基于零应力时刻的水泥混凝土路面板早期应变测量与分离方法研究

With the hydration of cement, concrete gradually changes from flowability to plasticity and further turn to hardening state. In the process, the strain of concrete has been changing while the stress gradually emerges at the moment when the material begins to harden. That is, there is a state of “zero stress” in concrete structure, and the state is completely out of sync with the moment of “zero strain”. In pavement sensing technology, the concrete slab stress analysis is on the basis of strain increment between initial moment and measuring time, however, the initial moment is often not “zero stress” and creep strain with few stress generation is included in measured strain. The two aspects result in low reliability of stress calculation..This project will firstly determine the full-time domain evolution rule of total strain and temperature in the concrete under constant temperature and humidity conditions, then the mapping relationship between “zero stress” moments and characteristic temperatures will be built based on Glisic theory. Next, on the strength of equivalence principle of temperature-time-product, the prediction model of “zero stress” moment under general conditions will be established using Lagrange multiplier method. After that, non-stress meter applied to concrete thin slab will be designed in order to separate strain component in association with stress from total strain, and the effect of separation will be verified by means of cracking-strain method. Ultimately, this project will put forward a strain separation method and a stress calculation method for concrete slab, and the findings will provide theoretical foundation to monitoring technology of concrete structure.

伴随着水泥的水化，混凝土逐渐由流动态向可塑态、硬化态转变。此过程中，混凝土的应变一直在变化，但应力直至材料开始硬化的那一刻才逐渐出现，即混凝土结构存在“零”应力时刻，且与应变为零的时刻不同步。但在路面感知技术中，混凝土板应力的测算以初始时刻与所测时刻之间的应变增量为基础，而初始时刻往往非“零”应力时刻，且所测应变包含蠕变类不产生应力的应变分量，导致应力计算的可靠性较低。.项目首先测定恒温恒湿条件下混凝土总应变、温度的全时域演变规律，基于Glisic理论建立“零”应力时刻与特征温度的映射关系；再基于温时积等效的原理，采用Lagrange乘数法建立与该条件等效的一般环境下“零”应力时刻的预估模型；然后，通过设计适用于混凝土薄板的无应力计，建立应力应变分量的分离方法；并借助切缝-应变法验证应变的分离效果，从而建立混凝土路面板应变的构成及其应力影响机制。成果可为混凝土结构监测技术提供方法借鉴。

项目针对水泥混凝土结构应力测定时应变初始时刻选择缺乏依据、实测应变包含与应力无关分量的问题，采用理论分析、模型试验、数值模拟和数据验证等方法，设计了三种应变测试环境，基于温时积等效原理，建立了一般环境条件下混凝土零应力时刻的预估方法，为应变测量初始时刻的选择提供了依据；在考虑应变的应力影响机理基础上，提出了应力应变分量的测量和分离方法，解决了分离与混凝土结构应力相关应变的问题；在此基础上，建立了水泥混凝土路面板早龄期结构应力的测算方法。成果可为水泥混凝土路面板乃至其他混凝土结构物应力测定及安全评价提供理论和方法借鉴。