Turning TorsoHSB Turning Torso is the tallest skyscraper in Sweden and the Nordic countries, situated in Malmö, Sweden, located on the Swedish side of the Öresund strait. Upon completion, it was the tallest building in Scandinavia, the tallest residential building in the EU and the second tallest residential building in Europe, after the 264-metre (866 ft) Triumph Palace in Moscow. The tower is situated in Malmo’s former western docks and is part of a massive regeneration project. This area had become a ‘backwater’ in southern Sweden, particularly following the closure of its docks. This all changed with the opening of the Oresund Bridge linking to the Danish capital, Copenhagen. Today, with traffic movement and train passengers exceeding projected targets between the two cities, the area has seen a property boom. The entire building turns 90° as it climbs upwards over nine blocks or cubes, each of which consists of five floors. This very impressive structure contains 54 storeys and reaches a dizzying height of 190 meters. The vision of HSB Turning Torso is based on a sculpture called Twisting Torso. The sculpture is a white marble piece based on the form of a twisting human being, created by Santiago Calatrava, a trained sculptor, architect and engineer. Foundation The foundation of the building was built directly on the limestone bedrock. Profiled steel plates forming the foundation shaft, were driven 15 metres into the ground and a further 3 metres into the limestone bedrock by an enormous vibrating sheeting machine. Above ground, the structure turns around a spine-like core as it rises. An exoskeleton of white steel tubes embraces the glassy "front" facade. The foundation slab has 30m in diameter x 7 m thickness, wich was poured for 3 days in continous. Superstructure Each floor consists of an irregular pentagonal shape rotating around the vertical core, which is supported by an exterior steel framework. The two bottom segments are intended as office space. Segments three to nine house 147 luxury apartments. There is also one floor between all the cubes - these floors are used for different purposes (rooms with a view, conferences areas or activity/gym room). With perimeter walls that both "swirl" and cut back to the core, the 26,000-sq-m tower in Malmö, already a landmark, has demanded some highly tailored vertical supports. Yet despite the tricky geometry, wind at the coastal site has been the contractors’ biggest gripe. The gusts have caused delays in both concrete work and, after a difficult beginning, erection of the steel "exoskeleton." The 7-meter thick concrete structure will sway less than 30 centimeters during the heaviest wind load that statistically happens only once every 100 years. At the heart of the tower, a central core shaft is being poured using an automatic climbing system weighing 140 tons. Progressing three levels above the slab construction, the system completes the shaft walls to a thickness of 2.5 m at the base reducing to 40 cm by the 54th story. Completion of each floor slab was originally anticipated to take seven days, but the projected completion cycle was reassessed as a result of the excessive reinforcement necessary for such a structure. There is no other building like this, claims the project director. At 250 kg/m2, it has the same reinforcement as a nuclear power plant. This extreme level of reinforcement is necessary to withstand the tower’s forces through the core and slabs. As a direct consequence, the contractors were able to achieve an eightday cycle for standard slabs and nine days for each conical slab. The lower and upper slabs of each cube incorporate a higher degree of reinforcement and met 12- and 10-day cycles respectively. When it was completed, the project used more than 64,000 tons of steel reinforcement and concrete at a pour rate of up to 150 tons of concrete/h. The tower also established a new Swedish record for pumping concrete to a height of 190 m. Each of the buildings’ 54 floors is turned by about 1.6° relative to the one below, so that the whole tower twists 90° from bottom to top. The concrete structure rises 184 m, centered on a cylindrical core with an internal diameter of 10.6 m and walls varying in thickness from 2 m at the base and 40 centimeter near the top. Inside the core there are lift shafts and staircases. Tower floors are shaped roughly like an arrowhead. Three of their five perimeter walls are 17 m long, slightly curved, and set some 5 m from the core. The other two project out to form a triangular floor area, its tip 10 m from the core. Full-height curtain walls enclose the two facades of the triangular area. The other three faces are arranged in five-floor-deep "stacked" modules with walls perforated by windows. There is a 2-m-deep gap between each module, from the perimeter to the core. The gap exposes the core like the backbone of a human, explains Christian Brändle, Calatrava’s project architect. Because the modules’ perimeter walls are not vertically continuous, full-height perimeter columns are not possible. Instead, in each module, the lowest slab cantilevers from the core to support floors above with 11 slim, steel columns hidden in perimeter walls. While floors are 27 cm thick, the lowest slab of each module is 90 cm thick at the core, reducing to 40 cm at its edge. With no primary columns in the curtain walls, the triangular floor areas are propped only at their tip by a concrete perimeter column that gradually spirals to the ground within the building envelope. The roughly 60-cm-wide multifaceted column is heavily reinforced with about 100 kilograms per cu m of rebar, says Bjorn Nordgren, project manager with concrete contractor NCC Construction Sverige A.B., Solna. The stark exoskeleton around the building’s front face is made of tapered white steel tubes with diameters up to 90 cm. Following the concrete perimeter column, the exoskeleton’s single upright is fixed to the tower between each module mainly with horizontal and inclined tubes. These tubes reach back to 4.5-tonne-steel anchorages embedded in shear walls at the building’s back corners. It connects to each floor by 2 stabilizing elements, it rotates with the building and weighs 360 tons. While the spine column takes perimeter vertical loads, the exoskeleton around it provides wind resistance and dampens the building’s vibrations, according to Calatrava. The Torso's exoskeleton is effectively a steel truss erected on the outside of the building with the same clockwise rotation as the tower itself. The truss consists of aspine column at the corner of each floor plus horizontal and diagonal elements thatreach to each side of the glazed spine. Stabilisers also connect the floor slabs withthe framework. The outer steel