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In this paper, a promising approach is studied that can efficiently mitigate seismic effects on a frame structure by coupling it with an protection system. Various devices are employed to achieve this objective, including tuned mass dampers, dynamic mass absorbers, elastoplastic dampers, and rocking rigid walls. This paper delves into the efficacy of a vibro-impacting nonlinear energy sink in reducing seismic effects on a frame structure. More precisely, a supplementary apparatus, consisting of an auxiliary structure equipped with a vibro-impacting nonlinear energy sink, is rigidly linked to the first story of the targeted frame structure. The seismic response of this coupled system is derived through a dynamically equivalent, low-dimensional model. As a result of the rigid connection between the frame structure and the protection system, the low-dimensional model includes only three degrees of freedom: two displacements that represent the motion of the frame structure, which is rigidly connected to the external structure, while the third characterizes the motion of the vibro-impacting mass. For the vibro-impacting nonlinear energy sink, an ideal model, which assumes instantaneous impacts, is used for the vibro-impacting mass. The proposed model is used for an in-depth parametric analysis, and the outcomes are presented in gain maps that illustrate the effectiveness of the coupling within a designated parameter plane. The findings demonstrate that the coupling with the external structure, which is equipped with a vibro-impacting mass, effectively mitigates displacements and drifts in the frame structure across a broad range of parameter values that define the protection system. [ABSTRACT FROM AUTHOR]

The recent seismic events in Italy, including the earthquakes in L'Aquila in 2009 and central Italy in 2016, have significantly impacted the historical centers of small and medium-sized cities. These events directly affected their ancient masonry building heritage, resulting in severe damage. In order to minimize the risk of collapses and prevent further harm to people and structures until restoration efforts can be carried out, provisional post-seismic shorings have been extensively employed. These occurrences motivated several studies focused on the selection and assembly of post-seismic shorings, considering the various rigid failure mechanisms that may occur in a wall or section of an ancient masonry building. Yet, thus far, the critical considerations concerning the disassembly of these shorings, which significantly influence the repair process of a compromised structure from safety, organizational, and economic perspectives, have been overlooked. This research endeavors to establish a protocol for the dismantling of provisional shorings. To this end, a preliminary risk assessment tool has been devised, furnishing a safety index that correlates with the level of risk associated with shoring removal, along with corresponding risk categories. The study recommends preliminary interventions, categorized as mandatory or optional, to mitigate the risk prior to shoring removal. Furthermore, specific guidelines are provided based on the assessed risk level indicated by the safety index. To illustrate the application of this risk assessment tool, a case study involving an ancient masonry building in L'Aquila is presented. [ABSTRACT FROM AUTHOR]

The introduction of an intermediate discontinuity in frame structures is commonly named inter-storey isolation. Inter-storey isolation is an effective technique for the seismic protection of new or existing frame structures. The devices that are used to perform the discontinuity, mainly of the structural stiffness, are placed at a higher storey level of the structure and not at the base level. In the latter years, this technique has gained increasing interest because, especially for existing buildings, it is cheaper and technically easier to implement than base isolation. In this paper, the attention is focused on the effects on a frame structure of an intermediate elasto-plastic discontinuity that can be described by a Bouc-Wen model. The frame structure with the intermediate discontinuity is modelled with a 3-DOF reduced model. Its dynamical behaviour is investigated by considering both harmonic and seismic external excitation. The results are summarized in gain maps aimed at finding the parameters that optimize the seismic behaviour of the structure. [ABSTRACT FROM AUTHOR]

The coupling of frame structures with external oscillating bodies, such as rigid walls, dynamic mass absorbers, elastoplastic dampers, or tuned mass dampers, can be effective in reducing the displacements of the structure and protecting it against seismic loads. This paper proposes connecting an external oscillating body to the first story of a frame structure and studying the effectiveness of the coupling by evaluating the reduction in the displacements of the frame structure. The inertial effects of the oscillating body are increased by introducing a virtual mass, provided by an inerter device. The oscillating body, characterized by physical and virtual masses, is connected to the frame structure through a hysteretic device. The study is performed on a dynamically equivalent three-degree-of-freedom (3-DOF) model, whose equations are written using a direct approach. To verify the effectiveness of the protection device, named hysteretic mass damper inerter (HMDI), in reducing the displacements of the frame structure, the displacement of the first story and the drifts of the upper stories are compared to those of the frame structure not connected to the external oscillating body. An initial spectral analysis, performed on the linearized mechanical system, clarifies the role of the parameters of the external device in the dynamic behavior of the coupled system. An additional seismic analysis is performed by using three single earthquake records first, and then a set of seven additional earthquake records selected to be compatible with the design spectrum of Los Angeles. Specific spectral gain maps are used to organize the results of an extensive parametric analysis. They show that the HMDI reduces both displacements and drifts of the structure in large ranges of the parameters that characterize the HMDI. It is found that the proposed protection method is particularly effective for low- and medium-rise frame structures. [ABSTRACT FROM AUTHOR]

The protection of rigid block-like structures against seismic hazards is a widely studied topic and has been achieved to different degrees with active and passive protection methods. For the protection of rigid block-like structures, this paper proposes the coupling of a rigid block-like structure, modelled as a single rigid block, with an external, auxiliary system through a hysteretic elasto-plastic device. The auxiliary system is constituted by an oscillating mass, whose inertial effects are amplified by the use of an inerter device. The auxiliary system works as a hysteretic mass damper. The elasto-plastic behaviour of the coupling device is described by the Bouc–Wen model. The mechanical model of the coupled system has two degrees of freedom, and its equations of motion can be written by following a direct approach. A preliminary analysis is performed by exciting different coupled systems and the corresponding stand-alone rigid blocks with harmonic base accelerations. Such an investigation is aimed at understanding the sensitivity of the dynamics of the coupled systems to the characteristics of the rigid blocks and auxiliary systems and is performed by comparing the frequency–response curves of the coupled systems with those of the corresponding stand-alone rigid blocks. A further analysis is performed to verify the effectiveness of the proposed protection methodology under seismic excitation. Both the harmonic and seismic analyses show that the main parameter to be tuned to achieve the protection of the rigid block-like structures is the apparent mass of the inerter device. A proper choice of such a mass improves the dynamics of the rigid block-like structures, leading to smaller oscillations for the same level of excitation. [ABSTRACT FROM AUTHOR]

The coupling with external mechanical systems such as oscillating masses working as tuned mass dampers, dynamic mass absorbers, elasto-plastic dampers, and rigid walls is an effective method to reduce the displacements and drifts of structures under external loads. An alternative method is provided by the coupling of the structure with an independent, auxiliary elasto-plastic system. This paper investigates the dynamic and seismic behaviour of a structure rigidly coupled with an auxiliary yielding mechanical system under harmonic and seismic ground excitation. A two-degree-of-freedom model is used to describe the dynamic and seismic behaviour of the main structure rigidly coupled to the yielding system, which is described by a one-degree-of-freedom model. The auxiliary system has an elasto-plastic constitutive behaviour that is modelled by a Bouc-Wen model. The equations of motion of the coupled system are obtained by a direct approach. The coupling with the yielding system is considered beneficial if the displacements of the coupled system reduce with respect to those of the stand-alone frame structure. An extensive parametric analysis is performed to point out the role of the mechanical parameters that describe the elasto-plastic constitutive behaviour of the auxiliary system. Results reveal that in large ranges of the parameters' values, the coupling with the elasto-plastic system improves the performance of the frame structure. [ABSTRACT FROM AUTHOR]