Chaka Salt Lake Tourist Railway Station is located at Chaka Salt Lake, Wulan County, Qinghai Province. The project as the landmark building of scenic area upgrading and based on the tourism publicity image with the characteristics of the scenic spot is made by prefabricated steel structure and membrane structure and the digital technology of the project combines the concept of the scheme, the design deepening and construction, which creates a free space for transportation organization and leisure and sightseeing.

Concept Origin – A Red Silk Scarf Fluttering in the Wind Over theSalt Lake
Chaka Salt Lake, known as the "Mirror of the Sky," features a brine lake with solid-liquid coexistence, creating a natural wonder where water reflects the sky, merging heaven and earth, and visitors walking across the lake feel like moving through a painting. The project's overall shape is inspired by the scenic area’s iconic check-in image formed over years, with a free-form surface of steel and membrane structures resembling a red silk scarf fluttering on the salt lake.

The Station is the largest among numerous station structures, with a total construction area of 3996㎡. Due to the needs of salt lake ecological protection, the building can only adopt a steel structure system. How to give the huge steel structure standing on the calm lake surface a "sense of wind" was a challenge, but it also provided a rare opportunity for the design team to attempt integrating installation art concepts with architectural techniques. "Seeing the wind, hearing the wind, and leaving memories of the wind" is the experience we hope this place can bring to visitors.

The platform is divided into two levels: the ground floor is elevated above three railway tracks, with staircases and elevators arranged in line with the flow of visitors entering and exiting the station as well as accessing the lake, while the upper floor mainly serves as a leisure platform for sightseeing and retail services; the roof features an integrated free-form curved surface composed of a composite steel and membrane structure, which presents a dynamic posture as if dancing in the wind when viewed from afar across the lake, and when stepping into the platform, hanging fabrics in red, orange and yellow flutter along with the sound of the wind, offering an intimate sensory experience of the breeze.

The orientation of the station tracks themselves dictates the building’s dynamic, north-south "flowing" posture, making the east-west direction an ideal viewing axis. Flanked by the Qilian Mountains to the east and the Kunlun Mountains to the west, the site boasts exceptional natural scenery, and the second-floor platform perfectly caters to visitors’ sightseeing needs. Meanwhile, the platform also physically separates the ticket-checking area from the boarding platform, ensuring that each area can accommodate large crowds of visitors simultaneously.

While fulfilling its core function of facilitating visitor entry and exit, the platform is designed to enhance the sightseeing experience. At high - points and specific locations, the platform roof and station boundaries are broken to create viewing areas, with commercial facilities nearby. The overhanging sections are integrated with vertical transportation for user - friendly flow buffers, streamlining circulation and allowing visitors to enjoy the lake view during entry or exit. The west side is the main viewing orientation. To avoid obstructing sight lines, the second - floor roof has partial openings, and the platform extends to form an observation deck. The undulating roof and platforms interact and merge into an organic whole.

Form Construction – Multi-layered Form Evolution Aided by Digital Design
The overall curved surface is mainly composed of three layers: the main steel structure, two types of membrane structures with different properties on the top, and three colors of fabrics hanging on the bottom layer that can flutter with the wind. While integrating requirements for space, appearance, and mechanics, the design takes the flying red silk scarf as the foundation and also draws on the ripples on the lake surface caused by raindrops falling into the water, using them as the conceptual inspiration for the curved surface formation.

Instead of a floating curved roof supported by columns, the main steel structure extends from the ground to the platform as an integrated design, enhancing the building's "fluttering with the wind" effect. Despite its free-form curved surface, the steel - structure's generation logic is clear. Constrained by railway - track layout, three grounding points were chosen on the platform and side - platforms. Then, combined with preliminary stress analysis, four large "blooming columns" were installed. After structural simulation, areas of weak local stress were found, and three small "blooming columns" were added for stability without affecting the curved - surface shape. The "blooming columns" are inspired by raindrops on a lake surface, and their shape is determined by the curved - surface's elastic force to achieve a smooth connection with the curved roof.

