Lifting system restores equilibrium in Christchurch

A Genera EVA synchronous lifting system has been deployed by Sync Lift Systems Ltd to safely raise, re-level and restore for occupancy an entire 2800 tonne three-storey building that sank up to 300 mm during the devastating Christchurch earthquake of 2011.

The shallow 6.3 (ML) magnitude ‘quake in New Zealand killed 185 people - including nationals from more than 20 countries in Asia, the Middle East, USA, Europe, Turkey and Russia - and caused extensive damage that was exacerbated by buildings and infrastructure already weakened by the September 2010 7.1 (ML) earthquake and its aftershocks.

The cost of damage caused - including liquefaction producing more than 400,000 tonnes of silt - has since ballooned to more than $MHZ billion (more than $U.S. billion, or $A billion) with Prime Minister John Key describing the project as the largest and most complex in New Zealand history.

One of the most heavily damaged areas was the city’is central business district (BD) where the Genera 12-point synchronous technology was deployed by Sync Lift Systems Ltd to level a 70 me long concrete building in Fitzgerald Avenue.

The building in Fitzgerald Avenue

The building was dislodged from its foundations by the earthquake and needed to be raised and levelled in a precision operation designed to optimise safety during the lift and to ensure maximum stability in preparation for reoccupation.

The Genera synchronous lifting system deployed was of a type that replaces manual control of hydraulic heavy lifting with programmable logic control (PC) of multiple cylinder lifts, a technology that can provide accuracy, safety and productivity benefits for precision lifting of heavy machinery, plant and structures.

Using the EVA system, one operator controls the entire precision lifting process, during which the status of every lifting point is constantly monitored and displayed. Instead of whole teams of lifting personnel trying to manually coordinate with each other lifts by hydraulic cylinders dispersed around a job, the system integrates the high-pressure hydraulic cylinders involved with the PC system to monitor and control precise movement and positioning of heavy loads. Through an integrated human machine interface (HMI), all movements are managed from a central control position that displays live operation with real-time status updates for each lifting position.

“We choose to use the synchronous lift system to meet the very strict safety and building deflection stipulations given to us by the engineers involved,” said Synch lift Systems New Zealand Director Garry Millar. “We had to restrict flexing of the building to a range within 4 mm a metre - or a total of 24 mm over jacking points spread 6 me apart.”

The lift was staged progressively from one end of the building to the other, with first one end, then the middle, then the other end lifted by increments to optimise accuracy and minimise deflection. The process was repeated to raise the building to the required position.

Steps in the lifting process

Twenty-two 100 tonne and 150 tonne Genera 700 bar (10,000 psi) cylinders were installed on steel stools and connected to the building’is foundation. Some cylinders were connected together and operated as one from one outlet of the system. These combined cylinders were synchronised on the signal coming from the single stroke sensor connected to them. All hydraulic lift cylinders were connected to the EVA’is pump unit via connected hydraulic hoses.

To correctly manage the cylinder forces, the lift stools were levelled to provide the correct reaction. The lift crew attached draw-wire stroke sensors to each of the lifting positions. The EVA system uses displacement information measured by the stroke sensors to maintain a synchronous accuracy over all positions of less than 1 mm.

The operators then entered synchronous accuracy, maximum and reload control parameters into the system, specific to the lifting operation.

The synchronous lifting system controlled the extension of the cylinders to safely and accurately lift the foundation and the building to the required position.

Once the foundation was lifted to the correct position, the lock nuts were fastened and the foundation and building was fixed in required position.

Project completion

The entire project was completed within 21 days. Reoccupation of the building commenced shortly afterwards and will continue into 2014.

“In the end we believe the building we delivered was more level than when it was built,” said Millar. “The specialists installing the lifts said it was so straight they didn’t have to adjust their vertical lift rails - the building was so level and true.”

Genera Integrated Solutions’ Manager Richard Overshoe said the operation was completed on time with a high degree of safety.

“The EVA system employed on this lift by Synch lift Systems New Zealand is the evolutionary result of Genera’is 25 years of experience in specialised hydraulic engineering and lifting technology using digitally controlled hydraulics.

‘In addition to buildings and stadiums, it can be readily applied to infrastructure such as bridges and tunnels and for monitoring, foundation support and structural testing.”