A finite element model for seismic response analysis of deformable rocking frames

SummaryThis paper presents a macroelement formulation for the prediction of the planar dynamic response of inelastic deformable rocking bodies. The formulation is based on a previous macroelement developed by the authors able to describe the cyclic response of inelastic rocking bodies, which takes into account the deformability both along the height of the member, as well as near the rocking end. Modifications of this formulation to account for other motion modes of rocking members during their dynamic response, namely, sliding and upthrow, as well as modifications to account for damping in a uniform manner during the whole motion, including impacts, are introduced. The dynamic response predicted by the macroelement for free‐standing rigid and deformable rocking bodies is presented and compared with existing theoretical solutions, and the effect of deformability, damping, inelasticity, and friction on the response is discussed.

The fluid–structure interaction (FSI) effect should be carefully considered in a seismic analysis of nuclear reactor internals to obtain the appropriate seismic responses because the dynamic characteristics of reactor internals change when they are submerged in the reactor coolant. This study suggests that a seismic analysis methodology considered the FSI effect in an integral reactor, and applies the methodology to the System-Integrated Modular Advanced Reactor (SMART) developed in Korea. In this methodology, we especially focus on constructing a numerical analysis model that can represent the dynamic behaviors considered in the FSI effect. The effect is included in the simplified seismic analysis model by adopting the fluid elements at the gap between the structures. The overall procedures of the seismic analysis model construction are verified by using dynamic characteristics extracted from a scaled-down model, and then the time history analysis is carried out using the constructed seismic analysis model, applying the El Centro earthquake input in order to obtain the major seismic responses. The results show that the seismic analysis model can clearly provide the seismic responses of the reactor internals. Moreover, the results emphasize the importance of the consideration of the FSI effect in the seismic analysis of the integral reactor.

Using a quasi‐static method based on an axisymmetric finite element model for seismic response analysis of seismically isolated tunnels, the seismic isolation effect of the isolation layer is studied, and the seismic isolation mechanism of the isolation layer is clarified. The results show that, along the longitudinal direction of the tunnel, the seismic isolation effect is mainly affected by the shear modulus of the isolation material. The smaller the shear modulus is, the more evident the seismic isolation effect is. This is due to the tunnel being isolated from deformation of its peripheral ground through shear deformation of the isolation layer. However, along the transverse direction of the tunnel, the seismic isolation effect is mainly affected by the shear modulus and Poisson’s ratio of the isolation material. When Poisson’s ratio is close to 0.5, a seismic isolation effect is not evident because the tunnel cannot be isolated from deformation of its peripheral ground through compression deformation of the isolation layer. Finally, a seismic isolation system comprising a shield tunnel in which flexible segments are arranged at both ends of an isolation layer is proposed, and it is proved that the seismic isolation system has significant seismic isolation effects both on the longitudinal direction and on the transverse direction.

Model updating-based dynamic collapse analysis of a RC cable-stayed bridge under earthquakes

Impact resistance of recycled-PET fiber strengthened wave-dissipating concrete block considering rocking motion

The fatigue life of mechanical components subjected to variable loading conditions is a crucial parameter in the design of automotive and aerospace mechanical components. The fatigue strength of the component can be improved by inducing compressive residual stress in the surface and subsurface layers by the shot peening process. This increases the failure strain magnitude for crack nucleation and propagation. Extensive experimental results have been published on the effect of shot peening process parameters on residual stress distributions and subsequently on fatigue performance. Numerical simulation of residual stres induced by the shot peening process is important for understanding and optimization of the process in terms of the residual stress profile and maximum shot coverage in the shortest time. In this paper, an elastoplastic finite element (FE) model will be presented to simulate the shot peening process in three-dimensional configuration. The FE model takes into account numerical and material damping, thermal elastic—plastic material behaviour, a rigid or deformable body for the shot and the effects of multiple shot impacts. The workpiece material modelled was AISI 4340 steel at HRC 52 ± 2. The effects of strain hardening, strain rate and temperature were considered in the non-linear material model. Results show that the predicted residual stress profile agreed well with that acquired from published experimental results provided the shot was modelled as a deformable body and material damping was considered.

