This article presents the results and analysis of Acoustic Emission (AE) as recorded in a reinforced concrete (RC) slab supported by four steel columns and subjected to earthquake-type dynamic loading on a shake table. Fifteen seismic simulations were conducted using an accelerogram registered during the Campano-Lucano earthquake (Italy, 1980). The peak acceleration applied to the shake table was increased until the slab reinforcement was on the brink of yielding and slippage of the bars within the concrete occurred. This limit state is commonly associated with low-to-moderate intensity earthquakes in earthquake-prone regions. The evolution of damage to the slab was monitored in terms of AE energy and the history of plastic strain energy was calculated from the acceleration and displacement measurements. A good correlation was found between the energy dissipated by the concrete through plastic deformations and the AE energy associated with concrete cracking and friction. On this basis, a tentative formula is proposed for predicting the level of damage to RC slabs, based on the AE energy recorded by sensors located near the region of expected damage concentration under lateral loads.

It is not common to purposely subject the web of wide-flange or I-sections to out-of-plane bending. However, yielding the web under this loading condition can be a stable source of energy dissipation as the transition at the corner from the web to the flanges is smooth and weld-free; this prevents stress concentrations causing premature failure and eliminates uncertainties and imperfections associated with welding. Further, short segments of wide-flange or I-sections constitute a simple and inexpensive energy dissipating device as minimum manufacturing is required and leftovers not useful for other structural purposes can be re-utilized. This paper proposes a new type of seismic damper in the form of braces based on yielding the web of short length segments of wide-flange or I-shaped steel sections under out-of-plane bending. The hysteretic behavior and ultimate energy dissipation capacity is investigated via component tests under cyclic loads. The experimental results indicate that the damping device has stable restoring force characteristics and a high energy dissipation capacity. Based on these results, a simple hysteretic model for predicting the load-displacement curve of the seismic damper is proposed, along with a procedure for predicting its ultimate energy dissipation capacity and anticipating its failure under arbitrarily applied cyclic loads. The procedure considers the influence of the loading path on the ultimate energy dissipation capacity. Finally, shaking table tests on half-scale structures are conducted to further verify the feasibility and effectiveness of the new damper, and to assess the accuracy of the hysteretic model and the procedure for predicting its failure.

The seismic performance of two RC interior wide beam-column connections representative of existing frames designed and detailed according to past construction practices in the moderate-seismicity Mediterranean area was investigated experimentally. The specimens were subjected to axial loads, moderate levels of gravity loading and cyclic displacements up to failure. The specimens exhibited a "strong column-weak beam" type of flexural yielding mechanism. The wide beams did not reach the expected capacities corresponding to the formation of a full-width plastic hinge. The wide-beam longitudinal bars exhibited significant slippage, and the transverse beams underwent severe torsion cracking and even failure; this caused severe pinching in the load versus displacement hysteretic loops and exacerbated the intrinsic flexibility of this type of connection. The average drift ratios at first yielding of the wide beam longitudinal reinforcement and at failure were 2.7 and 4.5%, respectively. The displacement ductility ratio was about 2.8. The ultimate energy dissipation capacity of each specimen-obtained by dividing the total plastic strain energy by the product of the yield load and yield displacement-was approximately 9, which is about one fourth of the value recommended for providing adequate seismic performance. Finally, a simple approach is suggested for prediction of the bending capacity of existing connections.

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Wavelet analysis and bispectrum was applied to Acoustic Emission (AE) signals from scratch tests on corroded hot-dip galvanized samples in order to achieve the detection of corrosion products in pieces non reachable by visual inspection. AE signals were correlated with the fracture mechanisms occurring during scratch tests, while the contact force increased. Results were corroborated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and X-Ray Diffraction (XRD).