Novel Post-Tensioning Anchorage Solution with UltraHigh-Performance Concrete for Seismic Retrofit of Nonductile Reinforced Concrete Walls

This study introduces a new anchorage strategy using ultra-high-performance concrete (UHPC) to attach unbonded posttensioning (PT) strands to existing foundations. This solution complements a seismic retrofit scheme investigated by the authors, which transforms nonductile cast-in-place reinforced concrete (RC) shear walls into unbonded PT rocking shear walls following concepts of selective weakening and self-centering. In the proposed PT anchorage scheme, mild steel reinforcements are inserted through the shear wall thickness and into the foundation. Subsequently, UHPC is cast around the wall base, forming a vertical extension connected to the foundation, which is used to anchor the unbonded PT strands. The feasibility and performance of the anchorage scheme was investigated through a combination of laboratory testing and numerical simulations. Pullout testing on four scaled-down anchorage specimens was conducted in the laboratory. Hairline cracks were observed in the UHPC during testing. Additionally, three-dimensional (3-D) finite element (FE) models were created, validated, and used to study the performance of the proposed anchorage scheme under lateral loading. The simulation results support the effectiveness of the proposed anchorage strategy.