Capital Gate, Abu Dhabi

ctbuh.org/papers

Title: Case Study: Capital Gate, Abu Dhabi

Author: Jeff Schofield, Associate, RMJM

Subjects: Architectural/Design Building Case Study

Keywords: Core Design Process Façade Sustainability

Publication Date: 2012

Original Publication: CTBUH Journal, 2012 Issue II

Paper Type: 1. Book chapter/Part chapter 2. Journal paper 3. Conference proceeding 4. Unpublished conference paper 5. Magazine article 6. Unpublished

Tall buildings: design, construction and operation | 2012 Issue II

Capital Gate, Abu Dhabi Securing Iconic Structures Environmental Performance of the TTDI Developing Rotterdam’s Skyline Talking Tall: The Skyscraper Index Debating Tall: Is UNESCO Going Too Far? Tall Buildings in Numbers: Occupiable Telecommunication & Observation Towers Case Study: Capital Gate, Abu Dhabi

“It is the first building in the world to use a pre-cambered core with a built-in lean of 350 millimeters that has been engineered to straighten with the addition of the upper floors. Jeff Schofield It is also the first building in the world to use Author Jeff Schofield, Associate vertical post-tensioning of the core to counter RMJM Floor 27, Monarch Office Tower movement and support stresses created by the PO Box 6126 Dubai UAE building’s overhang.” t: +971 4 702 7626 f: +971 4 329 6444 Throughout history, a strong link has existed between iconic architecture and exhibitions. e: [email protected] One of the best known examples is Paris’ Eiffel Tower, which was built as a visual symbol of the www.rmjm.com Exposition Universelle, World’s Fair of 1889. More recently, cities like Seville have used powerful and innovative architecture as a way to highlight the cultural significance of their Jeff Schofield Since moving to RMJM Dubai in 2005, Jeff Schofield exhibitions. has lent his design expertise to a variety of large scale building developments, including mixed use, The Concept aesthetic splendor and technical excellence to hospitality and high-rise projects. In 2005, the Abu Dhabi National Exhibitions celebrate human achievement and reflect the As an Associate at RMJM, Jeff leads the effort in dynamism of Abu Dhabi. Capital Gate is the providing sustainable solutions to all design projects in Company (ADNEC) was created to drive the office. He has developed a holistic approach to result. design that integrates sustainability, structure and forward the development of Abu Dhabi’s architectural expression with the built form, in order to events sector. Plans were created with RMJM The tower’s curvaceous shape draws strongly provide meaningful solutions for high-quality building designs. Jeff seeks to design in a contemporary yet to build a state-of-the-art exhibition center on the sea and desert – two elements that contextual manner, to create modern sustainable which would be the largest in the Gulf region have great resonance in Abu Dhabi. The buildings using the latest technology. and provide world class facilities for live events building’s form is meant to represent a Jeff currently lives and works in Dubai. He began his career in New York City and pursued his professional to flourish in Abu Dhabi. swirling spiral of sand, while the curved practice for more than 15 years in Paris, France. He has It was strongly felt that the entire canopy, known as the “splash,” which runs over project management and design experience on a the adjoining grandstand and rises on one range of high profile projects and has specific development required a signature tower, a experience in sustainable design and project side of the building, creates a wave-like effect, management of large-scale public projects throughout cutting-edge structure with a futuristic design, Europe, United States and the Middle East.

12 | Capital Gate, Abu Dhabi CTBUH Journal | 2012 Issue II reflecting the building’s proximity to the water • Four hundred and ninety foundation piles and the city’s sea-faring heritage. were driven 20 to 30 meters underground By integrating with the National Day to support the structure and counter Grandstand – one of Abu Dhabi’s most stresses. The piles, which were initially in historic structures – Capital Gate underscores compression during construction to the bond between the traditional and support the lower floors of the building, are modern that is characteristic of Abu Dhabi’s now in tension as the stresses caused by developmental approach. the overhang have been applied. • The vertical and horizontal cross-sections of the tower are all unique. First of its Kind • There is an asymmetric shape – no two There are several innovations within the rooms are the same (see Figure 2). Every project’s design, including the dramatic one of the 12,500 panes of glass on the 18-degree westward lean, which has earned it façade is a different size, although each the title of “world’s furthest leaning man- pane is triangular. made tower” from the Guinness book of world records (see Figure 1). It is the first building in • Floor plates change shape and orientation the world to use a pre-cambered core with a to create the distinctive “overhang” moving built-in lean of 350 millimeters that has from “curved triangular” to “curved been engineered to straighten rectangular,” while increasing in overall size with the addition of the upper and migrating from east to west as they floors. It is also the first building progress up the tower. in the world to use vertical • Capital Gate is one of the few buildings in post-tensioning of the core to the world that use a diagrid structure; it also counter movement and features two diagrid systems, an external support stresses created by the diagrid defining the tower’s shape and an building’s overhang. internal diagrid linked to the central core by The construction also adopted eight unique pin-jointed structural a variety of leading-edge members. approaches to create the • All 8,250 steel diagrid members are desired result: different thicknesses, length and orientation. 

