Simulating the Response of Free-Standing Rocking Rigid Blocks using Abaqus/Standard

This work presents detailed finite element models developed in Abaqus/Standard to study the rocking response of free-standing rigid blocks, which is characterised by the alternation of impacts between the block and the foundation that suddenly change the contact point between the two members. Nonlinear dynamic analysis with implicit time integration is carried out to study rocking initiation (uplift) and rocking attenuation (at impact) of free-standing rigid blocks with different slenderness under pulse-type motions. The attenuation effects are further studied by allowing the block to rock freely on the foundation. Solid homogenous sections are analysed with fully integrated 4-node plane stress quadrilateral elements (CPS4) for the block and the equivalent reduced integration elements (CPS4R) for the foundation. Rigid body constraints are used to refer the motion of each body to the respective centre of gravity. Contact is treated using the small-sliding formulation and the resulting system of equations of dynamics is solved by means of the Abaqus/Standard HHT algorithm, with the value of alpha that provides the maximum numerical dissipation. A sensitivity analysis is conducted for the time incrementation and mesh element size. Large time steps lead to higher attenuation of rocking movement due to the increment of the contact constraint discontinuity work (ALLCCDW), an energy component which highly influences rocking movement. However, smaller values of the step time yield very accurate results in comparison with the analytical solution. The element size sensitivity analysis revealed that the rocking initiation is generally well captured, but the coarse mesh results in inaccurate capture of the instant at which impact occurs and unrealistic attenuation of the rocking response. On the contrary, the fine mesh (defined as 1% of the corresponding contact surface) seems to capture well the rigid rocking response. These suggest that the selection of the analysis parameters is crucial to capture the desired response of free-standing rigid blocks

Analytical and numerical investigation of the seismic behaviour of bridges with rocking piers

Conventional seismic design of bridges aims to provide to the structure the necessary strength and ductility to withstand seismic forces. However, significant level of damage is expected in these structures, as clearly demonstrated after recent strong earthquakes; this damage is deemed as acceptable by current code provisions. In recent years, the need for alternative design methodologies that can limit structural damage and guarantee post-earthquake serviceability was highlighted. An alternative seismic isolation technique that can combine these concepts is based on the rocking behaviour. The rocking movement is expected to relieve the structure from deformation, stresses and ultimately damage due to the lack of monolithic joints. The research community has explored the feasibility of rocking isolation in structures that included columns, then frames, and finally bridges. The relatively few real-life applications of rocking isolation in bridge piers and the several simplifications that were adopted to study this behaviour in previous works, motivated the present study to examine this isolation technique in realistic bridge configurations and determine its effectiveness in earthquake-resistant bridges. Therefore, in view of the identified gaps in the literature on bridges with rocking pier isolation, the present study presents (i) simplified analytical tools to predict the longitudinal rocking response of bridges with rocking piers, (ii) proposals of rocking piers with non-conventional shapes in cross-section and in elevation accounting for the concept of accelerated bridge construction, and (iii) a comparative numerical assessment of conventional seismic isolation and rocking pier isolation in bridges, accounting also for the effect of the pier height/slenderness. In this context, simplified models for predicting the longitudinal response of regular and irregular bridges with rocking piers are presented to expand the initial studies on the corresponding frame models without end supports presented in previous studies. This is done by accounting for all the salient features of a bridge structure in a performance assessment context, and by integrating the dynamic interaction between the structural members. It is shown that the simple frame model without end supports is not capable of predicting the behaviour of a realistic bridge configuration. Additionally, the effect of asymmetry in the height of the piers seems to be negligible in a seismic performance context, although the response parameters vary considerably. Rocking piers with non-conventional shapes are proposed to enhance the seismic performance of the ‘traditional’ configurations that are usually employed in earthquake-resistant bridges. These proposals build on the inherent advantages that rocking mechanism and accelerated bridge construction offer, thus leading to lighter sections compared to the ‘traditional’ configurations, but leaving open the question of seismic performance due to the fact that the inherent restoring mechanisms are also reduced. The results from several analyses using both single- and multi-frequency ground motions show that rocking piers with relatively light section reduce the rocking amplitudes and protect to higher extent the integrity of the abutment-backfill system than the relatively heavy section that is the one usually adopted in earthquake-resistant bridges. The comparative numerical assessment of the ‘conventional’ seismic isolation technique and the ‘unconventional’ one based on the rocking mechanism considers a bridge configuration that is expected to be unfavourable for the latter, while several simplifications that were found in previous studies with regard to the analysis of bridges with rocking pier isolation are addressed. It is shown that the rocking alternative improves some aspects of the conventional design, especially in terms of the recentring capability of the entire system. However, considerable flexural strains are found in the rocking piers and this should be considered in the design, while the vertical movement of the rocking piers is detrimental to the flexural response of the superstructure. These effects seem to be less severe in bridges with tall/slender piers compared to those on short/squat members. Finally, proposals for future research are made with a view to (i) progressively improving and validating the analytical tools presented herein, and (ii) further examining the seismic performance of bridges with rocking pier isolation as well as enhancing the seismic performance of the ‘bare’ configurations that were addressed herein

