Seismic performance assessment and design tools for structural concrete elements having hybrid reinforcement

加拿大保险局估计，在不列颠哥伦比亚省发生9.0级地震后，总损失近750亿美元，这反映了加拿大民用基础设施的脆弱性。严酷的冬季是加拿大基础设施恶化的另一个关键因素，除冰盐会加速钢铁的腐蚀。纤维增强聚合物（FRP）筋被引入作为混凝土结构中的钢筋以防止腐蚀。然而，FRP是一种脆性材料，没有非弹性分支。因此，FRP加固混凝土（RC）结构的延性差，耗能能力低，导致抗震设计的一个主要问题。这个问题可以通过引入混合加强件来解决，其中FRP筋可以与延性材料（例如钢或形状记忆合金（SMA）钢筋）一起沿着使用以引入延性。FRP钢筋笼可以放置在外部笼中以提供耐腐蚀性，而钢可以用于内部笼中以提供延展性。由于SMA也具有良好的抗腐蚀性，但价格昂贵，因此可以将其放置在塑性铰区域，并与其他钢筋类型拼接在RC构件的外笼中。对于FRP筋与另一种韧性材料一起沿着使用并使用拼接连接的混合加固，研究很少。本研究将确定具有混合钢筋的混凝土桥墩的抗震性能，并将其性能与常规钢筋混凝土桥墩的荷载-位移、弯矩-转角和耗能能力以及纵向和横向钢筋的应变进行比较。目前，还没有数值工具来预测钢筋混凝土元件的混合钢筋的反应。因此，本研究的另一个重要目标是开发数值工具来预测钢筋混凝土元件的弯矩-曲率响应，推覆响应和地震响应方面的混合钢筋的响应，并实现它们在S-框架软件。这些工具将有助于制定基于性能的设计指南，并对此类混合RC元件和结构进行脆弱性评估。

Insurance Bureau of Canada estimated the overall loss after a 9.0-magnitude earthquake in British Columbia at almost $75B, which reflects the vulnerability of Canadian civil infrastructure. Harsh winter is another critical factor for deterioration of Canadian infrastructure where de-icing salt causes accelerated corrosion to steel. Fibre-reinforced polymer (FRP) bars were introduced as reinforcement in concrete structures to prevent corrosion. However, FRP is a brittle material without inelastic branch. Thus, FRP reinforced concrete (RC) structures exhibit poor ductility with low energy dissipation capacity leading to a major problem in seismic design. This issue can be addressed by introducing hybrid reinforcement where FRP bars can be used along with a ductile material, e.g. steel, or shape memory alloy (SMA) rebar to introduce ductility. FRP rebar cage can be placed in the exterior cage to provide corrosion resistance whereas steel can be used in the inner cage to provide ductility. Since SMA is also good against corrosion but costly, it can be placed at the plastic hinge region, and spliced with other rebar type in the outer cage of RC elements. Little research has been directed towards hybrid reinforcement where FRP rebar is used along with another ductile material and using spliced connections. This study will determine the seismic behavior of concrete bridge piers having hybrid reinforcement, and compare its performance to that of a regular steel RC bridge piers in terms of load-displacement, moment-rotation and energy dissipation capacity, and strains in the longitudinal and transverse reinforcements. Currently, there is no numerical tool available to predict the response of RC elements having hybrid reinforcements. Hence, another important objective of this study is to develop numerical tools to predict the response of RC elements having hybrid reinforcements in terms of moment-curvature response, pushover response, and seismic response and implement them in S-Frame Software. These tools will assist in developing performance-based design guidelines and performing fragility assessment for such hybrid RC elements and structures.