钢板条-UHPC组合桥面结构静力及疲劳试验

应用UHPC加固正交异性钢桥面时，由于钢面板存在贯穿型裂缝导致UHPC底面抗裂无法满足要求，提出一种新型钢板条-UHPC组合桥面结构。对12个正弯矩作用下钢板条-UHPC组合桥面构件进行静力参数试验，讨论构件的破坏模式及裂缝的发展与分布；对4个构件进行抗弯疲劳试验，研究构件在不同荷载幅作用下的刚度衰减、裂缝扩展、剩余强度，并提出适用于该类构件的S-N曲线。研究结果表明：带钢板条构件裂缝宽度达到0.05 mm时，具备超过20.1~28.0 MPa的名义开裂强度，相比无钢板条构件的7.2~9.7 MPa，对UHPC的抗裂性能强化作用明显；提高钢板条宽度对于UHPC的开裂抑制作用明显，可有效降低平均裂缝间距而延缓裂缝宽度的持续扩展；提高钢板条宽度与UHPC层厚均可大幅提高组合桥面构件的刚度，使得构件在弹性极限后进入更高的强化阶段；钢板条-钢面板连接方式对于构件的破坏模式和裂缝发展无影响；荷载比S≤0.43时，构件在1 000万次疲劳作用后，刚度未现折减，裂缝宽度仅0.03 mm，可认为当S<0.43时，构件具备无限疲劳寿命；S≥0.76时，构件早期存在极高的损伤积累，当刚度开始衰减后，短期内即会达到疲劳寿命极限；对于S为0.43~0.76的构件，UHPC裂缝扩展缓慢，开裂后在短期内不会出现明显刚度衰减，剩余疲劳寿命较高；直接采用目前的疲劳寿命评估方法对4个构件的进行评估，结果差别较大；结合试验结果，提出了针对钢板条-UHPC组合构件的S-N曲线，可为类似结构的疲劳寿命评估提供参考。

Experiment on Static and Fatigue Performances of Steel Strip-UHPC Composite Deck

A modified steel strip-UHPC composite deck system was proposed to increase the tensile strength at the bottom of UHPC when the UHPC-based strengthening technique was used for OSDs with through-thickness cracks on the deck plate. The parametric static tests were conducted on twelve steel strip-UHPC composite deck members under sagging moment. The failure mode, propagation, and distribution of cracks at the bottom of UHPC were investigated. Additionally, four flexural fatigue tests were conducted. The stiffness reduction, crack propagation, and residual strength of the composite members were investigated in the fatigue tests. The following details can be observed from the results. The tensile strength of the UHPC layer in the composite members with steel strips can reach 20.1~28.0 MPa when the maximum crack width is 0.05 mm. Compared to members without steel strips having a strength of 7.2~9.7 MPa, the steel strips have an obvious strengthening effect on the cracking resistance of UHPC. Increasing the width of the steel strip has an obvious effect of cracking inhibition on UHPC. This can effectively reduce the average crack spacing and delay the continuous expansion of crack width. The stiffness of the composite members can improve significantly by increasing the steel strip width and UHPC layer thickness. This makes the members have a longer strengthening stage after the elastic limit. The connection method between steel strips and steel plates has no influence on the failure mode and crack propagation. After 10 million fatigue cycles, the stiffness of the members did not decrease. Furthermore, the crack width is only 0.03 mm at S ≤ 0.43. This implies that the member has infinite fatigue life at S<0.43. However, the member experiences high damage accumulation at the early stage of S=0.76. When the stiffness begins to reduce, the member will attain the fatigue life limit in a short term. For members at S=0.43~0.76, the cracks propagate slowly. No significant stiffness reduction is observed in the short term after cracking. Moreover, the members have a high residual fatigue life. The deviations are quite large between the evaluation results and experimental data when the current evaluation method for fatigue life is directly used to evaluate the four members. An S-N diagram of the steel strip-UHPC composite members, which can provide a reference for the fatigue life evaluation for similar structures, was proposed.