铁道建筑

超高性能混凝土(UHPC)与钢桥面板组合可显著提升桥面刚度，降低应力幅，是改善大跨悬索桥正交异性钢桥面板疲劳性能的有效手段。本文以某大跨悬索桥为工程背景，对钢-UHPC组合桥面的纵肋-面板（RD）、纵肋-横隔板（RF）、横隔板弧形切口（Cutout）三类关键疲劳细节开展实桥应力监测，基于热点应力法与Miner 准则进行疲劳寿命评估。结果表明：组合桥面使各关键细节应力幅显著降低，均低于常幅疲劳极限，疲劳损伤累积速率大幅放缓，可满足100年设计使用寿命要求；RD、RF的纵肋侧及Cutout细节应力梯度较小，RF横隔板侧、RF的围焊侧细节应力梯度明显，更宜采用热点应力法进行疲劳评价；结构应力局部效应显著，RD 细节可识别单轴应力循环，其余细节仅能识别轴组循环；RF围焊侧细节应力幅最大，是组合桥面最薄弱的疲劳控制部位。

The composite structure of ultra-high-performance concrete (UHPC) and steel bridge deck can effectively improve the flexural stiffness of bridge decks and reduce structural stress ranges， serving as a reliable technical method to ameliorate the fatigue performance of orthotropic steel bridge decks in long-span suspension bridges. Taking a long-span suspension bridge as the engineering background， this paper carries out on-site stress monitoring on three typical critical fatigue details of Steel-UHPC composite bridge decks， including rib-to-deck (RD)， rib-to-floor beam (RF)， and floor beam cutout details. The fatigue life of these structural details is evaluated quantitatively based on the hot-spot stress method and the Miner linear cumulative damage criterion. The analytical results indicate that the Steel-UHPC composite deck can substantially reduce the stress ranges of all key fatigue details， which are lower than the constant amplitude fatigue limit (CAFL). Meanwhile， the cumulative rate of fatigue damage is greatly decreased， enabling the bridge deck to satisfy the 100-year design service life requirement. Small stress gradients are found at the longitudinal rib side of RD and RF details as well as the cutout details， whereas prominent stress gradients occur at the floor beam side and weld-around side of RF details， demonstrating that the hot-spot stress method is more applicable for the fatigue evaluation of these positions. Obvious local structural stress effects exist in the composite deck: uniaxial stress cycles can be accurately identified for RD details， while only axle-group stress cycles can be captured for other fatigue details. In addition， the weld-around side of RF details presents the maximum stress range， which is identified as the weakest fatigue control position of the Steel-UHPC composite deck. This study can provide a technical reference for the fatigue design， daily maintenance and safe operation of similar long-span suspension bridges with Steel-UHPC composite bridge decks.