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The seismic resilience of structures and infrastructures is affected by damage accumulation phenomena, mainly related to the type of hysteresis. Specifically, pinching drives the cyclic response of several building materials, such as reinforced concrete and masonry. Structural systems affected by pinching phenomena are prone to exhibit a dramatic increment of their displacement response after multiple cycles (e.g. repeated earthquakes). The authors estimate a reinforced concrete pier's response using truncated incremental dynamic analysis by concatenating three earthquake scenarios. The authors adopted a Bouc–Wen class hysteresis model to simulate the reinforced concrete pier's cyclic response, matching its experimental cyclic response. The current analysis proved that ductility and resistance primarily drive the seismic response after a single earthquake. However, the performance after multiple earthquakes strongly depends on the pinching, degradation and drift accumulation, which are generally neglected in standard design practices. [ABSTRACT FROM AUTHOR]

This paper estimates the effect of a pre-hole filled with high-damping material on the inelastic response spectrum of Integral Abutment Bridges (IAB) with pile foundation. The hysteretic response of the pile, described by a Winkler beam model, is obtained from the piece-wise definition of the subgrade stiffness, calibrated on experimental data. The pre-hole with damping pre-hole determines a reduction of the demand spectral acceleration. The force modification factors of the acceleration response spectrum of the bridge superstructure under a large set of strong/motion earthquakes are estimated. The force-reduction factors for the elastic design of IABs with damping pre-hole are proposed. [ABSTRACT FROM AUTHOR]

Pinching characterizes the hysteretic response of several structural systems. It is associated with a reduced dissipated hysteretic energy under cyclic loading and can significantly affect seismic performance, especially under repeated earthquakes. Although several scholars proposed advanced joint arrangements with reduced pinching, ordinary timber structures present pronounced pinching effects due to the local damage to the timber joints. This paper quantifies the impact of variable pinching on the seismic performance of a timber structural archetype. The authors modeled the hysteretic response of a light-timber framed assembly using an empirical hysteresis model and assessed the sensitivity of the displacement demand of the chosen archetype to pinching, number of earthquake repetitions, and spectral acceleration. The choice of an elementary structural archetype, rather than a more complex system, allows isolating the effects of pinching, which could otherwise be disguised by other phenomena, like force redistribution between structural assemblies due to plasticization. [ABSTRACT FROM AUTHOR]

Engineered Wood Products like Cross-Laminated-Timber (CLT) are transforming capabilities of wood as a construction material, enabling architects and engineers to create innovative buildings. Using CLT can have many advantages compared with using traditional materials, not least of which is reducing total superstructure gravitational weights. Reducing gravitational weight can simplify and speed up construction processes and reduce foundation costs. Plus, being made from wood, CLT has desirable 'green' credentials like renewability of forest resources and carbon sequestration for the lifespans of buildings. However, like other lightweight structural systems, CLT buildings can be susceptible to high-amplitude motions during ambient or other dynamic force and displacement disturbances. Studies reported here address the dynamic behaviour of mid-rise multi-storey buildings constructed from massive CLF elements, with a focus on predicting lateral modal response characteristics of such buildings. The vehicle for this is detailed Finite Element (FE) models verified as accurate replicators of ambient dynamic motions of completed CLT buildings. Here applications of FE models relate to performances of buildings during seismic events. However, the intent is to also use them to predict motions of buildings during windstorms. [ABSTRACT FROM AUTHOR]

The seismic vulnerability of existing RC framed buildings in seismic-prone areas requires affordable and practice-oriented solutions for their retrofitting. In this paper, the authors present a retrofitting solution for RC buildings based on the combined use of cross-laminated timber (CLT) panels and asymmetric friction connections (AFCs). The AFC connection is activated when the force level reaches the design threshold. The energy dissipation of the AFC increases the structural dissipation capacity and reduces the displacement demand. This research presents the outcomes of an experimental campaign on selected prototypes of these AFC connectors. The authors assess their dissipative capacity from cyclic load tests in four different connector arrangements and examine the contribution of aluminum shim layers. The first results highlight the significant dissipation potential of the AFC, although they also provide evidence of the notable sensitivity on the design and constructive details. The authors present a modeling approach to simulate the experimental results. [ABSTRACT FROM AUTHOR]

