CTBUH Technical Paper http://technicalpapers.ctbuh.org

Subject:

Building Case Study / Architecture/Design

Paper Title:

Capital Gate, Abu Dhabi

Author(s):

Schofield, J.

Affiliation(s):

RMJM

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 Unpublished conference paper 5.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 Unpublished

© Council on Tall Buildings and Urban Habitat/Author(s)

CTBUH Journal International Journal on Tall Buildings and Urban Habitat

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

Inside News and Events 02 This Issue Steve Watts, CTBUH Trustee 04 CTBUH Latest Antony Wood, CTBUH Executive Director 05 Debating Tall: Is UNESCO Going Too Far? 06 Global News Highlights from the CTBUH global news archive

Case Study

CTBUH

12

Case Study: Capital Gate, Abu Dhabi

46 Helsinki: Developing a Finnish Vernacular for the High-rise? Antony Wood

Jeff Schofield Author Jeff Schofield, Associate RMJM Floor 27, Monarch Office Tower PO Box 6126 Dubai UAE t: +971 4 702 7626 f: +971 4 329 6444 e: [email protected] www.rmjm.com

Jeff Schofield Since moving to RMJM Dubai in 2005, Jeff Schofield has lent his design expertise to a variety of large scale building developments, including mixed use, hospitality and high-rise projects.

48 CTBUH Young Professionals Committee Launches Ambitious Agenda Kevin Brass 49 CTBUH Research Development Initiative: An Update Payam Bahrami 51 CTBUH on the Road CTBUH events around the world.

As an Associate at RMJM, Jeff leads the effort in providing sustainable solutions to all design projects in the office. He has developed a holistic approach to design that integrates sustainability, structure and architectural expression with the built form, in order to provide meaningful solutions for high-quality building designs. Jeff seeks to design in a contemporary yet contextual manner, to create modern sustainable buildings using the latest technology. g his Jeff currentlyy lives and works in Dubai. He began career in New York City and pursued his professional practice for more than 15 years in Paris, France. Jeff has projec pro jectt mana m anagem gement ent an and d desi d esign gn exp experi erienc ence e on on a project management design experience range of high profile projects. Jeff has specific exp erienc i e in i sustainable sustain i abl ble design design i and d project proje j ctt experience manage man agemen mentt of of llarg arge-s e scal cale ep publ ublic ic pro projec jects ts thr throug oughou houtt management large-scale public projects throughout Europe, U.S.A and the Middle East.

18 24

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Securing Iconic Structures Sean Ahrens & Stephen Yas The Environmental Performance of the TTDI Suraksha Bhatla & Joanna Gonçalves

18

Developing Rotterdam’s Skyline Frank van der Hoeven & Steffen Nijhuis

Sean Ahrens

Stephen Yas

Aon Fire Protection Engineering Security Division 1000 Milwaukee Avenue, 5th floor Glenview, IL 60025 United States

51 Diary Upcoming tall building events

t: +1 847 461 9359 f: +1 847 953 7793 [email protected] www.aonsecurity.com

Stephen Yas, Design Principal MulvannyG2 (Shanghai) Architecture Ciro’s Plaza Suite 1905 388 Nanjing Xi Road Shanghai 200003 China

Features 38 Tall Buildings in Numbers A Look at Occupiable Telecommunication & Observation Towers 40 Design Research University of Nottingham 42 Talking Tall: The Skyscraper Index Andrew Lawrence

52 Reviews Review of new books in the CTBUH Library

Sean A. Ahrens Sean leads the security consulting practice at Aon FPE with over 19 years of experience, a majority of which has been in a security consulting function. He has been responsible for providing security threat and risk analysis, contingency planning, loss prevention, and force protection design and planning. Sean has provided design and construction administration for government, public, and private entities that encompass telecommunications, security, surveillance, and access control systems. He is well versed in the various trade and local authority issues impacting projects, and has specialized professional competence in security, access control systems, and force protection systems.

Stephen Yas Stephen has over 35 years experience working internationally. He specializes in architecture, urban design and interior design for large mixed-use projects. As design principal in the Shanghai office of MulvannyG2 Architecture, he is the design leader in china for the firm. Prior to MulvannyG2, Stephen leads his own firm in Chicago for 22 years. Prior to that he was a senior designer at SOM Chicago and Lohan Associates, as well as working in England and the Middle East.

