【作者】 杨俊；

【导师】 郭彤；

【作者基本信息】 东南大学 ， 防灾减灾与防护工程， 2020， 博士

【摘要】 几十年来,针对预制结构已有大量的研究和应用。通过使用施工质量好、可快速安装的预制构件,可取得良好的综合效益。然而,出于对其抗震能力的担忧,预制结构在抗震地区的应用往往受限。为此,各国研究人员开展了大量的研究来提高预制结构的抗震能力,特别是预制构件节点的抗震能力,并提出了一系列预制装配结构体系,如预应力混凝土装配整体式框架体系(世构体系)。对于预制混凝土结构,由于连接部位和后浇叠合层的存在,锈蚀介质更容易侵入到混凝土中;同时,锈蚀过程高度依赖于结构构造及建造方法。值得注意的是,目前预应力混凝土装配整体式框架结构已应用于沿海环境,锈蚀可能导致其结构性能发生退化。然而,针对锈蚀预制预应力混凝土结构抗震性能的研究尚鲜有报道。本论文通过试验和数值分析,对锈蚀预应力混凝土装配整体式框架结构的时变抗震性能进行了研究,具体包括:(1)介绍了氯离子侵蚀过程和材料性能的退化,以及预应力混凝土装配整体式框架结构的构造。对不同锈蚀程度下预应力混凝土装配整体式框架梁柱节点的抗震性能进行了试验研究。制作了5个不同锈蚀程度的预应力混凝土装配整体式框架梁柱节点,并进行循环加载测试。对其开裂模式、滞回曲线、骨架曲线、承载能力、延性和耗能能力进行了对比分析,得到了承载能力、延性以及耗能能力的退化规律及退化模型。(2)试验研究了不同锈蚀程度及不同U形钢筋搭接长度对梁柱节点的抗震性能影响。制作了十个不同锈蚀程度及不同搭接长度的梁柱节点,并进行低周反复加载,对滞回曲线、骨架曲线、承载能力、延性、耗能能力进行了对比分析。结果表明,锈蚀显著影响了结构的抗震性能。大部分试件呈现出弯曲失效的破坏模式,而对于锈蚀极为严重的试件,预制梁和键槽接触界面可能出现失效破坏。总体上,拥有较短键槽长度的试件抗震性能优于键槽长度相对较长的试件。然而,随着锈蚀率的增加,这个差距有所减小。根据试验结果,给出了锈蚀环境下预应力混凝土装配整体式框架结构的设计建议。(3)通过长期加载试验,研究了恒载和锈蚀耦合作用下预应力混凝土叠合梁的时变性能。在加速锈蚀过程中,对6根预应力叠合梁施加不同等级的恒载,同时记录预应力损失及混凝土应变随时间的变化。试验结果表明,不同的恒载等级明显影响了预应力钢绞线的局部锈蚀损伤(坑蚀)。同时,恒载和锈蚀耦合作用所产生的的损伤大于单个因素所产生的损伤。通过长期监测试验,给出了不同条件下预应力混凝土叠合梁预应力损失及混凝土应变时变曲线,为理解和评估预应力混凝土叠合梁的长期性能提供参考。(4)为评估锈蚀预应力混凝土装配整体式框架的时变抗震性能,对一个不同锈蚀程度的4层框架进行了多尺度建模。在ABAQUS中通过用户自定义材料(UMAT)模块建立了一个纤维单元模型来模拟锈蚀钢筋的滞回行为,并通过先前的节点试验数据验证了多尺度模型建模方法的有效性。该多尺度建模方法可以有效地平衡计算工作量和计算精度。基于所提出的多尺度模型,通过增量动力分析方法开展了锈蚀框架的易损性分析。分析结果表明,不同地震动和锈蚀率下的结构响应存在高度的离散性。同时,结构地震易损性与锈蚀率高度相关。随着锈蚀率的增加,结构失效概率呈指数增长趋势。(5)基于可靠度理论,以Fick第二定律为基础,阐述了氯离子扩散规律及钢筋锈蚀机理,结合Duracrete模型及以往试验结果,确定了沿海环境参数及锈蚀参数的概率分布类型及统计特征。基于路径概率模型建立了综合考虑离子输运、钢筋锈蚀及承载力退化等多过程的装配式混凝土结构时变性能不确定性分析框架,针对各个极限状态开展了结构时变可靠性分析,揭示了结构可靠度指标的时变规律。最终,建立起一种预制预应力混凝土结构全寿命抗震性能评估模型。更多还原

