Surveying technical Surveying on the Green Point Stadium by Clare van Zwieten, PositionIT

Construction on Cape Town’s Green Point Stadium got off to a somewhat controversial start, but is now well on the way towards its completion date at the end of 2009. The complexity of the stadium’s design is providing some interesting and challenging work for the surveyors on the project.

s hosts of the 2010 FIFA World Green Point Stadium to a stringent environmental impact Cup, South Africa will see 64 assessment which resulted in a record The Green Point Stadium is being football matches played in of decision that influenced the design A built for the City of Cape Town who nine of its cities – Johannesburg, fairly fundamentally in particular the are the contracting party and a 2010 Cape Town, Durban, Port Elizabeth, aesthetics, the profile, the acoustics, World Cup semi-final host city. It Nelspruit, Polokwane, Bloemfontein, traffic and parking. These requirements will be owned by the city and will be Rustenburg and Pretoria. For this have been included in the design of South Africa's second largest stadium. purpose ten stadiums are being built the stadium and have influenced the The new stadium replaces the or upgraded across South Africa. height, the profile, the roof, the façade, 18 000-seater Green Point Stadium, These stadiums are expected to seat parking and traffic impact. more than 570 000 people during the that was demolished in 2007, and will World Cup. be surrounded by a 60 hectare urban The stadium is intended to have a park [2, 3]. capacity of 68 000 spectators and The five stadiums under construction is scheduled to host five first-round The multi-billion rand stadium is are located in the following areas – matches, one second-round, one located in an extremely sensitive Cape Town (Green Point Stadium), quarter-final and one semi-final during Port Elizabeth (Nelson Mandela Bay environment on the Green Point the course of the 2010 FIFA World Cup. Multi-purpose Sports Facility), Durban Common, adjacent to residential After the event the stadium will be (Moses Mabhida Stadium), Nelspruit areas, close to the central business reduced to a 55 000 capacity stadium (Mataffin Stadium) and Polokwane district, adjacent to the Victoria & to comply with stringent environmental (Peter Mokaba Stadium). The five Alfred Waterfront, and being under requirements as stipulated in the stadiums undergoing upgrades Table Mountain it will be a prominent record of decision. are situated in Rustenburg (Royal landmark impacting on the image of Bafokeng Stadium), Bloemfontein the city. Stadium design (Vodacom Park Stadium), Pretoria (Loftus Versfeld Stadium) and The stadium design is in part a The design of the Green Point Johannesburg (Soccer City Stadium response to its situation in this Stadium is the most complex of all and Ellis Park Stadium)[1]. environment. The stadium was subject South Africa’s world cup stadiums.

Fig. 1: An artist's impression of the completed Green Point Stadium in its final form at night.

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Fig. 2: Paul Edgecome, Dirk Wolters and Keith Lee of Edgeworks Surveys. Fig. 3: Julian Gray of GNA Geomatics.

