近场爆炸作用下UHPC-FST墩柱的性能劣化机理及损伤评估方法

恐怖袭击和偶然性爆炸作用下桥梁墩柱产生损伤，为延续其正常使用，应以残余轴向性能和抗震性能作为加固指标，但对爆炸作用下墩柱的抗震性能劣化机理及其评估方法的研究仍处于起步阶段。钢管-超高性能混凝土（UHPC-FST）具有优异的轴向承载力、侧向抗爆和抗震性能，在桥梁结构中有广阔的应用前景。因此，本项目针对近场爆炸作用下UHPC-FST墩柱的性能劣化机理及损伤评估方法展开研究。拟开展UHPC静、动载试验，建立UHPC动态本构模型及其参数快速确定算法；进行UHPC-FST墩柱野外爆炸试验，揭示墩柱损伤机理及破坏模式，提出近场爆炸下的高效数值计算方法；开展爆炸后UHPC-FST墩柱的拟静力试验与数值仿真分析，揭示爆炸对墩柱抗震性能的劣化机理，提出基于残余抗震性能的墩柱损伤指标及评估方法。预期研究成果对于完善墩柱抗爆分析理论体系，指导灾后墩柱性能评估与加固设计，保障公共交通设施安全具有重要的研究价值。

Blast load arising from terrorist attacking and accidental explosion event will deteriorate the mechanical performance of bridge pier. The strengthening of the blast damaged pier can be carried out if the residual mechanical performance of the blast damaged pier is kept to some extent. The residual axial and seismic capacity of the blast damaged pier should be first evaluated for the strengthening design. However, at present only the residual axial capacity of the blast damaged pier is considered in the strengthening design. For the pier located in the seismic zone, it is necessary to take into account the residual seismic capacity of the blast damaged pier during the phase of strengthening design. Ultra-high performance concrete filled steel tube (UHPC-FST) column performs superior axial loading capacity, higher blast and seismic resistance compared to that of the normal concrete column. Therefore, the UHPC-FST has recently gained widely applications in bridge engineering. The purpose of the current research is to investigate the deterioration of mechanical performance of UHPC-FST bridge pier subjected to close-in range detonation and to evaluate the damaged situation of the blast damaged piers. A series of static and dynamic tests will be conducted to investigate the effects of type and volume content of fibers on the static and dynamic properties of UHPC. Based on the experimental results, the dynamic constitutive model of UHPC will be developed. At the same time, the formula with inclusion of the fiber effects will be established and used to determine the key parameters for the developed UHPC dynamic constitutive model. Furthermore, a series of field blast tests will be carried out to investigate the dynamic response and failure mode of UHPC-FST piers under close-in range detonation. After that, the high fidelity finite element model will be developed to analyze the dynamic response of the UHPC-FST pier under blast load, and the numerical results will be validated and compared with that of field blast tests. The pseudo-static test and corresponding numerical model will then be employed to investigate the residual seismic performance of the blast damaged UHPC-FST piers. And then the residual seismic performance of blast damaged UHPC-FST pier will be evaluated. The damage assessment criteria will further be developed to characterize the observed damage of UHPC-FST piers caused by blast loading in terms of the loss in the pier’s seismic performance capability. The prospective achievements will significantly improve the theoretical system of UHPC-FST piers under intensive dynamic loadings, and provide the guideline for the strengthening of the blast damaged bridge piers, so as to guaranteeing the transportation system securities.