This paper attempts to formulate an expression for the estimation of equivalent viscous damping (EVD) for cross-laminated timber (CLT) structural archetypes as a function of ductility. The paper aims at contributing toward the direct displacement-based design procedure (DDBD) of CLT structures, which makes use of equivalent viscous damping and secant stiffness estimations as proxies for the estimation of the nonlinear behavior of structures. The available hysteretic models of CLT structures are very elaborate, and the inelastic time-domain simulations using hysteretic models are not easily manageable. Hence, the adoption of equivalent viscous damping is a crucial feature of any DDBD method. In this paper, the authors estimate the EVD of a set of 16 typologies of CLT buildings with an increasing slenderness ratio. The minimum of the squared error between the maximum drift of the elastic time-history and the hysteretic response gives the EVD. The extended energy-dependent generalized Bouc Wen (EEGBW) model, calibrated on experimental data, is used to predict the inelastic seismic response of the single CLT shear wall. The correlation between EVD and ductility is compared to existing EVD formulations referring to concrete and steel structures. [ABSTRACT FROM AUTHOR]

The seismic response of masonry monumental structures is a debated matter. In this paper, the authors compare the dynamic response of the Santa Maria di Collemaggio basilica under low-intensity earthquakes to the dynamic response under operational conditions. A permanent number of accelerometers records the dynamics of the Santa Maria di Collemaggio basilica under both operational and seismic excitation. It is questioned whether the earthquake intensity and the ambient parameters affect the modal parameters. The Least-Squares Complex Exponential (LSCE) method leads to the FRF function estimation. The stable frequencies identify the linear modal parameters which are likely to reproduce the seismic response. The authors endeavour to discuss whether the detected variations of the modal parameters are due to possible structural or material non-linearities. A time-frequency analysis confirms the results of the linear identification method. Further, the estimate of the dynamic amplification factors gives a glance over the global response by evidencing the possible existence of a macro-element response pattern. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on structural verification and proposed improvements for an ancient masonry arch bridge. The research encompasses multiple stages, starting with a detailed survey utilizing LiDAR and aerial techniques to collect precise data on the bridge's condition. Mechanical inspections assess deterioration levels and identify critical areas requiring attention. Based on the gathered data, a structural model of the bridge is developed, considering geometric parameters and material properties. The model undergoes rigorous verification procedures to assess its seismic response and ensure compliance with safety standards. The analysis includes identifying potential collapse mechanisms, such as the formation of plastic hinges, which can lead to structural failure. The study proposes structural improvements to enhance the bridge's performance and safety. These interventions specifically target vulnerabilities identified during the verification process. They include additional support elements, reinforcing critical areas, and utilizing advanced materials to improve tensile strength and durability. The feasibility of the proposed retrofitting solutions will be proved by performing a cost analysis, while environmental impacts are evaluated through an environmental assessment (Lifecycle Assessment — LCA) in which all the main bridge refurbishment phases have been included. Finally, some of the advantages of bridge refurbishment measures are shown by comparing the proposed intervention with a bridge reconstruction in terms of costs and environmental impacts. The outcomes of this study contribute to the existing knowledge on the rehabilitation of masonry arch bridges and serve as a valuable reference for engineers and practitioners involved in preserving architectural heritage. • Multi-stage digital assessment of an ancient masonry bridge. • Non-linear analysis to identify potential collapse mechanisms. • Study of the interventions to enhance the bridge's performance and safety. • Additional cost analysis and environmental assessment (LCA). • Comparison among the proposed interventions compared, and reconstruction. [ABSTRACT FROM AUTHOR]

Defining a reference shear wave velocity profile (V s) is crucial for seismic-hazard assessment and seismic response analysis. However, selecting a reference velocity profile is not straightforward, mainly because of the high variability of shear wave velocity in complex formations. This study considered 26 shear wave profiles from downhole tests carried out in the Laga Basin (Gran Sasso, Central Apennines), where the soil can be categorised as complex owing to the chaotic succession of turbidite and Quaternary continental deposits. Downhole tests and stratigraphy were used to (i) develop a probabilistic model for predicting the shear wave profiles calibrated on the collected test data and (ii) propose an outlier detection method for estimating the first fundamental frequency of the deposit from horizontal-to-vertical spectral ratio (HVSR) analyses. Specifically, the stochastic shear wave model provides the uncertainty of the first fundamental frequency estimated from downhole tests based on a simplified mechanics-based formulation. The defined bounds, were forward uncertainty propagation following a Monte Carlo approach, have been used to define the criteria for outlier detection in HVSR frequency assessments, given an approximate estimate of the equivalent depth. • Reference Vs profiles for complex soils. • Down-Hole seismic site characterisation. • Probabilistic model for predicting the shear wave profiles. • Outlier detection method for estimating the first fundamental frequency from HVSR. [ABSTRACT FROM AUTHOR]

