What gap width should be reserved when splicing UHPC panels?

The reserved joint width when splicing UHPC panels is a systematic design result that comprehensively accounts for 'thermal deformation, structural displacement, installation tolerances, visual performance, and sealant performance'—it is by no means a fixed value. The core design principle is 'to pursue the optimal visual proportion while ensuring joint function (waterproofing and deformation accommodation)'. Based on extensive engineering practice, Qinglong Group defines the panel joint width range for conventional UHPC curtain wall panels at 8mm to 20mm, with 12-15mm being the most common and technically and economically optimal choice. For example, in the Shenzhen Pingshan High-tech Zone Comprehensive Service Center project, we set the standard panel joint at 12mm through calculation, which both met the local thermal deformation requirements and created refined, modern façade lines.

Thermal Deformation Calculation Is the Mechanical Basis for Determining Joint Width

This is the first rigid condition that must be met. The joint width must be able to absorb the expansion and contraction of UHPC panels caused by temperature changes. The calculation formula is: ΔL = α L ΔT, where α is the linear expansion coefficient of UHPC (~1.1×10⁻⁵/℃), L is the panel length, and ΔT is the annual extreme temperature difference. For example, a 3-meter-long panel in a region with an annual temperature difference of 50℃ will have a length change of ΔL = 1.1e-5 3000 50 ≈ 1.65mm. The designed joint width must be greater than this value, taking into account the allowable movement capability of the sealant (usually ±25%). If the designed joint width is 12mm, the sealant can compress or stretch ±3mm, far greater than 1.65mm, providing ample safety margin.

Allowance for Structural Inter-story Displacement and Construction Tolerances

Buildings produce inter-story drift angles under wind loads or earthquakes, causing relative movement between adjacent panels. The joint width must account for this displacement. At the same time, space must be reserved for panel manufacturing tolerances and on-site installation errors. Qinglong controls production dimensional tolerances within ±1.5mm and installation errors within ±2mm. Considering all these factors, the joint width should not be too small; otherwise, accumulated errors may cause installation difficulties or localized compression.

Coordination of Visual Proportion with Architectural Style

Joint width is an important element of façade composition. Narrower joints (e.g., 8-10mm) appear refined with a strong sense of unity and suit modern minimalist styles, but they demand extremely high construction precision. Wider joints (e.g., 15-20mm) emphasize the modular quality and rhythm of the panels, offer greater tolerance for errors, and appear visually more substantial. Qinglong's designers provide façade effect simulations of different joint widths for architects' decision-making. Sometimes non-uniform joint designs such as 'narrow horizontal, wide vertical' or 'wide top, narrow bottom' are adopted to adjust visual proportions.

Matching Sealant Performance with Application Techniques

The final selected joint width must match the specifications of the chosen sealant. Sealants have minimum and maximum application thickness requirements. Generally, the width-to-depth ratio of the sealant joint should be controlled at around 2:1 (e.g., 12mm wide, 6mm deep). Joints that are too narrow make it difficult to apply sufficient sealant, compromising sealing quality; joints that are too wide require deep backer material filling, which is uneconomical and may affect sealant performance. Based on the determined joint width, Qinglong selects closed-cell foam backer rods of the corresponding diameter and matching application tools.

Therefore, determining the splicing joint width for UHPC panels is a multi-objective optimization process spanning structural safety to aesthetic expression. Qinglong Group's technical services become involved in this critical design at the early project stage, using scientific calculations and extensive case experience to help clients determine the most rational and visually appealing joint solution, laying the foundation for the project's perfect presentation.