【作者】 余芳；

【导师】 贾金青；

【作者基本信息】 大连理工大学 ， 结构工程， 2013， 博士

【摘要】 车辆超载和环境腐蚀是引起桥梁结构使用寿命降低的两个主要原因。车辆超载容易引起混凝土内部发生疲劳损伤,环境腐蚀会致使桥梁结构耐久性降低,从而进一步加重混凝土内部损伤程度。本文结合科技部“863”计划资助项目“基于疲劳和寿命的混凝土桥梁结构设计方法”(2007AA11Z133),对腐蚀钢绞线以及钢绞线腐蚀后的部分预应力混凝土梁开展了静力和疲劳试验研究与分析,主要研究内容和结果如下：1、通过对同批钢绞线进行的静力拉伸试验和疲劳试验,研究了腐蚀钢绞线的静力性能和疲劳性能。静力拉伸试验结果表明,钢绞线的塑性变形能力、极限强度以及弹性模量随腐蚀率的增加而衰减。疲劳试验结果表明,钢绞线的疲劳寿命随腐蚀率的增长按指数规律衰减,腐蚀缺陷与疲劳荷载之间的耦合作用是导致疲劳寿命下降的主要原因,腐蚀对钢绞线疲劳性能的影响远比对钢绞线的静力性能影响大。通过试验数据的回归统计建立了腐蚀钢绞线在静载作用下的本构关系模型与疲劳荷载作用下的S-N方程。2、通过对同批钢绞线腐蚀后的部分预应力混凝土梁进行四点弯曲的静载和疲劳试验,研究了腐蚀对试验梁静力和疲劳性能的影响。静载试验结果表明,在静载试验中,钢绞线的腐蚀不仅导致部分预应力混凝土梁的破坏形态由延性破坏转为脆性破坏,还影响了腐蚀梁的开裂荷载大小,腐蚀对延性的影响远比对极限承载力影响显著。疲劳试验结果表明,腐蚀梁的疲劳破坏是由腐蚀钢绞线的疲劳断裂引起的,试验梁的疲劳寿命与疲劳强度随着钢绞线腐蚀程度的增加而显著降低。根据试验结果回归建立了疲劳荷载下钢绞线腐蚀后的部分预应力混凝土梁跨中挠度和混凝土残余应变的计算公式。此外,鉴于超载对既有桥梁结构的影响,本章还对一种新型预应力混凝土梁开展了单调荷载与循环荷载下的受力性能研究,结果表明,该种类型梁在单调与循环荷载作用下均有良好的承载能力和延性,具有良好的应用前景。3、基于内力平衡方程和平截面假定,推导了试验梁的跨中挠度与钢筋应变关于混凝土受压区边缘应变的表达式,并引入分级加应变法对静载作用下钢绞线腐蚀后的部分预应力混凝土梁的受力过程进行分析。确立了受压区混凝土以及受拉钢筋(包括钢绞线)疲劳本构关系及疲劳破坏准则,运用分段线性方法并结合静载的分级应变法,建立了钢绞线腐蚀后的部分预应力混凝土梁的疲劳损伤全过程分析方法。4、运用ANSYS有限元软件对钢绞线腐蚀后的预应力混凝土梁在静力荷载下的受力行为进行了数值分析,分析了钢绞线腐蚀对预应力混凝土梁的静力性能影响,并与试验结果进行比较。根据Corten-Dolan累积损伤理论与ANSYS中的疲劳分析模块对三级变幅疲劳荷载下的试验梁进行了等效疲劳寿命预测。更多还原

【Abstract】 The vehicle overloading and the environment corrosion are two major reasons for the fatigue life reduction of bridge structures. The vehicle overloading is liable to cause the fatigue damages of interior concrete, while the environment corrosion degrades structure durability and further increases the damage degree of interior concrete. In this thesis, the mechanical properties of corroded strands as well as the mechanical behaviors of partial prestressed concrete beams after strand corroded were investigated under monotonic static loading and constant-amplitude fatigue loadings. This study is an important part of the project of High Technology Plan of the National Department of Technology "Design Method of Concrete Beam Structure Based on Fatigue and Life"(Grant No.2007AA11Z133). The contents include four chapters in the paper as follows.1. Monaxial tension tests and fatigue tests were carried on a batch of corroded strands. The static and fatigue properties were studied. The monaxial tension test results showed that the plastic deformation ability, ultimate strength as well as elastic modulus of strands significantly decreased with the increase of corrosion rate. The fatigue test results showed that the fatigue life of strands decreased exponentially with the increase of corrosion rate. The interaction of corroded defects and fatigue loads was the primary reason for a sharp reduction of fatigue life of strand. Strand corrosion had more notable effects on fatigue performance than on static performance. Based on statistics analysis of experimental data, a constitutive relation and S-N curves equation of corroded strand were established respectively in monaxial tensile tests and fatigue tests.2. The static and fatigue flexural tests were carried on a batch of partial prestressed concrete beams to study the effects of strand corrosion on the mechanical performance of specimen beams. The static test results showed that strand corrosion not only transformed the ductile failure mode into a more brittle one, but also affected the cracking load of beams. In comparison with ultimate load, ductility of the beams were worst affected by strand corrosion. The fatigue test results showed that the fatigue failures of corroded beams were caused by the fatigue rupture of the corroded strands. The fatigue life and fatigue strength of specimens decreased with the increase of corrosion rate. After experimental statistics, a regression model between midspan deflection and cycle number, and a regression equation between concrete residual strain and cycle number were established, respectively. In addition, due to the effect of overloading on existing bridge structures, a novel prestressed concrete beam was tested under monotonic and cyclic loading to study the mechanic performances in this chapter. The results showed that this beam had satisfactory capacity and ductility both under monotonic and cyclic loading, thus it had a favorable application foreground. 3. On the basis of the internal force equilibrium and plane section assumption, a simple method based on the strain of concrete at the upper edge of compression zone was derived to calculate the midspan deflection and reinforced steel strain. The step increasing strain method was introduced to analyse the loading procedure of partial prestressed concrete beams with corroded strands in static test. The fatigue rules including constitutive relations and failure criterion of concrete at the upper edge of compression zone and reinforced steel (including prestressing strand) in tension zone were established. And on the basis of the rules, an analysis method for the fatigue damage process of beams was proposed according to the piece wise linear method and the step increasing strain method.4、The behavior of partial prestressed concrete beams with corroded strands in static tests were simulated to analyse the effect of strand corrosion on the mechanical performances of test beams by using ANSYS software. The simulation results were also compared with the experimental results. On the basis of Corten-Dolan accumulative damage rule and fatigue analysis module of ANSYS software, the fatigue life of partial prestressed concrete beams with corroded prestressing strands under three variable-amplitude loadings and different corrosion rates of strands were predicted equivalently.更多还原