Strengthening Concrete Structures with Smart Materials

用智能材料加固混凝土结构

• 批准号: RGPIN-2015-05987
• 负责人: ElHacha, Raafat
• 金额: $ 1.6万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613865
• 关键词: Strengthening; Concrete; Structures; Smart; Materials

Deterioration of Reinforced Concrete (RC) structures is a never-ending problem that incites civil engineers around the world to seek innovative durable strengthening techniques and high performance advanced materials. Recently, a new class of smart materials called Shape Memory Alloys (SMA) has been attracting the attention of researchers from different fields due to their superior properties. The SMA is a unique class of alloy with the ability to undergo large deformations and return to its original shape through stress removal. Besides their super-elasticity, corrosion and fatigue resistivity, SMAs are mainly characterized by the Shape Memory Effect (SME) phenomenon that is inherited through their unique thermo-mechanical properties. The SME represents the ability of the SMAs to recover their original shape after being deformed beyond the elastic limits upon heating. SMAs with the SME property can be used as external prestressed reinforcement by providing active strengthening to RC members. The most common SMA is made of Nickel and Titanium (NiTi). The use of NiTi-SMAs in civil engineering applications was limited due to their relatively higher cost. However, the recent development of corrosion resistant iron-based Fe-SMA with considerably lower cost and high recovery stress, have made it to be the choice for structural applications. The motivation of this research is driven by the fact that Fe-SMA in strengthening RC beams and columns has not yet been addressed. The main objective of this research is to investigate experimentally and analytically the effectiveness and feasibility of two active strengthening techniques without the need of any mechanical anchorage/jacking systems for the prestressing operation. The proposed two techniques are: one for confining RC columns using Fe-SMA wires and one for flexural strengthening of RC beams using Fe-SMA bars. Both techniques rely on the recovery stress generated as the Fe-SMA transforms to its recovery (un-deformed) state upon heating. The SMA is temperature sensitive, and thus, it is important to investigate the environmental exposure effect on the performance of RC members strengthened with SMA. The effect of cyclic loading and unloading is also important to investigate if it affects the active stress in the SMA. With the unique properties of Fe-SMA, actively confining RC columns using Fe-SMA wires and actively strengthening RC beams in flexure using Fe-SMA bars is expected to produce a significantly ductile structural member. The findings of this research are expected to add valuable knowledge to the field and widen the potential applications of the Fe-SMA in strengthening RC structures. My research gives explicit priority to the education/training of HQP, seeks to promote increased network interactions/collaborations, and has the potential for technological impact for both immediate and long-term benefits to the research community.

钢筋混凝土（RC）结构的恶化是一个永无止境的问题，它促使世界各地的土木工程师寻求创新耐用的加强技术和高性能的高级材料。最近，由于其出色的特性，一种称为Shape Memory Alloys（SMA）的新型智能材料（SMA）吸引了来自不同领域的研究人员的注意。 SMA是一类独特的合金，具有大变形的能力，并通过减轻压力恢复其原始形状。除了它们的超弹性，腐蚀和疲劳电阻率外，SMA的主要特征是形状记忆效应（SME）现象，这些现象是通过其独特的热机械特性遗传而来的。中小企业代表了SMA在加热后变形超出弹性极限后恢复其原始形状的能力。 SMA具有SME属性的SMA可以通过为RC成员提供主动加强来用作外部预应力增强。 最常见的SMA是由镍和钛（NITI）制成的。由于成本相对较高，在土木工程应用中使用Niti-Smas受到限制。但是，最近的耐腐蚀基于耐铁的FE-SMA的成本较低和高回收应力的发展使其成为结构应用的选择。这项研究的动机是由Fe-SMA在加强RC梁和柱上尚未解决的事实所驱动的。 这项研究的主要目的是在实验和分析上研究两种主动加强技术的有效性和可行性，而无需任何机械锚固/千斤顶系统来进行预应力操作。提出的两种技术是：一种用于使用FE-SMA电线限制RC柱，另一种用于使用Fe-SMA条弯曲RC梁的弯曲。这两种技术都依赖于FE-SMA在加热后转化为恢复（未变形）状态时产生的恢复应力。 SMA对温度敏感，因此，研究环境暴露对使用SMA增强的RC成员的性能的影响很重要。循环载荷和卸载的影响对于研究它是否影响SMA的活动应力也很重要。具有FE-SMA的独特性能，使用FE-SMA线积极限制RC柱，并使用Fe-SMA条在挠曲中积极加强RC梁，预计将产生明显的延展性结构构件。 预计这项研究的结果将为该领域增加宝贵的知识，并扩大FE-SMA在增强RC结构中的潜在应用。 我的研究明确优先考虑了HQP的教育/培训，试图促进网络互动/协作的增加，并具有对研究社区的直接和长期收益产生技术影响的潜力。