framework has a weight of 900 tons. The diagonal pins are 25 meters long and have a weight of 25 tons. The Swedish construction company, NCC Construction AB in Malmö, commissioned the Weissenhorn-based formwork and scaffolding manufacturer, PERI, to develop a costeffective formwork concept and deliver the required systems for the project. The ACS-P (P = platform) self-climbing scaffold concept allowed concreting of the ring wall on the main level and the retightening of the internal core walls one floor below. The ACS-P weighs over 110 tons and is anchored on twelve fixing points. A concrete placing boom has been installed on its own climbing scaffold using four fixing points in the core. PERI Automatic Climbing System (ACS) The Automatic Climbing System (ACS) is a hydraulically operated self-climbing formwork system used for the construction of tall concrete structures such as building core walls and bridge pylons. Tall concrete structures have historically been formed with crane lifted formwork often referred to as “jump” forms. These systems require a worker to ride the formwork as it is raised to its next position in order to insert reties through the previously cast lift to secure the form. This procedure requires extensive crane time and is too slow, unsafe and unproductive for tall structures where the concrete walls are typically on the critical path. All formwork, working scaffold, storage areas and equipment used to form the internal and external walls are self-climbed in one single operation. During the climbing procedure, the complete climbing unit is enclosed. No open edges are created which could be a fall hazard. The working platforms are able to carry high loads; forexample, the storing of reinforcing steel forthe next climbing section. Even the placing boom for the concrete pump can climb on the ACS self-climbing system if required. The core wall of the Torso was formed with PERI GRV articulated walers and externally using PERI RUNDFLEX formwork. Adapting to the changing wall thicknesses (from 2.00 m at the bottom to 40 cm at the top) is carried out with filler elements on the external formwork. The climbing mechanism is the heart of all ACS systems, with a lifting power of 100 kN. The positively-controlled climbing device lifts the climbing rail and formwork scaffold-ing to the next casting segment safely and jerk-free. All loads are safely transferred during every climbing phase. Due to the almost noiseless PERI climbing hydraulic, working outside of normal work-ing hours is possible without disturbing surrounding residential areas. The stroke speed is 0.5 m/min whilst the effective climbing speed is 0.3 m/min. The loads from the climbing scaffold must be safely transferred through the anchors into the building. This is particularly important because very often the system is climbed the day after concreting has taken place. After taking into consideration individual factors such as the structure of the building, loading, wall thickness and required concrete hardness, the optimum climbing shoe and anchor type are selected along with determining their position. All compression and tension forces can then be safely transferred into the wall. The climbing sequence begins by stripping the formwork from the previously cast lift using the carriages on the brackets or platform. The leading climbing shoes are then bolted to the anchors in the previous lift. The hydraulic climbing mechanism then raises the climbing rails located at each bracket or platform beam to the leading climbing shoes where they engage and lock automatically. The climbing mechanism is switched from climbing the rails to climbing the unit. The ACS unit then climbs on the rails at the speed of 0.50 m (1'-8") per minute. After the unit has reached the leading climbing shoe, it is secured with a locking bar and the hydraulic system is disengaged. With the unit in its new location, the rebar is installed from the work platform and the formwork is positioned using the carriages. The formwork is now ready for concrete placement to complete the construction cycle. All the concrete is mixed 30 km from Turning Torso, arriving on site ready to be pumped immediately into place. The special large-aggregate mix, which includes a high volume of chunky locally ground rounded stone, is critical to the success of the fast-track core build, being carefully adjusted as the building rises to ensure it is fluid enough to be pumped at ever higher pressures. Curing is fast, with formwork removed for reuse on the next level after between one and two days, depending on weather influences. With formwork being dismantled, NCC built the top three levels of core interior walls out of precast concrete. Facade The facade’s complex appearance was similarly the subject of thorough studies to find recurrence patterns. All windows in the tower are flat and rhomboid, designed to follow the natural curved shape of the building as it twists its way towards the sky. Because the building twists, the façade is double curved, wich made its construction very complicated. The façade is a glass and aluminum construction. There are aproximately 2800 panels and 2250 windows in the façade. The aluminum panels are curved and the glass ones are flat. Six different families of windows are used, depending upon where they are situated. The most visual difference can be seen by comparing windows in the ‘square’ section of a cube with those used in the ‘triangular’ section. Eco-Tower Turning Torso in Malmo, Sweden is a good example of the theatrical representation of a structural technology in architectural form whilst environmental technologies remain invisible. Turning Torso has an environmental agenda. Kitchen waste, for example, is transported to a collection tank where it is then piped to a decomposition plant producing biogas. There is diode lighting in common corridors. Its energy efficient envelope has passed several laboratory tests concerning air and water sealing and heat insulation according to stringent Swedish standards. None of these technologies are signified in the visual appearance of the building and their inclusion in the media releases is subordinate to the celebration of the twisted form. The energy supplying the tower, as electricity and heating come from wind power, biogas, geothermal and solar sources. The Finished Building consists in 4.400 metric tons of steel reinforcement, 25000 metric tons of concrete poured and 900 metric tons of steel in spine and ribs. Fire safety is supported by an extensive sprinkler system with fi re zones limited to individual cubes. References: www.wikipedia.com http://enr.construction.com/ www.designbuild-network.com ConcreteQuarterly – Sept 2004 www.peri.de HSB Turning Torso