Experimental Tests

The experimental tests concerned five specimens with different column-to-foundation connections and approximately the same maximum bending moment capacity. All the specimen tested had a 400x400mm column cross section and a clear height from the foundation to the top equal to 3200mm. The geometry of the tested specimens and the mechanical characteristics of concrete and reinforcing steel are shown in Fig. 1.

Specimens CS and PF are representative of a typical cast-in-situ column-to-foundation connection and grouted pocket foundation, respectively. Specimens GS4 and GS4B are both characterized by having four grouted sleeves. The difference between the two specimens consist in the anchorage length of the ф26 bars in the foundation: the former has straight anchored bars, whereas the latter has 90° hooks at the bar ends. Specimen GS8 has 8 grouted sleeves with ф22 bars.

The experimental setup adopted is shown in Fig. 2. For all the tests, the axial force, equal to 600kN, was first applied by means of two hydraulic jacks. A cyclic horizontal displacement was then applied at the top of the column by means of a 1000 kN electromechanical screw jack having a 500 mm maximum stroke.

The applied displacement history is shown in Fig. 3. It is observed that the maximum imposed displacement is equal to 200 mm, corresponding to a 6.0% drift, much larger than the maximum drift commonly accepted for prefabricated columns under a design seismic event, equal to 2.5%.