The construction effect chart © KPF
Jinan Ping An Financial Center is located in the core area of Jinan Central Business District, with a total construction area of about 226000 square meters and a height of 360 meters. It is another urban complex integrating Grade A office buildings and commercial shopping centers in Quancheng. It took 6 years to build, and the project was officially completed recently, adding light to the urban skyline of Jinan.
The project is invested by Ping An Real Estate, the architectural design is in the charge of American KPF Architecture Firm, and Arup provides structural and curtain wall design consulting services, driving high-quality design with rich experience and digital advantages, and creating a future oriented commercial space for the city.
01. Massive research and evaluation verification
Realize irregular elevation
Focusing on the image of "river", the project adopts the design language of vertical smooth and flowing changes to create a flexible architectural shape. The facades of the building are all glass curtain wall systems, with constantly changing surfaces converging upward. The middle section of the tower is retracted from bottom to top, and the base and tower crown are straight sections.
The construction effect chart © KPF
The four corners of the outer facade of the tower are made of curved glass, presenting a smooth and warm architectural appearance. For the adduction tower body, the glass plate inclines inward, and there are many irregular separations in the groove and corner areas. The design team of Arup curtain wall closely cooperated with the architect to conduct detailed analysis and optimization of the BIM model of the external skin, which greatly improved the convenience and economy of construction.
BIM analysis of special areas © Arup
The team carried out professional research on the image optical distortion of curved glass, adjusted the corner curved glass from a cone to an inclined cylinder, and optimized the application of curved glass in the project by selecting appropriate arc radius and reflectivity, achieving a balance between the architectural appearance and the user's indoor observation comfort.
Corner arc glass model © Arup
Arc corner diagram of visual model © Arup
The groove area is more complex: due to the difference in the tilt angle of the side plates, there are many irregular shaped plates and unreasonable separation, which brings great difficulties to the processing and production. In combination with model analysis and node design, curtain wall engineers fine tune the vertical separation locally, and adopt adjustable angle profile system, which improves the utilization rate of profiles and saves costs on the premise of satisfying the appearance effect and convenient construction.
Scheme design of groove inclined parts (outward and inward inclination) © Arup
02. Multiple structural system design
Dealing with extreme environmental tests
The super high-rise structure system should not only bear its own gravity, but also be tested for wind resistance and earthquake resistance. Seismic action and wind load are the main control loads affecting lateral displacement and horizontal torsion in structural design. Referring to the wind tunnel test results, the wind load design value of the main tower is selected on the basis of the code value to ensure that the building structure has sufficient capacity to bear and resist deformation.
At the same time, the team considered the multi-level seismic effects of frequent earthquakes, fortification earthquakes, and rare earthquakes, and adopted a multiple lateral force resistant structural system formed by "steel reinforced concrete outer frame reinforced concrete core tube outrigger truss", greatly improving the overall safety and structural efficiency of the building.
Schematic diagram of main tower structure system © Arup
The design team used the electromechanical/refuge floor of the tower to set up three strengthening floors. In the strengthening layer, we set a closed ring steel truss along the circumference of the outer frame column to improve the overall stiffness of the outer frame. In addition, the floor beams and floors connecting the outer frame and the inner tube are strengthened to improve the horizontal force transfer efficiency of the structure.
Structure Diagram of Main Tower Reinforcement Floor © Arup
Through comparative analysis of structural optimization schemes, the team only set two-way outrigger steel truss at the most effective second strengthened floor to connect the outer frame column and the inner core tube, thus reducing the structural cost and facilitating the construction speed. The steel truss is continuously arranged inside the concrete core tube, further strengthening the tie linkage between the outer frame and the inner core tube, improving the collaborative work efficiency and common lateral resistance of the internal and external systems, thus forming a more cost-effective structural system.
The pile foundation type of the main tower adopts large-diameter reinforced concrete rock socketed piles. In view of the karst geological characteristics in this area, special countermeasures such as advance drilling construction survey and karst grouting reinforcement are taken to ensure the safety of the foundation design.
03. Special design of tower crown and connecting bridge
The glass curtain wall around the tower extends upward from the main house to form a 38 meter high tower crown. The inner core tube of the tower extends about 26 meters upward from the main house, and the design function includes the machine room and the top helicopter apron. Using the space between the inner tube and the outer curtain wall, the architect specially set up a leisure green plant area to create a sky garden.
In order to support the glass curtain wall, the external vertical space steel truss structure system is adopted in the structural design. The design team has set up two layers of steel beams between the internal and external steel structures, which can not only serve as a tie, but also serve as the supporting structure of the roof building envelope hoisting system (BMU), and help the project to save materials and reduce carbon with efficient structural design.
Sketch map of commercial bridge © KPF
Schematic Diagram of Commercial Link Bridge Structure and Analysis of Deck Vibration © Arup
Basic analysis model
Between the commercial podium and the podium on the adjacent plot to the south, there is a double deck commercial bridge with a length of 38 meters. The connecting bridge is of space steel truss structure, and the outdoor viewing platform is overhanging on both sides of the first floor deck, with the longest overhanging distance of 7.8 meters. The team adopts the structural scheme of not setting up columns, which is connected to the commercial podium on both sides through sliding bearings. The bridge deck on the top floor is open to the air, with green flower beds and pedestrian rest areas arranged, which are ingeniously connected with the podium roof gardens on both sides, forming a flowing and changing linear green space in the air.
Through finite element analysis, while ensuring that the bearing capacity of the components of the bridge and the deflection deformation of the long-span structure meet the design requirements, Arup focuses on the floor vibration in the end area of the bridge span and the overhanging viewing platform to ensure a comfortable pedestrian experience in these areas.
04. Application of parametric model
Collaborative optimization of super massive structural space
The height of the main tower is 360 meters. The facade gradually retracts along the height and presents a concave shape. The structural space of each floor changes accordingly. In order to maximize the indoor office space, the design team fully considered the impact of structural beams and columns. With the building shape changing layer by layer, the outer frame columns of the tower were pushed outward toward the curtain wall as far as possible, so as to reduce their obstruction to the internal space.
Therefore, the structural plane layout of each floor of the tower is also different. The positioning of structural columns and beams changes layer by layer, which needs to be constantly adjusted with the deepening of the building scheme, resulting in a huge amount of structural adjustment work.
Basic analysis model
Schematic diagram of main tower parametric model © Arup
At the beginning of the design, the Arup team introduced the self-developed Ovabacus digital module and parametric design process, which are used to quickly establish and iterate the structural geometry and analysis model, and can cooperate with the changes of other professional schemes to provide timely structural scheme comparison and design feedback.
In addition, this digital model can also be connected with the BIM platform system, improve the efficiency of drawing management, and lay a good foundation for the subsequent deepening of construction drawings and BIM management in the construction phase.