52 CTBUH in the Media Selection of media coverage

53 What’s on the CTBUH Web? Featuring new content now available on the website

The Concept In 2005, the Abu Dhabi National Exhibitions Company (ADNEC) was created to drive forward the development of Abu Dhabi’s events sector. Plans were created with RMJM to build a state-of-the-art exhibition centre which would be the largest in the Gulf region and provide world class facilities for live events to flourish in Abu Dhabi. It was strongly felt that the entire development required a signature tower, a cutting-edge structure with a futuristic design,

• The vertical and horizontal cross-sections of the tower are all unique

First of its Kind There are several innovations within the project’s design, including the dramatic 18-degree westward lean, which has earned it the title of “world’s furthest leaning manmade tower” from the Guinness book of world records (see Figure 1). It is also 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. And it is the first building in the world to use vertical post-tensioning of the core to counter movement and support stresses created by the building’s overhang.

aesthetic splendor and technical excellence to celebrate human achievement and reflect the dynamism of Abu Dhabi. Capital Gate is the result. The tower’s curvaceous shape draws strongly on the sea and desert – two elements that have great resonance in Abu Dhabi. The building’s form is meant to represent a swirling spiral of sand, while the curved canopy, known as the “splash,” which runs over the adjoining grandstand and rises on one side of the building, creates a wave-like effect,

CTBUH C CTB CT TBU TB UH H Jo JJou Journal ou ourna rn rn naal | 2011 20 011 11 1 1 Issue Isssue Is Iss su ue IIII ue

“In sophisticated urban planned environments, security should be subtle, but allow for the potential for heightened threats. The key is to find a suitable balance between security and preserving the designer’s vision. A security program for any structure should employ a variety of controls to deter, delay, detect, deny and respond to threats, as well as mischievous or potential accidental acts.” This paper emphasizes the importance of integrating security programming into building design, allowing for different uses and threat levels for the life of the building. Security strategies will be evaluated that can be applied to any building, as well as review procedures to address concerns early in the design process, especially in politically and economically charged international environments. General concepts and approaches to building security will be examined, demonstrating the benefit of collaboration between architects and security professionals at an early stage to meet the project’s goals without detracting from the planner’s vision for the project. The “Fortress” To the untrained eye, this graphic (see Figure 1) may appear “fortress” like. However, in its most basic format, the diagram describes the security program for building at any security level. Early dialogue between security professionals and the designer can limit the fortress or bunker aesthetic by careful placement of technical security, including cameras, setbacks, gates, fencing and spatial provisions for security staffing. In many cases, consideration is not given to the potential for a future modification to the building, such as the addition of a casino, parking garage, skate park or theater, which may increase the potential for malevolent acts. The addition of new tenants, such as a dignitary or VIP, may require a change in the security status not considered in the original design process. The modification of the physical and architectural security component is the most important, most expensive and, therefore, most difficult to modify post-design. Done early in the design process there is significant indirect and direct return on investment that can be achieved by preplanning.

When planning a facility, design professionals need to think outside-the-box. Although fear of terrorism typically drives the mindset for iconic building security, there are other more likely threats, including workplace violence, domestic spill over issues, intellectual theft, property theft and other malicious acts against persons or property that can affect the building and its occupants. Unforeseen dangers can create significant security challenges for building owners post-design and may detract from the marketing, image and status of the project. Planning for a single threat may not be effective and may miss potential threats in the future. The best approach is to create generalized controls designed to address a broad range of threats. Unlike other building elements, there are no standards for the provision of security based on building occupancy. As a result, the evaluation and development of security controls is purely based on a quantitative risk and consequence analysis which evaluates all aspects of the proposed building, not simply such critical assets as electrical and telecommunications systems. Conducting a risk and consequence analysis will assist the

18 | Securing Iconic Structures

32

• Four hundred and ninety foundation piles were driven 20 to 30 meters underground to support the structure and counter stresses. The piles, which were initially in compression during construction to support the lower floors of the building, are now in tension as the stresses caused by the overhang have been applied.

The construction also adopted a variety of leading-edge approaches to create the desired result, including:

• Asymmetric shape – no two rooms are the same (see Figure 2); every single pane of the 12,500 panes of glass on the façade is a different size although each pane is triangular • Floor plates change shape and orientation to create the distinctive “overhang” moving from “curved triangular” to “curved rectangular,” while increasing in overall size and migrating from east to west as they progress up the tower • Capital Gate is one of few buildings in the world that use a diagrid structure; it also features two diagrid systems, an external diagrid defining the tower’s shape and an internal diagrid linked to the central core by eight unique pin jointed structural members. • All 8,250 steel diagrid members are different thicknesses, length and orientation 

Figure 2. Typical hotel floor plan © ADNEC

CTBUH Journal | 2011 Issue II

Capital Gate, Abu Dhabi | 13

Securing Iconic Structures

Sean A. Ahrens, Practice Leader/Manager

53 Comment Feedback on the past journal issue

By integrating with the National Day Grandstand – one of Abu Dhabi’s most historic structures – Capital Gate underscores the bond between the traditional and modern that is characteristic of Abu Dhabi’s developmental approach.

Figure 1. Typical section © ADNEC

t + 86 21 6032 0100 f + 86 21 6217 8525 e: [email protected] www.mulvannyg2.com

Research

reflecting the building’s proximity to the water and the city’s sea-faring heritage.

