WO2020042781A1 - 预应力混凝土桥梁腐蚀疲劳寿命预测方法及系统 - Google Patents

预应力混凝土桥梁腐蚀疲劳寿命预测方法及系统 Download PDF

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WO2020042781A1
WO2020042781A1 PCT/CN2019/096061 CN2019096061W WO2020042781A1 WO 2020042781 A1 WO2020042781 A1 WO 2020042781A1 CN 2019096061 W CN2019096061 W CN 2019096061W WO 2020042781 A1 WO2020042781 A1 WO 2020042781A1
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fatigue
concrete
steel
stress
corrosion
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PCT/CN2019/096061
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English (en)
French (fr)
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马亚飞
苏小超
王磊
张建仁
郭忠照
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长沙理工大学
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Priority to US16/758,868 priority Critical patent/US11486815B2/en
Publication of WO2020042781A1 publication Critical patent/WO2020042781A1/zh

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    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D22/00—Methods or apparatus for repairing or strengthening existing bridges ; Methods or apparatus for dismantling bridges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D1/00—Bridges in general
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0008—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of bridges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
    • G01N17/006—Investigating resistance of materials to the weather, to corrosion, or to light of metals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D2101/00—Material constitution of bridges
    • E01D2101/20—Concrete, stone or stone-like material
    • E01D2101/24—Concrete
    • E01D2101/26—Concrete reinforced
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D2101/00—Material constitution of bridges
    • E01D2101/20—Concrete, stone or stone-like material
    • E01D2101/24—Concrete
    • E01D2101/26—Concrete reinforced
    • E01D2101/28—Concrete reinforced prestressed
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0005—Repeated or cyclic
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0073—Fatigue

Definitions

  • the invention relates to the field of service bridge safety assessment, in particular to a method and system for predicting the corrosion fatigue life of prestressed concrete bridges.
  • Prestressed concrete bridges have strong spanning capacity and account for a large proportion of highway bridges in China. In recent years, the durability problems of such bridges have gradually appeared.
  • the construction process requires that the pre-stressed tendons be grouted after being stretched.
  • the post-tensioned pre-stressed concrete bridges built in the early days are not universally filled with pre-stressed concrete beams due to construction defects and bleeding. Insufficient grouting will accelerate the invasion of corrosion ions and cause corrosion of steel strands, reducing the cooperativity between prestressed steel strands and concrete.
  • the service bridge also bears repeated vehicle loads.
  • the prediction of fatigue residual life of prestressed concrete bridges is mostly based on empirical formulas obtained from fatigue test data. Factors such as material performance degradation and steel strand stress growth are not considered, and there is no quantitative evaluation standard. After the corrosion of steel strands in post-tensioned prestressed concrete bridges, the stress state becomes more complicated, and the determination of fatigue damage parameters becomes more difficult. Corrosion fatigue failure of prestressed concrete bridges is mainly caused by concrete tension and compression fatigue failure, fatigue failure of steel strands and ordinary steel bars. As the degree of corrosion increases, different failure modes may change. How to effectively consider the residual prestressing of the structure, the stress concentration caused by the corrosion of steel strands, and the degradation of the performance of concrete materials in the fatigue life prediction analysis need to be resolved.
  • the technical problem to be solved by the present invention is to provide a method and system for predicting the corrosion fatigue life of prestressed concrete bridges that are reasonable, highly applicable, and closer to the damage evolution of actual bridges, in view of the shortcomings of the existing technology.
  • the technical solution adopted by the present invention is: a method for predicting the fatigue life of corrosion of prestressed concrete bridges, including the following steps:
  • Step 1 Calculate the elastic strain and plastic strain of the concrete in the compression zone under fatigue load, and calculate the elastic modulus of the concrete after degradation;
  • Step 2 Use the corrosion current density to characterize the corrosion rate of the steel strand, predict the corrosion loss of the steel strand, and calculate the remaining effective pre-stressing force of the steel strand; according to the deformation coordination conditions, consider the degradation of the elastic modulus of the concrete, and integrate it into the pitting corrosion The effect of the stress concentration on the strand strain increase, the elastic strain of the strand caused by fatigue load is calculated; considering the influence of the plastic strain of the concrete in the compression zone on the strain of the strand, the plastic strain of the strand is calculated, and the corrosion and fatigue are obtained Steel strand stress under the common action;
  • Step 3 Consider the effect of prestressing of the stranded steel bar on the prestressing force of the common steel bar in the tensile zone to obtain the initial stress of the common steel bar in the tensile zone; calculate the elastic stress of the common steel bar in the tensile zone under fatigue loading; The influence of strain on the steel bar strain in the tensile zone, the plastic stress of the steel bar is calculated, and the total stress of the steel bar in the tensile zone under the combined action of rust and fatigue is obtained;
  • Step 4 With the increase of the number of fatigue loads, calculate the stress-strain of the concrete, tensile zone steel bars, and steel strands in real time, and combine the stress-strain growth relationship model and failure criterion of concrete, ordinary steel bars, and steel strands to determine Structural failure mode, evaluation of structural fatigue life.
  • Step one includes,
  • the strain of concrete in compression zone includes elastic strain And plastic strain
  • x n can refer to the calculation method of compression zone height in partially prestressed concrete bending members.
  • Concrete strain is divided into two parts, elastic strain and plastic strain.
  • the influence of stress history on the degradation of concrete elastic modulus is considered, and the strain growth mechanism of concrete is quantified.
  • the moment of inertia of the cracking section can be expressed as:
  • the failure criterion of concrete in the compression zone is:
  • ⁇ c0 is the ultimate compressive strain of concrete under static load.
  • Step two includes,
  • Peak stress of steel strands under fatigue loading Divided into three parts: the remaining effective pre-strength of the steel strand at time t Initial tensile stress Stress concentration due to pitting and elastic stress due to fatigue loading Caused by plastic deformation of concrete in concrete and compressed areas
  • the quality corrosion rate can be expressed as:
  • i ccor is the corrosion current density
  • L is the corrosion length
  • E P and ⁇ P are the elastic modulus and strain of the stainless steel strand, respectively, and T 0 is the initial tensile force.
