PSI - Issue 44

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Michele Angiolilli et al. / Procedia Structural Integrity 44 (2023) 870–877 M. Angiolilli et al./ Structural Int grity Procedia 00 (2022) 000 – 000

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Fig. 6. Numerical response (obtained by applying monotonic increasing displacement) compared with the cyclic experimental response.

Figure 7 focuses on the evolution of both microcracks and strain in three different steps (before, during, and after the attainment of V =67 kN). Note that the figure refers to the application of the positive displacement (along Y +). In the first step (on the left of Fig. 7), one can see that no significant microcrack involves the joint, which is subjected to compressive strain along the diagonal. In correspondence of V =67 kN (central plots of Fig. 7), one can see that microcracks developed along the diagonal under tension and that strain also developed in that direction. In the successive step analysis (on the right of Fig. 7), one can see that the band of microcracking increased along the diagonal under tension as well as that strain considerably increased in the joint. Hence, the attainment of that shear force, for which a drastic stiffness decrement can be observed, can be associated with the first tensile crack. Therefore, the maximum shear force can be attained by the contribution of the concrete strut developed in compression.

Fig. 7. evolution of both micro crack (first line) and strain (second line) in the numerical simulations.

5. Conclusions The present work describes preliminary outcomes that are part of a larger experimental campaign performed on different typologies of RC beam-column joints under both unreinforced and reinforced conditions. In order to emphasize the joints' brittleness typical of 1960s-70s Italian RC buildings and, as a result, to produce shear failure