Throughout history, a strong link has existed between iconic architecture and exhibitions. One of the best known examples is Paris’ Eiffel Tower, which was built as a visual symbol of the 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 exhibitions.

12 2 | Cap Capital pit ittaal ita al G Gate, aatte ate te, A te, Abu bu Dha bu Dh Dhabi haab h habi bii

Authors

12 Capital Gate, Abu Dhabi Jeff Schofield

“From the beginning of concept design, the architects and engineers integrated many passive and active sustainable systems into Capital Gate, its most visible sustainable feature is the “splash,” which twists around the building towards the south to shield itself as much as possible from direct sunlight.”

CTBUH Journal | 2011 Issue II

designer with understanding the exposure to threats. For example, a building near a proposed or existing mall will make criminal incidents more likely. In similar fashion, integrating a train or metro into a large high-rise project could increase exposure to chemical or explosive attacks, while the creation of a building near a government facility or embassy may escalate the tertiary terrorism risk. The type of building and its tenants may also affect risk rating, which can change over time. Understanding the risks early in the process will assist organizations in making decisions. The planner should ensure that the security analysis provides specific guidance and recommendations on vehicular access, security placement of cameras, access control and the overall security compartmentalization program. From a security perspective, designers need to think about the “what-ifs.” They need to have a vision. That does not necessarily mean implementing controls from day one, but designing provisions into the architecture so security controls can be easily and quickly adopted in the future if higher threat scenarios arise. The downside of shortsighted preplanning is evident in the airports built 20 years ago. The functions and usage of airports have changed dramatically. The free flowing public environment of yesterday is now a series of mazes and security compartmentalization

which could have been avoided, if only designers had taken a more open-minded approach during the design process. Preparing for the Future To prepare for tomorrow’s uncertainties, today’s international planners should start by evaluating the site and potential setbacks and standoff distances from the façade of the building. Even with constricted site layouts, there are opportunities that can be explored. Setback can be achieved through a number of programming elements. To increase the affect of clear space, the perception of setback can be somewhat masked through architectural programming, such as the creation of multi-tiered planting areas, water features, structures and natural boulders. The proposed US Embassy in London employs an enveloped glass façade and a water feature to support security. The water feature provides a visual element to the project, but it also creates a defined perimeter and clear zone. When developing building placement, roadways should be carefully evaluated. Centralized or limited roadway access is preferred, while incorporating standards and requirements for emergency access. In some cases, emergency access roadways will need to be secured and may create a conflict with first responders. Proper signage and clear access routes can limit frustration by people who are not familiar with the site, which could

be a key to minimizing negative interactions with security. Site confusion can lead to anger. Roadways are integral to the project, but simple and cost effective techniques, such as using a serpentine access road, can create elegant and effective solutions to reduce the potential for a vehicle to approach a building at high speed. Counter terrorism and counter surveillance techniques are extremely beneficial to identifying an aggressor. For this reason, building layout, whenever applicable, should afford natural sight lines to allow the detection of an intruder. As a result, landscaping is extremely important. Trees and other foliage that can obscure sight lines should be discouraged. Lighting, the number one deterrent to crime, may become obscured by growing tree canopies. As a result, lighting plans and photometric should take into account tree growth over the life of the tree and the effect on the light distribution. By doing this more effective light placement can be identified. Hotels will often employ a porte cochere, which can expand setback from the primary structure while providing continuity in architecture and limit the perception of distance from the entry to the building. Setback is more than maintaining vehicle proximity, setback increases natural lines of sight as well as the area that must be traversed prior to accessing a facility, while supporting the potential for early detection of an aggressor. Designs should limit components that may be used by aggressors for criminal acts. Loose rocks of substantial size could be used to break windows to gain entry to a building or be picked up as a makeshift weapon in an ambush scenario. If rocks are integral to design, they should be kept small or be large enough that they can’t be easily picked up. The Worst Case Scenario When designing setback and site placement, consideration should be equally afforded to the planning for emergency vehicles and muster points for evacuating tenants. Muster points need to account for the expected mass of people and should be as far away from 

Figure 1. The “fortress” © Aon CTBUH Journal | 2011 Issue II

Securing Iconic Structures | 19

Developing Rotterdam’s Skyline

Frank van der Hoeven

Steffen Nijhuis

Authors Frank van der Hoeven, Associate Professor Steffen Nijhuis, Assistant Professor Delft University of Technology Faculty of Architecture Julianalaan 134 2628 BL Delft The Netherlands t: +31 15 278 9805 e: [email protected] e: [email protected] www.graduateschool.abe.tudelft.nl

Frank van der Hoeven Prof. van der Hoeven is an associate professor of urban design at the Faculty of Architecture at the Delft University of Technology, the Netherlands. He conducted his PhD research in the field of underground space technology and multifunctional and intensive land-use. The core of his work deals with urban design issues related to mixed-use development: transit-oriented development, urban greenhouse horticulture, the use of underground space, high-rise urban areas and climate change. Currently he combines his associate professorship in urban design with the position of Director of Research of the Faculty of Architecture.

