Post Tension slabs used to maximize number of units - Wardian, Canary Wharf, London
17 November 2020
Interspan designed 200mm thick thisk with local 250mm edge thickenings. An equivalent reinforced concrete (RC) slab would have been 275mm thick. The application of post-tension resulted in 2 additional levels, which was essential in delivering the 800 units over a combined 105 levels within a height of 340m. The client benefited from 16 additional units versus an RC solution by using post-tension.
Two iconic residential apartments Towers
The Wardian is a twin-tower residential structure appropriately located in the London borough of Tower Hamlets. It affords wonderful, unique views overlooking the South Dock.
One of the tallest post-tensioned residential developments in Europe, the towers, referred to as the East and the West, provide a total of over 800 residential units.
The East Tower is over 55 storeys and is 178m tall while the West tower is over 50 storeys and is 162m tall. The towers share a two-storey reinforced concrete podium, above the basement.
The project was delivered by O’Halloran & O’Brien Ltd for Ballymore Group Limited. Interspan (Europe) Limited executed the post-tensioning from May 2017 to April 2019. The first of 136 affordable homes at the scheme went on sale in the summer of 2020, with a penthouse however setting you back £2.5million.
Design Considerations for the Wardian Post Tension Structure
The post-tension floors needed to comply with a design life of 60 years, and for a fire rating of 2 hours. This limited the minimum slab depth to 200mm. Given the heights of the towers, the structure is considered as Class 3 for Robustness. A systematic risk assessment was required to comply with this classification to consider normal and abnormal hazards. In addition to this systematic approach, the horizontal and vertical tying requirements associated with a Class 2 structure also needed to be satisfied. For the slabs, a combination of post-tension and reinforcement was used to satisfy this requirement.
The lateral stability system of the structure relies on a combination of the central lift/ stair core in combination with cross-walls cantilevering from the foundation level. The post-tension slabs are required to transfer wind loadings from the cladding brackets to the cores by acting as a stiff diaphragm in the permanent case. In the temporary case, crane and hoist ties induced lateral loadings which were resisted by the design of post-tension ties along the defined load path to the core walls. This approach was adopted on both towers.
Detailed design of the Post-Tension slabs at Wardian
Extensive design coordination of external fixings for finishes and balconies had taken place prior to commencing the detailed design of the post-tension slabs. This detailed level of coordination was carried out on both the East and West Towers (both 38m x 18m). The application of thermally broken steel balconies was introduced to minimise slab edge loadings and resulting in reduced incremental and long-term deflections.
To save large quantities of plywood, which would have traditionally been utilised during construction, preformed steel edge shutter containing all the cast in fixings were used on this project. The anchors were attached to them utilising pre-drilled holes. The shutters once stripped were cleaned and reused.
During the design process, consideration was required to assess the impact of the cross walls on the applied slab stress. The stiffness of the walls about the major axis and its inherent impact on the axial shortening of the slabs during the stressing operation meant that some local areas contained tendons in one direction and reinforcement in the orthogonal direction.
Given that the central core and the geometry of each tower had no movement joint present in the structure. Careful consideration of shrinkage strain, elastic strain, creep strain and thermal contraction/ expansion was required during the modelling process particularly given the differential deflection constraint after cladding is 8mm between levels.
Our designers worked closely with the main client structural engineer (WSP) to ensure that project changes during both the design and construction phases were captured and dealt with promptly.
Execution Considerations for the Wardian Superstructure
The superstructure of the towers consists of varying post-tensioned slab thicknesses with significant transfer structures on the lower levels. The area of the slabs alone is an excess of 60,000m2
The design and construction programme on the project demanded the towers to be built simultaneously. With the substructure consisting of a piled raft foundation system, a simultaneous construction mitigated the risk of overloading and differential settlement during construction. The 100-week programme requiring 1 pour per week per tower ensured continuity in personnel, workflow and logistics.
As with other projects of this type, logistics was a major challenge. A lack of on-site space, delivery restrictions and the speed of construction of follow on trades meant that each delivery had to be well-timed to avoid bottlenecks. Close cooperation with the Frame Contractors team lead to successful and positive ‘can-do’ attitudes all round.
Execution of the Post Tension slabs at Wardian
The relatively small site, located in the Isle of Dogs, is approximately 5,700m2. Considering the 1,700m2 podium, detailed planning of the logistics was required for the duration of the site works. Weekly coordination of deliveries was utilised covering all trades. Coordination of labour when deliveries arrived was also essential.
