XinY structural consultants ltd 袁鑫工程顾问（上海）事务所

The museum is located at the entrance of a new cultural park situated on the outskirts of a small town. It integrates functions such as a visitor center, restaurant, chocolate exhibition area, etc. The building is built on an artificial lake situated between a river and hills, extending from one end of the lake to the other, with a length of about 885m and spans ranging from 4.615 to 19.750 meters. The structural system is steel bent structure, all column sections are 140x250mm slender and clad with 50mm thick concrete facing.

The double-curved roof is supported by steel columns rising from the bottom of the lake. The elevations of the cornice range from 1.046~4.848m, undulating up, down, left and right over the water.

The lightweight structure harmoniously integrates with nature, rendering the building itself a seamless part of the landscape and environment.

There are glass curtain walls on the north and south sides of the building. Each bay is divided into three pieces of glass of equal width. The heights vary with the undulations of the roof, and the maximum glass is over 4.8m high without frames and stiffeners, giving a transparent effect. Lake water can flow into the building through the gap under the glass.

The surrounding nature is introduced indoors, allowing people, the building, wind, sunshine, lake, trees, insects, and distant mountains to coexist. It’s creating a truly unique experience. Even when the lake freezes in winter, the water beneath the glass continues to flow.

About half of the indoor area is water, and the sandbanks are connected by winding paths. People, especially children, like to squat and play by the shallow water in the sun.

During the hot summer months, when the glass panels are fully opened, the wind ruffles the surface of the water, and the sunlight is reflected to the ceiling, making the light and shadow mottled. Meanwhile the indoor and outdoor water can also flow through the gaps under the glass to naturally adjust the building's temperature and reduce energy consumption. In extreme climates, the performance-oriented air conditioning system focuses solely on regulating the areas where people are actively present, creating a comfortable small environment without trying to change the temperature and humidity above the water, saving a lot of energy and operating costs.

The building plan consists of curves, and the roof is a two-way free-form surface, which makes all steel columns and steel beams different. Parametric design improves the efficiency of all parties involved. The architectural scheme necessitated thin columns and roofedges, making steel structures a suitable choice due to their stress-bearing capabilities. The 50mm thick fair-faced concrete exterior not only achieves the effect expected by the architect, but also avoids the need for anti-rust work on the steel structure during operation, making the entire structure almost free of maintenance costs.

This is a cross-border collaborative design and research initiative. Despite its immense scale, it is intentionally designed to be user-friendly and environmentally friendly, aiming to boost the local culturaltourism industry and win the hearts of property owners, tourists, and locals alike. The project has garnered significant media coverage, resulting in an increase in business volume for some participants. Their technology has advanced, and their reputation has been enhanced.

Anti-cracking of ultra-large (20mx18m) and thin (50mm) concrete ceiling
The entire length of the building features concrete slabs as indoor ceilings, with 6mm wide gaps set every 18m. The maximum size of a single ceiling panel is close to 20mx18m. To prevent cracking in oversized concrete slabs, we incorporated a two-level pre-cambering design.The curvatures of steel beams and thoese plates are all parameterized differently. The ceiling concrete formworks are pre-bent downwards, and the bending values are based on the deflection value that will occur under the roof and ceiling loads. After 28 days of the concrete pouring, the ceiling is lifted upwards from the formwork by tightening the regulating bolts, returning it to the desired finish lines of the design. This ensures that the lower surfaces of the ceiling are always under compression, thus preventing cracking. Carefully designed camber values also ensure the safety of the concrete upper surface.
Temperature stress problem of the ultra-long structure

Extremely long and extremely large buildings usually have large temperature stresses that are difficult to deal with. In the design and research of this project, we constructed a new simple but useful theory: ‘a statically indeterminate structural system without temperature stress.'

In the Fig11, the rods of all supports on the structure/object are perpendicular to their corresponding control lines, and all control lines converge at the same point O. When the temperature of the environment changes, the structure/object can freely deform along the radial directions (control lines) based on point O. Since the expansion or contraction directions (control lines) are all perpendicular to the rods of the supports, it is obvious that the supports will not restrict the structure/object under temperature loads. That is to say, if the two conditions of ‘Vertical’ and ‘Converging to one point’ are met, the temperature stress of the structure will always be zero during linear analysis.

For a statically indeterminate structure system under any temperature-field, when it experiences complex temperature changes, what kind of supports arrangement can obtain the minimum temperature stress during nonlinear analysis? We capitalized on the project to conduct research and obtained further results. In the Fig12, any point P on the structure/object deforms to point P' with temperature changing. Point A is the vertical foot of the support on the line segment PP'. The temperature stress is the lowest when the ratio PA/PP' is approximately equal to 0.42. The materials of the structure can be arbitrary or composite, the same results apply. This theory has been successfully applied in the design of some large-scale or great temperature changing projects, and has been reported at international academic conferences.