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Project Profile

 

2005 Jury Commendation for Innovation

Meridian Gate Exhibition Hall

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Project Title: Meridian Gate Exhibition Hall of the Palace

Location: Beijing, China

Size: 1,000 square metres

Cost: Approximately US$ 3,000,000

Responsible Party: Lang Hongyang

Client: Palace Museum

Heritage Architect: Lang Hongyang, Shi Xudong, Zhu Yingxing, Li Xiaofeng, Chen Xing, Tan Zhongbo, Cao Li, Xu Weiguo, Wu Wenjian and Suo Yongfeng

Contractor: Engineering Management Department, Palace Museum

Date of Completion: March 2005


Jury Citation

The construction of a modern exhibition hall located within the historic Meridian Gate building of the Imperial Palace complex is exemplary for its innovative technical and design solutions that have enabled the space to meet international museum standards. The choice of a contemporary architectural vocabulary provides an effective counterpoint to the vernacular timber structure, and indeed, serves to highlight the building’s heritage values. The self-effacing sealed glass box that encloses the exhibition space demonstrates tremendous respect for and enhances the understanding of the historic building, while at the same time provides ideal conditions for sophisticated climate control. The project demonstrates how the application of modern engineering principles results in an honest and direct architectural solution. The project has demonstrated that through innovation, a perceived dilemma of having to adapt a historic building to house an important artefact collection can create a win-win situation: a formula that can serve as a model for others facing similar challenges.

Context

The Imperial Palace in Beijing, also known as the Forbidden City, was the symbolic and administrative centre of two dynasties, the Ming (1368–1644) and Qing (1644–1912). The palace was converted into a museum in 1925 and is today known as the Palace Museum. 

Built in 1420, Meridian Gate (Wu Men) is the southern entrance to the Imperial Palace. Meridian Gate is the largest of the four gateways of the palace and is a two-storey building composed of several halls built above the entryway to the palace. The main building is 60.5 metres in length and 25 metres wide and is flanked by two small towers: a bell tower and a drum tower. In its entirety, the Meridian Gate building is in the shape of a phoenix unfolding its wings, and features five doorways, so the structure is also known as the Five-Phoenix Tower. In this hall emperors would issue the lunar calendar for the following year and receive captives after war. Special ceremonies were also held here to celebrate important holidays and demonstrate the supreme reign of the emperor.

Project History

In 2000, the Palace Museum decided to construct a modern exhibition space inside the main hall of Meridian Gate. Preliminary research and layout planning for the exhibition hall began in November 2000 and was completed in January 2001. Following significant modifications and improvements, the design was finalized in June 2004. Construction began in September 2004 and was completed by March 2005.

Project Scope and Framework

The project aimed to ensure the safety and integrity of exhibited artworks and create a comfortable environment for visitors. The exhibition hall covers an area of 1,000 square metres, including the display area; housing for air-conditioning, located at the two ends of the main hall; an electricity and fire-alarm room, situated close to the east end of the main hall; and a VIP room and service room, located on the west end of the main hall.

Design and Materials

Although located within the main hall of Meridian Gate, the exhibition space has been designed to be structurally independent and can be dismantled in the future, if necessary, restoring the main hall of Meridian Gate to its original appearance. The new installations have no direct impact on the building, except for the load of their weight. The designers adopted a lightweight structural system to obtain the necessary mechanical properties and deal properly with issues of load. Throughout the construction work, the project’s designers were careful not to impact the historic structure. The process of designing the exhibition space began with thorough assessments of mechanical needs, necessary structural security and an appraisal of the types of lightweight building materials that might be employed. After comparing the features and pricing of titanium, aluminium alloy and steel, especially their strength and fire performance, the design team decided to use high-strength steel for the main frame of the exhibition cases and aluminium alloy for the other parts. The team employed a system of self-balanced cables attached to the steel frame to reinforce the structure and solve the problem of beam deflection.

The overall design intent was maximum transparency, so glass was used for the roof and walls of the exhibition enclosures. The column footings of the steel structure are adjustable to ensure stability. The total load of the new interventions, which includes the art objects, exhibit stands and cabinets, tests well below the calculated safe load of the historic building. In addition, the design of air-sealing for the exhibition hall has minimized carbon dioxide emissions and thereby minimized any potential damage to the original building and its artworks. The air-conditioning equipment, including the condenser units, was installed inside the main hall so that the supply-air ducts and return-air ducts do not interrupt the enclosure walls of the original building. The supply-air is channelled through the hollow floor via an isotactic pressure box, thereby allowing for an open view of the exhibition hall’s ceiling.

The designers for the project paid particular attention to the installation of the electrical system, including the lighting for the displays. They were guided by published guidelines on the maintenance of cultural relics. To illuminate the main hall, lighting technicians installed directional lights and also placed floodlighting at strategic points. Floodlights illuminate the original ceiling frescos and the decorated columns, thus emphasizing the historic elements within the building. Illumination is also focused on the space above the roof of the exhibition hall in order to underscore the relationship between the exhibition hall and the main hall. Track lighting on the ceiling directs light to individual objects on display, and central controls allow for adjustments to the intensity of the lighting.

Important Issues

One disadvantage of the ancient building is its poor heat retention, so the indoor temperature fluctuates as with changes in the temperature outside. The optimum temperature for the artworks exhibited in the hall is 20 degrees Celsius, with humidity of 55 percent. Installation of an air-conditioning system to control the indoor temperature and humidity, so as to protect the items on display, was therefore an important component of the project. The combination of the air-conditioning system with the glass walls of the exhibition space serves to maintain ideal temperatures.

The glass walled enclosures effectively divide the interior of the hall into two volumes. The space between the historic main hall and the glass walled enclosures is called the transition space. In the transition space, the air-conditioning system maintains a stable temperature and eliminates impacts from the outside temperature by transferring the heat generated by people and equipment in the exhibition hall to the outside. It also stabilizes the humidity level within the enclosed area. The relative humidity inside the exhibition spaces is controlled at 40 per cent below the level outside the glass walled enclosures.

As the main hall of Meridian Gate is a wooden structure, there was some concern regarding the potential impact of air-conditioning on the ancient building. An investigation revealed that over the building’s centuries of existence the physical characteristics of the building’s wood had reached a stable state, with relatively low humidity levels. Experts concluded that the new air-conditioning system would therefore have no deleterious impact on most of the older wooden elements. To protect the vulnerable “golden columns” of the main hall, however, technicians added a special surface coating to prevent changes in the relative humidity level, thus ensuring minimal impact on the decorated surfaces.

Project Impact

One of the first large-scale projects at the Palace Museum aimed at integrating modern facilities into one of its historic buildings, the project expanded the function of the palace through the provision of a well-functioning exhibition space. The project married modern technology and heritage conservation in ways that illuminate the important heritage values of the building and its contents, and reinforce visitors’ appreciation of the past and its Transparency was an important design feature therefore glass relationship to the present.

Quote from the Project Team

“The structural design of the exhibition hall is designed to maintain the intactness and mechanical behaviour of the original building structure and, at the same time, meet with the requirements of a modern exhibition hall.”