The Hong Kong–Zhuhai–Macau Bridge runs 55-kilometre across the open waters of the Pearl River Delta in China, so regular inspections are required to keep the steel and reinforced concrete structure in good condition. But how are they carried out?
Some sections of the bridge have catwalks leading underneath the deck.
Others sections have ones that go right across the underside.
But the main tool for inspecting bridge is this MBI 200-1,5/S model under-bridge access unit built by Moog GmbH of Germany.
Acquired specially for the bridge.
The Dragages – China Harbor – VSL Joint Venture has already ordered a second MOOG under-bridge access unit for a special bridge in Hong Kong. This time, MOOG was faced with the task of finding a suitable access solution for the Hong Kong Link Road. This bridge has a length of about 7.5 miles with not only space for a six-lane highway, but also for some tricky access situations to address:
With this bridge the 6 lanes required a long reach platform to perform inspections and maintenance work, so MOOG chose the MBI 200-1,5/S model. This machine was mounted on a trailer chassis and has a horizontal range under the bridge of up to 65 ft. 7 in. Using the additionally delivered platform extension, even 72 ft. 2 in. can be reached under the bridge.
In order to make the crossing of the existing fuse boxes possible, the machine was additionally equipped with an elevating frame, which makes a crossing height of up to 11 ft. 9 in. possible.
In some places the bridge demanded a larger lowering depth than that provided by a standard MOOG unit. Again, a suitable solution was found by shortening the frame 3 ft. 3 in. and extending the tower by 6 ft. 6 in. The maximum lowering depth of the under-bridge access unit on the Hong Kong Link Road is therefore 40 ft. 4 in.
In addition, the bridge underside presented challenges with some very deep hollow box girders in place, for which access had to also be guaranteed. For this purpose a hydraulic Alplift was provided, which can be mounted inside the telescopic platform. With this a working height of up to 36 ft. 1 in. can be achieved. Two smaller scaffolds can be used to inspect hollow box girders with less depth. These can be combined in three different variants (working heights of 13 ft. 1 in. or 16 ft. 4 in.) and can be used on the base and/or telescopic platform.
Not only the upward inspection is made possible by the additional equipment of this under-bridge access unit, but also the inspection into the depths below: The pier inspection basket reaches lowering depths of up to 164 ft. and thereby permits the assessment of the bridge piers.
A hydraulic crane has also been installed at the front of the trailer to lift both to the platform, the optional equipment described above and various materials required for inspection and service.
Auxiliary equipment is completed with a wired remote control and night lighting.
The machine was shipped to the customer in mid-September 2017. The on-site training took place in late October.
The trailer is driven out onto the bridge.
The main tower raised up.
Then over the edge of the bridge.
Allowing a cantilevered work platform to be extended underneath the roadway.
Like so.
Footnote
The Tsing Ma Bridge also has a bridge inspection unit – a Barin AB 23/SL unit, which uses a multi-jointed hydraulic boom lift to manoeuvre a work platform around the bridge.
The HZM Bridge is a very interesting civil engineering and infrastructure project and I imagine the amount of equipment and personnel required to maintain it must be equally awe inspiring. The MBI 200-1,5/S didn’t disappoint in that regard! The personnel on the work platform must need nerves of steel. I know I would personally have many second thoughts about being there!
I’d have second thoughts too!