On the rocking behavior of rigid objects

A novel formulation for the rocking motion of a rigid block on a rigid foundation is presented in this work. The traditional piecewise equations are replaced by a single ordinary differential equation. In addition, damping effects are no longer introduced by means of a coefficient of restitution but understood as the presence of impulsive forces. The agreement with the classical formalism is very good for both free rocking regime and harmonic forcing excitation

Rocking isolation of a typical bridge pier on spread foundation

It has been observed that after some earthquakes a number of structures resting on spread footings responded to seismic excitation by rocking on their foundation and in some cases this enabled them to avoid failure. Through application to a standard bridge supported by direct foundations, this paper discusses the major differences in response when foundation uplift is taken into consideration. Special focus is given on the modifications of rocking response under biaxial and tri-axial excitation with respect to uniaxial excitation. It is found that inelastic rocking has a significant isolation effect. It is also shown that this effect increases under biaxial excitation while it is less sensitive to the vertical component of the earthquake. Finally, parametric analyses show that the isolation effect of foundation rocking increases as the size of the footing and the yield strength of the underlying soil decreases

Seismic response assessment and protection of statues and busts

Recent post-earthquake surveys carried out in Europe have shown that earthquake actions pose an immense threat to museums and their contents. For example, during the earthquake on 21 July 2017 in the island of Kos (Greece), severe and widespread damage on the city’s archaeological museum was reported (Figure 1). The earthquake extensively damaged the sculpture exhibition, where many pieces were dislocated, leaned against the walls, or overturned. Fortunately, the earthquake occurred when human visitors were not in the museum, since the damage to the exhibits varied from very light (minor fracturing) to severe (complete overturning and fracture of artefacts). In the case of heavy and slender sculptures, the overturning mechanism, apart from damaging the sculptures themselves, is a serious threat to other standing exhibits in the gallery and the visitors. It is, therefore, of paramount importance to have at our disposal methods and tools for characterising the seismic risk of museum artefacts and, where necessary, proposing cost-efficient protective measures. The study of the seismic vulnerability of museum artefacts, especially of slender, human-formed statues, is related to the research on the dynamic response of rocking rigid blocks. The dynamic characteristics of the hosting structures are also important. This is evident from the fact that, on many occasions, damage to the structure was reported leaving the exhibits intact and vice-versa. Although the problem is coupled, it can be studied looking separately at the structure and its contents, provided that the contents are not attached to the building. The seismic response of building contents is a topic of growing interest, since it is directly related to seismic loss assessment and earthquake community resilience. Building contents can be either attached to the structure, or may consist of objects that are simply standing. Museum exhibits belong to the latter category, while free-standing components are often studied as rocking objects and hence their response is sensitive to acceleration and velocity-based quantities and also to their geometry. Today, there is lack of standards, while the existing approaches are general in concept and do not sufficiently address the variety of rocking objects. The problem becomes more complicated when it comes to priceless objects such as museum artefacts where more refined and targeted studies are required for understanding their seismic response and also for proposing rapid tools for assessing their seismic risk. The paper presents an extensive experimental campaign on the seismic response of artefacts, with emphasis on statues and busts. The tests took place in the framework of SEREME project (Seismic Resilience of Museum Contents) at the AZALEE seismic simulator of CEA in Saclay, Paris under the auspices of the SERA project. The aim is to understand the seismic response of statues and busts and then develop novel and cost-effective risk mitigation schemes for improving the seismic resilience of museum valuable contents. The study is focused on the investigation of the seismic response of two real-scale marble roman statues and three busts of three roman emperors standing on pedestals of different types and size. Both isolated and non-isolated artefacts are considered, while two new and highly efficient base isolation systems, tailored to art objects, will be tested. The first isolator is a pendulum-based system, while the second utilizes Shape Memory Alloy wires. Furthermore, the paper examines the importance of the hosting building, i.e. building type and story. Specifically tailored, numerical models of varying complexity, for single and two-block rocking systems, were developed for the needs of this study and are also assessed against the experimental results

Cyclic shear tests on RC precast beam-to-column connections retrofitted with a three-hinged steel device

Recent European earthquakes demonstrated that the seismic response of RC precast structures can be significantly influenced by the connection systems. Moreover, during past seismic events, many failures of the beam-to-column connections occurred due to their inadequate strength under seismic loads. The seismic safety of these connections has a crucial role in the overall seismic capacity of existing precast structures. A new connection system is employed as a retrofitting solution for a damaged beam-to-column connection and its cyclic shear performance is investigated by means of two cyclic shear tests on two different configurations. In both the experimental tests, the results demonstrate an efficient behavior of the retrofitted connections under horizontal cyclic loads. The comparison between the performance of the investigated connection and the response of a typical beam-to-column dowel connection allows to discuss the main critical features of the dowel connection system

Toward Rare-Earth-Free Permanent Magnets: A Combinatorial Approach Exploiting the Possibilities of Modeling, Shape Anisotropy in Elongated Nanoparticles, and Combinatorial Thin-Film Approach

The objective of the rare-earth free permanent magnets (REFREEPM) project is to develop a new generation of high-performance permanent magnets (PMs) without rare earths. Our approach is based on modeling using a combinatorial approach together with micromagnetic modeling and the realization of the modeled systems (I) by using a novel production of high-aspect-ratio (>5) nanostructrures (nanowires, nanorods, and nanoflakes) by exploiting the magnetic shape anisotropy of the constituents that can be produced via chemical nanosynthesis polyol process or electrodeposition, which can be consolidated with novel processes for a new generation of rare-earth free PMs with energy product in the range of 60 kJ/m3 < (BH)max < 160 kJ/m3 at room temperature, and (II) by using a high-throughput thin-film synthesis and high-throughput characterization approach to identify promising candidate materials that can be stabilized in a tetragonal or hexagonal structure by epitaxial growth on selected substrates, under various conditions of pressure, stoichiometry, and temperature. In this article, we report the progress so far in selected phases.This work is supported by European Commission (REFREEPERMAG project) grant number GA-NMP3-SL-2012-280670

Engineering reconnaissance following the August 24, 2016 M6.0 Central Italy earthquake

An earthquake with a moment magnitude reported as 6.0 from INGV (Istituto Nazionale di Geofisica e Vulcanologia); occurred at 03:36 AM (local time) on 24 August 2016 in the central part of Italy. The epicenter was located at the borders of the Lazio, Abruzzi, Marche and Umbria regions, about 2.5 km north-east of the village of Accumoli and about 100 km from Rome. The hypocentral depth was about 8 km (INGV). We summarize preliminary findings of the Italy-US GEER (Geotechnical Extreme Events Reconnaissance) team, on damage distribution, causative faults, earthquake-induced landslides and rockfalls, building and bridge performance, and ground motion characterization. Our reconnaissance team used multidisciplinary approaches, combining expertise in geology, seismology, geomatics, geotechnical engineering, and structural engineering. Our approach was to combine traditional reconnaissance activities of on-ground recording and mapping of field conditions, with advanced imaging and damage detection routines enabled by state-of-the-art geomatics technology. We anticipate that results from this study, will be useful for future post-earthquake reconnaissance efforts, and improved emergency respons