多因素耦合作用下混凝土的冻融损伤模型与寿命预测

发布时间：2018-04-20 01:32

本文选题：混凝土耐久性 + 多因素耦合作用　；参考：《中国建筑材料科学研究总院》2014年博士论文

【摘要】：实际服役混凝土结构通常处于复杂的环境因素作用下，其劣化过程是物理、化学和力学等因素耦合作用的过程，这些因素耦合作用造成的混凝土损伤远大于各因素单独作用的叠加。为指导实际工程中混凝土的配合比设计，混凝土耐久性及寿命预测体系的研究趋势和热点已由单一因素向多因素耦合作用发展。然而，以冻融为主因素的多因素耦合作用下的混凝土耐久性研究还显得不足，存在以下问题：多因素耦合作用下的混凝土耐久性评价还采用以往用于单因素作用下的评价指标，即评价方法相对落后于实际的耐久性研究；现有混凝土损伤模型和寿命预测体系多是基于单因素作用下的；对已经取得的成果还缺乏归纳总结。为解决上述问题，本文首先开发了混凝土冻融耐久性数据库系统，对以往学者的试验数据与参考模型进行归纳总结，以此作为建模的前提基础之一；然后，用应变表征了多因素耦合作用下混凝土的耐久性能，以此作为建模的另外一个前提基础；最终，建立了两个多因素耦合作用下的混凝土损伤模型并结合寿命预测方法对实际工程进行了寿命评估和预测，为有抗冻要求的服役混凝土耐久性设计和寿命预测研究提供了新思路。本文主要试验工作及结果如下： 1）开发了混凝土冻融耐久性数据库系统。借助于RILEM TC246-TDC技术委员会平台，收集到来自15个国家和地区的34位著名学者关于多因素耦合作用下混凝土耐久性研究成果以及冻融损伤与寿命预测模型；经过严格的筛选得到入库试验数据和模型，并与计算机技术相结合，打造了数据管理的集成化平台，具有跨平台性和可扩展性等优点以及查询和搜索功能。 2）用应变表征了多因素耦合作用下混凝土的耐久性能。无损监测的应变具有实时性、连续性，冻融（简称FTC）单因素作用下，混凝土残余应变的产生证明了混凝土基体的损伤是一个不断累积的不可逆的劣化过程，它与基体内部裂纹的不断萌生与扩展直接相关；冻融和盐溶液侵蚀（简称FTC-Cl）双因素作用下，同一配合比混凝土在3.5wt.%的NaCl溶液中冻融产生的残余应变比水冻大，，说明盐溶液加速了混凝土的冻融损伤；冻融、盐溶液侵蚀和弯曲应力（简称FTC-Cl-BS）三因素耦合作用下，施加恒定的弯曲应力比越大，混凝土试件拉应力区的应变与残余应变均越大，说明应力的施加加速了混凝土的损伤劣化。 3）建立了混凝土的残余应变冻融损伤演化方程。在FTC单因素、FTC-Cl双因素和FTC-Cl-BS三因素耦合作用下，混凝土的残余应变变化规律均符合单段或双段变化模式，单段变化模式一般适用于抗冻性较强的混凝土，双段变化模式一般适用于抗冻性较差的混凝土；结合混凝土冻融耐久性数据库系统中其他学者的残余应变数据，对演化方程进行验证，结果显示计算值和实测值之间具有较高的吻合度。 4）建立了基于残余应变的FTC-Cl双因素耦合作用下混凝土冻融损伤数值模型（M-FTC+Cl）。该损伤数值模型适用于FTC单因素和FTC-Cl双因素作用，对混凝土损伤程度变量曲线的拟合相关系数在0.95以上；该模型还可以预测特定条件下混凝土的最终快速冻融循环次数，再结合寿命预测方法可以预测特定环境下服役混凝土的安全使用寿命。 5）将冻融损伤、盐溶液侵蚀等环境因素进行了力学统一等效转化，建立了基于应变的FTC-Cl-BS三因素耦合作用下混凝土损伤力学模型（M-FTC+Cl+BS）。该损伤力学模型适用于FTC-BS双因素和FTC-Cl-BS三因素作用，模型建立了应变与快速冻融循环次数之间的关系；利用该模型计算的混凝土最终快速冻融循环次数与实际测量值非常接近；该模型结合寿命预测方法可以预测特定环境下服役混凝土的安全使用寿命。 6）将冻融损伤模型与实际工程的寿命预测相关联，对实际工程进行了寿命预测。通过计算，长白山飞行区跑道、停机坪混凝土的使用寿命预测值分别为43年和52年，符合最低设计年限为30年的要求；青岛海湾大桥承台、箱梁混凝土的使用寿命预测值分别为144年、110～123年，也符合设计使用寿命100年的使用要求。
[Abstract]:In order to guide the concrete mix proportion design , the research trend and hot spot of concrete durability and life prediction system have been developed from single factor to multi - factor coupling .
Existing concrete damage models and life prediction systems are based on single factor ;
There is also a lack of inductive summary of the results that have been achieved .