【Abstract】 Prefabricated buildings have been extensively investigated and applied for decades.By using durable and rapidly erectable prefabricated members,high-quality structures could be created at a relatively low cost.However,the seismic capacity of precast concrete structures has long been one major concern that prevents their wide application in seismic regions.Therefore,extensive investigations have been made to develop structures that have desirable seismic capacities especially at the joints of prefabricated components.Among these research efforts,the frame structure comprised of precast prestressed concrete components(SCOPE)has been put forward.For precast concrete structures,corrosion medium are easier to penetrate into structural joints where precast components are connected or post-casting is applied.The corrosion process and structural deterioration,however,highly depend on structural configuration and construction procedure.It is worth noting that the SCOPE system has been used in coastal region,where corrosion-induced deterioration may be a concern.However,so far no researches have been made with regard to the seismic performance of the corroded SCOPE system.This paper presents experimental study and numerical investigation on the seismic behaviors of corroded SCOPE system.In detail,this study includes contents as follows:(1)In order to provide basis for the use of SCOPE system in chloride area,an experimental study on the seismic behaviors of corroded beam-column joints of the SCOPE system was carried out.Five specimens with different levels of corrosion were tested under cyclic loading,and crack propagation,hysteretic loops,envelope curves,bearing capacity,ductility and energy dissipation were compared and analyzed.Based on the experimental results,the degradation characteristics and models of bearing capacity,ductility and energy dissipation were analyzed and developed.(2)According to previous research,the length of non-contact lapped splice between U-shape bars and the steel strands plays an important role in seismic performance of the beam column joint.However,the splice may deteriorate due to corrosion when the frame is used in coastal region.This paper presents an experimental investigation on seismic behaviors of the corroded beam-column joints of the SCOPE system.Ten specimens with different key slot lengths and different corrosion levels were tested under cyclic loading,and their hysteretic loops,envelop curves,bearing capacity,and energy dissipation were compared and analyzed.It is observed that the corrosion of steel bars would significantly affect seismic behaviors of the structure,and most specimens showed flexural failure,while for the seriously corroded specimens with long key slots,failure might occur at the interface between the precast beam and the key slot due to severe corrosion and bond failure of the lapped splice.In general,the energy dissipation of specimens with shorter slot length was greater than that of specimens with the longer key slot under the same corrosion level.However,as the corrosion level increases,the difference became smaller.Based on the experimental results,the design suggestion of the SCOPE system under corrosion environment is given.(3)This paper presents an experimental investigation on long-term behavior of PSC beams under the coupled effect of sustained load and corrosion.During the accelerated corrosion process,six PSC beams were subjected to different levels of sustained loads,and time-dependent prestress loss and concrete stains were recorded and analyzed.It is observed that the local corrosion(i.e.pitting corrosion)of the steel strands was significantly affected by the sustained load level,and the coupled effect led to more serious damage on the beams than individual sustained load or corrosion.The monitored data during the sustained load is very valuable for understanding and evaluating the long-term behavior of PSC beams.(4)To evaluate the time-dependent seismic performance of the corroded SCOPE system,a multi-scale finite element model is proposed to modeling of four-story moment frames with different levels.A fiber model is proposed to simulate the hysteretic behavior of corroded steel bars by using the User-defined material subroutine in the ABAQUS.The proposed multi-scale finite element model is validated through existing experiments,so that the balance between accuracy and computational costs is realized.Based on the proposed finite element model of frame,the influence of corrosion on seismic fragility of the frames is investigated through incremental dynamic analysis.Four limit states regarding the maximum interstory drift ratio are defined to evaluate the seismic fragility.The analysis results show that structural responses are highly random under different ground motions and corrosion levels.Meanwhile,the seismic fragility of the frame is significantly influenced by corrosion ratios,and the probabilities of exceedance show an exponential growth with the increase of corrosion level for all four limit states.(5)Based on the reliability theory and Fick’s second law,the chloride diffusion law and the corrosion mechanism of steel bars are elaborated in detail.The probability distribution types and statistical characteristics of coastal environmental parameters and corrosion parameters are determined by combining duracrete model and previous test results.Based on the path probability model,the uncertainty analysis framework of time-dependent seismic performance of prefabricated concrete structure is established,which considers the multiple processes of ion transport,reinforcement corrosion and bearing capacity degradation.The time-dependent reliability analysis of the structure is carried out for each limit state.Finally,the whole life seismic performance evaluation model of prestressed concrete structure is established.更多还原