As previously mentioned, the construction programme required 1 pour per week per tower. Given the height of the structures, the project spanned over a 2-year period. This programme was adhered to throughout this duration of the project, with seasonal variances in temperature accounted for through changing concrete mixes. This ensured the concrete final stressing strength was achieved in line with the programme. Concrete cubes were kept on and crushed on site. Maintaining the cubes in the same environment as the slabs was essential to mitigating any potential delays associated with incorrect strength readings.
Utilising the coordinated steel formwork slab edges which were designed prior to the detailed design of the post-tension slabs – allowed for the speed advantages of pre-set slab edges. This solution allowed for efficient use of materials given they were reusable, as well as labour efficiency helping to maintain the site programme.
Value added to the client through adopting a Post-Tension slab solution
From a cost base, the post-tension slabs used were typically 200mm thick on the East Building and 225mm thick on the west building, the equivalent RC slab would be 275mm and 300mm respectively. This resulted in a saving of 7,000m3 of concrete and a circa 25% reduction in the load from the superstructure to the foundations. A post-tension solution also resulted in an effective saving in the reinforcement of 350 tonnes in slab loose reinforcement.
This saving in concrete thickness per level also resulted in 16 additional units based on the height of the structure. With the optimization exercise to adopt post-tension slabs, the 75mm saving has resulted in a reduction in the combined height of both towers of almost 8m equating to 2 levels. This was essential to delivering the 800 units over a combined 105 levels within a height of 340m.
Chris Canham appointed national GM (AU/NZ)
24 July 2019
Interspan is pleased to announce the appointment of Mr Chris Canham as National General Manager – Australia / NZ. Chris has commenced with Interspan on 24th July 2019 and is responsible for all facets of our operations in Australia, along with seeking opportunities for further expansion in New Zealand.
Chris is an experienced General Manager, delivering successful business outcomes from senior professional teams.
With a background in the construction industry, he brings over 28 years of robust experience in successful project and business management. Creating valued partnerships with clients through innovative and strategic thinking underpins his management performance.
His passion combined with his broad technical and business management skills united with exceptional people management and construction knowledge has facilitated the successful management of senior staff and large multidisciplinary teams in high-pressure environments.
Chris is a strategic thinker that is results-driven, loyal and adaptable. He is passionate to learn, mentor and lead the outcomes of the business and to support teams to ultimately deliver outstanding business performance.
Concrete Society Awards celebrates 50th anniversary
22 November 2018
Black tie and glamorous evening wear were the order of the evening when Interspan’s London team attended the annual Concrete Society Awards.
It was the 50th anniversary of the prestigious event, which saw more than 450 of the industry’s finest come together at the Royal Lancaster Hotel in London on November 21.
The ceremony, hosted by BBC presenter Huw Edwards, celebrated the achievements of the concrete industry as well as other frame contractors and designers.
The awards are highly esteemed within the industry.
“The ceremony is seen as the most important occasion in the industry award calendar.
“This opportunity allowed us to mix with new and old contacts, sharing experiences within the industry and opening discussions for future work.
“Our guests enjoyed the evening and we look forward to seeing some of our projects being showcased in the future years.”
The Concrete Society, founded in 1966, is an independent, member-based body that is a leading provider of information to clients, architects, engineers, specifiers, suppliers, contractors and users of concrete.
Members come from all sectors of the construction industry to exchange information and experience with the aim of enhancing the performance, productivity and quality of concrete as a construction medium.
MERAAS ESTATE, DUBAI
17 December 2018
A new car dealership in Dubai seems likely to draw as many envious looks for its spectacular design as the vehicles on display in its showroom.
The futuristic, glass-fronted design in the Meraas Estate required heavy service loads, which made designing the PP elements challenging. The total tonnage of the building is 68.231.
This is where Interspan’s experience and knowledge of post-tension techniques came into play and helped to make the ADE725,000 (AU$273,488) project possible.
The project at Ras Al Khor includes an office building with basement, ground and first floors as well as the roof all of post-tensioned slab construction.
One part of the building is a warehouse, while the other houses offices. Both sections share a common basement. There is also shed consisting of basement, ground and mezzanine levels.
The ground floor post tension slab is uniquely designed by pattern loading and the live load is patterned as per the design standards.
The slab is heavily loaded at 50 Kpa, while the structural framing is a slab-beam system.
Interspan’s team designed a system that sees the load of the post tension slab transferred to a post-tension beam, while the remaining floors are designed as a post-tension flat plate.
The 10,913m2 project for Interspan’s UAE team is part of a development by Meraas Estates.
Interspan worked for Adnan Saffarini Architects and Engineering Consultants, which was, in turn, contracted to SBB Construction.
Structural work on the building is expected to be completed by May 2019.
