Why Are the Shear Performance Advantages of UHPC Difficult to Reflect in Design?

The shear performance advantages of UHPC (shear strength up to 15-25MPa, 3-5 times that of ordinary concrete) are difficult to fully realize in design practice, mainly due to four obstacles: outdated codes, imperfect calculation models, complex joint detailing, and designers' limited awareness. Qinglong Group's participation in standard revisions shows that current concrete design codes are based on the strut-and-tie model for ordinary concrete and do not account for UHPC's fiber bridging and strain-hardening characteristics, resulting in conservative designs. Meanwhile, UHPC shear resistance depends on the uniformity of fiber distribution, requiring high precision in design and construction. In the beam-column joints of the Shenzhen Pingshan High-tech Zone Comprehensive Service Center, we verified through full-scale tests that UHPC shear capacity reached 120% of the theoretical value, yet the design still applied it at a discount per code requirements. Realizing the shear advantages requires design theory and engineering practice to evolve in sync.

Outdated codes are the biggest constraint

Current codes in various countries mostly base shear calculations for fiber-reinforced concrete on empirical formulas, without fully considering UHPC's high toughness and crack control capability. Qinglong Group has partnered with research institutions to conduct full-scale tests, promoting the inclusion of fiber contribution terms in local standards, but widespread adoption takes time.

Refined design challenges traditional habits

UHPC shear resistance is related to fiber orientation and length, requiring customized design aided by finite element analysis, which traditional hand calculations can hardly handle. Qinglong's BIM team employs digital twin technology in complex joint design to optimize fiber distribution, though this increases design costs.

Construction quality affects performance realization

Fiber clumping or uneven distribution significantly reduces shear effectiveness. Qinglong Group uses robotic spraying to ensure three-dimensional random distribution, but quality control of cast-in-place UHPC is difficult, and designers often remain conservative due to this uncertainty.

Promoting the application of UHPC's shear advantages requires strengthening experimental research, updating codes, and improving construction standards. Qinglong Group is gradually eliminating design barriers through technical exchanges and project demonstrations.