In continuance of earlier work (references below) the rocking of bodies of other shapes resting on different supports has been studied. The examples afford a useful study of the dynamical equations appropriate to such vibrations and provide simple and inexpensive experiments for students in the laboratory. Rocking bodies are often observed in every day occurrence, and interest in such motion is well worth development.

The Campi Flegrei area, located in southern Italy, is characterized by complex geological stratigraphy and elevate seismic and volcanic risks, exacerbated by ongoing bradyseismic phenomena.This region, located in a densely populated context, poses significant challenges for seismic hazard assessment due to its geological complexity, frequent seismic activity and the vulnerability of infrastructuresThe recently recorded seismic swarms, including those of 2023, further highlight the need for accurate subsurface characterization to assess and mitigate seismic risks.In this context, a geophysical campaign is being conducted as part of a larger project aimed at advancing seismic microzonation and providing detailed data for risk mitigation strategies. This contribution focuses on the application of an integrated geophysical methodology for reconstructing a detailed subsurface model for local seismic response analysis at several sites of particular interest for civil protection purposes in the Campi Flegrei area.In this study, new geophysical data were acquired and then processed through integration with geological data. Geophysical surveys include both passive seismic measurements, carried out with single-station and array configurations, and active seismic testing using the Multichannel Analysis of Surface Waves (MASW) method. These passive and active seismic techniques yield information on shear-waves velocity profiles and subsurface heterogeneities.The ongoing analyses aim to explore the characteristics of the volcanic subsurface, contributing to a better understanding of its structural complexity. A strong emphasis is placed on integrating geophysical and geological data to improve the resolution and accuracy of the subsurface model.This work highlights the critical role of non-invasive geophysical methodologies, such as passive and active seismic methods, in urban and volcanic areas. These efforts support the strategic objectives of urban geophysics by promoting urban resilience and sustainability, while also providing actionable insights for prevention and urban planning in the Campi Flegrei area.By integrating advanced geophysical techniques, this research enhances the understanding of subsurface properties and their interaction with seismic phenomena, laying the foundation for effective risk mitigation and resilience-building measures in this highly complex and dynamic region.

Improved equivalent mass-spring model for seismic response analysis of two-dimensional soil strata

Machine learning and finite element integration-driven surrogate model for fluid-structure interaction seismic response analysis of aqueduct structures

Offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. In seismic design of offshore platforms, it is often necessary to perform a dynamic analysis that accounts for nonlinear pile soil structures interaction effects. This paper summarizes an inexpensive and practical procedure compatible with readily available structural analysis software (ANSYS) for estimating the nonlinear lateral response of fixed offshore platforms resting on flexible piles subjected to seismic loading. In the proposed model, piles and jacket members are modeled using BNWF (Beam on Nonlinear Winkler Foundation) and FE (Finite Element) approaches respectively in an integrated model. In this paper, nonlinear seismic response analysis of an existing sample offshore platform has been performed and sensitivity of the results to the model main parameters is investigated.

Liquid‐containing storage tanks are important structures in industrial complexes. Because earthquake damages to liquid storage tanks can cause structural collapse, fires, and hazardous material leaks, there have been continuous efforts to mitigate earthquake damages using seismic fragility analysis. In this regard, this study focuses on the seismic responses and fragility of liquid storage tanks. First, the characteristics of earthquake ground motions are a critical factor influencing the seismic fragility of structures; thus, this study employs real earthquake records observed in the target area, southeastern Korea, with the earthquake characteristics estimated based on the ratio of peak ground acceleration to peak ground velocity. When a liquid storage tank oscillates during an earthquake, additional forces can impact the tank wall owing to hydrodynamic pressures. Therefore, this study presents a sophisticated finite element (FE) model that reflects the hydrodynamic effect of an oscillating liquid. Another advantage of such an FE model is that detailed structural responses of the entire wall shells can be estimated; this is not possible in simplified lumped mass or surrogate models. Lastly, probabilistic seismic demand models are derived for three critical limit states: elastic buckling, elephant’s foot buckling, and steel yielding. Using the real earthquake ground motion records, constructed FE model, and limit states, a seismic fragility analysis is performed for a typical anchored steel liquid storage tank in Korea. In addition, for comparison purposes, a ring‐stiffened model is investigated to derive a seismic fragility curve. The results of the seismic fragility assessment show that elastic buckling is the most vulnerable damage state. In contrast, elephant’s foot buckling and steel yielding indicate relatively severe damage levels. Furthermore, it is observed that ring stiffeners decrease the elastic buckling damage, although there is no practical effect on elephant’s foot buckling and steel yielding in all ground motion intensities.