Dig Deeper Challenge 2018
21 September 2018
Interspan’s engineers are no strangers to encountering a bit of mud when working on site – but it was a whole new level of muck when our team entered the 2018 Dig Deeper race in Cumbria.
Dig Deeper is an adventure race that sees members of the construction industry run, cycle and compete in a water event to raise money for charity.
Interspan’s United Kingdom division entered a mixed team in this year’s event, held in the Lake District of Cumbria on September 21.
Our team of Tom Rees, Michal Kesy, Eric Dodd and Pamella Nnakayindi finished 38th in the challenge, which raised about £54,600 (AU$95,775).
As an organisation, we make sure that we take time to give back to our community.
This year was the second time Interspan has taken part in Dig Deeper, which was founded in 2015 by construction industry directors Paul Hargreaves of Lipton Rogers Development and Jeremy Edwards of Arup with Paul’s brother-in-law Gavin Anderson.
Gavin had lost his son to cancer in 2011 and it was during a few drinks in 2015 that the trio hatched a plan to create a charity endurance race.
The race involved three stages; running, mountain biking and a surprise water activity. (This year it was paddle boarding.)
Challenging as it may seem, it is also a great opportunity for the various construction companies to come together and compete using attributes such as fitness and navigation skills in Britain’s most spectacular scenery and toughest terrain.
The event is sponsored by companies we have worked with on many previous and current projects including Arup, Careys and Multiplex.
We are very proud of our team of four who battled mud, rain and water to raise funds for two great charities: Anthony Nolan and 353.
For more information about Dig Deeper, visit https://www.digdeeperrace.com/
Parramatta Square Tower 4
10 April 2018
Interspan (NSW) are currently working with the Built/Obayashi JV (BOJV) on Parramatta Square Tower 4.
The scope of works includes the design, supply and installation of post-tensioning systems to 92,000m2 of concrete floors along with a multistrand tie system to support the use of inclined ‘V’ columns over 3 levels.
Full details are available on the Parramatta Square website.
5 April 2018
The exclusive resort of Celtic Manor, host to the Ryder Cup has been expanding with a new International Exhibition Centre.
The post-tensioned ground bearing slab was executed by our team using 15.7mm diameter strand and anchor system, which is larger than the UK normal size. Whilst the project was prolonged on site due to design changes, the flexible Interspan team delivered this project to the timescale set by the client. Interspan worked for NJ Doyne which was in turn contracted to J Sisk and Son Contractors.
The 10,500m² project for Interspan Europe is part of the 50/50 development partnership between the Welsh Government and the Celtic Manor Resort.
The £83.7m scheme will be capable of accommodating up to 5,000 delegates with a total floor space exceeding 26,000m². It is projected that the new ICC will open for business in June 2019.
Aberdeen Exhibition and Conference Centre
29 March 2018
Aberdeen, the oil capital of the UK, is getting a new conference centre.
The new 48,000 m² exhibition space will attract concerts, exhibitions and conferences to Aberdeen, generating an estimated £50m per year for the local economy. The Exhibition centre is near to the airport and will be served eventually by three hotels.
The venue is state-of-the-art encompassing 48,000m² of internal exhibition space comprising of 33,000m² of subterranean space, a 9,000m² arena, 6,000m² hall which is divisible into three 2,000m² spaces, with an extra 10,000m² outdoor space. All making way for larger conference halls and suits, a superior arena, hospitality boxes and club lounge.
The 14,500m² post tensioned suspended slab was built over the summer of 2017 working to an accelerated programme. The project was delivered by our team based in Scotland.
For more information on this exciting venue, see https://www.aecc.co.uk/about-us/aecc-overview/aecc-evolves/.
World Expo 2020 Dubai
21 February 2018
Dubai is hosting the Word Expo in 2020 and Interspan has been charged with construction of three blocks – Parcel A, B and C situated around the domed trellis of central Al Wasl Plaza.
Each Parcel will be 10 levels developed with a mix design of Post Tensioned Band beam solutions with R.C slabs.
Working to a tight and fast program, Interspan will commence work in March 2018 and be completed by September 2018.
Expo 2020 Dubai hopes to attract 25 million visitors over the course of the event.
"The Orchards" - progressing ahead of schedule
21 December 2017
The first stage of “The Orchards” Norwest By Parkview Group is progressing ahead of schedule, with the basement shoring walls and carpark concrete pours now complete.
Ryde Gardens - now complete!
20 December 2017
Ryde Gardens is now complete and apartment fitout is progressing well. Thanks to the team at Watpac and BKH for a great project to work on and be involved with over the last 18 months!
