How Wide Should Joints Be When Splicing UHPC Panels? Thermal Deformation and Qinglong Group's Joint Design Standards

The design of UHPC panel joint gap width requires scientific calculation of three components: thermal deformation, drying shrinkage deformation, and construction tolerance. The general formula is: joint width W = α·L·ΔT + ε·L + δ, where α is the coefficient of linear expansion (1.0×10⁻⁵/°C), L is the panel length, ΔT is the annual temperature difference, ε is the drying shrinkage rate (0.02-0.04%), and δ is the construction tolerance (3-5mm). In the 120,000-square-meter roofing project at the Hainan International Convention and Exhibition Center, Qinglong Group calculated a joint width of 6.7mm for 6m panels under an annual temperature difference of 45°C, and actually adopted 15mm (including an 8.3mm safety margin). Verified over 10 years, the joints have functioned normally with no compression cracking. Scientific joint design is the key to ensuring the long-term safety of curtain wall systems.

Thermal deformation is the primary factor. The coefficient of linear expansion of UHPC is approximately 1.0×10⁻⁵/°C, and a 6m panel can deform up to 2.4mm under a 40°C temperature difference. Qinglong Group determines ΔT based on local meteorological data, adopting 40-50°C for coastal areas and 60-70°C for inland regions. In the Nanning project, we used finite element analysis to precisely calculate the deformation in each direction, achieving customized design.

Material deformation and construction tolerances must not be overlooked. The drying shrinkage rate of UHPC is approximately 0.03%, resulting in 1.8mm of shrinkage deformation for a 6m panel. Construction tolerances include installation deviations, measurement errors, etc., for which we allow 5mm. The three components are summed and multiplied by a safety factor of 1.5 to obtain the final joint width. This scientific approach avoids the shortcomings of relying on experience alone.

The joint system requires complete design. Once the joint width is determined, a sealant with corresponding movement capability (±25% or above) must be selected, and backer rods installed to control the sealant profile. Qinglong Group provides joint calculation reports, offering designers an authoritative basis. Scientific joint design allows buildings to "breathe freely".