Many prestressed concrete bridges are reported to suffer from excessive vertical deflections and cracking during their service life. Creep softens the structure significantly, and therefore an accurate prediction of creep is necessary to determine long-term deflections in elements under eccentric axial compression such as prestressed concrete girders. This study proposes a modification to the creep damage model of Model Code 2010 to account for the effect of load eccentricity. The modified creep model considers damage due to differential drying shrinkage. Initially, the creep behaviour of small scale concrete specimens under eccentric compression load is investigated experimentally. Twelve small-scale concrete prisms were subjected to eccentric axial loading to assess their shrinkage and creep behaviour. The main parameters investigated include the load eccentricity and exposure conditions. Based on the experimental results, an inverse analysis is conducted to determine the main parameters of the modified creep model. Subsequently, a numerical hygro-mechanical simulation is carried out to examine the effect of load eccentricity on the development of shrinkage and creep, and on the interaction between drying, damage and creep. The results indicate that eccentric loading leads to different tensile and compressive creep through the cross section, which contradicts the current design approach that assumes that tensile and compressive creep are identical. The proposed model also predicts accurately the long-term behaviour of tests on reinforced concrete elements available in the literature. This study contributes towards further understanding of the long-term behaviour of concrete structures, and towards the development of advanced creep models for the design/assessment of concrete structures.

中文翻译：

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偏心受压混凝土构件的实用蠕变模型

据报道，许多预应力混凝土桥梁在其使用寿命期间遭受过度的垂直挠度和开裂。蠕变会显着软化结构，因此需要准确预测蠕变，以确定在偏心轴受压下的元件（例如预应力混凝土梁）的长期挠度。本研究建议对 Model Code 2010 的蠕变损伤模型进行修改，以考虑负载偏心的影响。修改后的蠕变模型考虑了由于不同的干燥收缩造成的损坏。首先，实验研究了偏心压缩载荷下小规模混凝土试件的蠕变行为。十二个小型混凝土棱柱承受偏心轴向载荷以评估它们的收缩和蠕变行为。研究的主要参数包括负载偏心率和暴露条件。根据实验结果，进行逆向分析以确定修正蠕变模型的主要参数。随后，进行了数值湿力学模拟，以检查载荷偏心对收缩和蠕变发展的影响，以及对干燥、损坏和蠕变之间相互作用的影响。结果表明，偏心载荷导致横截面不同的拉伸和压缩蠕变，这与当前假设拉伸和压缩蠕变相同的设计方法相矛盾。所提出的模型还准确地预测了文献中可用的钢筋混凝土元件测试的长期行为。