In order to solve the above problems , this paper first develops the concrete freeze - thaw durability database system , summarizes the experimental data and reference model of past scholars , which is one of the preconditions for modeling .
Then , the durability of concrete under multi - factor coupling is characterized by strain , which is another precondition of modeling .
In the end , the concrete damage model under two multi - factor coupling is established and the life prediction method is used to evaluate and predict the life of the practical engineering with the life prediction method . The new idea is provided for the durability design and life prediction of the service concrete with the anti - freezing requirements . The main experimental work and the results are as follows :

1 ) The concrete freeze - thaw durability database system is developed . With the aid of the technical committee of RILE TC246 - TDC , 34 famous scholars from 15 countries and regions are collected , and the research results of durability of concrete under multi - factor coupling and the model of freeze - thaw damage and life prediction are collected .
The data and model of warehousing test are obtained through rigorous screening , and combined with computer technology , the integrated platform for data management is built , which has the advantages of cross - platform and scalability , as well as query and search functions .

2 ) The durability of concrete under multi - factor coupling is characterized by strain . The strain of non - destructive monitoring has the single factor of real - time , continuity and freeze - thaw ( FTC ) .
The residual strain produced by freeze - thawing in 3.5 wt . % NaCl solution was higher than that of the concrete under the action of freeze - thaw and salt solution erosion ( FTC - Cl ) , which indicated that the salt solution accelerated the freeze - thaw damage of concrete ;
Under three factors coupling action of freeze - thaw , salt solution erosion and bending stress ( FTC - Cl - BS ) , the greater the constant bending stress ratio , the greater the strain and residual strain of the tensile stress region of the concrete specimen , and the stress application accelerated the damage of concrete .

3 ) The residual strain freeze - thaw damage evolution equation of concrete is established . Under the coupling action of FTC single factor , FTC - Cl double factor and FTC - Cl - BS , the residual strain law of concrete is in accord with single - section or double - section change mode , and the single - section change mode is generally applicable to concrete with stronger frost resistance , and the double - section change mode is generally applicable to concrete with poor frost resistance ;
Based on the residual strain data of other scholars in the concrete freeze - thaw durability database system , the evolution equation is verified , and the result shows that the calculated value and the measured value have a high degree of coincidence .

4 ) The numerical model ( M - FTC + Cl ) of concrete freeze - thaw damage under the coupling of FTC - Cl with residual strain is established . The damage numerical model is suitable for FTC single factor and FTC - Cl double factors , and the fitting correlation coefficient of the variable curve of damage degree of concrete is more than 0.95 ;
The model can also predict the final quick freeze - thaw cycles of concrete under certain conditions , and the service life of the service concrete in a specific environment can be predicted by combining the life prediction method .

5 ) The mechanical model ( M - FTC + Cl + BS ) of concrete damage under three - factor coupling of strain - oriented FTC - Cl - BS was established . The damage mechanics model was applied to FTC - BS dual - factor and FTC - Cl - BS . The model established the relationship between strain and fast freeze - thaw cycles .
The final fast freeze - thaw cycle of concrete is very close to the actual measured value .
The model combined life prediction method can predict the safe service life of service concrete under certain circumstances .

6 ) The freeze - thaw damage model is associated with the life prediction of the actual project , and the life prediction of the actual project is carried out . Through the calculation , the predicted value of the service life of the runway and apron concrete in Changbai Mountain is 43 years and 52 years respectively , and the minimum design life is 30 years .
The predicted value of the service life of the bearing platform and box girder concrete of Qingdao Bay Bridge is 144 years , 110 - 123 years respectively , and also accords with the use requirements of the design service life of 100 years .

【学位授予单位】：中国建筑材料科学研究总院
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU528

【参考文献】