The geological conditions in coal mine tunnel construction are complex, the vibration impact of shield machine due to rock breaking easily leads to cutters failure, thus causing safety problems and causing economic losses. In order to explore the fault vibration characteristics of shield cutters in rock breaking process, numerical simulation of rock breaking of single-blade fault cutters is carried out based on finite element-multi-body dynamics coupling model. The accuracy and reliability of simulation results are verified by comprehensive application of dynamic energy conservation law and hourglass energy control theory, and the fault vibration characteristics of cutter center, cutter body outer side and rock surface outer side are analyzed. the result showed that: In the three stages of initial contact-leaving rock-secondary contact, the axial and lateral linear velocity of cutter body decreases sharply, the normal linear velocity increases sharply, and the axial and lateral angular velocity of cutter increases sharply at the initial stage of contact. During the second contact period, the axial and lateral linear velocity of the cutter body increases sharply, the normal linear velocity decreases sharply, and the axial and lateral angular velocity of the cutter decreases sharply, and an obvious deviation trend is formed. In addition, the fault characteristics of eccentric grinding cutter will appear earlier than fracture cutter, but it takes longer to fully manifest, and the vibration intensity of cutter decreases significantly with the increase of wear degree. Especially, angular velocity and angular acceleration data on rock surface are derived by displacement gradient tensor and numerical differentiation method, and it is found that fault vibration characteristics are not obvious on the outer side of rock surface. This paper provides theoretical basis and practical guidance for safe and rapid roadway construction.

A full‐scale three‐storey one‐bay‐by‐two‐bay steel rocking structure designed for the RObust BUilding SysTem (ROBUST) project consists of a central gravity frame (GF) and two exterior rocking frames (RFs) in the loading direction. Energy dissipation is provided by tension‐only friction dissipators and by moment connections in the beams extending from the central GF, which have the effect of partially restraining RF uplift. These beams, which span perpendicular to the loading direction, have nominally pinned connections adjacent to the exterior RFs and moment connections at the interface with the central GF. The moment connections on the two sides of the GF have different connection details with similar moment‐rotation loading characteristics but different unloading behaviour. Tests on the friction connection component of the tension‐only dissipators indicated that the sliding force varied during piecewise monotonic elongation. Shaking table tests with peak table accelerations up to 0.6 g exhibited RF uplift and showed the structure fully self‐centred with almost no damage. Despite similar loading characteristics, differences in unloading behaviour of the connections in the transverse beams on each side of the central GF caused significant floor plan torsion, and north and south RF peak absolute roof drifts of 0.92% and 0.42%, respectively. Three‐dimensional finite element model results matched the experimental behaviour well for the maximum applied shaking intensity. A parametric study using the experimental ground motion record showed roof displacements increased 54% due to the moment connection unloading difference, but this average value decreased to <8% considering multiple ground motion records.

The seismic response analysis model of a single-column pier surrounded by sea ice was established and it analyzed the nonlinear seismic response of the pier subject to different types of earthquakes. The results show that the maximum seismic responses of the pier occur when the mass of sea ice is about 5000~10000 ton, which should be used to design a pier. When the sea ice is considered, the curvature ductility demand coefficient，the maximum displacement and the maximum residual displacement of the pier are several times than those corresponding to without sea ice, and the M-Ø hysteretic curves of the cross-section of the pier subject to earthquakes present downfallen ‘S’ form significantly and the deformability and energy dissipation capability of the pier drop remarkably.