54 Meet the CTBUH Kevin Brass

Steffen Nijhuis Prof. Nijhuis is an assistant professor of landscape architecture at Delft University of Technology (the Netherlands). His PhD research, entitled “Landscape Architecture and GIS,” focuses on the application of geographic information science in landscape architectonic research and design. The core of his work deals with theories, methods and techniques in the field of landscape architecture and urban design, visual landscape assessment and visual knowledge representation. He is leader of the architecture and landscape research program, series editor of RiUS and advisor to governmental and regional authorities in the Netherlands.

55 CTBUH Organizational Structure & Member Listings

“The framework as presented carries the potential to underpin a city’s guidance on tall building development. This framework presents the context of a tall building design, providing a more balanced evaluation of a design proposal compared to studies that focus solely on individual tall buildings.” The planning and construction of tall buildings is often controversial, polarizing the public debate on architecture and urban life. In many cases the emotional discourse focuses on aesthetics and view corridors, more than city planning or economics. This paper introduces a framework that analyzes the visual impact a developing skyline has on a city and its surrounding region, using Rotterdam as a case study. By studying the height and completion year, identifying the tall building cluster as it is perceived visually and conducting a GIScbased visibility analysis, the framework provides context to tall building designs. The results make the assessment of individual projects more scientific and balanced, removing many of the emotional elements that often enter into the discussions. Introduction Research on the visual impact of tall buildings has the potential to make or break a tall building proposal. In the UK, debates over the appropriateness of projects in London and Liverpool are focused on view corridors, with UNESCO threatening to remove world heritage designations from historic complexes if the new developments damage their aesthetic impact (see “Debating Tall”).

Concerns about the appropriateness of tall buildings in the urban environment, the quality of the architecture and the impact on local real estate markets is increasingly reflected in municipal and metropolitan policymaking. Prominent cities with a longstanding tradition of urban management, building regulations and zoning plans often feel the need for additional instruments to control the development of what is described by McNeill as “an extremely complex spatial phenomenon” (McNeill, 2005). Scientific

literature, however, often neglects the substantial impact skyscrapers and their visual footprint can have on urban life. “The significance of these buildings – in terms of height, levels of human occupancy, aesthetic impact and popular representation and use – is in need of careful geographical interpretation.” (McNeill 2005) In 2007 the Netherlands Institute for Spatial Research (Lörzing et al. 2007) published an investigation on the visibility of the proposed Belle van Zuylen tower. At 262 meters the Belle van Zuylen tower would become Holland’s tallest residential building and the centerpiece of Leidsche Rijn, the new city district, west of Utrecht. But the Netherlands Institute for Spatial Research analysis showed that the Belle van Zuylen could be seen from most of the “Green Heart,” the semi-rural region enclosed by the cities of Rotterdam, Amsterdam, The Hague and Utrecht. The report was the last blow for the proposed development – construction was cancelled soon after the release of the report (Lörzing 2011). The Belle van Zuylen case is a fine example of using research for tactical purposes through the selective presentation of findings. The study did not present the Belle van Zuylen in its true context. The joint visual impact of all the tall buildings in the region on the Green Heart was not considered, nor how much that impact would change as a result of the construction of the Belle van Zuylen. If the study had included these elements, it may not have caused such stir. In fact, a nearby television tower, the 367-meter Gerbrandytoren tower, built 42 years earlier, dominates the visual impact of the area. A framework that helps to picture the context of a proposed tall building can potentially neutralize public and political debates that so often lead to polarization. This framework is based on three key elements: Rotterdam’s tall building development Rotterdam is one of the prominent European tall building cities with a mature tall building policy in place (see Figure 1). Several databases, including the CTBUH’s The Skyscraper Center, make it clear that only four

Figure 1. Rotterdam as a prominent west European tall building city © authors 30 | Developing Rotterdam’s Skyline

