Integrating Modern Skyscrapers into Historic Cities: The Shard's Success Story
Introduction:
The Shard and The Place at London Bridge are groundbreaking projects by Sellar Properties / Qatari Diar, designed by the acclaimed architect Renzo Piano. These projects highlight the intricate balance engineers and architects must strike to preserve the character of historic cities while introducing the tall building phenomenon. By working within the ancient street layout of Southwark, these buildings illustrate how modern development can rejuvenate historic areas without compromising their unique character.
Balancing Modernity with History:
One of the foremost challenges of erecting tall buildings in historic cities is maintaining the delicate and permeable nature of streetscapes. Traditionally, architectural development has often neglected the interaction between tall buildings and ground-level life. However, contemporary designs now prioritize the impact at ground level as much as the skyline, ensuring that new constructions integrate seamlessly into the urban fabric. The Shard and The Place are prime examples of this approach, contributing positively to their surroundings.
Urbanization and the Need for Tall Buildings:
As urbanization accelerates globally, there is an increasing need to utilize space efficiently. Tall buildings offer a practical solution by providing vertical space for living, working, and recreation. Engineers play a critical role in designing these structures to meet the diverse needs of urban populations while respecting the historical and cultural contexts of their locations.
Streetscape Integration:
Effective integration of tall buildings into historic cities requires meticulous consideration of street design and public spaces. Analyzing different street typologies and public realm treatments helps create balanced streetscapes that accommodate pedestrians, public transport, and traffic. The concept of the "vertical city" is gaining traction, emphasizing mixed-use tall buildings that offer spaces for living, leisure, shopping, and working. The Shard, for instance, includes winter gardens on each office floor, enhancing the environment for tenants and integrating green spaces into the urban landscape.
Addressing Underground Infrastructure:
Constructing buildings on historic inner-city sites often involves navigating a complex web of existing ground-level and underground infrastructure. At The Shard, the foundations were impacted by piles from the previous Southwark Towers, a 26-story building. New piles had to be designed to navigate around the old ones while avoiding extensive underground utilities, including London Underground tunnels and Victorian water mains. Advanced 3D finite element analysis and real-time monitoring were crucial in managing the ground movement and ensuring the safety of surrounding infrastructure.
Managing Archaeological Challenges:
The potential presence of archaeological artifacts presents significant challenges for construction in historic cities. Excavations must be meticulously inspected, which can delay construction schedules. At The Place, the team minimized risk by reducing the basement depth by utilizing Building Information Management (BIM) to efficiently adjust plant positions. Top-down construction was employed to allow simultaneous above-ground and below-ground work, mitigating delays due to archaeological digs.
Innovative Construction Techniques:
Both The Shard and The Place employed innovative construction techniques to overcome site constraints. At The Place, the building's frame was cantilevered outwards to maximize air space while leaving underground infrastructure unaffected. Raking columns extended from the cores to the façades, creating a robust triangulated structure. At The Shard, the spire was constructed using modular techniques, allowing rapid and safe assembly despite the lack of lay-down space at ground level.
Utilizing Modern Modeling Techniques:
Computer modeling is central to realizing complex projects. At The Place, non-linear analysis helped understand asymmetrical load impacts, while BIM facilitated efficient design and construction processes. These techniques enable developers to address the economic and physical challenges inherent in historic cities, ensuring that new buildings complement rather than dominate their surroundings.
Navigating Complex Underground Challenges:
The Shard's foundations had to maneuver around old piles from the Southwark Towers and existing underground utilities such as the London Underground’s Jubilee Line tunnels, Victorian water mains, and other subterranean infrastructure. Through meticulous 3D finite element analysis and real-time monitoring, the engineers managed to predict and control ground movement, ensuring safety and stability. Additionally, innovative techniques like plunge columns and top-down construction allowed simultaneous above and below-ground work, efficiently tackling the constraints of the site.
Architectural and Structural Innovation:
The architectural vision for The Shard as a "vertical city" required a blend of large floor plates for commercial spaces and smaller, intimate layouts for residential and hotel uses. This vision influenced the choice of materials and structural systems. Lower floors used steel framing for large spans, while upper floors utilized post-tensioned concrete to allow for smaller spans and added structural damping, reducing the need for a tuned mass damper.
Sustainability and Modern Techniques:
Utilizing Building Information Management (BIM) allowed for innovative solutions like the reduction of basement levels at The Place and the efficient placement of plant rooms. BIM also played a crucial role in integrating the complex layout of the building with the existing underground infrastructure, minimizing the need for post-construction adjustments. These modern techniques not only enhanced the efficiency and cost-effectiveness of the construction process but also ensured that the new structures would harmonize with the historical context of their surroundings.
Enhancing Public Spaces and Perception:
Both buildings emphasized the importance of integrating public spaces and enhancing the pedestrian experience. By including features like winter gardens and public observation decks, they create welcoming environments that invite interaction and engagement, blending modernity with historical charm.
Successfully integrating modern tall buildings into historic cities is a challenging but achievable endeavor. The Shard and The Place demonstrate that with careful planning, innovative engineering, and respectful design, new developments can enhance urban character and contribute to its vitality.