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

加拿大保险局估计，不列颠哥伦比亚省发生9.0级地震后的总损失接近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）钢筋被引入混凝土结构中，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筋混凝土结构延性差，耗能能力低，是抗震设计中的一个主要问题。这个问题可以通过引入混合加固来解决，其中FRP筋可以与延展性材料（例如钢）或形状记忆合金（SMA）钢筋一起使用，以引入延展性。玻璃钢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RC元件外笼中的其他钢筋类型拼接。很少有研究针对混合加固，其中FRP钢筋与另一种延性材料一起使用，并使用拼接连接。本研究将确定混合配筋混凝土桥墩的抗震性能，并将其与普通钢筋混凝土桥墩在荷载-位移、弯矩-旋转和耗能能力以及纵向和横向配筋应变方面的性能进行比较。目前，还没有数值工具可用于预测混合钢筋混凝土单元的响应。因此，本研究的另一个重要目标是开发数值工具来预测具有混合钢筋的RC单元在弯矩-曲率响应，推覆响应和地震响应方面的响应，并在S-Frame软件中实现它们。这些工具将有助于制定基于性能的设计指南，并对这种混合RC元件和结构进行易损性评估。

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.