CTBUH Journal | 2011 Issue II

CTBUH Journal | 2011 Issue II

western European cities possess this type of mature skyline: London, Paris, Frankfurt, and Rotterdam. The leading position of Rotterdam is furthermore underscored by DEGW’s report on London’s Skyline, Views, and High Buildings commissioned by the Greater London Authority (GLA). The London policy document uses the same four European cities to compare established European practices of tall buildings policymaking: London, Paris, Frankfurt, and Rotterdam. The tall building policy document that emerged in the Netherlands is called hoogbouwbeleid or hoogbouwvisie. The Dutch policies resemble a number of policy documents recently produced in the United Kingdom and Germany. Height regulation is a key component of all these tall building policies. Height also translates into visibility. A modern history Over the years, the city of Rotterdam has carefully cultivated an image as a “city of architecture.” But “historic” architecture is not Rotterdam’s strong point. Few buildings were left standing after the bombing and fire of May 1940. The few buildings that survived were relatively modern buildings from the 1920s and 1930s. The city had to rebuild its center from scratch. Planners seized this opportunity to experiment with architecture and urbanism, which is why the Rotterdam city center now contains numerous monuments and icons from the modern and modernist period, sometimes referred to as “reconstruction architecture.” Discussions about the appropriateness of tall buildings surfaced from time to time, but never reached the emotional levels experienced in cities with a historic center. Tall buildings are now generally accepted and most are concentrated in the city center. While Rotterdam as a whole uses modern and modernist architecture to promote itself, tall buildings are an essential ingredient in the profile of the city: the skyline, including the famous Erasmus Bridge, has become the city’s iconic image (Ulzen 2007).

Rotterdam’s semi-official tall building history portrays a 100-year prelude from the late 19th century, with the completion of the 42-meter Witte Huis, built in 1898, to the so-called “first wave” of high buildings in the mid-1980s. Prominent city planners suggest that the city at the turn of the century was on the verge of a “second wave” of tall buildings, which would feature supertall buildings (Maandag 2001). However, this tale cannot be underpinned with facts. Neither the height nor the location of the high buildings dating from this early period relate to the municipal policy on high-rises. It was only in the 1970s that the current tall building area in the middle of the city center began to emerge. Essential data on tall buildings can be easily presented by means of a scatter plot. In the case of Rotterdam, the building height and the year of completion were plotted, including the primary use of such buildings. The beauty of Rotterdam’s scatter plot lies in the clear patterns that emerge. In her book Form Follows Finance, Carol Willis explains that the end of a tall building wave is typically marked by the construction of the “tallest building so far.” If we would consider these “tallest buildings so far” as anomalies and disregard them, the development of the Rotterdam tall building cluster is characterized by a remarkable continuity. However, if Carol Willis’ insights are applicable to Rotterdam, then the year in which the tallest building so far was completed could be used as the breaking points between tall building waves. Three such buildings stand out in Rotterdam: the Faculty of Medicine of the Erasmus University, also known as Hoboken (1969, 112 meters), the Delftse Poort (1991, 93 and 151 meters) and the Maastoren (2009, 165 meters). If the tall building history of Rotterdam is indeed characterized by waves, then these buildings are indicative of three such waves, as represented in the scatter plot (see Figure 2). The end of the wave is determined by the latest and tallest building in a development cycle. A first wave of tall building construction began in Rotterdam in the early 1970s and a second wave followed in the late 1980s and early 1990s. This second wave is not only defined by architectural height. The  Developing Rotterdam’s Skyline | 31

“Although commonly classified as a typology of high-energy demand, tall buildings can be beneficial in hot, humid climates. Considering both urban and building scales, the typology enhances the exposure of the built form to wind flow, generates more wind at the ground level and provides desirable shadows upon the immediate surroundings. ” Suraksha Bhatla & Joanna Gonçalves, page 24

CTBUH Journal | 2012 Issue II

Inside | 3

Case Study: Capital Gate, Abu Dhabi

Jeff Schofield Author Jeff Schofield, Associate RMJM Floor 27, Monarch Office Tower PO Box 6126 Dubai UAE t: +971 4 702 7626 f: +971 4 329 6444 e: [email protected] www.rmjm.com

Jeff Schofield Since moving to RMJM Dubai in 2005, Jeff Schofield has lent his design expertise to a variety of large scale building developments, including mixed use, hospitality and high-rise projects. As an Associate at RMJM, Jeff leads the effort in providing sustainable solutions to all design projects in the office. He has developed a holistic approach to design that integrates sustainability, structure and architectural expression with the built form, in order to provide meaningful solutions for high-quality building designs. Jeff seeks to design in a contemporary yet contextual manner, to create modern sustainable buildings using the latest technology. Jeff currently lives and works in Dubai. He began his career in New York City and pursued his professional practice for more than 15 years in Paris, France. He has project management and design experience on a range of high profile projects and has specific experience in sustainable design and project management of large-scale public projects throughout Europe, United States and the Middle East.

