Fragility curves and seismic demand hazard analysis of rocking walls restrained with elasto-plastic ties

AbstractThe dynamic stability of out‐of‐plane masonry walls can be assessed through non‐linear dynamic analysis (rocking analysis), accounting for transverse walls, horizontal diaphragms and tie‐rods. Steel tie‐rods are widely spread in historical constructions to prevent dangerous overturning mechanisms and can be simulated by proper elasto‐plastic models. Conventionally, design guidelines suggest intensity‐based assessment methods, where the seismic demand distribution directly depends upon the selected intensity measure level. Fragility analysis could also be employed as a more advanced procedure able to assess the seismic vulnerability in a probabilistic manner. The boundedness of this approach is herein overcome by applying a robust stochastic seismic performance assessment to obtain seismic demand hazard curves. A sensitivity study is carried out to account for the influence of wall geometry, the minimum number of seismic inputs, and the mechanical parameters of tie‐rods. Fragility analysis, prior to seismic demand hazard analysis is applied on over 6000 analyses, revealing that intensity measures are poorly correlated both for 1‐D and 2‐D correlation, hardly leading to the selection of the optimal intensity measure. The tie‐rod ductility, followed by its axial strength and wall size, is the mechanical parameter mostly influencing the results, whereas the wall slenderness does not play a significant role in the probabilistic response

Influence of the elasto-plastic behavior of tie-rods in the response of rocking masonry walls through seismic demand hazard curves

Rocking analysis is a powerful tool to assess the seismic vulnerability assessment of masonry walls subjected to out-of-plane modes, especially when in view of checking the efficiency of traditional retrofitting solutions, such as steel tie-rods restraining rocking blocks. The study focuses on a probabilistic approach for the seismic assessment of the out-of-plane behavior of masonry walls, mainly aiming to reliably predict fragility and seismic demand hazard curves in case steel tie rods are used as anti-seismic device. To identify the most appropriate steel tie-rod device, more than thousand multistripe analyses have been performed considering the Italian site with highest seismic hazard (Carlentini, Sicily), duly modifying ductility and strength of the tie rods themselves. The resulting fragility curves and seismic demand hazard curves are critically discussed, so allowing the definition of the most efficient and proficient intensity measures referring to five relevant limit states. As expected, remarkable changes in the response are recorded by passing from a brittle to a ductile tie-rod, but when the ultimate strain is bigger than 2%, an increased tie-rod ductility does not sensitively improve the response even for high-intensity earthquakes. The probabilistic approaches show that even low-ductility tie-rods can sensibly reduce the probability of exceedance of limited and moderate rocking limit states, up to an order of magnitude. As for the influence of the tie-rod strength, even low-medium values produce a remarkable reduction of annual exceedance rate. For instance, a severe rocking limit state occurs for the unrestrained monumental wall every 450 years and every 2000 years for the wall restrained by a tie rod of strength just fitting the minimum required design value

Mitigation of amplified response of restrained rocking walls through horizontal dampers

Failure mechanisms in masonry walls are commonly due to the low tensile strength of masonry that could cause overturning or pounding due to the interaction with transverse walls. In this paper, the influence of dissipative devices easing the dynamic stability of rocking blocks is studied considering the main parameters affecting the response. Normalized rotation time- histories are obtained for six geometrical configurations under several acceleration records in order to analyse possible resonant effects and beneficial reductions due to the presence of a damper, accounted for in the equation of motion of the one-sided restrained rocking block. Rocking response spectra obtained for undamped systems show that possible beat phenomena may arise for certain geometrical configurations and restraint stiffness values. A design equation for the damping coefficient is proposed for the anti-seismic device and its influence on restrained facade walls under real strong motions is analysed.(undefined

Do prior intra-articular injections impact on the risk of periprosthetic joint infection in patients undergoing total hip arthroplasty? A meta-analysis of the current evidences with a focus on the timing of injection before surgery

Purpose: Intra-articular injection is a well-established and increasingly used treatment for the patient with mild-to-moderate hip osteoarthritis. The objectives of this literature review and meta-analysis are to evaluate the effect of prior intra-articular injections on the risk of periprosthetic joint infection (PJI) in patients undergoing total hip arthroplasty (THA) and to try to identify which is the minimum waiting time between hip injection and replacement in order to reduce the risk of infection. Methods: The database of PubMed, Embase, Google Scholar and Cochrane Library was systematically and independently searched, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. To assess the potential risk of bias and the applicability of the evidence found in the primary studies to the review, the Newcastle-Ottawa scale (NOS) was used. The statistical analysis was performed by using the software 'R' version 4.2.2. Results: The pooling of data revealed an increased risk of PJI in the injection group that was statistically significative (P = 0.0427). In the attempt to identify a 'safe time interval' between the injection and the elective surgery, we conducted a further subgroup analysis: in the subgroup 0-3 months, we noted an increased risk of PJI after injection. Conclusions: Intra-articular injection is a procedure that may increase the risk of developing periprosthetic infection. This risk is higher if the injection is performed less than 3 months before hip replacement

