Experimental evaluation of beam elongation phenomenon in precast concrete frame subjected to cycilc loading

To evaluate the effect of beam elongation phenomenon on the lateral behavior of post-tensioned precast concrete frames subjected to cyclic loads, three two-span single-story post-tensioned precast concrete frames were fabricated with the unbonded reinforcing ratio and column-to-beam strength ratio considered as key variables. Quasi-static cyclic loading tests were conducted on each specimen, and the load–drift ratio responses, crack patterns, and failure modes, which varied depending on the key test variables were analyzed. In addition, the validity of the modified design method for the column-to-beam strength ratio presented in the authors’ previous study was verified based on the axial displacement of the beam caused by the beam elongation phenomenon and the local responses of the column (i.e., the longitudinal strain of the reinforcing bar within the column) measured in the experiment. The results demonstrated that the effect of beam elongation phenomenon on the lateral behavior of post-tensioned precast concrete frames was smaller than that observed in conventional reinforced concrete frames. It was also confirmed that the proposed design method to prevent column yielding in reinforced concrete frames subjected to cyclic loading could be applied to post-tensioned precast concrete frames.