12 | 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. It is also the first building in the world to use vertical post-tensioning of the core to counter movement and support stresses created by the building’s overhang.” Throughout history, a strong link has existed between iconic architecture and exhibitions. One of the best known examples is Paris’ Eiffel Tower, which was built as a visual symbol of the 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 exhibitions. The Concept In 2005, the Abu Dhabi National Exhibitions Company (ADNEC) was created to drive forward the development of Abu Dhabi’s events sector. Plans were created with RMJM to build a state-of-the-art exhibition center which would be the largest in the Gulf region and provide world class facilities for live events to flourish in Abu Dhabi. It was strongly felt that the entire development required a signature tower, a cutting-edge structure with a futuristic design,

aesthetic splendor and technical excellence to celebrate human achievement and reflect the dynamism of Abu Dhabi. Capital Gate is the result. The tower’s curvaceous shape draws strongly on the sea and desert – two elements that have great resonance in Abu Dhabi. The building’s form is meant to represent a swirling spiral of sand, while the curved canopy, known as the “splash,” which runs over the adjoining grandstand and rises on one side of the building, creates a wave-like effect,

CTBUH Journal | 2012 Issue II

reflecting the building’s proximity to the water and the city’s sea-faring heritage. By integrating with the National Day Grandstand – one of Abu Dhabi’s most historic structures – Capital Gate underscores the bond between the traditional and modern that is characteristic of Abu Dhabi’s developmental approach.

• The vertical and horizontal cross-sections of the tower are all unique.

First of its Kind There are several innovations within the project’s design, including the dramatic 18-degree westward lean, which has earned it the title of “world’s furthest leaning manmade tower” from the Guinness book of world records (see Figure 1). 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. It is also the first building in the world to use vertical post-tensioning of the core to counter movement and support stresses created by the building’s overhang. The construction also adopted a variety of leading-edge approaches to create the desired result:

Figure 1. Typical section © ADNEC CTBUH Journal | 2012 Issue II

• Four hundred and ninety foundation piles were driven 20 to 30 meters underground to support the structure and counter stresses. The piles, which were initially in compression during construction to support the lower floors of the building, are now in tension as the stresses caused by the overhang have been applied.

• There is an asymmetric shape – no two rooms are the same (see Figure 2). Every one of the 12,500 panes of glass on the façade is a different size, although each pane is triangular. • Floor plates change shape and orientation to create the distinctive “overhang” moving from “curved triangular” to “curved rectangular,” while increasing in overall size and migrating from east to west as they progress up the tower. • Capital Gate is one of the few buildings in the world that use a diagrid structure; it also features two diagrid systems, an external diagrid defining the tower’s shape and an internal diagrid linked to the central core by eight unique pin-jointed structural members. • All 8,250 steel diagrid members are different thicknesses, length and orientation. 

Figure 2. Typical hotel floor plan © ADNEC Capital Gate, Abu Dhabi | 13

• Each of the 822 diagrid nodes (702 external and 120 internal nodes) is a different size and angular configuration. Capital Gate forms the focal point of the Abu Dhabi National Exhibition Centre complex and the Capital Centre master development, a connected group of 23 towers including branded hotels, commercial buildings, residential and serviced apartment complexes and developments for mixed use. These facilities are built overlooking an urban highway along the south-western shore of Abu Dhabi. Capital Gate dominates this waterfront site from its position at the western edge of the ADNEC complex, adjacent to the exhibition halls and connected to the historic National Day Grandstand. The tower stands out on the skyline; it is slightly removed from ADNEC’s high-rise development on the eastern side of the site. Due to the location, views from Capital Gate are extensive in all directions. The preferred views are out to sea and along the coastline. Views towards the city are becoming more impressive as Abu Dhabi grows around it. Capital Gate cuts a strong profile against this emerging skyline. Architectural Expression The ground-breaking form of Capital Gate is due not only to its lean, but also to its funnel shape. It widens as it spirals upwards and outwards. This gesture creates the dramatic sculptural form which is expressed architecturally in a variety of ways (see Figure

Figure 4. Double-height lobby lounge © Devita Villanueva 14 | Capital Gate, Abu Dhabi

3). The façade glazing emphasizes the organic elements with diagonals spiraling up along the structural diagrid. This weaving pattern is further broken down with individual panes of glass in a complex mesh wrapping the entire building. The sheer skin is interrupted only by two entrances on the ground floor, the footbridge to the car park, and the terraces at the top of the “splash.” The potentially monumental scale of Capital Gate is tempered by this “splash” sun shading on the south façade. This metal mesh screen at the lower half of the tower adds complexity to the overall form as it highlights the different uses of the tower – offices in the lower half and hotel in the upper half. Architecture is about space making, and the architects sought to express the drama of Capital Gate in its interior spaces. The hotel arrival is at the top of the splash on the 18th floor, where visitors discover a panoramic view of Abu Dhabi. The lobby lounge is a double-height space cantilevered beyond the tower diagrid (see Figure 4), providing a dramatic arrival for guests . The restaurant located on this floor is also a dramatic double-height space positioned where the tower form leans at the steepest angle. Due to Capital Gate’s unique shape, the upper half of the tower widens to create an atrium at the hotel’s guest room floors (see Figure 5 and 6). This space is perhaps the most surprising discovery the visitor finds inside the building. The atrium is funnel shaped and appears carved out of the solid form around it, spiraling and leaning along with the tower. It