Figure 1. Typical section © ADNEC Figure 2. Typical hotel floor plan © ADNEC

CTBUH Journal | 2012 Issue II Capital Gate, Abu Dhabi | 13 • Each of the 822 diagrid nodes (702 external 3). The façade glazing emphasizes the organic and 120 internal nodes) is a different size elements with diagonals spiraling up along and angular configuration. the structural diagrid. This weaving pattern is Capital Gate forms the focal point of the Abu further broken down with individual panes of Dhabi National Exhibition Centre complex glass in a complex mesh wrapping the entire and the Capital Centre master development, a building. The sheer skin is interrupted only by connected group of 23 towers including two entrances on the ground floor, the branded hotels, commercial buildings, footbridge to the car park, and the terraces at residential and serviced apartment complexes the top of the “splash.” and developments for mixed use. These The potentially monumental scale of Capital facilities are built overlooking an urban Gate is tempered by this “splash” sun shading highway along the south-western shore of on the south façade. This metal mesh screen Abu Dhabi. Capital Gate dominates this at the lower half of the tower adds complexity waterfront site from its position at the western to the overall form as it highlights the different edge of the ADNEC complex, adjacent to the uses of the tower – offices in the lower half exhibition halls and connected to the historic and hotel in the upper half. National Day Grandstand. Architecture is about space making, and the The tower stands out on the skyline; it is architects sought to express the drama of slightly removed from ADNEC’s high-rise Capital Gate in its interior spaces. The hotel development on the eastern side of the site. arrival is at the top of the splash on the 18th Due to the location, views from Capital Gate floor, where visitors discover a panoramic are extensive in all directions. The preferred view of Abu Dhabi. The lobby lounge is a Figure 3. Capital Gate’s organic shape © Devita Villanueva views are out to sea and along the coastline. double-height space cantilevered beyond the Views towards the city are becoming more tower diagrid (see Figure 4), providing a is also expressed with a diagrid structure, impressive as Abu Dhabi grows around it. dramatic arrival for guests . The restaurant informing its organic shape. While vertical in Capital Gate cuts a strong profile against this located on this floor is also a dramatic proportion, the atrium is intimate in scale. emerging skyline. double-height space positioned where the Light filters down from the large skylight roof tower form leans at the steepest angle. above to create a serene environment.

Architectural Expression Due to Capital Gate’s unique shape, the upper half of the tower widens to create an atrium at The Structure The ground-breaking form of Capital Gate is the hotel’s guest room floors (see Figure 5 and Capital Gate’s base structure is a vertical due not only to its lean, but also to its funnel 6). This space is perhaps the most surprising concrete core surrounded by a steel diagrid shape. It widens as it spirals upwards and discovery the visitor finds inside the building. describing the external form of the tower. outwards. This gesture creates the dramatic The atrium is funnel shaped and appears Steel beams span between the two, sculptural form which is expressed carved out of the solid form around it, supporting metal deck and concrete architecturally in a variety of ways (see Figure spiraling and leaning along with the tower. It

