新型FRP-UHPC波形腹板组合箱梁桥结构的力学特性及全寿命周期预测

There has been an ever-increasing composite bridge degradation in recent years, including deck deterioration, reinforcing steel corrosion, prestressing force relaxation and stress-corrosion cracks, and fatigue-induced damage/defects. Substantial economic burdens and safety issues during high demanded maintenance and retrofitting associated with those structural degradation have highlighted the particular need for addressing deficiencies in the current performance of existing composite bridges and their effectiveness of durable control. To meet the need, the research project aims to develop and implement novel advanced-engineered material based prestressed composite box bridges with steel corrugated-plate webs system, striving for next-generation high-performance bridges. The new composite bridge, referred as FRP-UHPC, is to use new internally-cured Ultra-High Performance Concrete (UHPC), integrated with Glass fiber Reinforced Polymer (GFRP) as major reinforcement and Carbon Fiber Reinforced Polymer (CFRP) as prestressing tendons. By taking advantage of the superior material properties of new UHPC and FRP, the new composite bridges are expected to provide superior corrosion resistance and a significant durability that can possibly perform long-lasting without maintenance, and thus viable for alterative in current state practices. .To ensure a comprehensive investigation of the new developed FRP-UHPC prestressed composite bridge with steel corrugated webs, the proposed study will be conducted through large-scale experimental tests and numerical simulation. Major tasks will include the investigation of macro-scale physical and mechanical properties of the system (e.g., shear, bending and torsion), and micro-scale material characterization and optimization (e.g., bond, contact, damage and durability). Particular interest will be placed on the understanding of bar-concrete interface and degradation modeling under accelerated durability environments. The reliability-based accumulative damage fracture model will be derived from the damage evolution of fracture model, while the critical factors that affects the performance are identified and predicted using the new developed hybrid neural network with genetic algorithm. As such, a new framework of service-life prediction will be developed for assessing lifetime of the FRP-UHPC composite bridges. The research findings will pave a solid way to develop and implement the new enhanced high-performance bridge systems in the bridge industry and communities in China.

针对当前组合箱梁桥结构普遍存在的混凝土桥面开裂，钢筋腐蚀，预应力筋的松弛、应力腐蚀及其引发的疲劳开裂等问题，本项目提出一种新型波形钢腹板体外预应力组合箱梁桥结构，它采用内养护（Internally-Cured）超高性能混凝土材料（UHPC），结合碳纤维增强复合材料（CFRP）预应力绞索和玻璃纤维增强复合材料（GFRP）的混凝土桥板受力筋。建立其参数化数值模型并结合模型试验，研究该结构在宏观上的基本力学性能（受弯、受剪和抗扭，稳定性等）和在微观上的材料力学性能（粘结，接触，断裂演化和耐久性），并采用基于可靠度为基准的损伤断裂演化模型，通过耦合遗传算法与神经方法获取关键参数，推导累计损伤断裂函数，从而建立FRP-UHPC波形钢腹板组合箱梁结构全寿命周期预测的方法，不断优化波形钢腹板PC 组合箱梁的结构性能。项目研究成果将为完善和推广新型波形腹板组合箱梁桥结构在中国组合桥梁中的发展提供科学依据。

针对当前组合箱梁桥普遍存在的混凝土桥面开裂，钢筋腐蚀，预应力筋松弛和应力腐蚀及其引发的疲劳开裂等问题，本课题提出了一种新型波形钢腹板组合箱梁桥结构，它采用高性能混凝土材料（HPC），结合碳纤维增强复合材料（CFRP）的预应力绞索和玻璃纤维增强复合材料（GFRP）的混凝土桥板受力筋。共制作了84个GFRP/ECC、GFRP/SCC试块，通过拉拔试验对比了GFRP筋表面形式、GFRP筋直径、ECC与SCC基体强度、基体保护层厚度等不同变量因素下的黏结强度变化规律，归纳了拉拔破坏主要形式有，拔出破坏、筋剥离剪切破坏、劈裂破坏等。对比了同条件下，GFRP筋在ECC、SCC基体中拉拔时黏结滑移曲线在不同拉拔阶段的变化规律、试块裂缝的发展情况与表面的破坏形态、筋与基体交界面的破坏特征。后续又制作了66个GFRP/SCC中心拉拔试件，补充研究了SCC保护层厚度、GFRP筋粘结长度及直径、纤维种类等因素对GFRP筋与SCC黏结性能的影响。得到适用于GFRP筋与SCC以及掺纤维SCC的粘结滑移本构模型。同时，还对ECC在冻融及盐碱侵蚀条件下的耐久性进行了分析，通过57个中心拉拔试件，研究了不同试验环境、基体抗压强度、筋的表面形式对试件粘结性能的影响。采用粘结强度预测模型对冻融环境及盐碱侵蚀环境下试件的粘结强度进行了预测，得到冻融环境下75年后以及盐碱侵蚀环境下50和100年后的粘结强度保持率。对CFRP筋SCC(自密实)混凝土梁体外预应力损失展开研究，共设计了6根高性能混凝土试验梁，同时还有2根普通预应力混凝土梁(用于和SCC试件进行对比)。研究了在不同预应力水平，不同混凝土抗压强度下，CFRP筋高性能混凝土体外预应力梁的预应力损失。进而提出一种新型波形钢腹板组合箱梁桥结构，下翼缘采用槽型钢板组合板，采用GFRP筋代替普通钢筋、CFRP筋代替普通预应力筋。给出了针对该结构的多尺度建模建议方法，并对该新型组合箱梁桥在车道荷载作用下的静力性能和动力特性进行了分析，研究各结构参数变化对结构动力特性的影响程度，并采用地震反应谱分析方法研究该结构的抗震性能和各向地震作用下结构响应。参考山东鄄城黄河公路大桥截面尺寸，设计了一榀试验梁，长度方向按照1:10缩尺，横截面尺寸按照1:7缩尺进行调整，通过试验对箱梁结构的抗弯承载力、刚度、应力分布特征、裂缝分布特征等开展初步研究。