  • f u is the ultimate tensile strength of the prestressed steel strand.
  • N k-1 is the life value in the SN curve of the steel wire corresponding to the stress amplitude of the steel wire during the k-1th fatigue.
  • k t is the stress concentration factor caused by rust pits.
  • the plastic strain of the edge of the compression zone is The height of the compressed area is x n . From the assumption of a flat section, the deformation coordination conditions of concrete and steel strands can be obtained Induced plastic strain of steel strands:
  • strand stress Can be expressed as:
  • the stranded wire failure criteria are:
  • the invention considers the reduction of the remaining effective pre-stress of the steel strand after rusting, takes the area loss of the steel strand as the fatigue damage parameter, and takes into account the stress concentration effect of the steel strand caused by uneven pitting. Stress is divided into three parts, each of which is a dynamic process that changes with time and load.
  • Step three includes,
  • Peak stress of ordinary steel bars in the tensile zone under fatigue loading Divided into three parts: the remaining effective pre-strength of the strand at time t Common compressive stress Elastic stress due to fatigue loading Caused by plastic deformation of concrete in concrete and compressed areas
  • f y is the yield strength of ordinary steel bars.
  • the invention considers that the failure of the structure may start from the fracture of the ordinary steel bar, and the stress of the ordinary steel bar in the rusted tensile zone is divided into three parts. Similarly, each part is dynamically changed.
  • Step four includes,
  • the fatigue life calculation process of prestressed concrete bridges is as follows: First, for a given n, the stress calculation formulas (5), (15) and (20) of concrete, steel strands and tensile steel bars are substituted into the equilibrium equation (internal force balance) Equation, moment balance equation) can solve the corresponding stress magnitude; secondly, according to the failure criterion of each component material in formulas (6), (16), (21), determine whether the structure is fatigue failure; if not, Then increase n and repeat the above steps; repeat the process in this way until the failure of a material, and the number of fatigue times n experienced at this time is the fatigue life of the structure.
  • the present invention also provides a corrosion fatigue life prediction system for a prestressed concrete bridge, which includes:
  • Calculation unit for calculating the elastic strain on top of concrete in a compression zone under fatigue loading Cumulative plastic strain And concrete elastic modulus
  • Evaluation unit for real-time calculation of the stress-strain of concrete, tensile steel bars, and steel strands as the number of fatigue loads increases, combining the stress-strain growth relationship model and failure criteria of concrete, ordinary steel bars, and steel strands, Determine the failure mode of the structure and evaluate the fatigue life of the structure; the evaluation unit specifically implements the following operations:
  • the failure criterion of the concrete in the compression zone is ⁇ c0 is the ultimate compressive strain of the concrete under static load
  • the failure criterion of the steel strand is f u is the ultimate tensile strength of the prestressed steel strand
  • the failure criterion of ordinary steel bars is f y is the yield strength of ordinary steel bars
  • the technical effect of the present invention is that for the prestressed concrete bridge structure with insufficient grouting, taking into account factors such as corrosion of steel strands, stress concentration, degradation of concrete elastic modulus, residual strain, and other factors, the peak stresses of steel strands and ordinary rebars are respectively Divided into three parts, the two stress growth models are proposed; integrated into the vehicle load, a set of fatigue life analysis methods for prestressed concrete bridges under corrosive environment and load is formed. The method is reasonable, applicable and closer to the actual bridge damage Evolution can provide effective support for fatigue life assessment of prestressed concrete bridges in service.
  • Figure 1 is a schematic diagram of the fatigue life assessment of the present invention.
  • Figure 2 is a schematic diagram of the strain of concrete, ordinary steel bars and steel strands.
  • Strand strain under the remaining effective pre-stressing with Elastic strains of steel strands and ordinary steel bars under fatigue loads; with They are the plastic strain of steel strands and ordinary steel bars caused by the plastic deformation of concrete in the compression zone.
  • Fig. 3 is a calculation flowchart of the invention.
  • x n can refer to the calculation method of compression zone height in partially prestressed concrete bending members.
  • the moment of inertia of the cracking section can be expressed as:
  • ⁇ c0 is the ultimate compressive strain of concrete under static load.
  • the corrosion rate of the steel strand represented by the corrosion current is:
  • i ccor is the corrosion current density
  • L is the corrosion length
  • E P and ⁇ P are the elastic modulus and strain of the stainless steel strand, respectively, and T 0 is the initial tensile force.
  • f u is the ultimate tensile strength of the prestressed steel strand.
  • N k-1 is the life value in the SN curve of the steel wire corresponding to the stress amplitude of the steel wire during the k-1th fatigue.
  • the stress peak of the steel strand is divided into three parts: the residual effective pre- energization at time t , the tensile stress caused by t Elastic stress due to fatigue loading and stress concentration caused by pitting Caused by plastic deformation of concrete in concrete and compressed areas
  • k t is the stress concentration factor caused by rust pits.
  • the plastic strain of the edge of the compression zone is The height of the compressed area is x n . From the assumption of a flat section, the deformation coordination conditions of concrete and steel strands can be obtained Induced plastic strain of steel strands:
  • strand stress Can be expressed as:
  • the stranded wire failure criteria are:
  • the peak stress of ordinary steel bars in the tensile zone is divided into three parts: the remaining effective prestressing force of the steel strand at time t , the common steel bar compressive stress ⁇ s caused by t , 0 , and the elastic stress caused by fatigue loads.
  • f y is the yield strength of ordinary steel bars.
  • the fatigue life calculation process of prestressed concrete bridges is as follows: First, for a given n, the stress calculation formulae (5), (15), and (20) of concrete, steel strands, and ordinary steel bars are substituted into the equilibrium equation (internal force equilibrium equation) , Moment balance equation) to solve the corresponding stress magnitude; Secondly, according to the failure criterion of each component material in formulas (6), (16), (21), determine whether the structure is fatigue failure; if not, then Increase n and repeat the above two calculation steps; repeat this way and perform cyclic iterative calculations until one of the above three constituent materials reaches the failure criterion, and the structure fails. At this time, the number of load cycles n experienced by the structure is the structure. The number of fatigue times, the time t corresponding to n is the fatigue life of the structure.

