• Document: Structural Design Challenges for Plaza 66 Tower 2
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Structures 2008: Crossing Borders © 2008 ASCE Structural Design Challenges for Plaza 66 Tower 2 Authors: Dennis C.K. Poon P.E., Managing Principal, Thornton Tomasetti, Inc. dpoon@thorntontomasetti.com Ling-en Hsiao, PhD, Principal, Thornton Tomasetti, Inc. lhsiao@thorntontomasetti.com Steve Zuo, PE. Associate, Thornton Tomasetti, Inc. szuo@thorntontomasetti.com Yi Zhu, MSSE: Principal, Thornton Tomasetti, Inc. yzhu@thorntontomasetti.com ABSTRACT: The Plaza 66 Tower 2, recently completed in Shanghai, China, balances the demands of structural engineering, architectural vision and construction constraints. This is a 46-story concrete moment frame and core wall structure. The unique design by architect KPF posed many engineering challenges to be resolved. Although modern computer technology allows for precise analyses and design of various systems for high-rise buildings, it does not readily provide insight for choosing among the alternative systems to arrive at the best overall design. This paper presents our design and analysis process, from the conceptual phase to detailed design, during which we resolved the following engineering challenges: (1) Determining and mitigating effects of pile mat foundation differential settlement, addressed through multiple stages of finite element analysis models. (2) Determining a cost-effective structural system by developing multiple options, using approximate analysis, and a cost comparison database. (3) Designing a curved 65 m (215 ft) long span steel bridge between two towers, an important architectural and functional feature. (4) Designing and detailing another important architectural feature, a two-way sloped steel cantilever thin steel lantern, using a three-dimensional structural information model to help both analysis and accuracy in connection details to benefit all members of the project team. 1.0 INTRODUCTIONS Plaza 66 Tower 2 is the new addition to the Plaza 66 Tower 1 project in Shanghai, China. Tower 1, with a height of 281.5-m (925-ft) and 62- stories, which was completed in 2001, is the tallest concrete building in the Pu Xi area. Tower 1 has a five-story retail podium and three levels of below-grade parking. Together the complex forms a three-million square-foot mixed-use commercial development. (See Figure 1) Tower 2 is adjacent to the existing Tower 1 and its podium. Tower 2 was completed in 2006, a 46 story tall building reaching 223.5 m (735 ft) high. The structural system is a concrete moment frame with concrete shear walls. Tower 2 has three below-grade podium parking levels connecting to existing below-grade parking levels. Finding the most appropriate structural solution for Tower 2 to fulfill a given set of performance requirements required a complex, multi-disciplinary process. This paper explores the design challenges of the tower and the solutions found for poor foundation conditions in a Structures 2008: Crossing Borders © 2008 ASCE seismic and typhoon area, settlement effects on the new tower and the existing tower on site, a curved bridge connecting between two towers and a complex steel roof lantern with two-way slopes. 2.0 PROJECT DESCRIPTION Plaza 66 Tower 2 is in the Shanghai Pu Xi Business District. The West boundary of the tower is Xi Kang Road. South and East of Tower 2 is the Plaza 66 Tower 1 complex completed in 2001. The current project footprint is approximately 6,800 sq. meters. Tower 2 is a 46 story structure with a three level basement to be constructed on site. (See Figure 2) Tower 2 is approximately 235 m (735 ft) tall, with a comparatively small 40 m by 69 m (131.2 ft by 223 ft) footprint. At levels 13 and 14, a two-story curved pedestrian bridge connects with existing Tower 1. At level 45, partial shear core walls with four super composite steel columns standing on four one-story high concrete transfer girders lift the steel roof lantern 43.5 m (142.5 ft) towards the sky. Tower 2 Tower 1 FIGURE 1 - PLAZA 66 TOWER 2 (NEW) AND TOWER 1 (EXISTING) Where three underground parking levels connect to adjacent existing underground parking levels, special details were developed to permit removing a temporary slurry wall between the existing structure and new structure while maintaining the same floor elevation. The tower stand

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