先张法UHPC-NC组合小箱梁设计与弯曲性能试验

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中图分类号：TU997，TU378，U443 文献标志码：A DOI： 10.15935/j.cnki.jggcs.202504.0012

AbstractThis study proposes a lightweight and industrialized pretensioned composite small box girder structure combining Ultra-High Performance Concrete（UHPC）and ordinary concrete（NC），leveraging the superior mechanical properties of UHPC. Compliance verification with the Swiss ultra-high performance fibre reinforced concrete structural code and the Chinese bridge design code confirms that the composite beam satisfies Class A prestressed component requirements while achieving a 30% weight reduction compared to conventional NC box girders of identical span.To validate flexural performance，a bending failure test was conducted on ascaled specimen.As observed，upon ordinary reinforcement yielding，the UHPC at the bottom edge completed tensile strain hardening with strains of 1930-2100με ，developing fine cracks below O.2 mm width.Steel strand yielding marked the stiffness degradation inflection point，where UHPC compressive strain at the top edge reached 1060με （below its ultimate strain），followed by steel fiber pullout and tensile zone stress redistribution.Final failure occurred due to NC top slab crushing，yielding a displacement ductility coefficient of 2.3.Scaling analysis incorporating a structural importance factor of 1.1 indicates that for the prototype beam，the partial factor for vehicle loads under fundamental combinations is 2.O3 （exceeding the standard 1.4），while the frequent value coefficient under frequent combinations is O.87（surpassng the standard O.7）. The pretensioned system demonstrates enhanced prestressing eficiency in UHPC sections and effective post-cracking material collaboration，confirming its viability for practical applications.

Keywordsbridge engineering，UHPC，composite beam，bending test，ultimate state

0 引言

传统混凝土材料因自重较大、脆性大、抗拉强度低、耐久性不足等问题限制了其在大跨径结构、特种结构、恶劣环境中的应用。（剩余10050字）