Why Is the Shear Performance Advantage of UHPC Difficult to Reflect in Design?

The shear performance advantages of UHPC (high shear strength, good toughness, minimal deformation) are difficult to reflect in design, primarily due to three bottlenecks: lack of design codes, insufficient test data, and complex joint construction. Through technological innovation and engineering practice, Qinglong has developed a “test verification + joint optimization + code adaptation” solution to gradually unlock its shear potential.

1. Lack of Design Codes: No Clear Design Basis

The absence of codes is the core obstacle preventing shear advantages from being realized. Poor adaptability of current codes: China's Code for Design of Concrete Structures (GB 50010) has no specific provisions for UHPC shear design and still references ordinary concrete or high-strength concrete design methods, failing to reflect UHPC's advantages of high shear strength (3-5 times that of ordinary concrete) and good toughness; lack of shear calculation models: UHPC shear performance is significantly affected by fiber type, dosage, aggregate gradation, and other factors, and without unified calculation models, designers struggle to precisely quantify shear capacity and can only design conservatively; limited international code references: although some international codes (such as fib Bulletin 100) address UHPC shear design, they differ from domestic engineering practices and material systems, making direct application risky; the General Technical Conditions for Non-Load-Bearing Ultra-High Performance Concrete (UHPC) Components, whose development Qinglong participated in, has added some shear performance indicators to provide design references.

2. Insufficient Test Data: Lack of Systematic Performance Support

The complexity of shear testing limits data accumulation. High testing difficulty: UHPC shear tests require specialized equipment and specimens, involve complex loading methods (such as diagonal section shear tests on beams), and entail high testing costs, so most enterprises and research institutions lack systematic test data; high data dispersion: UHPC material formulations and production processes vary greatly among manufacturers, resulting in shear strength dispersion (coefficient of variation ≥10%) that makes it difficult to build a unified performance parameter database; lack of long-term performance data: insufficient data on long-term degradation of UHPC shear performance (such as after freeze-thaw cycles or corrosion) leads designers to favor conservative designs to avoid risk; Qinglong has accumulated over 500 sets of UHPC shear test data covering different strength grades and fiber types, and has established an internal performance database to support project design.

3. Complex Joint Construction: Shear Advantages Hard to Realize Through Detailing

In actual engineering, joint detailing restricts shear performance. Complex joint loading: connection joints between UHPC components and other structures (such as steel or concrete structures) are subject to combined shear, tension, and bending, making it difficult to exploit UHPC's shear advantages alone; construction process constraints: dense reinforcement and cramped space in joint areas make UHPC casting difficult, and inadequate vibration compaction often results in actual shear strength below design values; insufficient protective measures: joint areas are prone to environmental erosion, which affects the bond between UHPC and connectors, thereby reducing shear capacity; Qinglong's solutions: optimize joint detailing by adopting precast joints + on-site assembly to ensure dense casting; select specialized connectors (such as stainless steel shear studs) to enhance joint shear capacity; provide dedicated joint design and test verification services—in one bridge project, Qinglong's optimized UHPC joints achieved a 30% increase in shear capacity.