It will be 55 m at its highest point and positioned on a daily basis using The lead structural design consultants and the construction will involve 250 ton and 450 ton Crawler Cranes. for the stadium are BKS. The lead 130 000 m3 of concrete, 390 000 m2 architectural consortium is made The roof structure will primarily of formwork, 12 000 tons of comprise a 1300 ton perimeter up of GMP (the German architects reinforcing steel, 6-million bricks, a compression ring mounted on the responsible for the concept design) fabric façade and a unique steel cable pylons, an internal cable tension and Louis Karol Associates (the local tensioned glazed roof [4]. More than ring, steel trusses radiating inwards architects of record). The work on the 1800 people are currently involved in towards the pitch, and glass panels roof is being done by Birdair Pfeifer, its construction. installed on top of the steel trusses. a joint venture between US company As the site where the stadium is being The roof’s construction will involve the Birdair and German firm Pfeifer. To constructed is subject to high winds compression ring, being placed on big date the net construction costs for and has been labelled an area of box girder intersections that sit on top the project stand at approximately potential seismic activity, the design of all the 72 raked pylons. Seventy-two R2,75-billion. has needed to accommodate high cable strands with the internal tension wind and seismic loading factors. ring forming a doughnut, will then Surveying teams be strand-jacked into final position The stadium has a specific height Paul Edgecome of Edgeworks Surveys by huge hydraulic jacks. Secondary restriction of 55 m stipulated in the has been contracted to undertake the support in the form of steel trusses will environmental impact assessment surveying work on the Green Point then be hung all the way around and report and as a result it will not have Stadium. Keith Lee and Dirk Wolters, glass placed on top. the dome-shaped roof typically found along with six surveying assistants, on these structures. The need to The roof’s shape as well as the are assisting Edgecome with all the accommodate the height restriction exterior fabric facade will reduce the setting out for the Murray & Roberts/ and to provide spectators with the noise level of the stadium by about six WBHO joint venture (see Fig. 2). The best possible views of the pitch has decibels, compared to the old Green Edgeworks engineering surveying added to the complexity of the roof Point Stadium. Unsightly structures team also takes measurements for design. To accommodate 68 000 such as flood lighting masts have been planning purposes and checks the spectators the height of the tiers has avoided by incorporating the flood volumes calculated by Martin & East, had to be maximised and, due to the lighting for the pitch in the hub [5]. the subcontractors responsible for the earthworks, roads and services height restriction, the roof will have a This is the first time that a roof of construction. Thaaniyah Abrahams is complex, concave and super elevated this nature has been assembled in the surveyor for Martin & East. roof structure. South Africa and it is scheduled to be installed by September 2009, ahead The stadium structure itself comprises A number of other surveyors of FIFA's scheduled inspection at the an external oval of 72 pylons acting for and on behalf of various end of October 2009 [5]. which vary in height from 30 m to contractors work on the project, all of whom look to the Edgeworks Surveys 50 m, and an internal network of Contractors team for primary survey control and radial concrete columns supporting to ensure conformality between all seven floors, lift shafts, and access Murray & Roberts in joint venture with surveys done on site. stairways. Pitchside, the pylons, floors WBHO are the contractors for the stadium. The project got underway and columns support a series of raked High precision specialist Julian A beams creating three tiers on which in March 2007 and involves a Gray of GNA Geomatics, an MRICS more than 2000 pre-cast horizontal 34-month programme from the date registered geomatics engineer, has elements are mounted to carry the of handover to ensure completion been contracted by the project stadium seating. The 20 ton precast in time for the 2010 Soccer World management team to act as the horizontal elements are manufactured Cup [3]. The project managers are a quality assurance surveyor off-site, delivered in the evenings consortium between BKS and MDA. (see Fig. 3). Acting on behalf of the

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Fig. 4: The 16 m tower that has been erected in the centre of the Fig. 5: Construction of the pylons is being done in lifts of 3,8 m. For future pitch. each lift the formwork has to be positioned correctly.

client, he is managing the various Town survey marks (TSM) were general as well as the setting out for the coordinate systems used by the handed over to Edgeworks Surveys embedded mounting plates for the roof various consultants and relating by the client as the control points. structure. Management accepted the these to the project survey system (The TSM points are maintained by proposal and the tower was erected in as well as undertaking audit and 3D the City of Cape Town and are on January 2008 (see Fig. 4). It has proved verification surveys of all primary the WG Lo19 coordinate system.) to be a great success with good visibility and critical elements during the Although the TSMs were around the from the tower enabling setting out to construction period. perimeter of the golf course, only two be done of all the various decks, slabs, were used in order to establish the raked beams and the pylons relative to Surveying operations site control. Planners for the Murray one point. Surveying work on the Green Point & Robert / WBHO Joint Venture Stadium involves the setting out of initially used a base map provided by An additional high precision control everything. This includes setting out the consultants. comprising a network of permanent the bases and columns, raked beams prisms mounted on columns At first eight 1,5 m high concrete and pylons as well as the grid lines surrounding the pitch, has been pillar beacons with forced centring on the concrete slabs. Basically from established by GNA Geomatics using were constructed around the the start of the job, this involves a Trimble S8 robotic total station to perimeter of the site and, once the setting out the excavation positions enable the positions of the embedded initial stadium excavations had been to enable the construction team to completed, two further pillars were plates on the pylon tops, (upon which dig the holes for the bases in the constructed on the future pitch of the the roof structure is to be mounted), ground, and providing reference stadium. The two pillars on the pitch to be fixed to a high level of accuracy. lines (grid lines) on blinding (the were 4 m high, in order for them to working surface inside a hole) to Site surveyors are using free be visible over obstacles. enable the construction team to positioning techniques to locate their position formwork and reinforcing Well into the project, John Trangos, the total stations in positions suitable for steel required for the base. In the chief surveyor at Murray & Roberts came the setting out of bases, columns, early stages of construction the up with an innovative idea involving the raked beams and pylons and grid lines survey work was quite difficult erection of a 16 m high tower in the on the concrete slabs. A particularly with the team surveying into holes centre of the pitch. A Leica robotic total challenging aspect has been the setting 4 m deep that were surrounded by station was then mounted on top of this out of formwork in three dimensions, safety barricading. tower to assist with the setting out in high above the ground under congested