DYWIDAG Interspan Group is growing its European presence
24 November 2017
New Joint Venture Holding company DYWIDAG Interspan Group is making its presence felt in the European market with a growing presence in several European countries, such as, Germany, Netherlands, Belgium, Luxembourg, Poland, Italy and Spain.
With innovative design concepts, technical and economical solutions and a team of international engineers – DYWIDAG Interspan Group is providing the market with a full service solution for post tensioned and reinforced concrete slabs including connection to surrounding frame structure.
Nieuwbouw Hogeschool Utrecht Building for the University of Utrecht is the first project for the new Joint Venture Holding company DYWIDAG Interspan Group in the Netherlands. Nieuwbouw Hogeschool Utrecht Building will be 8 levels high and sit on an area of 20,000m².
Interspan announces Joint Venture with DSI Construction
20 June 2017
Interspan is pleased to announce the establishment of the Joint Venture Holding company DYWIDAG Interspan Holdings B.V.. Headquartered in Zaltbommel, Netherlands, it consists of the partners Interspan and DSI.
The new JV will support the DSI Group on core international markets with its know-how in civil and ground engineering and will create synergies for both companies. The technical expertise and the global experience of DSI, combined with the agility and engineering expertise of Interspan, will permit an intensification of market cultivation and an expansion of their scope of services.
The group has appointed Mr. Philipp Demelt as the new General Manager of DYWIDAG-Interspan. We congratulate him on his new position and wish him the best of success. The JV will initially develop regions within Europe, with a targeted future growth in global markets.
In the short time since its establishment, DYWIDAG-INTERSPAN has already successfully acquired several major projects in Belgium and the Netherlands. Within the first 5 months, more than 30.000 sq m of floor slabs have been post-tensioned using DSI’s bonded and unbonded systems.
James Laws, owner and director of Interspan, comments: “DSI is a strong global partner with an extraordinary history and an excellent reputation. The joint enterprise strategically strengthens our market position in important regions of growth. It also represents a major step in our medium to long term growth strategy. We would like to warmly welcome all employees of DYWIDAG-INTERSPAN.”
Hans Wlodkowski, RCEO for DSI’s construction business in the EMEA region, comments: “Partnering with Interspan in the European Economic Area will allow DSI to transfer its experience in post-tensioning to the building industry. Thanks to this strong partner with huge competences in the design and execution of floor slabs, we can now target new major building projects. I am convinced that the Joint Venture will provide best services and products to our customers.”
Meet us at fib 2017
2 May 2017
Interspan is presenting a paper on the comparison between punching shear capacity of PT and RC slabs according to different design codes at the annual fib symposium in 2017 in Maastricht in June. Visit fibsymposium2017.com to register.
Simon Weir appointed UK GM
19 April 2017
We’re happy to announce that Simon Weir has been appointed General manager of Interspan UK.
44 Metre Beams for Port of Tyne, UK
20 March 2017
We recently completed some large post tensioned beams spanning 44 metres used to support the roof on three silos at the Port of Tyne in the northeast of England. These beams changed as part of value engineering carried out by Interspan and replaced steel beams. These beams were built ground level adjacent to the silos and lifted into place.
13 March 2017
We are about to start two 50 storey residential towers in Canary Wharf which will be the tallest towers undertaken by our European business. More details of this revolutionary project are on the developer’s website at www.wardianlondon.com.
Interspan partners with DYWIDAG
1 January 2017
We recently signed a joint venture partnership with DYWIDAG Systems International to undertake design and construct building projects in mainland Europe.
As a result of this partnership we have recently started new projects in Holland, and Belgium and completed our first project in Luxemburg.
Ryde Gardens Project Commenced
1 January 2017
The Ryde Gardens project was commenced today.
It’s development will include the construction of three residential towers of 13, 23 and 27-storeys.
It will feature 830 residential apartments with basement parking for 730 cars, 2,100 square metres of public park, roof top gardens and a communal pool, 1,100 square metres of non-residential floor space including retail space, gymnasium and an area dedicated for a future child care centre.
Stockland Wetherill Park completed
10 December 2016
Interspan has completed the project Stockland Wetherhill Park.
This project was done for Brookfield Multiplex, an important client from Australia, NSW.
It had a duration of 21 months.
TAILOR'S WALK PROJECT LAUNCHED
27 January 2016
The Tailor’s Walk project has started.
Tailor’s Walk is a project to build a brand new community offering crafted living spaces beautifully designed by GroupGSA.
Amidst intimate green spaces and landscaped connections, this brand new collection of 1, 2 and 3 bedroom apartments and 4 bedroom terrace homes are filled with character and charm.