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Abstract

一种预应力混凝土桥梁腐蚀疲劳寿命预测方法及系统，将钢绞线的应力分为三部分：剩余有效预加力引起的拉应力、疲劳荷载引起的弹性应力和受压区混凝土塑性变形引起的应力。通过预测钢绞线锈蚀水平得到结构剩余预加力；引入应力集中因子来考虑坑蚀引起的应力集中影响，提出了腐蚀和疲劳共同作用下钢绞线弹性应力增长模型；以钢绞线截面损失作为疲劳损伤参量，考虑疲劳后混凝土弹性模量退化，建立了钢绞线塑性应力增长模型；明确了混凝土、钢绞线和普通钢筋的失效准则，形成了一整套腐蚀环境和疲劳荷载作用下预应力混凝土桥梁寿命分析方法。预测方法合理，适用性强，可为服役预应力混凝土桥梁的安全评定提供支持。

Description

预应力混凝土桥梁腐蚀疲劳寿命预测方法及系统 技术领域
本发明涉及服役桥梁安全评估领域，特别是一种预应力混凝土桥梁腐蚀疲劳寿命预测方法及系统。
背景技术
预应力混凝土桥梁跨越能力强，在我国公路桥梁中占很大比重。近年来，该类桥梁的耐久性问题逐渐显现。对于后张预应力混凝土梁，施工工艺要求预应力筋张拉后需进行孔道压浆。然而，早期修建的后张预应力混凝土桥梁，由于施工缺陷、泌水等原因，预应力混凝土梁孔道压浆不饱满的问题较为普遍。压浆不饱满会加速腐蚀离子侵入并导致钢绞线腐蚀，降低预应力钢绞线和混凝土间的协同工作性。同时，服役桥梁还承受反复的车辆荷载，随着经济的发展，交通量和轴重呈上升趋势。腐蚀减小了钢绞线截面积，钢绞线承受的实际应力幅增大，腐蚀和疲劳的共同作用加速了材料的疲劳损伤累积，结构失效概率显著增加。
目前，对预应力混凝土桥梁的疲劳剩余寿命预测多是基于疲劳试验数据得到的经验公式，未考虑材料性能退化和钢绞线应力增长等因素，缺乏定量的评价标准。后张预应力混凝土桥梁中的钢绞线锈蚀后，其应力状态更加复杂，疲劳损伤参量的确定难度加大。预应力混凝土桥梁的腐蚀疲劳主要失效形式为混凝土拉压疲劳破坏，钢绞线和普通钢筋疲劳失效。随着锈蚀程度的增加，不同失效形式可能发生转变。疲劳寿命预测分析中如何有效考虑结构剩余预加力、钢绞线锈蚀引起的应力集中及混凝土材料性能退化等因素亟待解决。
发明内容
本发明所要解决的技术问题是，针对现有技术不足，提供一种合理，适用性强，更加接近实际桥梁的损伤演化的预应力混凝土桥梁腐蚀疲劳寿命预测方法及系统。
为解决上述技术问题，本发明所采用的技术方案是：一种预应力混凝土桥梁腐蚀疲劳寿命预测方法，包括以下步骤：
步骤一：计算疲劳荷载下受压区混凝土的弹性应变与塑性应变、计算退化后的混凝土弹性模量；
步骤二：采用锈蚀电流密度表征钢绞线的锈蚀速率，预测钢绞线的锈蚀损失，由此计算钢绞线剩余有效预加力；根据变形协调条件，考虑混凝土弹性模量退化，融入坑蚀导致的应力集中对钢绞线应变增长的影响，计算疲劳荷载引起的钢绞线弹性应变；考虑 受压区混凝土塑性应变对钢绞线应变的影响，计算钢绞线塑性应变，得到锈蚀和疲劳共同作用下钢绞线应力；
步骤三：考虑钢绞线张拉锚固后对受拉区普通钢筋预压力的影响，得到受拉区普通钢筋初始应力；计算疲劳荷载作用下受拉区普通钢筋弹性应力；考虑受压区混凝土塑性应变对受拉区钢筋应变的影响，计算钢筋塑性应力，得到锈蚀和疲劳共同作用下受拉区钢筋总应力；
步骤四：随疲劳荷载次数的增加，对混凝土、受拉区钢筋、钢绞线的应力-应变进行实时计算，结合混凝土、普通钢筋、钢绞线的应力-应变增长关系模型和失效准则，判定结构失效模式，对结构疲劳寿命做出评价。
步骤一包括，
在疲劳荷载作用下，受压区混凝土的应变包括弹性应变
Figure PCTCN2019096061-appb-000001
和塑性应变
Figure PCTCN2019096061-appb-000002
首先，计算受压区混凝土顶部的弹性应变
Figure PCTCN2019096061-appb-000003
为：
Figure PCTCN2019096061-appb-000004
式中，
Figure PCTCN2019096061-appb-000005
和
Figure PCTCN2019096061-appb-000006
分别为经历n-1次疲劳后的混凝土弹性模量和钢绞线有效张拉力引起的弯矩效应；
Figure PCTCN2019096061-appb-000007
x n和
Figure PCTCN2019096061-appb-000008
分别为n次疲劳后车辆荷载引起的截面弯矩效应、受压区高度和开裂截面惯性矩，其中x n可参照部分预应力混凝土受弯构件中受压区高度的计算方法。
将混凝土应变分为弹性应变和塑性应变两个部分，考虑了应力历程对混凝土弹性模量退化的影响，进而量化了混凝土的应变增长机制。
开裂截面惯性矩可表示为：
Figure PCTCN2019096061-appb-000009
式中，b为截面宽度；y n为n次疲劳后开裂截面中性轴与混凝土受压区边缘的距离；h s、h p和a′ s分别为受拉区普通钢筋、钢绞线和受压区普通钢筋的截面重心至混凝土受压区边缘的距离(假定受力筋在直径方向截面损失相同，则h s、h p和a′ s在疲劳周期内为定值)；
Figure PCTCN2019096061-appb-000010
和
Figure PCTCN2019096061-appb-000011
分别为n次疲劳后，钢绞线与混凝土弹性模量
Figure PCTCN2019096061-appb-000012
比值、普通钢筋与 混凝土弹性模量
Figure PCTCN2019096061-appb-000013
的比值；
Figure PCTCN2019096061-appb-000014
和
Figure PCTCN2019096061-appb-000015
分别为钢绞线、受拉区普通钢筋和受压区普通钢筋有效剩余面积。
其次，计算n次疲劳后受压区混凝土顶部应力相关系数α r,n：
Figure PCTCN2019096061-appb-000016
式中，
Figure PCTCN2019096061-appb-000017
和
Figure PCTCN2019096061-appb-000018
分别为n次疲劳后受压区混凝土顶部的最大和最小弹性应力，
Figure PCTCN2019096061-appb-000019
受压区混凝土顶部的累积塑性应变
Figure PCTCN2019096061-appb-000020
为：
Figure PCTCN2019096061-appb-000021
式中，
Figure PCTCN2019096061-appb-000022
为混凝土轴心抗压强度初始实测值；
Figure PCTCN2019096061-appb-000023
为混凝土弹性模量初始实测值；n i为第i级疲劳荷载作用次数，(n与车辆荷载有关，为t的函数)。