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and very difficult conditions. The Being responsible for quality assurance, customised high precision accessories. rodmen make extensive use of man GNA Geomatics is required to guarantee GPS work where applicable is done cages to access high points, wearing results to an accuracy of 3 mm with using the Trimble R8 GPS system, safety harnesses to ensure their safety 99% confidence, and therefore works while sub-millimetre levelling is done on high and exposed positions. to a SE of 1 mm for their survey using Leica levels with invar staves. operations. This is achieved through Network and GPS processing is done Tolerances the use of specialist equipment and using Trimble’s TGO, and the 3D Although the setting out works field procedures, and extensive numeric analysis of the structure scans is done undertaken by Edgeworks Surveys is filtering and statistical checking of field using System Euclyd, a specialist 3D expected to achieve an accuracy of observations prior to processing. analysis software package developed 5 mm, their teams strive to achieve by GNA Geomatics. a standard error (SE) of 2 mm on all Precast seating their surveys. Their field practises and As the S8 has only just been released The precast seating is measured by procedures are designed to achieve this worldwide, this is one of the first the manufacturers and delivered to accuracy while faced with the difficulty high precision projects on which the the site. The manufacturer has a of positioning flexible formwork, metres instrument is being used. There is surveyor on site checking the placing in size, weighing many hundreds of very close cooperation between GNA kilogrammes apiece. There is much position of the precast seats Geomatics and the S8 development inter-dependency between the setting (see Fig. 6 and 7). The precast team (Sweden), the Trimble TGO out surveyors and the formwork manufacturer is a joint venture development team (USA), and the local positioning teams to enable the between Concrete Units and Trimble suppliers (Optron, Cape Town). required accuracies to be met. Cape Concrete. Other software being used includes Several techniques are used when Equipment Civil Designer, AutoCad and various setting the tolerances. These include: other proprietary CAD packages. Edgeworks Surveys is using a Leica • Using forced centring on all the TCRP1201+R400 Robotic Total Station beacons. Challenges which is mounted on the centre tower • Using free positioning in order to and controlled by a RX1250Tc WinCE Construction of the Green Point fix the instrument position which System 1200 Controller. They are also Stadium has provided the minimises an error setting up over survey teams with some a point. using a Leica TCRP 1203 R100 and a Leica TCA1100L. Software packages interesting challenges. • Using support poles to stabilise being used include Leica Geo Office, the prism pole when setting out. Shape of the stadium Surpac, Model Maker and AutoCad. High tolerances are required due to A major surveying challenge has GNA Geomatics is using the recently the seating being made up of precast been provided by the oval shape concrete units which need to sit on developed Trimble S8 high precision of the stadium. Basically each row top of the raked beams. If the raked robotic total station, controlled by the of columns is in no relation to the beams are not built in the correct Trimble TSC2 controller, and combined adjacent column. The professional position, the precast units won’t fit. with a range of imported and consultants are using an elliptical and radial grid system to reference the internal elements of the stadium. There are further grid systems defined for the external works and for the roof structure. These systems need to be combined and converted into the survey system used by the field teams. GNA Geomatics is tasked with overseeing this operation in collaboration with the architects who manage the drawing database for the stadium development, to ensure that the integration and conversion of the various systems is successfully executed.