14 | Capital Gate, Abu Dhabi CTBUH Journal | 2012 Issue II Figure 6. Model section showing the funnel-shaped Figure 7. External diagrid structure © ADNEC Figure 8. The “splash” © ADNEC atrium © Jeff Schofield composite floor slabs. Above the base, the framing connections. The core has two The Capital Gate’s wind bracing is designed as atrium is formed with an internal steel diagrid innovative features: a separate system. Abu Dhabi has light winds, attached to the core. Steel girders span • During construction a pre-cambered core which Capital Gate counteracts through a directly between the external and internal was poured slightly off vertical, so when combination of a dense network of core walls th diagrids, creating column-free floor spaces the tower floors were framed in to the and outriggers at the 17 floor mechanical with typical spans of about 12 meters. opposite side, the added load straightened level, connecting the core to the external The external diagrid is composed of hollow the tower. diagrid. The tower’s round form and diagrid square sections 600 x 600 millimeters on a structure provide inherent resistance to • A post-tensioned core was designed with torsion. At the ground floor, a massive side. They carry floors four meters high. Each vertical cables in one side tensioned to diagrid member is a different length, concrete ring beam transfers the thrust of the counteract the lean on the other side. diagrid into the foundations. It is noteworthy depending on the angle at which it leans. The These cables were installed in vertical external diagrid elements are made from that Abu Dhabi is in a low seismic hazard segments that overlap each other every zone, and the appropriate factors of safety welded steel plates, 80 millimeters thick at the seven floors. Strung together, they span the bottom floors, and progressively lightening to and stiffness were applied for structural entire height of the core to maintain it in a integrity.  40 millimeters at the top floors. The internal perfectly vertical position. diagrid around the atrium is made of round steel profiles 400 millimeters in diameter, ...water feature which are also hollow. The diagrid connections are nodes located at the floor slab levels where girders frame in. The external diagrid nodes are also designed Putting a water feature in a lobby gets you LEED points, but for the façade panels to frame on the outside it“ doesn’t save energy, doesn’t improve the environment and it (see Figure 7). Designers studied these doesn’t change the world. connection details extensively to optimize construction, as well as structural integrity. Anthony Malkin, President of Malkin Holdings,” owner of the Empire State Building on the building’s The concrete core occupies the only vertical retrofit. From “An Interview With Empire State Building’s Anthony Malkin: Bike Racks and Showers Won’t Change the World,” Huffington Post “The Blog,” March 28, 2012 . space available in the tower profile. It has high reinforcement levels, especially at the steel

CTBUH Journal | 2012 Issue II Capital Gate, Abu Dhabi | 15 The curtain wall units are made of two architects and engineers integrated many components: steel and glass. The steel passive and active sustainable systems into framing was manufactured in Austria. The Capital Gate, including metal mesh sun frame profile is triangular to take loads in all shading, a double skin façade, high- directions. The glass was made in the United performance glazing, reduced amount of Arab Emirates. It is a low-emissivity glass, very materials, vegetated roof on the basement, transparent, yet provides good thermal low-flow water fixtures, district cooling, insulation and glare reduction. variable speed air conditioning, heat These components were assembled in Abu exchange for ventilation, and energy Dhabi into panels, which were transported to monitoring and controls. the site on over-sized flatbed trucks custom- Capital Gate’s most visible feature is the made to accommodate the large units. “splash,” which twists around the building The metal mesh sun shading is made of towards the south to shield Capital Gate as light-weight metal framing with stainless steel much as possible from direct sunlight. The wire mesh, 90% open. The “splash” is a flexible metal mesh eliminates 30% of the sun’s heat system designed to follow Capital Gate’s before it reaches the building, reducing the air curving forms. It is braced to the tower every conditioning load on the protected floors. It Figure 9. Curtain wall diamond-shaped panels © Jeff five floors with round steel profiles. There are also provides outdoor shade to the main Schofield cross-bracing rods every floor. The connec- entrance on the ground floor. The sun shading for the tower is a lightweight tions for these elements are located at each The upper half of the tower has a double skin metal mesh hung from the terraces on the diagrid node and extend through the curtain façade to reduce the solar heat gain at the 18th and 19th floors (see Figure 8). In turn, the wall joints to reach the steel structure. Above hotel levels. This is a modified double façade, terraces are cantilevered 12 meters from the the ground floor, as the geometry turns from which recycles interior air from the guest tower. They are braced to the external diagrid vertical to horizontal, steel tree structures rooms into the façade cavity. Here it creates with steel profiles reaching diagonally down reach up to hold the splash form in place. an insulating buffer between the hot outside to the plant floor level. At this same Façade maintenance is performed in various air and the cool inside air (see Figure 11). The mechanical level, on the opposite side of the ways. The curtain wall elements are repaired air is re-used in the room rather than tower, the atrium internal diagrid framing is and replaced from the inside, cleaning is from exhausted and replaced with outside air. transferred to the core with steel profiles the outside via abseiling, and lightweight sun The glass used on Capital Gate’s façade is a placed diagonally in sections. The plant floor shading elements are repaired via abseiling. It low emissivity glass never before used in the at mid-height ties together all the primary is common in the Middle East to use abseiling, United Arab Emirates. It’s designed to keep structural elements of the tower. a form of rappelling for external building the inside of the building cool and eliminate maintenance (see Figure 10). Capital Gate has glare, while maintaining the transparency of Façade Design eye-hooks in the curtain wall joints at every the façade. node, so the abseilers can hoist themselves Capital Gate’s cladding consists of two distinct Capital Gate’s organic shape also lends itself to close to the overhanging surfaces. Inside the elements – a curtain wall glazing system and savings in construction materials, in several splash, abseilers maneuver between the metal mesh sun shading system. Both were ways, despite the lean. Its rounded form is braces and rods to installed by the same manufacturer in order to clean both glass and ensure close coordination between these mesh at the same interlocking systems and the steel diagrid to time. which they are attached. The curtain wall consists of diamond shaped panels stacked up floor by floor (see Figure 9). Sustainable strategies Each unit is two-floors high and one diagrid ADNEC is committed wide, about 8 x 8 meters on average. They to being one of Abu follow the geometry of the structural diagrid, Dhabi’s leaders in which carries their weight vertically. The sustainable panels are braced for wind resistance at the development. From middle floor slab, which carries the horizontal the beginning of load. concept design, the Figure 10. Façade maintenance via abseiling from the outside © ADNEC

