Cyclic behaviour of precast beam-to-column connections with low seismic detailing
Description
The main objective of this experimental research was to understand the influence of some parameters on the response of the precast beam-to-column connections, namely: (i) friction between concrete faces; (ii) friction between concrete and neoprene pad; (iii) connection with a mechanic connector (dowels); (iv) influence of the dowel position in the column corbel; (v) axial load influence on the overall response of the connection.
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The test setup was based on the review of the state-of-art of experimental works on precast beam-to-column connections. The detail of the specimens was established through the work of the typical properties of Portuguese precast industrial buildings. A total of 12 tests were performed. The nomenclature adopted to each specimen was “SPC_xx_yy” where ‘xx’ stands for the interface type, namely i0 for the concrete interface, i1 for one neoprene pad layer, i2 for two neoprene pads layers, c1 for specimens with 2 dowels of 16 mm of diameter and placed 13 cm from the internal face of the column and c2 for specimens with 2 dowels of 16 mm of diameter and placed 6 cm from the internal face of the column. The ‘yy’ stands for the axial load applied. The specimens were defined aiming to represent an existing precast beam-to-column connection. The models were constructed at full scale. The column has a rectangular cross-section of 0.50×0.35 m2 with six 16 mm plus four 20 mm diameter bars on the longitudinal reinforcement. On the transversal reinforcement, it was designed 10 mm diameter stirrups spaced at 125 mm. All the specimens have a 25 mm cover. The columns were cast in a foundation with a rectangular area of 0.80×0.70 m2 and a height of 0.35 m (see Figure 3a). The beam has 1 m of length, with a variable rectangular cross-section of 0.35×0.50 m2 on a 0.60 m of length and on the last 0.40 m has a cross-section of 0.35×0.70 m2 with eight 16 mm plus four 20 mm diameter bars on the longitudinal reinforcement and, on the transversal reinforcement, 10 mm diameter stirrups spaced at 75 mm on the 0.60 m of length being more reinforced in the last 0.40 m. In the case of the specimens with dowels (c1 & c2) and like what is practiced on-site, the connection between the beam and the column is provided embedding the dowels in the column and inserting them in the two holes/sleeves left in the beam, and then filled with grout in order to give bond, seal the dowels and improve the behavior of the connection. The horizontal actuator applied displacement-controlled lateral cyclic loading at a constant velocity of 0.2mm/s. The displacement history was defined to capture the stiffness and strength degradation through the cycle repetition.