Figure 3. Capital Gate’s organic shape © Devita Villanueva

is also expressed with a diagrid structure, informing its organic shape. While vertical in proportion, the atrium is intimate in scale. Light filters down from the large skylight roof above to create a serene environment. The Structure Capital Gate’s base structure is a vertical concrete core surrounded by a steel diagrid describing the external form of the tower. Steel beams span between the two, supporting metal deck and concrete

Figure 5. Hotel atrium, looking up © ADNEC CTBUH Journal | 2012 Issue II

Figure 6. Model section showing the funnel-shaped atrium © Jeff Schofield

Figure 7. External diagrid structure © ADNEC

Figure 8. The “splash” © ADNEC

composite floor slabs. Above the base, the atrium is formed with an internal steel diagrid attached to the core. Steel girders span directly between the external and internal diagrids, creating column-free floor spaces with typical spans of about 12 meters.

framing connections. The core has two innovative features:

The Capital Gate’s wind bracing is designed as a separate system. Abu Dhabi has light winds, which Capital Gate counteracts through a combination of a dense network of core walls and outriggers at the 17th floor mechanical level, connecting the core to the external diagrid. The tower’s round form and diagrid structure provide inherent resistance to torsion. At the ground floor, a massive concrete ring beam transfers the thrust of the diagrid into the foundations. It is noteworthy that Abu Dhabi is in a low seismic hazard zone, and the appropriate factors of safety and stiffness were applied for structural integrity. 

The external diagrid is composed of hollow square sections 600 x 600 millimeters on a side. They carry floors four meters high. Each diagrid member is a different length, depending on the angle at which it leans. The external diagrid elements are made from welded steel plates, 80 millimeters thick at the bottom floors, and progressively lightening to 40 millimeters at the top floors. The internal diagrid around the atrium is made of round steel profiles 400 millimeters in diameter, 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 for the façade panels to frame on the outside (see Figure 7). Designers studied these connection details extensively to optimize construction, as well as structural integrity. The concrete core occupies the only vertical space available in the tower profile. It has high reinforcement levels, especially at the steel CTBUH Journal | 2012 Issue II

• During construction a pre-cambered core was poured slightly off vertical, so when the tower floors were framed in to the opposite side, the added load straightened the tower. • A post-tensioned core was designed with vertical cables in one side tensioned to counteract the lean on the other side. These cables were installed in vertical segments that overlap each other every seven floors. Strung together, they span the entire height of the core to maintain it in a perfectly vertical position.

“

...water feature

Putting a water feature in a lobby gets you LEED points, but it doesn’t save energy, doesn’t improve the environment and it doesn’t change the world.

”

Anthony Malkin, President of Malkin Holdings, owner of the Empire State Building on the building’s 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 .

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The curtain wall units are made of two components: steel and glass. The steel framing was manufactured in Austria. The frame profile is triangular to take loads in all directions. The glass was made in the United Arab Emirates. It is a low-emissivity glass, very transparent, yet provides good thermal insulation and glare reduction. These components were assembled in Abu Dhabi into panels, which were transported to the site on over-sized flatbed trucks custommade to accommodate the large units.

Figure 9. Curtain wall diamond-shaped panels © Jeff Schofield

The sun shading for the tower is a lightweight metal mesh hung from the terraces on the 18th and 19th floors (see Figure 8). In turn, the terraces are cantilevered 12 meters from the tower. They are braced to the external diagrid with steel profiles reaching diagonally down to the plant floor level. At this same mechanical level, on the opposite side of the tower, the atrium internal diagrid framing is transferred to the core with steel profiles placed diagonally in sections. The plant floor at mid-height ties together all the primary structural elements of the tower. Façade Design Capital Gate’s cladding consists of two distinct elements – a curtain wall glazing system and metal mesh sun shading system. Both were installed by the same manufacturer in order to ensure close coordination between these interlocking systems and the steel diagrid to which they are attached. The curtain wall consists of diamond shaped panels stacked up floor by floor (see Figure 9). Each unit is two-floors high and one diagrid wide, about 8 x 8 meters on average. They follow the geometry of the structural diagrid, which carries their weight vertically. The panels are braced for wind resistance at the middle floor slab, which carries the horizontal load.