16 | Capital Gate, Abu Dhabi CTBUH Journal | 2012 Issue II Capital Gate houses Abu Dhabi’s first Hyatt Hotel, the five-star Hyatt Capital Gate, as well as approximately 15,000 square meters of office space. The tower is also strategically important to Abu Dhabi and visually represents the emirate’s progress and evolution. It is the focal point of a world class business district, and is inter-connected with the thriving Abu Dhabi National Exhibition Centre , which hosted more than 200 events in 2011, welcoming around one million visitors. Capital Gate’s visitors or tenants have access to the world-class amenities within the building as well as elsewhere within the ADNEC development, including facilities such as a Figure 11. Double skin façade system © Jeff Schofield fully-operational airport check-in facility. aerodynamic, presenting less resistance to the Partnering Solutions The Guinness world record for “world’s furthest leaning manmade tower” has shone a wind than a rectangular building, thereby The huge technical challenges that had to be requiring less structure for lateral loads. The spotlight on Capital Gate and Abu Dhabi, as confronted in bringing Capital Gate to life has a “Megastructures” documentary on round perimeter encloses space more have been overcome through a structured efficiently than a rectangle, so less façade National Geographic Channel (“The Leaning partnering program. It is a fairly unusual Tower of Abu Dhabi”), broadcast in more than surface is needed than for a conventional technique in this part of the world, which floor plate of identical area. The result is that 166 countries to an estimated television ADNEC has employed with much success on audience of more than 200 million. fewer materials are required for structure and all of its construction projects. Essentially, all façades. This is a reduction in concrete, steel the key organizations working on a project The people of Abu Dhabi feel a sense of and glass, materials which all have high are located together in one location. The honor in Capital Gate. They are confident carbon content and embodied energy. architect sits next to the project manager, Capital Gate’s aesthetic splendor and technical Landscaping around Capital Gate creates a who sits next to the quantity surveyor, who achievement will generate admiration and vegetated roof over the basement, increasing sits next to the contractor and the rest of the discussions around the world for years.  the thermal insulation and reducing the need team. The objective is simple: to remove for air conditioning. Native plants are used, confrontation and create a single team Project Data which require less irrigation than conventional mentality with one single goal – to get the landscaping. To further reduce potable water project completed in the most effective way. Completion Date: 2011 use in this desert context, low-flow water JCP International, the partnering consultants Height to Architectural Top: 165 meters fixtures are installed in the public areas and who worked at a strategic level with the joint Stories: 35 washrooms, including WCs and faucets. leadership team, worked from the project and Total Area: 53,100 square meters Primary Uses: Hotel/Office District cooling is provided by Abu Dhabi construction management level to the front Project Developer: ADNEC Group Municipality, a more energy-efficient means line supervisors and staff to instill a culture of Architect: RMJM of obtaining chilled water than installing collaborative working within and across Structural Engineer: RMJM chillers on site. The chilled water is distributed organizational boundaries. MEP Engineer: RMJM by variable speed pumping, which reduces Façade Consultant: Hyder Consulting energy use in operating the air conditioning. Conclusion Landscape Consultant: Al Khatib Cracknell Heat recovery wheels reduce energy use for Main Contractor: Al Habtoor Engineering ventilation by exchanging hot and cool air While clearly a unique structure was built Steel Contractor: Eversendai during the intake and exhaust process. Energy using some of the world’s most advanced Façade Contractor: Waagner Biro monitoring and controls in the Building construction techniques, ADNEC believes the Project Manager: Mace Maintenance System further reduce energy tower’s appeal goes far beyond an use by implementing efficient operation of architectural and engineering marvel. lighting, air conditioning and other power- Functionality and purpose have been a prime consuming and heat-generating functions. focus.

CTBUH Journal | 2012 Issue II Capital Gate, Abu Dhabi | 17