ONE-SIDED rocking analysis of corner mechanisms in masonry structures: Influence of geometry, energy dissipation, boundary conditions

The corner mechanism in masonry structures is one of the out-of-plane modes that may frequently occur under dynamic actions such as earthquakes. The three dimensional motion, in principle complex to treat, can be simplified into a two-dimensional problem, where a prismatic equivalent block is associated to the corner mechanism. This paper provides a method to treat the corner mechanism in two dimensional rocking analysis, taking into account the roof actions especially the roof thrust that acts as destabilizing force in the preliminary phases of motion and the boundary conditions such as the transverse walls. A case study is taken as benchmark to perform rocking non-linear analyses and discuss the role of geometry, energy dissipation and boundary conditions. It is shown the relevant influence of the geometry and of the coefficient of restitution on the stability conditions, whenever the oscillation produce horizontal displacement values of some cm. The results of the case study, subjected to the Central Italy earthquake, are compared to the actual response of the corner mechanism, which collapsed during this seismic swarm, showing that the rocking analysis on the equivalent block correctly predicts the collapse occurred.The Authors thank the Italian Department of Civil Protection and the Consortium RELUIS (2018) for funding this research activity. This work was partially financed by FEDER funds through the Competitiveness Factors Operational Program - COMPETE and by national funds through FCT - Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633

"Dynamic Mediterranean”: an educational path through Earth science and geophysical research at Genova Science Festival 2010

Science Festivals are events world wide organized, and they have became more and more one of the most effective playground where science meet people. Genova Science Festival, held since 2003, is the Italian most interesting event of that type. The Istituto Nazionale di Geofisica e Vulcanologia (INGV), one of the largest European scientific institution deal- ing with Earth Sciences research and real-time surveillance, early warning, and forecast activities in geophysics and volcanology, participates every year developing a specific educational path, concerning some of its research areas. For the 2010 Genova Science Festival, the INGV has produced an educational exhibition called “Mediterraneo Dinamico” (Dynamic Mediterranean). This is a journey in the geodynamical history of the Mediterranean region from 200 million years ago till present. This long process took place also through some instantaneous dramatic events as eruptions, tsunami, earthquakes, whose studies have revealed their strong impact on cultural Mediterranean evolution as well as on environmental aspects as climate. The exhibition path aim is to illustrate and explain to general public, and especially to teachers and students, the results from researches conducted by INGV also in collaboration with other Italian and International partners, as well as from the real time Mediterranean sea water monitoring. The chosen exhibition instruments are wide colourful illustrated posters, greatly illustrated, together with smart interactive exhibits. In particular the path starts with a “Time Machine”, that allows visitors to retrace the main steps of the Mediterranean geological evolution, supported by posters. The following section concerning the “Mediterranean catastrophic event” welcome visitors with a glass pyramid projecting a virtual eruption almost as an “ologramma”, and side panels with two short videos explaining two great explosive eruptions and a tsunami event. The section on Mediterranean Tsunami are equipped with an interactive large map of the location of Mediteranean where occurred tsunami events, illustrated posters and also a microscope with a camera where visitors can analyse a core with a tsunami deposits. Also an interactive model of a GEOSTAR - Geophisical and Oceanographic Station of Abyssal Research provide visitors an entertaining approach on how a submarine observatory works with all his sensors, while a computer station permits visitors to read real time measures of some marine environmental indicators. The exhibition journey trough the Mediterranean geo-history and Earth Science and Geophysical research shows how the continuous knowledge and monitoring of to this Region dynamics are fundamental to design a future bearable development for the 30 million people living along the Mediterranean shores

SCIENZAPERTA: EARTH SCIENCE FOR EVERYONE... FINALLY IN MILAN!

