ETFE Air Membrane Structure Creates a Benchmark For the "City Tree" Roof Project, Anji Yun'anli

As a leading enterprise in China's spatial structure sector, Wanhao Group employs air-cushion ETFE membrane structure systems.to create the "City Tree" dome at the Anji Yun'anli project, integrating architectural aesthetics, regional culture, and sustainability through innovative spatial tension structure applications. The project breaks new ground with a composite glass-ETFE membrane roofing system: parametric form-finding analysis transforms Anji bamboo cultural elements into biomimetic textures of hyperbolic air-cushion units, achieving precise morphological construction via interlayer pressure differential control. This creates a translucent space with over 90% light transmittance while forming an aerodynamic streamline building envelope.

The membrane structure engineering.is advancing with industrial-grade precision. Upon completion of the main steel structure, a stringer dome skeleton with spatial geometric rigidity has been established, featuring node welding precision controlled within ±1.5mm and surface fluorocarbon coating meeting ISO12944-C5-M high-weather resistance standards. Commencing in May 2025, the ETFE membrane unit installation utilizes modular pre-tension integration technology: BIM-modeled 3D coordinate positioning, combined with pre-stressed tensioning of the cable-membrane system, enables accurate hoisting of 200㎡ air-cushion units. In response to subtropical monsoon climate conditions, a cavity drainage system is being concurrently implemented: thermal welding technology ensures membrane splicing, with seam airtightness tested to the industry's top standard of 10Pa/min・㎡, forming an integrated building envelope system for waterproofing, air ventilation, and thermal insulation.

Wanhao's technical advantages demonstrate systematic innovation in membrane engineering: ETFE membrane, with a surface density of 1.5kg/㎡ (1/100th of tempered glass), creates large-span coverage structures. Hyperbolic air-cushion unit grid layouts achieve a 35m unsupported span, reducing structural weight by 60% compared to traditional glass curtain walls. A parametric algorithm inspired by bamboo growth dynamics enables initial membrane form-finding and load-state nonlinear analysis, controlling dome surface displacement under 1.5kPa wind load within L/800. Membrane thermal performance optimization achieves a 22% energy consumption reduction. Material-wise, 150μm-thick ETFE membrane produced via three-layer co-extrusion, coated with hydrophilic treatment, withstands Category 12 typhoons, while its 95% recyclability meets LEED Gold certification circular economy requirements.

As Zhejiang's first over-limit large-span ETFE membrane project, Anji Yun'anli establishes a full-industry-chain technical system from material R&D to intelligent operation. Wanhao leverages its 50,000㎡ intelligent manufacturing base for digital processing with ≤0.5mm membrane cutting precision, complemented by a health monitoring system deploying over 200 stress sensors for real-time modal analysis of membrane tension and thermal deformation. Approaching the dome waterproofing milestone in Q3 2025, the project will complete pre-stress tensioning acceptance of the cable-membrane system. Future phases will integrate building-integrated photovoltaics and prism light-guiding systems within membrane cavities, creating an iconic spatial structure that unifies natural lighting, energy efficiency, and cultural narrative—setting a benchmark for GB/T 51435-2023 Technical Standard for Membrane Structures and continuing to lead China's large-span spatial structure innovation.