Design and experimental study on RC modular superimposed shear wall boundary elements with new inter-module connections

Connections between modules affects the overall stability, reliability, and safety of modular buildings. However, connecting techniques for high-rise reinforced concrete (RC) modular buildings are rare, and the seismic requirements for confining the boundary elements of RC modular shear walls are technically challenging. In this study, a new RC modular superimposed shear wall (RC-M-SSW) structural system was developed for the fast construction of high-rise buildings. An innovative double U-shaped connector (DUSC) was proposed to connect stirrup segments embedded in adjacent module walls to form closed stirrups. To clarify the confinement mechanism of the connected stirrups, nine superimposed boundary element (SBE) columns with different DUSC dimensions and a cast-in-place (CIP) column were designed and axially tested. The results showed that the SBE specimens failed mainly in a ductile manner with higher stiffness and load carrying capacity compared to the CIP column. The effectiveness of the DUSC-based connection was demonstrated to be reliable by the strain analysis. To simplify the production of the connectors, an configuration optimized DUSC was proposed. Besides, the 8 mm-thick steel plates were recommended for the manufacturing of the DUSCs, and the design implications for ensuring the confinement performance of the TSPs were provided.