Complexity of the site

The site itself is highly congested (see Fig. 8). With over 14 tower cranes, mobile cranes, telescopic handlers, articulated dump trucks, excavators

Fig. 6: Checking the placing position of the precast seating elements from a 4 m high pillar of various sorts and sizes, ready-mix on the future pitch. concrete trucks, mobile concrete

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pumping units, delivery vehicles, tractor trailer combinations, and fork lifts amongst others, operating within a confined space, which also contains the stadium itself, secondary steel yards, rebar preparation areas, a berm and haul road and various office complexes. There are also over 1800 workers on the site. The survey teams do not have the luxury of ideal locations for their instruments and need to operate quickly and accurately within this extremely busy location.

Pegs cannot be knocked into the ground and be expected to remain in position especially when such high tolerances are required. With vehicles and materials being moved around the pegs are often damaged. To compensate for this the surveyors

have kept the required information Fig. 7: Raked beams on which the 20 ton precast seating elements will rest. onboard the total stations, then basically fixed the position of their two coordinates established the accurately accept the embedded plate instruments and set the required orientation as well as the slope upon which the roof elements will be marks where the construction or rake of the pylon. By using mounted. Between the two teams, the employees are working. the reference line program on the pylons that have reached their final lift Pylons instruments it was possible to adjust have done this successfully to date. the formwork's verticality or rake at Construction of the stadium’s any elevation. Once this method was Roof construction 72 pylons is the biggest surveying settled on, the actual site work was Surveying work for the stadium roof challenge on the project so far (see relatively easy. is quite tricky. The design information Fig. 5). To accommodate the roof provided by the consultants was on The surveyors are responsible for design, the pylons vary in height by a different grid system and was only positioning the formwork correctly 11 m with the tallest pylon being for a quarter of the stadium. It then before the concrete is poured and for 50 m high and the shortest 39 m. had to be related to the project’s rechecking and adjusting the position A pylon is 800 mm wide, 3 m long coordinate system. after the concrete has been poured. and is constructed at an angle of The wet concrete weighs about Work on the roof structure has 17,35°. The construction on the 18 tons and the formwork about recently started with the assembly pylons is being done in lifts of 3,8 m 3 tons, making it a huge weight to try of the first two embedded plates. and a pylon may consist of anywhere and push around. This is sometimes This involves adjusting the formwork between seven and ten lifts. For each tedious and frustrating work. It is that is going to hold the concrete lift the formwork has to be positioned essential therefore that the formwork for the last section of the pylon correctly. be in the precise position and to and then positioning the embedded Finding a practical solution to setting secure the formwork, in order to mounting plate. the pylons was the first challenge. minimise the movement. Fortunately, As part of this process GNA One could calculate the position the control has been very stable and Geomatics provides the results of of each corner of the pylon at the this has enabled the surveying team the extrapolation data to the design elevation of each pour, but this would to work as accurately as possible. engineers who use this information mean that the formwork had to be While the Edgeworks Surveys team to adjust the design location of the positioned to an exact elevation. devised a successful method for embedded plates for construction Practically this wasn't going to be positioning the formwork, GNA deviations and the anticipated achieved. If any movement occurred, Geomatics developed a scanning and deflections in the pylon due to new coordinates would have to analysis procedure which takes into the weight of the roof structure be calculated. consideration the deviations of each and concrete shrinkage and creep Edgeworks Surveys decided to of the lifts while extrapolating the after pouring. calculate a coordinate for the top readings to determine the accuracy Using a specially manufactured jig, outside centre and the bottom to which the pylon should achieve the embedded plates are mounted outside centre of the pylon. These its final location in space, in order to in three dimensions on the adjusted

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accuracy and progress of the project. In accordance with the “Team Green Point” attitude of all involved with the project, there is close cooperation between Edgeworks Surveys representing the contractor, and GNA Geomatics representing the client. Information and data is freely passed between both teams, all the while preserving the independence of the checking procedures. Both parties have one goal in mind – to construct the stadium to the accuracies required – and through joint co-operation this has been successfully achieved to date. Edgeworks Surveys present their reports to the contractor, while GNA Geomatics presents their reports to the project management team.