然后，得到n次疲劳后混凝土的弹性模量：
Figure PCTCN2019096061-appb-000024
式中，
Figure PCTCN2019096061-appb-000025
为n次疲劳荷载后混凝土弹性模量；修正系数β为统计结果(C20～C50为0.61，C60～C70为0.875)；其余符号含义同上。
受压区混凝土失效准则为：
Figure PCTCN2019096061-appb-000026
式中，ε c0为静载作用下混凝土的极限压应变。
步骤二包括，
在疲劳荷载作用下，钢绞线的峰值应力
Figure PCTCN2019096061-appb-000027
分三部分：t时刻钢绞线剩余有效预加力
Figure PCTCN2019096061-appb-000028
引起的初始拉应力
Figure PCTCN2019096061-appb-000029
坑蚀所致应力集中和疲劳荷载引起的弹性应力
Figure PCTCN2019096061-appb-000030
和受 压区混凝土塑性变形引起的应力
Figure PCTCN2019096061-appb-000031
质量锈蚀率可表示为：
Figure PCTCN2019096061-appb-000032
式中，i ccor为锈蚀电流密度；L为锈蚀长度；R是结构中不同钢筋种类的锈蚀变异系数，对于钢绞线，R＝1。
t时刻剩余有效预加力
Figure PCTCN2019096061-appb-000033
为：
Figure PCTCN2019096061-appb-000034
式中，E P和ε P分别为未锈钢绞线的弹性模量和应变，T 0为初始张拉力。
在疲劳荷载作用下，锈蚀钢绞线会在其坑蚀位置产生疲劳裂纹，裂纹不断扩展直至断裂。若经历N次疲劳荷载后钢绞线断裂，此时钢绞线有效剩余面积为
Figure PCTCN2019096061-appb-000035
则钢绞线总损失面积为
Figure PCTCN2019096061-appb-000036
记第n次荷载下钢绞线承受的最大应力为σ p,max,n，则钢绞线在该特征荷载下疲劳断裂时的有效面积为：
Figure PCTCN2019096061-appb-000037
式中，f u为预应力钢绞线的极限抗拉强度。
假定疲劳荷载下钢绞线的面积呈线性减小，经历n次疲劳数后，钢绞线剩余有效面积
Figure PCTCN2019096061-appb-000038
为：
Figure PCTCN2019096061-appb-000039
式中，N k-1为第k-1次疲劳时钢绞线应力幅所对应的钢绞线S-N曲线中的寿命值。
在t时刻，剩余有效预加力
Figure PCTCN2019096061-appb-000040
引起的钢绞线拉应力
Figure PCTCN2019096061-appb-000041
为：
Figure PCTCN2019096061-appb-000042
钢绞线剩余有效面积的减小以及受压区混凝土弹性模量的退化会导致应力重分布，受压区高度、钢绞线和普通钢筋的应力-应变关系则相应发生变化。
疲劳荷载引起的钢绞线弹性
Figure PCTCN2019096061-appb-000043
为：
Figure PCTCN2019096061-appb-000044
式中，k t为锈坑引起的应力集中系数。
经历n次疲劳后，受压区边缘混凝土塑性应变为
Figure PCTCN2019096061-appb-000045
受压区高度为x n。由平截面假定、混凝土与钢绞线的变形协调条件可得到
Figure PCTCN2019096061-appb-000046
引起的钢绞线塑性应变：
Figure PCTCN2019096061-appb-000047
受压区混凝土塑性变形引起的钢绞线应力
Figure PCTCN2019096061-appb-000048
为：
Figure PCTCN2019096061-appb-000049
即，钢绞线应力
Figure PCTCN2019096061-appb-000050
可表示为：
Figure PCTCN2019096061-appb-000051
钢绞线失效准则为：
Figure PCTCN2019096061-appb-000052
本发明考虑了锈蚀后钢绞线剩余有效预加力的降低，将钢绞线面积损失作为疲劳损伤参量，并计入了不均匀坑蚀引起的钢绞线应力集中效应，钢绞线的总应力被分为了三个部分，每个部分均是随时间和荷载变化的动态过程。
步骤三包括，
在疲劳荷载作用下，受拉区普通钢筋峰值应力
Figure PCTCN2019096061-appb-000053
分为三部分：t时刻钢绞线剩余有效预加力
Figure PCTCN2019096061-appb-000054
引起的普通钢筋压应力
Figure PCTCN2019096061-appb-000055
疲劳荷载引起的弹性应力
Figure PCTCN2019096061-appb-000056
和受压区混凝土塑性变形引起的应力
Figure PCTCN2019096061-appb-000057
由于在计算混凝土弹性应变过程中，已考虑了钢绞线有效预加力的作用效应(即
Figure PCTCN2019096061-appb-000058
)，为避免重复计算，
Figure PCTCN2019096061-appb-000059
记为0。
疲劳荷载引起的受拉区普通钢筋弹性应力
Figure PCTCN2019096061-appb-000060
为：
Figure PCTCN2019096061-appb-000061
由平截面假定、混凝土与普通钢筋的变形协调条件可得到
Figure PCTCN2019096061-appb-000062
引起的受拉区普通钢筋塑性应变：
Figure PCTCN2019096061-appb-000063
受压区混凝土塑性变形引起的受拉区普通钢筋应力
Figure PCTCN2019096061-appb-000064
为：
Figure PCTCN2019096061-appb-000065
受拉区普通钢筋应力
Figure PCTCN2019096061-appb-000066
为：
Figure PCTCN2019096061-appb-000067
普通钢筋的失效准则为：
Figure PCTCN2019096061-appb-000068
式中，f y为普通钢筋的屈服强度。
本发明考虑到结构失效可能始于普通钢筋断裂，将锈蚀后的受拉区普通钢筋应力分为三个部分，同样，每个部分均是动态变化的。
步骤四包括，