ScienzAperta is an outreach science venue that the Istituto Nazionale di Geofisica e Vulcanologia started in 2011 as the spring of science: the doors of the headquarters of science were finally opened to public. A number of events, conferences, seminars, guided tours through the Institute and its laboratories are every year offered to general public. The venue is held in most of the cities where the Institute is located, priority to high seismic and/or volcanic risk regions. On May 2014 we held ScienzAperta for the first time in Milano and open up the doors to schools specifically dealing mostly with seismic hazard in a region where general public not necessarily think it might We offered students conferences, seminars and educational activities to highlight the fun of science and jet raise awareness on proper behaviours in case of earthquake shaking. We asked students and teachers, from elementary to high schools, to fill in a questionnaire that we use to evaluate the appreciation the venue had. One hundred years after Giuseppe Mercalli’s death we could not forget to celebrate his science the city where he was born.UnpublishedMilano3T. Pericolosità sismica e contributo alla definizione del rischiorestricte

Wall-to-horizontal diaphragm connections in historical buildings: A state-of-the-art review

Wall-to-horizontal diaphragm connections play a crucial role in the global stability of historical buildings under seismic actions. When these links are ineffective or absent, engineered measures should be considered to enhance the earthquake-resistant box-type behavior. Besides the great variety on the construction systems and materials, common damages were observed in recent seismic events showing the high vulnerability of local mechanisms promoted by the lack of structural integrity. Although the acknowledged importance of connections, this topic has been practically neglected over time among the research community and practitioners and only few of them focused on the influence of diaphragm-to-wall connections on the dynamic behavior of the building as a whole.This paper presents a literature review of the traditional wall-to-floor or wall-to-roof connections in unreinforced masonry buildings and summarizes typical and innovative strengthening solutions, taking into account the indications provided by the few design codes addressing this topic. Experimental laboratory researches are investigated, including shaking table tests on global and local scale, and cyclic or monotonic tests to characterize anchoring systems. An overview of the typical vulnerability assessment approaches and modelling techniques is given, considering present standards that account for connections.This work was partly financed by FEDER funds through the Operational Programme Competitiveness Factors (COMPETE) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project POCI-01-0145-FEDER-007633. The financial support of FCT to the first author, through the PhD grant SFRH/BD/131652/2017, is also acknowledged

Can Clinical and Surgical Parameters Be Combined to Predict How Long It Will Take a Tibia Fracture to Heal? A Prospective Multicentre Observational Study: The FRACTING Study

Background. Healing of tibia fractures occurs over a wide time range of months, with a number of risk factors contributing to prolonged healing. In this prospective, multicentre, observational study, we investigated the capability of FRACTING (tibia FRACTure prediction healING days) score, calculated soon after tibia fracture treatment, to predict healing time. Methods. The study included 363 patients. Information on patient health, fracture morphology, and surgical treatment adopted were combined to calculate the FRACTING score. Fractures were considered healed when the patient was able to fully weight-bear without pain. Results. 319 fractures (88%) healed within 12 months from treatment. Forty-four fractures healed after 12 months or underwent a second surgery. FRACTING score positively correlated with days to healing: r = 0.63 (p < 0.0001). Average score value was 7.3 \ub1 2.5; ROC analysis showed strong reliability of the score in separating patients healing before versus after 6 months: AUC = 0.823. Conclusions. This study shows that the FRACTING score can be employed both to predict months needed for fracture healing and to identify immediately after treatment patients at risk of prolonged healing. In patients with high score values, new pharmacological and nonpharmacological treatments to enhance osteogenesis could be tested selectively, which may finally result in reduced disability time and health cost savings

Shake‑table testing of a stone masonry building aggregate: overview of blind prediction study

City centres of Europe are often composed of unreinforced masonry structural aggregates, whose seismic response is challenging to predict. To advance the state of the art on the seismic response of these aggregates, the Adjacent Interacting Masonry Structures (AIMS) subproject from Horizon 2020 project Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA) provides shake-table test data of a two-unit, double-leaf stone masonry aggregate subjected to two horizontal components of dynamic excitation. A blind prediction was organized with participants from academia and industry to test modelling approaches and assumptions and to learn about the extent of uncertainty in modelling for such masonry aggregates. The participants were provided with the full set of material and geometrical data, construction details and original seismic input and asked to predict prior to the test the expected seismic response in terms of damage mechanisms, base-shear forces, and roof displacements. The modelling approaches used differ significantly in the level of detail and the modelling assumptions. This paper provides an overview of the adopted modelling approaches and their subsequent predictions. It further discusses the range of assumptions made when modelling masonry walls, floors and connections, and aims at discovering how the common solutions regarding modelling masonry in general, and masonry aggregates in particular, affect the results. The results are evaluated both in terms of damage mechanisms, base shear forces, displacements and interface openings in both directions, and then compared with the experimental results. The modelling approaches featuring Discrete Element Method (DEM) led to the best predictions in terms of displacements, while a submission using rigid block limit analysis led to the best prediction in terms of damage mechanisms. Large coefficients of variation of predicted displacements and general underestimation of displacements in comparison with experimental results, except for DEM models, highlight the need for further consensus building on suitable modelling assumptions for such masonry aggregates