Reinforced concrete (RC) damage over time can cause severe structural problems (e.g. Morandi Bridge in Italy). Many factors contribute to concrete deterioration (thermal conditions, chemical attacks, shrinkage, creep, carbonation, corrosion, etc). Reinforced concrete deterioration starts at early-age and continues with structure aging. Early-age shrinkage, creep and thermal conditions or initial cracks can have a significant impact on the dynamic behavior of concrete structures. The CEOS.fr National program for instance showed that the natural frequency of a RC beam subjected to early-age restrained shrinkage is highly affected. In order to quantify the impact of early-age drying shrinkage on the dynamic behavior of structures, the GEOMAS Lab at INSA Lyon has conducted a research project combining both numerical modeling and pseudo-dynamic tests on two types of RC portal frames. The first one was kept in endogenous conditions (by covering it using a plastic sheet to stop water exchange with the surrounding environment) during its early age period in a way to limit drying effects leading to cracks, while the second one was kept in non-endogenous conditions (water exchange was possible) similar to construction site conditions, which induced cracks apparition. Both RC portal frames were subjected after their early age period to the same seismic loading. The present paper focuses on the experimental part of the project based on the use of pseudodynamic tests in order to evaluate the behavior of such structures under a seismic loading. The portal frames were instrumented using optical fiber sensors, displacement and load sensors and velocimeters. Image correlation was also used in order to monitor the structures.

中文翻译：

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早期干缩对钢筋混凝土结构地震反应的影响

随着时间的推移，钢筋混凝土 (RC) 损坏会导致严重的结构问题（例如意大利的莫兰迪大桥）。许多因素会导致混凝土劣化（热条件、化学侵蚀、收缩、蠕变、碳化、腐蚀等）。钢筋混凝土的老化开始于早期，并随着结构老化而继续。早期收缩、徐变和热条件或初始裂缝会对混凝土结构的动态行为产生重大影响。例如，CEOS.fr 国家计划表明，受到早期约束收缩的 RC 梁的固有频率受到很大影响。为了量化早期干缩对结构动力行为的影响，INSA Lyon 的 GEOMAS 实验室开展了一项研究项目，结合了对两种类型的 RC 门式框架的数值建模和伪动力测试。第一个在其早期保持内源性条件（通过用塑料布覆盖以阻止与周围环境的水交换），以限制导致裂缝的干燥影响，而第二个则保持在非内生条件（水交换是可能的）类似于施工现场条件，这会导致裂缝的出现。两个 RC 门式框架在其早期阶段后都承受了相同的地震载荷。本论文侧重于该项目的实验部分，该部分基于拟动力测试的使用，以评估此类结构在地震载荷下的行为。门式框架使用光纤传感器、位移和负载传感器以及速度计进行检测。还使用图像相关性来监测结构。