Fig. 8: Cranes towering over the Green Point Stadium construction site. (Credit: Ian du Toit) Conclusion

location with the use of the central clear reports on which critical decisions Construction of the Green Point Stadium control pillar by the Edgeworks could be easily and reliably made by the is proving highly challenging to the Surveys team. Once the plate has management teams. surveyors working on the project and been cast and the pylons settled this has been compounded by the need into their final positions, their final As-built surveys to meet tight time schedules. Much locations are surveyed in three A large amount of the Edgeworks lateral thinking has been required to dimensions and radial orientation, to Surveys team’s time is spent solve the unique and unusual survey millimetre accuracy, using a specially doing as-built surveys. This entails problems and the survey teams are manufactured prism mount by GNA surveying concrete structures using proving themselves up to the task. Geomatics from independent control. the reflectorless feature on the Overall “Team Green Point” is satisfied This information is then used to Leica TC 1200s, then comparing the that the stadium will be constructed confirm the final location of the plate as-built position to the design position. “on time and within specification” for and to verify that the roof structures Monthly reports are then submitted to handover to FIFA by 15 December 2009, will mount correctly on the plates. the consultants. and this certainly seems to be the case.

When the installation of the roof The greatest challenge here was Acknowledgements structures starts, it is anticipated that presenting understandable as-builts of the pylons. Each pour of 3,8 m had I would like to thank Paul Edgecome, both survey teams will be extremely to be checked and a comparison done Andrew Fanton and Julian Gray for their busy with the setting out and assistance with this article. to the design. This involved surveying checking procedures, while the roofing four points on each pylon at each lift. References contractor will also make use of his Considering that there are 72 pylons, own survey team. The high precision this amounts to a lot of observations. [1] South Africa 2010, accessed 10 total stations will come in handy with June 2008: www.sa2010.gov.za/ The surveyed points were then dumped southafrica/stadiums.php this element of the work. It is also into a CAD drawing and the vertical sides [2] Wikipedia: Green Point Stadium, anticipated that use will be made of of the pylon could simply be dimensioned accessed 10 June 2008: terrestrial scanners to capture and from the gridlines. The raked sides were http://en.wikipedia.org/wiki/Green_ Point_Stadium analyse mass data of the structures more difficult. The team needed to be [3] WBHO, 2010 World Cup Stadia on during the erection process. able to compare the as-built position with Track, accessed 10 June 2008 the design's position anywhere along the While the survey teams understand the www.wbho.co.za/article.php?a_id=73 sloping surface. This required that the complex three dimension vagaries of the [4] Murray and Roberts, 2010 Projects pylon be drawn in 3D. A dimension could survey systems, the management teams Update, accessed 10 June 2008 then be taken from the surveyed point www.murrob.com/News/publications/ are not trained surveyors, challenging to the design surface. This provided the robust/march07/March2007/projects. the manner of presentation of results. information, but looked very confusing htm Extensive use is made of simple graphics in plan view. The data could then be [5] Green Point Stadium roof tender and clear, uncomplicated spreadsheets. tabulated but still required a clear head awarded, BuaNews, 27 Nov 2007, accessed 19 June 2008 Although GNA Geomatics uses 3D to interpret. www.buanews.gov.za/view.php?ID=0 graphic imaging and displacement 7112716151004&coll=buanew07 Quality assurance surveys vectors for the analysis of the results, Contact Paul Edgecome, Edgeworks this has proven too complex for the Extensive use is made of the quality Surveys, Tel (021) 789-1223, client’s decision-making process, and assurance surveys undertaken by GNA [email protected] or Julian Gray, much time and effort was needed by Geomatics by the project management GNA Geomatics, Tel (021) 712-4915, both survey firms to produce simple and team to independently monitor the [email protected] 

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