预应力混凝土桥梁的疲劳寿命计算流程如下：首先，对于给定的n，将混凝土、钢绞线和受拉钢筋的应力计算式(5)、(15)和(20)代入平衡方程(内力平衡方程、力矩平衡方程)即可解出相应的应力大小；其次，分别根据公式(6)、(16)、(21)中各组成材料的失效判别准则，判别结构是否疲劳失效；若未失效，则增大n，重复以上步骤；如此往复，进行循环迭代计算，直至一种材料失效，此时所经历的疲劳次数n即为结构的疲劳寿命。
相应地，本发明还提供了一种预应力混凝土桥梁腐蚀疲劳寿命预测系统，其包括：
计算单元，用于计算疲劳荷载下受压区混凝土顶部的弹性应变
Figure PCTCN2019096061-appb-000069
累积塑性应变
Figure PCTCN2019096061-appb-000070
和混凝土弹性模量；
预测单元，用于预测钢绞线锈蚀水平得到结构剩余预加力，以锈蚀钢绞线截面损失为疲劳损伤参量，利用所述弹性应变
Figure PCTCN2019096061-appb-000071
累积塑性应变
Figure PCTCN2019096061-appb-000072
和退化后的混凝土弹性模量， 计算锈蚀和疲劳共同作用下持续增长的钢绞线应力
Figure PCTCN2019096061-appb-000073
和受拉区钢筋应力
Figure PCTCN2019096061-appb-000074
评价单元，用于随疲劳荷载次数的增加，对混凝土、受拉区钢筋、钢绞线的应力-应变进行实时计算，结合混凝土、普通钢筋、钢绞线应力-应变增长关系模型和失效准则，判定结构失效模式，对结构疲劳寿命做出评价；评价单元具体实现如下操作：
a)在典型疲劳荷载下，当n＝1时，计算得到混凝土累积塑性应变
Figure PCTCN2019096061-appb-000075
钢绞线应力值
Figure PCTCN2019096061-appb-000076
和受拉区钢筋总应力值
Figure PCTCN2019096061-appb-000077
n为疲劳次数；
b)根据以下公式中各组成材料的疲劳失效判别准则，判别梁是否疲劳失效：受压区混凝土失效准则为
Figure PCTCN2019096061-appb-000078
ε c0为静载作用下混凝土的极限压应变；钢绞线失效准则为
Figure PCTCN2019096061-appb-000079
f u为预应力钢绞线的极限抗拉强度；普通钢筋的失效准则为
Figure PCTCN2019096061-appb-000080
f y为普通钢筋的屈服强度；
c)若未失效，则增大n，重复步骤a)、b)，直至一种材料失效，此时所经历的疲劳次数n即为结构的疲劳寿命。
结合车辆荷载信息得到关键截面的荷载效应，循环计算腐蚀和实桥荷载共存情况下钢绞线、普通钢筋和混凝土的应力，结合各自材料的失效判别准则，评估结构的腐蚀疲劳寿命。
本发明的技术效果在于，针对压浆不饱满的预应力混凝土桥梁结构，考虑钢绞线锈蚀、应力集中、混凝土弹性模量退化和残余应变等因素，分别将钢绞线和普通钢筋的峰值应力分为三部分，提出了二者应力增长模型；融入车辆荷载，形成了一整套腐蚀环境和荷载作用下预应力混凝土桥梁疲劳寿命分析方法，该方法合理，适用性强，更加接近实际桥梁的损伤演化，可为服役预应力混凝土桥梁的疲劳寿命评估提供有效支持。
附图说明
图1为本发明的疲劳寿命评估整体示意图。
图2为混凝土、普通钢筋和钢绞线应变示意图。图2中，
Figure PCTCN2019096061-appb-000081
为剩余有效预加力作用下钢绞线应变；
Figure PCTCN2019096061-appb-000082
和
Figure PCTCN2019096061-appb-000083
分别为疲劳荷载作用下钢绞线和普通钢筋弹性应变；
Figure PCTCN2019096061-appb-000084
和
Figure PCTCN2019096061-appb-000085
分别为受压区混凝土塑性变形引起的钢绞线和普通钢筋塑性应变。
图3为发明的计算流程图。
具体实施方式
(1)确定疲劳荷载下受压区混凝土弹性应变
首先，计算受压区混凝土顶部的弹性应变
Figure PCTCN2019096061-appb-000086
为：
Figure PCTCN2019096061-appb-000087
式中，
Figure PCTCN2019096061-appb-000088
和
Figure PCTCN2019096061-appb-000089
分别为经历n-1次疲劳后的混凝土弹性模量和钢绞线有效张拉力引起的弯矩效应；
Figure PCTCN2019096061-appb-000090
x n和
Figure PCTCN2019096061-appb-000091
分别为n次疲劳后车辆荷载引起的截面弯矩效应、受压区高度和开裂截面惯性矩，其中x n可参照部分预应力混凝土受弯构件中受压区高度的计算方法。
开裂截面惯性矩可表示为：
Figure PCTCN2019096061-appb-000092
式中，b为截面宽度；y n为n次疲劳后开裂截面中性轴与混凝土受压区边缘的距离；h s、h p和a′ s分别为受拉区普通钢筋、钢绞线和受压区普通钢筋的截面重心至混凝土受压区边缘的距离(假定受力筋在直径方向截面损失相同，则h s、h p和a′ s在疲劳周期内为定值)；
Figure PCTCN2019096061-appb-000093
和
Figure PCTCN2019096061-appb-000094
分别为n次疲劳后，钢绞线与混凝土弹性模量
Figure PCTCN2019096061-appb-000095
比值、普通钢筋与混凝土弹性模量
Figure PCTCN2019096061-appb-000096
的比值；
Figure PCTCN2019096061-appb-000097
和
Figure PCTCN2019096061-appb-000098
分别为钢绞线、受拉区普通钢筋和受压区普通钢筋有效剩余面积。
计算n次疲劳后受压区混凝土顶部应力相关系数α r,n：
Figure PCTCN2019096061-appb-000099
式中，
Figure PCTCN2019096061-appb-000100
和
Figure PCTCN2019096061-appb-000101
分别为n次疲劳后受压区混凝土顶部的最大和最小弹性应力，
Figure PCTCN2019096061-appb-000102
受压区混凝土顶部的累积塑性应变
Figure PCTCN2019096061-appb-000103
为：
Figure PCTCN2019096061-appb-000104
式中，
Figure PCTCN2019096061-appb-000105
为混凝土轴心抗压强度初始实测值；
