Why Are UHPC's Shear Performance Advantages Difficult to Realize in Design?

UHPC offers outstanding shear performance, with shear strength up to 3-5 times that of ordinary concrete. However, in actual engineering design, this advantage is often difficult to fully exploit, mainly due to multiple factors such as the absence of standards, complex testing methods, and the difficulty of joint design. As a company that has participated in developing UHPC industry standards, Qinglong Group draws on 28 years of project experience to analyze the key reasons behind this issue and the paths to optimization.

Industry standards lag behind, lacking a clear design basis. Current domestic UHPC-related standards (such as the 'General Technical Conditions for Ultra-High Performance Concrete (UHPC) Non-Load-Bearing Components') mainly focus on indicators such as compressive and flexural strength, and lack detailed provisions on design parameters, calculation methods, and structural requirements for shear performance. Designers have to refer to shear design standards for ordinary concrete or steel structures, which hardly reflects the material characteristics of UHPC. For example, the shear strength of ordinary concrete has a linear relationship with its compressive strength, whereas the shear strength of UHPC is more significantly affected by fiber content, interface bonding, and other factors—designing according to ordinary standards would underestimate its performance. Qinglong Group is participating in the revision of the 'General Technical Conditions for Ultra-High Performance Concrete (UHPC) Non-Load-Bearing Components', which is advancing the improvement of shear design provisions, but these have not yet been formally implemented, leaving designers reluctant to readily adopt UHPC's shear advantages.

Shear performance testing is complex, and data accumulation is insufficient. UHPC shear performance data must be obtained through specialized shear tests (such as double shear tests and beam shear tests), which demand high-specification equipment and complex operations, and most small and medium-sized testing institutions lack such testing capabilities. Although Qinglong Group's provincial-level R&D center can perform these tests and has accumulated substantial data (e.g., standard-type UHPC shear strength ≥15 MPa, economy-type ≥10 MPa), the industry as a whole lacks sufficient data accumulation, unified testing standards, and databases, making it difficult for designers to obtain reliable reference data. In addition, UHPC shear performance is significantly affected by component dimensions, fiber distribution, loading methods, and other factors, and product performance varies considerably between manufacturers, further increasing design difficulty. In the sculpture project at the Shanghai Astronomy Museum, Qinglong provided a dedicated shear test report before the design team dared to adopt UHPC's shear capacity, avoiding the need for additional shear reinforcement.

Joint design is complex and prone to creating shear weak points. The shear advantage of UHPC components depends on the integrity of the overall structure, but in actual projects, joints such as component splices and anchorages are prone to becoming weak points, reducing overall shear performance. For example, with the hanging joints of UHPC curtain wall panels, if poorly designed, shear forces will concentrate at the hanging points, causing stresses at the joint to exceed the material's shear strength and triggering failure. In the Pingshan High-Tech Zone Comprehensive Service Center project in Shenzhen, Qinglong Group optimized joint design using BIM technology, adopted multi-point hanging to disperse shear forces, and locally increased fiber content at the joints—only then was UHPC's shear advantage fully exploited. However, most designers lack experience in UHPC joint design and still design joints in the manner of traditional materials, failing to reflect its shear performance.

Designers have limited awareness and a marked tendency toward conservative design. Since UHPC has been applied in China for a relatively short time, some designers lack a deep understanding of its performance characteristics, especially a clear grasp of the advantages and applicable scenarios of its shear performance. They tend to adopt conservative schemes in design, adding extra shear reinforcement or reducing component spans, so UHPC's shear advantage cannot be realized. Qinglong Group popularizes UHPC shear performance knowledge among designers through industry training, technical white papers, and project case sharing, but raising overall awareness still takes time. In addition, owners' cost concerns about UHPC also influence design decisions; some projects choose the ordinary concrete + shear reinforcement option to control costs, forgoing UHPC's shear advantage.

The difficulty of realizing UHPC's shear performance advantage in design is the combined result of multiple factors: standards, testing, design, and awareness. Qinglong Group is promoting the resolution of this issue by participating in standard development, accumulating test data, optimizing joint design, and spreading technical knowledge. Customers with projects involving shear requirements are advised to choose manufacturers with technical strength and project experience, carry out dedicated shear testing in advance, and collaborate with designers to optimize joint design, so that UHPC's shear advantage can be fully realized, achieving a balance between structural safety and economy.