Considering the construction difficulty and cost constraints, the structure adopts a design approach where straight elements simulate curved forms. While ensuring the structural force is reasonable, additional components were added to transform the original rhombus structural unit modules (with a side length of approximately 3 meters) into smaller units: two types of modules, namely triangles and hexagons, each with a side length of about 1.5 meters. This adjustment creates a relatively human-scaled division from the viewer’s perspective.

The roof membrane structure and the steel structure work together to form an integrated load-bearing system. During the initial design phase, three materials for the roof membrane structure were compared and evaluated:

Air pillow membrane: High in cost and relatively complex in craftsmanship, it failed to meet the construction schedule requirements. Additionally, the form of the "silk scarf" appeared less smooth when viewed from a distance.

Aluminum panels: Low in cost but rigid and dull in appearance, which was far from matching the texture of a silk ribbon. Single-layer membrane: With moderately priced cost and inherent ductility, it allowed for smooth transitions at the focal points where straight elements simulate curves. Thus, it was selected as the final material.

Furthermore, given that the undulating shape and structural dimensions of the roof are significantly affected by wind loads, two types of PTFE membranes were ultimately adopted: semi-transparent PTFE membranes and opaque PTFE membranes with an additional coating. These materials not only fulfill the basic functions of sunshade and rain protection but also minimize wind loads as much as possible. The tensile force of the membrane material itself also exerts a certain influence on the steel structure, and the two work together to form an integrated load-bearing system.

The PTFE membrane with an additional coating forms a light - permeable and rainproof composite material, providing a rain - sheltered area for visitors. Hanging fabrics are arranged below this area to avoid rain exposure that could affect their visual effect. The uncoated PTFE membrane has a porosity of about 21% due to its material properties. Structural simulations show that arranging it in high - wind - load areas can reduce wind impact on the structure, let wind flow smoothly into the platform interior, and make the hanging fabrics flutter. Light and wind entering through the membrane structure weaken the enclosure sense, creating a transparent - to - semi - transparent - to - enclosed transition. The two membrane types are distributed according to visitors' main movement paths on the platform, minimizing the impact of rain and snow on those entering/exiting the station and using the platform's commercial spaces.

For the design of the fabrics hanging from the bottom, the large "blooming columns" are taken as the centers of ripples. Curved line groups resembling ripples are simulated and projected onto the roof to determine the overall layout of the fabrics. The three-colored fabrics flutter with the wind; the changing sunlight during the day and the breathing-style lighting design at night further enhance the sense of water ripples.

The local area has a long, windy winter, and the salt lake region has high humidity and strong corrosiveness. Ordinary fabrics can't meet durability requirements, so an outdoor sunshade fabric with better weather resistance was chosen. Initially, the fabric was to have the same all - red color as the roof. But simulations showed that full color integration with the roof reduced the ribbon's flowing elegance from afar. Inspired by local cultural traditions, yellow and orange were selected to match the red. The circular bands of the three - color membranes start with red at the transition joints between the blooming columns and the roof and then gradually transition outward layer by layer following the ripple pattern. Due to the limited color options of the custom - made membrane material, a smooth multi - color gradient couldn't be achieved. So, the design approach shifted to a mosaic style: the complete ripple rings were divided into modular units, and a gradual color transition was achieved by setting discrete random values. Moreover, the color variation was enriched by fine - tuning local unit color blocks, enhancing the overall layered texture of the hanging fabrics.

Construction Optimization-Structural Refinement for Form-Finding and Performance-Based Detailed Design
Chaka Wind features a ribbon-like form with dynamic curved surfaces, adopting a single-layer reticulated shell structure. When the reticulated shell is subjected to vertical gravity loads, several vertical supporting points are required. The primary goal of architects and structural engineers is to fully integrate aesthetic form with structural efficiency.

After multiple rounds of model iteration and optimization, the structure finally adopts 4 large blooming columns and 3 small blooming columns as the main vertical load-bearing components. Among them, the large blooming columns not only bear vertical loads but also resist horizontal seismic forces and horizontal wind loads. The small blooming columns mainly carry vertical loads to ensure that the vertical deformation and vertical stiffness meet the design requirements. Weak points in the spatial stiffness of the thin shell are identified through the analysis of linear buckling modes, and targeted local reinforcement measures are implemented.