Dynamics and seismic performance of asymmetric rocking bridges

The governing equations of motion for bridges with rocking piers of unequal height and unequal span lengths are derived accounting for the effect of end joint gaps and the abutment-backfill system. The attenuation of the rocking motion stems from the impacts at the rocking interfaces, described through the coefficient of restitution, and also from the impacts (pounding) of the superstructure on the abutment backwalls. This is the first study that combines both energy dissipation sources in the analytical derivation of the equations of motion. The results of response-history analysis of bridges with different levels of asymmetry in their pier height show that the performance of both the symmetric and asymmetric configurations is very similar with regard to longitudinal displacements. Although the studied bridges safely resisted ground motions with an intensity about twice that of the design earthquake, regardless of the degree of asymmetry, it was found that the higher the difference in the pier height, the larger is the rotation of the superstructure due to the differential uplift of the piers, a point that has to be addressed in seismic design for rocking response

Mapping aerial metal deposition in metropolitan areas from tree bark : a case study in Sheffield, England

We investigated the use of metals accumulated on tree bark for mapping their deposition across metropolitan Sheffield by sampling 642 trees of three common species. Mean concentrations of metals were generally an order of magnitude greater than in samples from a remote uncontaminated site. We found trivially small differences among tree species with respect to metal concentrations on bark, and in subsequent statistical analyses did not discriminate between them. We mapped the concentrations of As, Cd and Ni by lognormal universal kriging using parameters estimated by residual maximum likelihood ({\sc reml}). The concentrations of Ni and Cd were greatest close to a large steel works, their probable source, and declined markedly within 500~metres of it and from there more gradually over several kilometres. Arsenic was much more evenly distributed, probably as a result of locally mined coal burned in domestic fires for many years. Tree bark seems to integrate airborne pollution over time, and our findings show that sampling and analysing it are cost-effective means of mapping and identifying sources

A de novo 2.9 Mb interstitial deletion at 13q12.11 in a child with developmental delay accompanied by mild dysmorphic characteristics

Background: Proximal deletions in the 13q12.11 region are very rare. Much larger deletions including this region have been described and are associated with complex phenotypes of mental retardation, developmental delay and various others anomalies. Results: We report on a 3-year-old girl with a rare 2.9 Mb interstitial deletion at 13q12.11 due to a de novo unbalanced t(13;14) translocation. She had mild mental retardation and relatively mild dysmorphic features such as microcephaly, flat nasal bridge, moderate micrognathia and clinodactyly of 5th finger. Molecular karyotyping revealed a deletion on the long arm of chromosome 13 as involving sub-bands 13q12.11, a deletion of about 2.9 Mb. Discussion: The clinical application of array-CGH has made it possible to detect submicroscopical genomic rearrangements that are associated with varying phenotypes.The description of more patients with deletions of the 13q12.11 region will allow a more precise genotype-phenotype correlation

Alzheimer's disease: using gene/protein network machine learning for molecule discovery in olive oil

