Novel design of inter-module joint in reinforced concrete modular construction using high-strength fiber-reinforced cementitious composites (HSFRCC)

The development of modular construction is surging in recent years. It has been popularized worldwide due to better quality control, environmental-friendliness and potential construction time and cost savings. A specific challenge associated with reinforced concrete modular construction is the design of inter-module joint. Minimizing the size of in-situ cast joint between prefabricated units is of great importance for improving construction efficiency. In addition, reinforcement details should be as simple as possible to enhance constructability. This study proposes a novel connection design for wall-to-wall inter-module joint using high-strength fiber-reinforced cementitious composites (HSFRCC) and steel plate-induced confining stresses. Small-scale direct tension pull-out tests were performed with specially designed loading fixtures to simulate the bond behavior between HSFRCC and high-yield steel bars in the proposed joint design. The effects of joint material properties, embedment length and confinement conditions were evaluated. Results showed that the combined use of HSFRCC with plate confinement greatly improves bond capacity. The preferred rebar yielding failure (rather than bond failure) was achieved with embedment length of only 8d (d being the bar diameter). A rigorous finite element model was established by incorporating explicit geometry of rebar and mechanical properties of joint material, and the numerical results showed good agreement with test observations. Therefore, the applicability of the FE analysis in facilitating the proposed inter-module joint is demonstrated.