The metal mesh sun shading is made of light-weight metal framing with stainless steel wire mesh, 90% open. The “splash” is a flexible system designed to follow Capital Gate’s curving forms. It is braced to the tower every five floors with round steel profiles. There are cross-bracing rods every floor. The connections for these elements are located at each diagrid node and extend through the curtain wall joints to reach the steel structure. Above the ground floor, as the geometry turns from vertical to horizontal, steel tree structures reach up to hold the splash form in place. Façade maintenance is performed in various ways. The curtain wall elements are repaired and replaced from the inside, cleaning is from the outside via abseiling, and lightweight sun shading elements are repaired via abseiling. It is common in the Middle East to use abseiling, a form of rappelling for external building maintenance (see Figure 10). Capital Gate has eye-hooks in the curtain wall joints at every node, so the abseilers can hoist themselves close to the overhanging surfaces. Inside the splash, abseilers maneuver between the braces and rods to clean both glass and mesh at the same time.

architects and engineers integrated many passive and active sustainable systems into Capital Gate, including metal mesh sun shading, a double skin façade, highperformance glazing, reduced amount of materials, vegetated roof on the basement, low-flow water fixtures, district cooling, variable speed air conditioning, heat exchange for ventilation, and energy monitoring and controls. Capital Gate’s most visible feature is the “splash,” which twists around the building towards the south to shield Capital Gate as much as possible from direct sunlight. The metal mesh eliminates 30% of the sun’s heat before it reaches the building, reducing the air conditioning load on the protected floors. It also provides outdoor shade to the main entrance on the ground floor. The upper half of the tower has a double skin façade to reduce the solar heat gain at the hotel levels. This is a modified double façade, which recycles interior air from the guest rooms into the façade cavity. Here it creates an insulating buffer between the hot outside air and the cool inside air (see Figure 11). The air is re-used in the room rather than exhausted and replaced with outside air. The glass used on Capital Gate’s façade is a low emissivity glass never before used in the United Arab Emirates. It’s designed to keep the inside of the building cool and eliminate glare, while maintaining the transparency of the façade. Capital Gate’s organic shape also lends itself to savings in construction materials, in several ways, despite the lean. Its rounded form is

Sustainable strategies ADNEC is committed to being one of Abu Dhabi’s leaders in sustainable development. From the beginning of concept design, the Figure 10. Façade maintenance via abseiling from the outside © ADNEC

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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 fully-operational airport check-in facility.

Figure 11. Double skin façade system © Jeff Schofield

aerodynamic, presenting less resistance to the wind than a rectangular building, thereby requiring less structure for lateral loads. The round perimeter encloses space more efficiently than a rectangle, so less façade surface is needed than for a conventional floor plate of identical area. The result is that fewer materials are required for structure and façades. This is a reduction in concrete, steel and glass, materials which all have high carbon content and embodied energy. Landscaping around Capital Gate creates a vegetated roof over the basement, increasing the thermal insulation and reducing the need for air conditioning. Native plants are used, which require less irrigation than conventional landscaping. To further reduce potable water use in this desert context, low-flow water fixtures are installed in the public areas and washrooms, including WCs and faucets. District cooling is provided by Abu Dhabi Municipality, a more energy-efficient means of obtaining chilled water than installing chillers on site. The chilled water is distributed by variable speed pumping, which reduces energy use in operating the air conditioning. Heat recovery wheels reduce energy use for ventilation by exchanging hot and cool air during the intake and exhaust process. Energy monitoring and controls in the Building Maintenance System further reduce energy use by implementing efficient operation of lighting, air conditioning and other powerconsuming and heat-generating functions. CTBUH Journal | 2012 Issue II

Partnering Solutions The huge technical challenges that had to be confronted in bringing Capital Gate to life have been overcome through a structured partnering program. It is a fairly unusual technique in this part of the world, which ADNEC has employed with much success on all of its construction projects. Essentially, all the key organizations working on a project are located together in one location. The architect sits next to the project manager, who sits next to the quantity surveyor, who sits next to the contractor and the rest of the team. The objective is simple: to remove confrontation and create a single team mentality with one single goal – to get the project completed in the most effective way. JCP International, the partnering consultants who worked at a strategic level with the joint leadership team, worked from the project and construction management level to the front line supervisors and staff to instill a culture of collaborative working within and across organizational boundaries. Conclusion While clearly a unique structure was built using some of the world’s most advanced construction techniques, ADNEC believes the tower’s appeal goes far beyond an architectural and engineering marvel. Functionality and purpose have been a prime focus.

The Guinness world record for “world’s furthest leaning manmade tower” has shone a spotlight on Capital Gate and Abu Dhabi, as has a “Megastructures” documentary on National Geographic Channel (“The Leaning Tower of Abu Dhabi”), broadcast in more than 166 countries to an estimated television audience of more than 200 million. The people of Abu Dhabi feel a sense of honor in Capital Gate. They are confident Capital Gate’s aesthetic splendor and technical achievement will generate admiration and discussions around the world for years.  Project Data Completion Date: 2011 Height to Architectural Top: 165 meters Stories: 35 Total Area: 53,100 square meters Primary Uses: Hotel/Office Project Developer: ADNEC Group Architect: RMJM Structural Engineer: RMJM MEP Engineer: RMJM Façade Consultant: Hyder Consulting Landscape Consultant: Al Khatib Cracknell Main Contractor: Al Habtoor Engineering Steel Contractor: Eversendai Façade Contractor: Waagner Biro Project Manager: Mace

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