PSI - Issue 78

Roberto Nascimbene et al. / Procedia Structural Integrity 78 (2026) 193–198

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4. Experimental Test, Setup and Assembly Procedure The experimental tests were conducted at the Structural Mechanics Laboratory of the University of Pavia. The test specimens consisted of two beam-to-column subassemblies, extracted from full-scale case-study frames. The first configuration featured an external anchorage system, where the protruding bars were secured using bearing plates and bolts inserted into pre-cut grooves within the column. The second configuration omitted these grooves entirely, with the bars terminating flush with the external column face and no mechanical anchorage. Each specimen included a column segment measuring 3.7 meters in height and a beam stub of 2.7 meters, both incorporating a reinforced concrete corbel to replicate support conditions. A 10 mm neoprene pad was positioned between the corbel and the

beam to simulate realistic bearing behavior. The column was supported on two 40 cm-high concrete blocks, designed to allow deformations at the joint region during testing. The base restraint system was composed of two sets of post tensioned steel beams, anchored to the laboratory’s stron g floor using Dywidag bars (Figure 4). The reinforcement layout for the column and beam was consistent with the previously designed frame from which the joint was extracted. Assembly began with the placement of the column on the concrete blocks, with a thin layer of grout applied to the contact surface to improve adherence. The beam was then lowered vertically into position, suspended 10 cm above the column face using wooden wedges. The external anchorage system, when present, was used to align and stabilize the beam. Once aligned, formwork panels were installed laterally to define the casting zone, deliberately leaving one side open, opposite the corbel, to allow for the injection of high-strength, free-flowing grout (Emaco S55). This grout filled the connection cavity, including four corrugated ducts embedded in the column, intended for the through-bars. To ensure proper grout filling and avoid air entrapment, the bearing plates were left unbolted during casting. The plates were tightened only once the grout began emerging from the bottom outlets, confirming full penetration. It is worth noting that, in on-site construction, this process is significantly simplified: with the beam placed horizontally, the grout can be poured directly from the top, allowing gravity to fill all cavities uniformly and efficiently. Fig. 4. Experimental beam-to-column joint specimen and External anchorage system for the threaded bars consisting of 10 mm-thick circular plates with a diameter of 150 mm, secured by bolts.

Fig. 5. Experimental force–displacement cycles and numerical predictions under varying assumptions.