Friction-based dampers are a valid solution for non-invasive seismic retrofitting interventions of existing structures, particularly reinforced-concrete (RC) structures. The design of friction-based dampers is challenging: underestimating the slip force prevents the full use of the potential of the device, which attains the maximum admissible displacement earlier than expected. By contrast, overestimating the slip force may cause delayed triggering of the device when the structure has suffered extensive damage. Therefore, designing the appropriate slip force is an optimization problem. The optimal slip force guarantees the highest inter-story drift reduction. The authors formulated the optimization problem for designing a specific class of friction-based dampers, the asymmetric friction connection (AFC), devised as part of the ongoing multidisciplinary Horizon 2020 research project e-SAFE (Energy and Seismic AFfordable rEnovation solutions). The seismic retrofitting technology involves the external application of modular prefabricated cross-laminated timber (CLT) panels on existing external walls. Friction dampers connect the CLT panels to the beams of two consecutive floors. The friction depends on the mutual sliding of two metal plates, pressed against each other by preloaded bolts. This study determines the optimal slip force, which guarantees the best seismic performance of an RC structural archetype. The authors investigate the nonlinear dynamic response of a coupled mechanical system (RC frame-friction damper) under a set of strong-motion earthquakes, using non-differential hysteresis models calibrated on the experimental cyclic responses. The solution of the optimization leads to the proposal of a preliminary simplified design procedure, useful for practitioners. • e-CLT is a seismic retrofit system for RC frames developed within Horizon 2020. • Proposal of a simplified design strategy for e-CLT. • Modeling of the response of an RC frame equipped with the e-CLT friction connection. • Experimental tests and calibration of a Coulomb-like hysteresis model. • Optimization of the slip force in the friction connection. • The optimum slip is associated with the yielding displacement of the RC frame. [ABSTRACT FROM AUTHOR]

• Reliability methods drive the assessment of overstrength ratios in Cross Laminated Timber structures. • There is a satisfactory agreement between the experimental lateral response of Cross-Laminated Timber panels and the simulations based on the Extended Energy-dependent Generalized Bouc-Wen model. • Given a certain failure probability, the overstrength factor is estimated as the ratio between the failure Peak Ground Acceleration of the ductile and brittle system. • The obtained overstrength ratios range between 1.5 and 2.5. • The obtained overstrength ratios are in accordance with those obtained by other scholars following non-probabilistic approaches. The ductile collapse mechanisms of structures should be less resistant than the brittle mechanisms to ensure a ductile seismic response: in this way, the ductile mechanisms activate before the brittle ones. This sort of chronological law of collapse is obtained in the design phase by providing a proper "overstrength" to the brittle mechanisms. The realization of overstrength plays a crucial role in the design, and several studies endeavoured to estimate the best overstrength factors, defined as the ratio between the characteristic load-carrying capacity of the non-ductile element and the characteristic load-carrying capacity of the ductile element. In this paper, the conventional definition of overstrength is discussed and compared to a probabilistic definition based on reliability methods. The probabilistic definition of overstrength drives the assessment of the overstrength factors of Cross-Laminated Timber buildings using a sort of indirect approach. The Extended-Energy dependent generalized Bouc-Wen model is used to estimate the nonlinear seismic response of a set of Cross-Laminated Timber shear walls with different ductility. The results are compared with the existing formulations, attempting to draw correlations possibly useful in the design phase. [ABSTRACT FROM AUTHOR]

• An OLS operator may be an effective tool in processing seismic response data. • The proposed method allows the identification of possible non-stationary dynamic responses. • Correspondence between the mode shapes and natural frequencies obtained from the proposed method and those from Output Only identification. • Damping of masonry facades could be amplitude-dependent during the seismic event. • Masonry facades may exhibit a non stationary dynamic response even to low excitation levels. A low magnitude seismic response of a historical masonry structure, the Santa Maria di Collemaggio basilica, was acquired by a complex monitoring system. Ten FBA accelerometers, nine placed on the basilica facade and one on the ground level, recorded respectively the base accelerogram (Input) and the structural response (Output). By means of an elementary form of dynamic identification, based on an Ordinary Least Square operator (OLS), it has been attempted to identify the dynamic properties of the facade during the seismic event. The results, in terms of mode shapes, natural frequencies and damping factors, identified by the proposed Input-Output method, are compared with the ones identified under operational conditions. Despite the low intensity earthquake, the assumed linearity of the response has been investigated from further analysis on the acquired data. [ABSTRACT FROM AUTHOR]