Figure PCTCN2019096061-appb-000106
为混凝土弹性模量初始实测值；n i为第i级疲劳荷载作用次数，(n与车辆荷载有关，为t的函数)。
然后，得到n次疲劳后混凝土的弹性模量：
Figure PCTCN2019096061-appb-000107
式中，
Figure PCTCN2019096061-appb-000108
为n次疲劳荷载后混凝土弹性模量；修正系数β为统计结果(C20～C50为0.61，C60～C70为0.875)；其余符号含义同上。
当混凝土累积塑性应满足下式时，即判断混凝土压溃，结构即丧失继续承载的能力：
Figure PCTCN2019096061-appb-000109
式中，ε c0为静载作用下混凝土的极限压应变。
(2)确定钢绞线锈蚀后剩余有效预加力
钢绞线在腐蚀环境下会形成微弱的腐蚀电流，用腐蚀电流表示的钢绞线锈蚀率为：
Figure PCTCN2019096061-appb-000110
式中，i ccor为锈蚀电流密度；L为锈蚀长度；R是结构中不同钢筋种类的锈蚀变异系数，对于钢绞线，R＝1。
钢绞线面积损失会导致预加力的降低，t时刻钢绞线剩余有效预加力T ρm,t为：
Figure PCTCN2019096061-appb-000111
式中，E P和ε P分别为未锈钢绞线的弹性模量和应变，T 0为初始张拉力。
(3)确定疲劳荷载下钢绞线的剩余有效面积
在疲劳荷载作用下，锈蚀钢绞线会在其坑蚀位置产生疲劳裂纹，裂纹不断扩展直至断裂。若经历N次疲劳荷载后钢绞线断裂，此时钢绞线有效剩余面积为
Figure PCTCN2019096061-appb-000112
则钢绞线 总损失面积为
Figure PCTCN2019096061-appb-000113
记第n次荷载下钢绞线承受的最大应力为σ p,max,n，则钢绞线在该特征荷载下疲劳断裂时的有效面积为：
Figure PCTCN2019096061-appb-000114
式中，f u为预应力钢绞线的极限抗拉强度。
假定疲劳荷载下钢绞线的面积呈线性减小，经历n次疲劳数后，钢绞线剩余有效面积
Figure PCTCN2019096061-appb-000115
为：
Figure PCTCN2019096061-appb-000116
式中，N k-1为第k-1次疲劳时钢绞线应力幅所对应的钢绞线S-N曲线中的寿命值。
(4)确定钢绞线应力峰值的三个部分
将钢绞线的应力峰值分为三部分：t时刻剩余有效预加力T ρm,t引起的拉应力
Figure PCTCN2019096061-appb-000117
疲劳荷载及坑蚀所致应力集中引起的弹性应力
Figure PCTCN2019096061-appb-000118
和受压区混凝土塑性变形引起的应力
Figure PCTCN2019096061-appb-000119
在t时刻，剩余有效预加力
Figure PCTCN2019096061-appb-000120
引起的钢绞线拉应力
Figure PCTCN2019096061-appb-000121
为：
Figure PCTCN2019096061-appb-000122
钢绞线剩余有效面积的减小以及受压区混凝土弹性模量的退化会导致应力重分布，受压区高度、钢绞线和普通钢筋的应力-应变关系则相应发生变化。
疲劳荷载引起的钢绞线弹性
Figure PCTCN2019096061-appb-000123
为：
Figure PCTCN2019096061-appb-000124
式中，k t为锈坑引起的应力集中系数。
经历n次疲劳后，受压区边缘混凝土塑性应变为
Figure PCTCN2019096061-appb-000125
受压区高度为x n。由平截面假定、混凝土与钢绞线的变形协调条件可得到
Figure PCTCN2019096061-appb-000126
引起的钢绞线塑性应变：
Figure PCTCN2019096061-appb-000127
受压区混凝土塑性变形引起的钢绞线应力
Figure PCTCN2019096061-appb-000128
为：
Figure PCTCN2019096061-appb-000129
即，钢绞线应力
Figure PCTCN2019096061-appb-000130
可表示为：
Figure PCTCN2019096061-appb-000131
钢绞线失效准则为：
Figure PCTCN2019096061-appb-000132
(5)确定普通钢筋应力峰值的三个部分
将受拉区普通钢筋峰值应力分为三部分：t时刻钢绞线剩余有效预加力T ρm,t引起的普通钢筋压应力σ s,0、疲劳荷载引起的弹性应力
Figure PCTCN2019096061-appb-000133
和受压区混凝土塑性变形引起的应力
Figure PCTCN2019096061-appb-000134
由于在计算混凝土弹性应变过程中，已考虑了钢绞线有效预加力的作用效应(即
Figure PCTCN2019096061-appb-000135
)，为避免重复计算，
Figure PCTCN2019096061-appb-000136
记为0。
疲劳荷载引起的受拉区普通钢筋弹性应力
Figure PCTCN2019096061-appb-000137
为：
Figure PCTCN2019096061-appb-000138
由平截面假定、混凝土与普通钢筋的变形协调条件可得到
Figure PCTCN2019096061-appb-000139
引起的受拉区普通钢筋塑性应变：
Figure PCTCN2019096061-appb-000140
受压区混凝土塑性变形引起的受拉区普通钢筋应力
Figure PCTCN2019096061-appb-000141
为：
Figure PCTCN2019096061-appb-000142
受拉区普通钢筋应力
Figure PCTCN2019096061-appb-000143
为：
Figure PCTCN2019096061-appb-000144
普通钢筋的失效准则为：
Figure PCTCN2019096061-appb-000145
式中，f y为普通钢筋的屈服强度。
(6)确定结构失效模式，预测疲劳寿命
预应力混凝土桥梁的疲劳寿命计算流程如下：首先，对于给定的n，将混凝土、钢绞线和普通钢筋的应力计算式(5)、(15)和(20)代入平衡方程(内力平衡方程、力矩平衡方程)即可解出相应的应力大小；其次，分别根据公式(6)、(16)、(21)中各组成材料的失效判别准则，判别结构是否疲劳失效；若未失效，则增大n，重复以上两个计算步骤；如此往复，进行循环迭代计算，直到以上三种构成材料的其中之一达到失效准则，则结构失效，此时结构经历的荷载循环次数n即为结构可以承受的疲劳次数，n对应的时间t即为结构的疲劳寿命。

