The tests are performed under displacement control, i. e. the horizontal displacement of the top of the column is imposed by the electro-mechanical displacement actuator and the corresponding horizontal force is measured by the load cell. The displacement time history is illustrated in Figure 13.
A first cycle is performed in order to evaluate Sy, i. e. that displacement at which, for the first time, yield is reached in a point of the steel reinforcement. Then three cycles are performed by reaching ±35y and another three cycles attaining ±65y. If the steel does not break, the steel could be defined as a high ductility steel reinforcement.
Fig. 14. Load-displacement curves of the top section of the column.