How to Design Connection Joints Between UHPC Curtain Wall Panels and Steel Keels? Joint Construction and Safety Solutions

The connection joint design between UHPC curtain wall panels and steel framing keels must balance firmness, durability, and flexibility, accommodating thermal deformation and structural settlement while avoiding damage caused by stress concentration. Scientific joint design is the key to ensuring long-term curtain wall stability. Drawing on multiple project practices, Qinglong analyzes the core design points.

1. Core Design Principles for Connection Joints

Safety principle: joint load-bearing capacity must meet requirements for wind load, seismic action, and component self-weight, with a single joint's pull-out capacity ≥15kN and shear capacity ≥10kN, plus a 1.5x safety factor. In the Shanghai Century Plaza project, Qinglong optimized the joint design through mechanical calculations to ensure no failure risk under extreme conditions. Durability principle: corrosion-resistant materials are selected—304 stainless steel connectors for standard environments and 316 stainless steel with surface passivation for coastal high-salt-fog environments—to prevent electrochemical corrosion. Flexibility principle: flexible connections are set to allow horizontal displacement of ±3mm and vertical displacement of ±2mm, absorbing thermal deformation and structural settlement and reducing stress concentration. Ease-of-maintenance principle: joints are designed for easy inspection and replacement, avoiding concealed, inaccessible structures. Qinglong adopted detachable joints in the Yangshengtang Pharmaceutical project to improve maintenance convenience.

2. Structural Forms and Suitable Scenarios of Mainstream Connection Joints

Slot-type joints: the UHPC panel has reserved slots connected to the steel framing keel via stainless steel clips; simple in structure and easy to install, they suit standard flat-panel curtain walls, such as the Shenzhen Yirui Biotechnology Building project, with good horizontal displacement adaptability but limited vertical displacement capacity. Bolt-type joints: stainless steel bolts fasten the UHPC panel to the keel connector; firm connection and high load capacity make them suitable for heavy-load components and large panels; Qinglong applied them in the 3-meter-high UHPC sculpture project at the Shanghai Astronomy Museum, where bolt adjustment fine-tunes installation precision. Clamp-type joints: L-shaped or T-shaped stainless steel clamps combined with reserved hanging grooves in the UHPC panel enable dry-hanging installation; with a clean appearance and detachability for replacement, they suit high-end commercial complex curtain walls, such as a commercial project in Guangzhou. Welded joints: connectors are welded and fixed to the steel framing keel; with the strongest load capacity, they suit irregular curved components and require anti-corrosion treatment of weld seams, such as the double-curved curtain wall of the Guangxi New Media Center.

3. Key Technical Details of Joint Design

Elastic gaskets made of EPDM rubber, ≥5mm thick, are set at the contact areas between connectors and UHPC panels to reduce vibration impact and electrochemical corrosion; a reinforcing layer is added at joint areas—steel mesh or steel fiber reinforcement is embedded in the hanging point zones of UHPC panels to prevent cracking caused by excessive local stress, with the reinforcing layer area ≥200×200mm; sealing uses neutral silicone weather-resistant sealant to fully cover joint gaps, preventing rainwater penetration from corroding the connectors; sliding bearings are set at the connections between the steel framing keel and the connectors to allow horizontal displacement and prevent keel distortion from thermal deformation. Qinglong applied this design in a Nanjing project, effectively absorbing thermal stress.

4. Testing and Optimization Measures for Joint Performance

Joints must undergo load capacity tests and fatigue performance tests. In the load capacity test, 1.5 times the design load is applied, and no deformation over 30 minutes counts as passing; the fatigue test simulates wind vibration with 100,000 loading cycles without damage; finite element analysis software is used to simulate joint stress, optimizing connector dimensions and layout to reduce stress concentration. In joint design, Qinglong combines simulation analysis with physical testing to ensure joint performance meets design requirements, while providing customized optimization for different project scenarios, achieving a perfect balance of safety and practicality.