Claims (10)

  1. 一种预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，包括以下步骤：
    1)计算疲劳荷载下受压区混凝土顶部的弹性应变
    Figure PCTCN2019096061-appb-100001
    累积塑性应变
    Figure PCTCN2019096061-appb-100002
    和退化后的混凝土弹性模量；
    2)预测钢绞线锈蚀水平得到结构剩余预加力，以锈蚀钢绞线截面损失为疲劳损伤参量，利用所述弹性应变
    Figure PCTCN2019096061-appb-100003
    累积塑性应变
    Figure PCTCN2019096061-appb-100004
    和退化后的混凝土弹性模量，计算锈蚀和疲劳共同作用下持续增长的钢绞线应力
    Figure PCTCN2019096061-appb-100005
    和受拉区钢筋应力
    Figure PCTCN2019096061-appb-100006
    3)随疲劳荷载次数的增加，对混凝土、受拉区钢筋、钢绞线的应力-应变进行实时计算，结合混凝土、普通钢筋、钢绞线应力-应变增长关系模型和失效准则，判定结构失效模式，对结构疲劳寿命做出评价。
  2. 根据权利要求1所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，步骤1)中，疲劳荷载下受压区混凝土顶部的弹性应变
    Figure PCTCN2019096061-appb-100007
    其中，
    Figure PCTCN2019096061-appb-100008
    和
    Figure PCTCN2019096061-appb-100009
    分别为经历n-1次疲劳后的混凝土弹性模量和钢绞线有效张拉力引起的弯矩效应；
    Figure PCTCN2019096061-appb-100010
    x n和
    Figure PCTCN2019096061-appb-100011
    分别为n次疲劳后车辆荷载引起的截面弯矩效应、受压区高度和开裂截面惯性矩；受压区混凝土顶部的累积塑性应变
    Figure PCTCN2019096061-appb-100012
    为
    Figure PCTCN2019096061-appb-100013
    Figure PCTCN2019096061-appb-100014
    为混凝土轴心抗压强度初始实测值；
    Figure PCTCN2019096061-appb-100015
    为混凝土弹性模量初始实测值；n i为第i级疲劳荷载作用次数；α r,i为第i级疲劳后受压区混凝土顶部应力相关系数。
  3. 根据权利要求1或2所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其 特征在于，步骤1)中，n次疲劳后混凝土的弹性模量
    Figure PCTCN2019096061-appb-100016
    其中，β为修正系数；
    Figure PCTCN2019096061-appb-100017
    为混凝土轴心抗压强度初始实测值；
    Figure PCTCN2019096061-appb-100018
    为混凝土弹性模量初始实测值；n i为第i级疲劳荷载作用次数；
    Figure PCTCN2019096061-appb-100019
    Figure PCTCN2019096061-appb-100020
    为弹性应变的最大值；
    Figure PCTCN2019096061-appb-100021
    为n-1次疲劳后混凝土的弹性模量。
  4. 根据权利要求2所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，开裂截面惯性矩
    Figure PCTCN2019096061-appb-100022
    表示为：
    Figure PCTCN2019096061-appb-100023
    ；其中，b为截面宽度；y n为n次疲劳后开裂截面中性轴与混凝土受压区边缘的距离；h s、h p和a′ s分别为受拉区普通钢筋、钢绞线和受压区普通钢筋的截面重心至混凝土受压区边缘的距离；
    Figure PCTCN2019096061-appb-100024
    和
    Figure PCTCN2019096061-appb-100025
    分别为n次疲劳后，钢绞线弹性模量与混凝土弹性模量
    Figure PCTCN2019096061-appb-100026
    比值、普通钢筋弹性模量与混凝土弹性模量
    Figure PCTCN2019096061-appb-100027
    的比值，其中，钢绞线弹性模量和普通钢筋弹性模量在疲劳寿命期内保持不变；
    Figure PCTCN2019096061-appb-100028
    和
    Figure PCTCN2019096061-appb-100029
    分别为钢绞线、受拉区普通钢筋和受压区普通钢筋有效剩余面积。
  5. 根据权利要求1～4之一所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，步骤2)中，锈蚀和疲劳共同作用下钢绞线应力
    Figure PCTCN2019096061-appb-100030
    其中，
    Figure PCTCN2019096061-appb-100031
    为t时刻剩余有效预加力
    Figure PCTCN2019096061-appb-100032
    引起的钢绞线拉应力；
    Figure PCTCN2019096061-appb-100033
    为疲劳荷载引起的钢绞线弹性应力；
    Figure PCTCN2019096061-appb-100034
    为受压区混凝土塑性变形引起的钢绞线塑性应力。
  6. 根据权利要求5所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，t时刻剩余有效预加力
    Figure PCTCN2019096061-appb-100035
    其中，E P和ε P分别为未锈钢绞线的弹性模量和应变，T 0为初始张拉力；
    Figure PCTCN2019096061-appb-100036
