From the onset of the Shanghai World Financial Center project, its developers targeted a cutting-edge, mixed use mega-complex that would serve a multitude of tenant lifestyle demands. When a desire to change the building size surfaced after the foundation was put in place, it was up to the structural designer to come up with a new approach to the building systems in order to keep the project on track. Following a substantial and fast-paced reconfiguration of the building’s structural design, the project team achieved a taller building without compromising the capability of the original foundation to support it. A discussion of the design process of the building and its cutting edge features follows.
Strategically located in the heart of Pudong’s Lujiazui district, an area that has emerged as China’s commercial and financial capital, the 492 meter Shanghai World Financial Center (SWFC) has become a symbolic icon of Shanghai. This 21st century vertical city symbolizes Shanghai’s status, China’s arrival, and a new era unfolding in Asia. It has become a destination where people from around the world come together to enjoy and to share a wealth of information, knowledge, and culture, as well as a place to explore new business opportunities.
In an effort to reduce commuting time and urban sprawl, projects like SWFC increase density and conserve valuable land. People can live, work, and play within the same area. Vertical complexes can accommodate these urban lifestyles, embodying a density that greatly enhances their accessibility.
|Figure 1. Floor Plan Diagram |
The tower’s basic form is that of a square prism, 58 meters on a side, intersected by two sweeping arcs to form a vertically-evolving six-sided shape in plan, ultimately tapering into a single diagonal line at the apex, 492 meters above the base.
The building is mixed-use, with a museum and sophisticated urban retail spaces at the base, a 174-room luxurious five-star hotel at the top, and sixty-two office floors with cutting-edge specifications between. Above the hotel, at the 94th to 101st levels, there is a visitor’s center and observatory. Much of the available space on the three floors below grade is devoted to mechanized parking.
|Figure 2. Lobby Approach |
|According to the developer, Mori Building Company, the tenants are world-renowned financial institutions. |
In order to provide these business people with entertainment and recreation opportunities after working long hours, this project will include restaurants, shops, and entertainment facilities. A multi-use project like SWFC will provide a more human-oriented place for people working in this ‘city within a city’.
The original designs began in 1993, with development by Mori Building Company, and with Kohn Pedersen Fox Associates (KPF) as the Design Architect. Following the completion of conceptual structural designs by Arup, New York, all design work, but for Architecture, then moved to Tokyo to be completed locally by the Shimizu Corporation.
||By 1995, the piling had been tendered and installed. Making use of reusable followers, about two hundred concrete-filled steel pipe friction piles were driven at minimum spacing to a depth of 78 meters from the ground surface. Pile cut-off was at the anticipated bottom elevation of the mat at 17.5 meters (58 feet) below street level. Steel H-piles extend from some of the piling to the ground surface, which were to be used for subsequent top-down construction, providing temporary vertical support for the below-grade concrete floors. (LERA) was approached by Nippon Steel Corp. with the goal of providing a lower-cost, faster-to-construct structural system for adoption prior to tendering of the structural steel. Structural designs were completed by LERA in sufficient detail for tendering; however the project was subsequently placed on hold.|
|Figure 3. Facade Detail |
|With the resurrection of the project in 1999, and with the foundation piling already in place, Mori Building Company initiated an extension to the overall height of the building from the previous 460 meters (1,509 feet) to 492 meters (1,614 feet) and an enlargement of the base dimension had been increased from 55.8 meters (183 feet) to 58.0 meters (190 feet) square. The exterior appearance of the proposed building remained essentially unchanged in subsequent design iterations.|
In order to address the looming challenge of building a taller tower atop an existing piled foundation sized for the previous design, Mori Building Company approached LERA seeking an alternative design to that contained in the preexisting construction documents. In part because the pile cut-off was well below grade and in part due to non-engineering considerations, the cost of reinforcing the existing piling was high.
|LERA determined that the installed pile foundation could accept a larger building, but only by decreasing by more than 10 % the weight of the original building and by re-distributing the loads to the piling so as to accept the increased lateral loads from wind and earthquake.
A New Structural System
In order to decrease the weight of the building, the majority of that decrease had to be found in a reduction of the thickness of the concrete shear walls of the services core. This reduction was achieved by decreasing the wind and earthquake-induced lateral forces resisted by those walls. That decrease was found by significantly increasing the stiffness of the lateral force resisting system of the perimeter wall and by decreasing the stiffness of the concrete walls of the services core.
Accordingly, abandoning the Developer’s original design which included perimeter framing elements (that of a Vierendeel moment-resisting space frame), LERA instead proposed the resurrection of its 1995 design: a diagonal-braced frame with added outrigger trusses. KPF, LERA, and Mori Building Company worked closely together to incorporate this new structural system into the existing architectural form.
||Figure 4. Model showing the mega-structure system|
| The change enabled a decrease in the thickness of the services core shear walls as well as a decrease in the weight of structural steel in the perimeter walls. Further, by making use of outrigger trusses coupled to the columns of the mega-structure, a further reduction was realized. |
Driven by the architectural form and by the limitations of the existing foundation piling, the new structural system reduced the cost of the structure and provided for speedier construction. KPF was able to capitalize on the presence of the outrigger trusses by incorporating them into the architectural design of the sky lobby floors.
Seeking to improve the quality of office spaces located on each of the four orthogonal faces, the new structural system decreased the perimeter framing from the seventeen wide columns of the moment-resisting frame to a maximum of just three narrow columns. Depending on the breadth of the two sloping faces, there is at most only one narrow column along its width. Hence, building occupants are provided with an extraordinary sense of openness and unparalleled views of the surrounding city of Shanghai.
|Figure 5. Building's top |
|The mega-structure is displayed subtly behind the facade of the building. Architecturally founded on a heavy stone base, the mega-structure gives the impression of both strength and of permanence. Indeed, it is one of the goals of both KPF and Mori Building Company to communicate these two attributes while retaining the elegance of the architectural form.|
At the time that this project was initiated, Green Technology was not mainstream. Currently, it is the guideline of choice. As the project is now advancing, SWFC will apply green technology to its interiors, such as formaldehyde-free carpet tiles throughout the entire building. A recycling system will be used by the tenants building-wide, along with education on how to become more recycling-conscious. The HVAC system will be variable air volume. Each floor will contain multiple zones for tenant comfort along with high efficiency.
|Figure 6. Observation deck|
The Shanghai World Financial Center reflects the creativity and passion of many individuals, all with the common goal of providing a place in which people are encouraged to meet and mingle, share ideas, and give birth to new knowledge, culture and values.