Alzheimer's disease (AD) poses a profound human, social, and economic burden. Previous studies suggest that extra virgin olive oil (EVOO) may be helpful in preventing cognitive decline. Here, we present a network machine learning method for identifying bioactive phytochemicals in EVOO with the highest potential to impact the protein network linked to the development and progression of the AD. A balanced classification accuracy of 70.3 ± 2.6% was achieved in fivefold cross-validation settings for predicting late-stage experimental drugs targeting AD from other clinically approved drugs. The calibrated machine learning algorithm was then used to predict the likelihood of existing drugs and known EVOO phytochemicals to be similar in action to the drugs impacting AD protein networks. These analyses identified the following ten EVOO phytochemicals with the highest likelihood of being active against AD: quercetin, genistein, luteolin, palmitoleate, stearic acid, apigenin, epicatechin, kaempferol, squalene, and daidzein (in the order from the highest to the lowest likelihood). This in silico study presents a framework that brings together artificial intelligence, analytical chemistry, and omics studies to identify unique therapeutic agents. It provides new insights into how EVOO constituents may help treat or prevent AD and potentially provide a basis for consideration in future clinical studies

On the relations between historical epistemology and students’ conceptual developments in mathematics

There is an ongoing discussion within the research field of mathematics education regarding the utilization of the history of mathematics within mathematics education. In this paper we consider problems that may emerge when the historical epistemology of mathematics is paralleled to students’ conceptual developments in mathematics. We problematize this attempt to link the two fields on the basis of Grattan-Guinness’ distinction between “history” and “heritage”. We argue that when parallelism claims are made, history and heritage are often mixed up, which is problematic since historical mathematical definitions must be interpreted in its proper historical context and conceptual framework. Furthermore, we argue that cultural and local ideas vary at different time periods, influencing conceptual developments in different directions regardless of whether historical or individual developments are considered, and thus it may be problematic to uncritically assume a platonic perspective. Also, we have to take into consideration that an average student of today and great mathematicians of the past are at different cognitive levels

Thorough investigation of the phenolic profile of reputable Greek honey varieties:varietal discrimination and floral markers identification using liquid chromatography–high-resolution mass spectrometry

Honey is a highly consumed commodity due to its potential health benefits upon certain consumption, resulting in a high market price. This fact indicates the need to protect honey from fraudulent acts by delivering comprehensive analytical methodologies. In this study, targeted, suspect and non-targeted metabolomic workflows were applied to identify botanical origin markers of Greek honey. Blossom honey samples (n = 62) and the unifloral fir (n = 10), oak (n = 24), pine (n = 39) and thyme (n = 34) honeys were analyzed using an ultra-high-performance liquid chromatography hybrid quadrupole time-of-flight mass spectrometry (UHPLC-q-TOF-MS) system. Several potential authenticity markers were revealed from the application of different metabolomic workflows. In detail, based on quantitative targeted analysis, three blossom honey markers were found, namely, galangin, pinocembrin and chrysin, while gallic acid concentration was found to be significantly higher in oak honey. Using suspect screening workflow, 12 additional bioactive compounds were identified and semi-quantified, achieving comprehensive metabolomic honey characterization. Lastly, by combining non-targeted screening with advanced chemometrics, it was possible to discriminate thyme from blossom honey and develop binary discriminatory models with high predictive power. In conclusion, a holistic approach to assessing the botanical origin of Greek honey is presented, highlighting the complementarity of the three applied metabolomic approaches

Dissolution and sorption processes on the surface of calcite in the presence of high Co2+ concentration

The interaction of the calcite surface with Co2+-rich aqueous solutions ([Co2+aq]initial = 1000 ppm, i.e., ca. 17 mM) was investigated by means of macroscopic experiments and surface spectroscopic techniques. In the case of the macroscopic experiments, calcite powder and monocrystals were immersed into solutions for different time periods (from 1 min to one month). The Ca concentrations in the filtrates was measured by means of atomic absorption spectrometry (AAS) while the interacted solids were studied using a combination of X-ray photoelectron spectroscopy (XPS) and 12C-rutherford backscattering spectrometry (12C-RBS). The macroscopic data showed a characteristic surface dissolution process, in parallel to the surface sorption processes. Adsorption and co-precipitation were seen for almost the entire immersion period for both calcite powder and monocrystals. The surface study by XPS (analyzed at a depth of approximately 12 nm) suggested that adsorption takes place in the first hour of the interaction, followed by incorporation of Co2+ into calcite surface layers, leading to the formation of a Co2+-bearing surface (co)precipitate, which occurs over a period of hours and days. The 12C-RBS measurements on calcite { 10 1 ¯ 4 } indicated that the thickness of this surface co-precipitate was 270 nm after one day and then stabilized at 320 nm after more than a week