    R是结构中不同钢筋种类的锈蚀变异系数；i ccor为锈蚀电流密度；L为锈蚀长度；A p为钢绞线初始截面积。
  7. 根据权利要求5所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，
    Figure PCTCN2019096061-appb-100037
    经历n次疲劳数后钢绞线剩余有效面积
    Figure PCTCN2019096061-appb-100038
    N k-1为第k-1次疲劳时钢绞线应力幅所对应的钢绞线S-N曲线中的寿命值；
    Figure PCTCN2019096061-appb-100039
    k t为锈坑引起的应力集中系数；E P为未锈钢绞线的弹性模量；A p为钢绞线初始截面积；
    Figure PCTCN2019096061-appb-100040
    为第K-1次疲劳后钢绞线有效剩余截面积；h p为钢绞线截面重心至截面受压区边缘的距离；
    Figure PCTCN2019096061-appb-100041
    为n次疲劳后受压区边缘混凝土塑性应变，
    Figure PCTCN2019096061-appb-100042
    Figure PCTCN2019096061-appb-100043
    为混凝土轴心抗压强度初始实测值；
    Figure PCTCN2019096061-appb-100044
    为混凝土弹性模量初始实测值；n i为第i级疲劳荷载作用次数；x n为n次疲劳后受压区高度；
    Figure PCTCN2019096061-appb-100045
    Figure PCTCN2019096061-appb-100046
    Figure PCTCN2019096061-appb-100047
    为钢绞线塑性应变。
  8. 根据权利要求1～7之一所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，受拉区钢筋总应力
    Figure PCTCN2019096061-appb-100048
    Figure PCTCN2019096061-appb-100049
    为0，
    Figure PCTCN2019096061-appb-100050
    Figure PCTCN2019096061-appb-100051
    为普通钢筋塑性应变，
    Figure PCTCN2019096061-appb-100052
    h s为普通钢筋截面重心至截面受压区边缘的距离；E s为普通钢筋弹性模量；k t为锈坑引起的应力集中系数；x n为n次疲劳后受 压区高度。
  9. 根据权利要求1～8之一所述的预应力混凝土桥梁腐蚀疲劳寿命预测方法，其特征在于，步骤4)的具体实现过程包括：
    a)在典型疲劳荷载下，当n＝1时，计算得到混凝土累积塑性应变
    Figure PCTCN2019096061-appb-100053
    钢绞线应力值
    Figure PCTCN2019096061-appb-100054
    和受拉区钢筋总应力值
    Figure PCTCN2019096061-appb-100055
    n为疲劳次数；
    b)根据以下公式中各组成材料的疲劳失效判别准则，判别梁是否疲劳失效：受压区混凝土失效准则为
    Figure PCTCN2019096061-appb-100056
    ε c0为静载作用下混凝土的极限压应变；钢绞线失效准则为
    Figure PCTCN2019096061-appb-100057
    f u为预应力钢绞线的极限抗拉强度；普通钢筋的失效准则为
    Figure PCTCN2019096061-appb-100058
    f y为普通钢筋的屈服强度；
    c)若未失效，则增大n，重复步骤a)、b)，直至一种材料失效，此时所经历的疲劳次数n即为结构的疲劳寿命。
  10. 一种预应力混凝土桥梁腐蚀疲劳寿命预测系统，其特征在于，包括：
    计算单元，用于计算疲劳荷载下受压区混凝土顶部的弹性应变
    Figure PCTCN2019096061-appb-100059
    累积塑性应变
    Figure PCTCN2019096061-appb-100060
    和混凝土弹性模量；
    预测单元，用于预测钢绞线锈蚀水平得到结构剩余预加力，以锈蚀钢绞线截面损失为疲劳损伤参量，利用所述弹性应变
    Figure PCTCN2019096061-appb-100061
    累积塑性应变
    Figure PCTCN2019096061-appb-100062
    和退化后的混凝土弹性模量，计算锈蚀和疲劳共同作用下持续增长的钢绞线应力值
    Figure PCTCN2019096061-appb-100063
    和受拉区钢筋应力值
    Figure PCTCN2019096061-appb-100064
    评价单元，用于随疲劳荷载次数的增加，对混凝土、受拉区钢筋、钢绞线的应力-应变进行实时计算，结合混凝土、普通钢筋、钢绞线应力-应变增长关系模型和失效准则，判定结构失效模式，对结构疲劳寿命做出评价；
    评价单元具体实现如下操作：
    a)在典型疲劳荷载下，当n＝1时，计算得到混凝土累积塑性应变
    Figure PCTCN2019096061-appb-100065
    钢绞线应力值
    Figure PCTCN2019096061-appb-100066
    和受拉区钢筋总应力值
    Figure PCTCN2019096061-appb-100067
    n为疲劳次数；
    b)根据以下公式中各组成材料的疲劳失效判别准则，判别梁是否疲劳失效：受压区混凝土失效准则为
    Figure PCTCN2019096061-appb-100068
    ε c0为静载作用下混凝土的极限压应变；钢绞线失效准则为
    Figure PCTCN2019096061-appb-100069
    f u为预应力钢绞线的极限抗拉强度；普通钢筋的失效准则为
    Figure PCTCN2019096061-appb-100070
    f y为普通钢筋的屈服强度；
    c)若未失效，则增大n，重复步骤a)、b)，直至一种材料失效，此时所经历的疲劳次数n即为结构的疲劳寿命。
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