. Our rigid quality control of tolerances ensured a smooth skidding operation of the rotary frame.

Full Simulation in our Jiangmen Fabrication Yard

To accurately assess both the functionality and installation of the turntable steel structure, we recommended running a comprehensive simulation in our Jiangmen factory, located in southern China. After the trial, the large and complex structure would then be disassembled and then reassembled onsite in Hong Kong.

The design was premised upon a series of inclined and diagonal members, which formed the complex geometrically round-shaped structure. A strict tolerance of 2mm to 5mm was implemented for the assembling of the 21m circular structure––this was a non-negotiable technical requirement. During the trial, 1150t of steel counterweight was carefully placed on the turntable to simulate the actual operational loads. Furthermore, load-testing equipment was established to accurately measure planned versus actual movements during the trial run. Safety in design became our challenge for this robust operation, but given our due diligence regarding best safety practice, the risks were mitigated.

Site Constraints

The construction site allowed absolutely no room for steel member storage. Therefore, from our Jiangmen factory to the Hong Kong site, the prefabricated components were delivered to the site in a prescision-timed manner and had to be installed on the same day. Logistics was a difficult task in terms of ensuring a precise delivery time, including material loading, customs clearance and also difficult traffic conditions.

The location of where the bridges were mechanically & electrically slewed & lowered was in close proximity to light rail transit. All possible measures were carefully planned to minimise disturbance.

One Solution Caters for Two Different Structure Systems

Onsite erection encountered not only the complex integration between structural steelwork and mechanical steelwork, but also connecting them to a heavy reinforced-concrete spiral ramp structure.

The entire steel structure was purposefully designed and built for the horizontal rotation movement of a steel turntable supporting frame, which facilitated two permanent bridges measuring 46m and 52m each in length––each bridge was installed over a two-night operation.

During the erection phase, a dimensional crosscheck was carried out for both individual steel bridges along with the overall structure to avoid misfit or misalignment. Skilful welding & assembling/bolting and diligent quality control measures were used with regular surveys and checks as a risk-prevention measure to avoid any potential errors.

SOLUTIONS

Ingenious Structure Design

We were engaged in the early design stage phase and we considered the overall operation when formulating solutions. We also identified and divided the different major components. Our safe and sound structural system:

a) catered for interface between steel frame with irregular concrete structure

b) ensured components were divided into the most effective size and geometry to suit logistics and crane capacity as well as enable the complex components to adjust to suit the fit-up on site.

c) enabled rigid structure components to provide stability and maintain precise geometry for the rotational operation.

d) ensured the A-frame structure was designed in a multi-functional jig which enabled assembly of the bridges’ structural frames, rotatory operation, vertical lifting, supporting heavy counterweight designed for rapid installation and demolition, able to adopt two different bridges’ designs with two other structural systems.

Fabrication Makes a Difference

The successful trial at our Jiangmen factory demonstrated our capabilities to fabricate a very complex steel structure by using advanced technology machinery and high-tech, powerful lifting equipment. Precise engineering contributed to our strength in fabricating a wide range of high-quality products in a competitive and diverse marketplace.

Precisely Timed Delivery

Due to a well-known shortage of storage areas in Hong Kong, particularly at the Yuen Long construction site, the logistics schedule had to be carefully planned to deliver all oversize and large, geometrically shaped segments from Jiangmen to Hong Kong with precise timing, premised upon a current and approved construction program.

Onsite Erection

Mitigation of disturbance to the public was one of our major objectives. Acoustic barriers and vertical safety net barriers were used.

As the heavy-lifting system involved rotation of a temporary turntable supporting structure together with a permanent bridge, geometric accuracy in both assembled components and the overall structure was a critical hold point.

The erection relied upon highly skilful welding and bolting to minimise shrinkage and any distortion generated by the welding process. Regular survey checks and fine adjustments were done throughout the erection. To secure a safe and smooth rotation, tight survey and QA geometry controls were required to ensure a tolerance limit of 3mm-5mm was adhered to––an uncompromising task premised upon a large and complex 21-metre circular structure.

The key to success of this project stemmed back to a close and respectful collaboration amongst our expert technical team and project management, including safe and efficient erection and welding on site. This experience has made us very proud in becoming a significant key player in the first slew and lowering bridge construction project in Hong Kong.

KEY DELIVERABLES

Higher Building Accuracy

Safer Operation

Shorter Erection Period

Mitigate Risk and Disturbance to Public

TEAM COLLABORATION

This mega project was definitely a huge challenge from start to finish. Enormous effort was required in structural steel engineering and early design coordination to yield the best solutions that include: Precision machining during fabrication phase; assembly/dismantling of the rotary frame; trial rotation under a rigid quality control process in our China factory; a precisely timed logistics plan; hoisting of each mega steel section in busy traffic; tight site space for reassembling, and the connection of large and heavy load structures into different levels of reinforced concrete structure zones––all defining our commitment and unmatched credentials.

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