Given the relatively complex shape of this single building, it is difficult to determine its response to wind loads by using the wind load shape coefficients specified in the codes. In the design process, we conduct a wind tunnel pressure measurement test on this building.Based on the test report, the first batch of wind loads was applied to the building corresponding to 12 wind directions (0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, 330°). For each direction, both the maximum and minimum wind load values were applied respectively to simulate the effects of wind-induced vibration under random vibration conditions.

In addition, to further enhance the structural safety of this standalone building, we consulted the relevant meteorological authorities during the design process to obtain the prevailing wind directions of the project site. According to the data obtained, the local dominant wind directions are mainly westerly and northwesterly winds.

Therefore, we added 8 additional wind directions (160°, 170°, 190°, 200°, 220°, 230°, 250°, 260°) as the second batch of wind loads in the design. Meanwhile, 13 wind directions (150°, 160°, 170°, 180°, 190°, 200°, 210°, 220°, 230°, 240°, 250°, 260°, 270°) were designated as the prevailing wind directions for the design considerations. To resist the highly corrosive extreme environment of the salt lake, and drawing on the scenic area’s past engineering experience, corresponding reinforcement designs have been implemented for all parts of the main structure. For instance, to withstand the strong corrosiveness of groundwater and soil in the foundation section, precast piles were selected for the pile foundation. Both the precast piles and bearing platforms achieve corrosion resistance through measures such as adding anti-corrosion mineral admixtures and increasing the thickness of the protective layer; for the above-ground steel structure components, the corrosion resistance is enhanced by means like applying thicker anti-corrosion coating films.

Economic efficiency and structural safety are crucial indicators for measuring a building’s performance, as well as key goals pursued by structural engineers. Through multiple rounds of procedural and manual iterative optimization, Chaka Wind Station has achieved a comprehensive stress ratio of 0.8–0.9 for its components under various working conditions, truly embodying the principle of "using quality steel where it matters most".

In addition to the overall structural optimization for form-finding, the four large blooming columns have also been specially designed to withstand the snow loads on the roof.The large blooming columns are funnel-shaped, which naturally creates a converging effect. Once snow loads accumulate, they will exert a significant impact on the main structure. The roof membrane structure controls the descending height along the curved surface of the columns to reduce the snow accumulation height, and is connected to a steel plate device at the center of the columns, which resembles an enlarged rainwater pipe. The upper part of the device is funnel-shaped to collect rain and snow, while the lower part is connected to a pipeline with a diameter of 0.6 meters. Electric tracing is installed at the joint between the membrane structure and the device to accelerate snow melting and further reduce snow accumulation.

Construction Implementation–Precise Industrial Prefabrication and Tolerance-Accommodating Artisanal Craftsmanship
Assisted by digital design tools and an intelligent construction system, the main steel structure was ultimately broken down into 1,292 grid units and 2,350 steel components with distinct shapes and dimensions. These components underwent CNC machining in the factory before being assembled on-site.The industrial prefabrication of modern steel structures ensures the precise construction of large-scale curved-surface structures from conceptual design to physical realization, and significantly shortens the on-site construction period. The on-site construction of the main steel structure and membrane structure took a total of 64 days, minimizing the impact on the ecological environment of the salt lake.

With digital design tools, intelligent construction systems, and industrial prefabrication of modern steel structures, precise construction of large curved surface structures from concept to implementation is ensured. This shortens on - site construction time and minimizes impact on the salt lake's ecological environment. The design of suspended fabrics relies on digital tools, and during construction, a tolerance - based craftsmanship control strategy is used. While keeping the water ripple effect of the fabrics, local color splicing can be adjusted on - site according to the design. Finally, the combination of traditional suspended craftsmanship and a solid steel structure framework creates a soft and relaxing effect, integrating seamlessly with the scenic area's natural atmosphere.

Conclusion
The Chaka Wind Station project has fully leveraged digital strategies and technologies throughout the entire process from conceptualization to construction implementation. It explores the integration of precise industrialized control and tolerance-accommodating artisanal craftsmanship, ultimately realizing a free-flowing, wind-dancing leisure and sightseeing station on the salt lake.