Salesforce Tower Construction Surveying Case Study
Reaching for the skies in Sydney’s tallest commercial tower.
One of our most challenging and prestigious projects to date, the Salesforce Tower at Sydney Place, Circular Quay presented our construction team with unique challenges and opportunities.
CMS provided a dedicated, on-site construction surveying team for the 4 year duration of the project.
Commissioned by Lendlease, the Sydney Place and Salesforce Tower precinct is a breath of fresh air. With high-calibre commercial tenants up top, and a revamped Jacksons on George, and vibrant retail and dining laneways down below, the precinct is already enjoying commercial and cultural success.
Project complexities
Salesforce Tower is a 56 storey commercial building. Standing at 265.8m tall, there are also 3 basement levels all excavated into sandstone bedrock, with the bottom slab at 9m below sea level. Works included in the revamp of Sydney Place were the redevelopment of Jacksons on George, Rugby Place, Crane Lane and a community building with a large open forecourt on George Street.
At the beginning of the project, a tight control network was established, starting from ground level and transferring to recovery points on surrounding buildings. This had to be established prior to any construction, as once the core started construction there would effectively be 2 sides of the building that had to be linked with no physical access for workers.
The first critical construction point for the steel frame was reached in March 2020 at the podium/Lower Ground with the beginning of the steel columns, that would become the main focus of the structure from then on.
Set out position was absolutely critical as these columns needed to stay vertically aligned for the next 56 levels and along with concrete core, would determine the position of everything else within the tower.
The next major construction stage was the 16m tall steel columns on Upper Ground Level needing to stay vertical, with a tolerance of less than 1mm horizontal per vertical metre. At the same time steel cleats needed to be set out from within the jump form trailing deck with limited space and with a jigger bracket bolted to the core. These cleats would be the connection for the steel beams running from the columns to the concrete core.
Visible control points needed to be millimetre accurate, to get the tight tolerances for steel beams joining the tops of columns to the cleats on the core, with some beam and column joins having over 80 bolts, alignment had to be perfect.
Keeping the steel columns vertical became extra challenging at the point where they spanned 3 levels or 12metres, meaning a 1mm error in position at the base became a 12mm error at the top of the column, which would mean that the connection beams would not fit between core and the column. These tall column locations had to be planned for in advance, in order to ensure they started from the correct location.
After setting the column positions, the steel beams would be installed between each column and the core. This would pull and push the columns around. Once the beams were in position a Work as Ex survey was done, and we would have to then try and correct the top of column position on the next level or 2 to without exceeding the verticality tolerances.
The set out, and as built surveys were under the control of Andrew Irwin then Byron Lindsay, who took over the structural steel set out at level 5 and continued right up to Level 30, when Jon Tutte took over.
On the other side of the core, 6 glass fronted elevators needed to be installed from the other side the jump form, again on a limited space trailing deck.
Fred Pall and his assistants Liam Bennett, Dominic Demyane and Ramez Shamoon would continue the set out of cleats, glass elevator beams and core walls all the way to Level 56.
Once all the steel frame and concrete was put together, the next challenge was aligning the glass façade, which wraps around the whole building and is also installed to millimetre accuracy. Brian Whiting started work on the adjusted grids from Level 1 and kept the control and grid system going all the way to Level 56, you can see the evidence of this with the façade gleaming in the sunrise as you cross the bridge each morning.
The adjusted grid system became a particular challenge at Level 25 with the installation of 2 storey high structural “sway bar” braces, causing a sudden movement of 25-30mm which had to be monitored and compensated for.
Technical resilience
Work for CMS commenced in August 2019 with Hamish Roberts and Andrew Irwin establishing a solid control network at ground level, then transferring to reflective targets on surrounding buildings. The location of reflective targets had to planned and strategically placed, as the building is the tallest building in the area towering above its neighbours. Not only would the targets need to be accurate, they would also have to be able to be viewed from Ground Level to all the way 265m up at Level 56.
CMS used our combined experience and knowledge of high rise construction and steel frame installation. Initially instructed to make columns vertical, we realised that due to fabrication issues that vertical precision was not enough and the column’s connection cleats would need to set out to the correct design to get steel beams to fit both horizontally and to the correct RL. The ability to calculate quickly on site the correct shim and packing at each column base kept the construction going. Regular monitoring of the core and columns from external locations, enabled us to anticipate shifts in building movement and adjust as necessary.
Other challenges
Salesforce Tower is a Covid baby. CMS along with all the other trades on site had to deal with site shutdowns, lockdowns, social distancing, mask wearing, isolating and everyone being sick at the same time. However, even during the worst of it we were able to maintain a presence on site and keep the project going.
Bushfire smoke from the 2019/2020 fires also proved a challenge. With sites being closed down or access restricted due to the smoke health hazard, we needed to adjust our schedule and manage our team to accommodate this.
Risks
Salesforce Tower, being a steel framed construction meant that traditional formwork was not used to form up concrete slabs, rather steel bondek was laid down. CMS often had to work at the edge of this wearing a safety harness secured to columns.
The entire jumpform structure was up to 6 levels high including leading deck to 3 levels of trailing decks with most vertical movement via ladders. A team of 2 was used for safety of movement, to share loads and ensure no one was trying to carry survey equipment up and down ladders.
Safety on site had a big emphasis from both Lendlease and CFMEU, with world leading standards with edge protection and safety barriers, always keeping within barriers and tethering equipment at the edges of buildings and a “no gaps” policy.
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