UHPC增强短搭接RC构件承载力可靠度分析与加固建议∗

Reliability Analysis of Load Capacity of UHPC⁃Reinforced Short Lap⁃Spliced RC Components and Strengthening Recommendation

摘要:

基于可靠度研究超高性能混凝土（Ultra?High Performance Concrete， UHPC）增强钢筋短搭接 RC 构件的失效模式与承载力特征。首先阐述了 UHPC 加固机理，建立了包含活恒荷载效应比、搭接系数 m、UHPC 强度、混凝土强度、钢筋型号、考虑水平地震作用的弯矩效应比和轴力效应比等关键参数的设计空间；确立分析 RC 构件承载力可靠度的功能函数，运用 Monte Carlo 法对设计空间中的关键参数组进行可靠指标计算，然后进行关键参数敏感性分析和计算结果拟合分区。结果表明：设计空间关键参数中，搭接系数、效应比、配筋率、钢筋型号和 UHPC 强度对可靠指标的影响均显著；UHPC 不仅具有良好的承载力增强能力，还能改变失效模式，梁和柱屈服时可靠指标分别提高 109.6% 和 12.9%，屈服时搭接系数分别为 0.58 和 0.57；对于受弯 RC 梁（压弯柱），m>0.67（0.65）时，钢筋基本能屈服，建议采用 UHPC 加固；0.50（0.49）<m≤0.67（0.65）时，存在钢筋屈服和粘结失效两种情况，建议谨慎加固； m≤0.50（0.49）时，容易发生粘结失效，不建议采用 UHPC 加固。

Abstract:

This paper investigates the failure modes and load-bearing characteristics of Ultra-High Performance Concrete (UHPC) reinforced short lap-spliced RC components. The reinforcement mechanism of UHPC was firstly demonstrated, and a design space was established, incorporating key parameters such as live-to-dead load ratio, lap-spliced coefficient m, UHPC strength, concrete strength, rebar type, and the bending moment effect ratio and axial force effect ratio considering horizontal seismic action. A performance function for analyzing the load-carrying reliability of RC components was established. The Monte Carlo method was applied to calculate reliability indices for critical parameter combinations within the design space, followed by a sensitivity analysis of key parameters and fitting of calculation results into zones. The results showed that among the key parameters in the design space, the lap-spliced coefficient, effect ratio, reinforcement ratio, rebar type and UHPC strength significantly influenced the reliability index. UHPC demonstrated excellent load-enhancing capabilities and the ability to alter failure modes. Reliability indices of beam and column yield increased by 109.6% and 12.9%, respectively, with lap-spliced coefficients at yield of 0.58 and 0.57 respectively. For flexural RC beams (compression bending columns), when m>0.67(0.65), the failure mode was steel reinforcement yielding, and UHPC reinforcement was recommended. When 0.50(0.49) < m≤0.67(0.65), the failure mode was either reinforcement yielding or bond failure, so UHPC reinforcement should be carefully employed. When m≤0.50(0.49), bond failure was likely, thus UHPC reinforcement was not recommended.