Cyclic behavior of unbonded post-tensioned precast segmental concrete columns fabricated by 3D printed concrete permanent formwork

A 3D printed concrete permanent formwork of composite unbonded post-tensioned precast segmental concrete (3DPCPSC) column is proposed in this research. Its hysteresis performance and the failure mode are researched by quasi-static experiment and compared with the precast segmental reinforced concrete (PSRC) columns. Two interface enhancement methods, stainless-steel-nails internal shear bonds and prestressed steel-hoops external active confinement are proposed, and the enhancement effect and mechanism of 3DPCPSC columns with two interface enhancement methods are studied. Furthermore, the pouring and vibration load of 3D printing concrete formwork is analyzed using a three-dimensional solid finite element model finite element model. The results indicate that the energy dissipation capacity of 3DPCPSC columns is better than that of the PSRC column when the 3DPC formwork does not spall. The largest accumulated energy dissipation of the 3DPCPSC specimen is 1.14 times of the PSRC column. The 3DPCPSC column without interface enhancement has the phenomenon of formwork spalling, the bearing capacity is lower than the PSRC column, and the bearing capacity of the 3DPCPSC columns with two interface enhancement methods is close to or higher than the PSRC column. The initial stiffness of all the 3DPCPSC specimens is larger than the PSRC column. A comprehensive evaluation factor & eta; is proposed to evaluate the hysteretic performance of precast segmental concrete columns. The comprehensive performance of the 3DPCPSC and PSRC is compared by the comprehensive evaluation factor & eta;.