Study on improvement of precision for prediction technique of cracking with volume change of concrete

为了提高混凝土结构裂缝随体积变化的预测技术，本研究开发了能够在实验室模拟温度应力的系统，同时开发了便于对施工现场混凝土的热性能和力学性能进行评估的系统。针对混凝土早期收缩行为，将既有结构的测试数据与利用温度应力试验机(TSTM)的实验结果进行了对比，从而可以在实验室模拟既有结构的温度应力行为。具体地说，是将现有结构的测量结果与混凝土的热性能和力学性能进行比较，在这些性能中，可以使用与测量的现有结构相当的配合比来评估混凝土的热膨胀系数、杨氏模量、应变和应力。调查是在三个建筑工地进行的。实验结果表明，利用TSTM可以比较准确地再现混凝土中的应力。通过将直接拉伸强度与实验结果进行比较，可以获得有用的数据，从而可以使用直接拉伸强度来评估开裂。

In this study, for the purpose of improving the prediction technique of cracking with volume change of concrete structures, it is to develop the system which can simulate thermal stress in the laboratory while the system which conveniently evaluates the thermal and mechanical properties of concrete in the construction site is developed.In this study, for the behavior of shrinkage of concrete at the early age, it was carried out to compare the data measured in the existing structures with experimental results using the thermal stress testing machine (TSTM) in which it is possible to simulate the behavior of thermal stress of existing structures in the laboratory. Specifically, it was carried out to compare the results of measurement by the existing structure with the thermal and mechanical properties of concrete in which it is possible to evaluate by this equipment such as the thermal expansion coefficient, Young’s modulus, strain and stress in concrete using the mix proportion which is equivalent to the existing structure of the measurement. The investigations were carried out for three construction sites. As the results of the experiments, it was confirmed that it was possible to comparatively reproduce the stress in the concrete at the good accuracy by using the TSTM. By comparing the direct tension strength with experimental results, it was possible to acquire the useful data in which it was possible to evaluate the cracking using the direct tension strength.