The effect of the number of response cycles on the behaviour of reinforced concrete elements subject to cyclic loading

The development of damage in reinforced concrete (RC) structures is a cumulative process. Some damage indices used to quantify damage make use of the number of response cycles as an Engineering Demand Parameter (EDP) relating with damage development. Other indices make use of deformation in terms of displacement or chord rotation. These functions are generally a function of whether the response is monotonic or cyclic, and are insensitive to the number of major deflection cycles leading to that state of damage. Many such relations are derived from experimental data from low-cycle fatigue tests performed on RC elements. The loading in such tests generally consists of either a monotonic increase in load or a gradually increasing cyclic load. Since damage development is a cumulative process, and hence depends on the load history, the loading pattern in low-cycle fatigue tests for assessment purposes should reflect the response of an earthquake. This paper will discuss a procedure to determine a loading history for cyclic tests, based on earthquake demands. The preliminary results of a campaign of low-cycle fatigue tests on RC elements to investigate the effect of using different load histories are also discussed

Low cycle fatigue tests of reinforced concrete columns and joints built with ribbed reinforcement and plain stirrups

The majority of existing reinforced concrete (RC) buildings were built prior to the introduction of seismic codes. As observed in various recent earthquakes, due to their lack of structural capacity and ductility such structures are very vulnerable and have suffered considerable damage. The number of cyclic tests that have been carried out to investigate the behaviour of RC components with detailing typical of these buildings is very limited. Such tests are very relevant for seismic vulnerability assessment purposes. In this paper, a low-cycle fatigue testing campaign on RC columns and connections specifically devised to investigate various physical parameters that affect damage development, is presented. The campaign consists of 19 columns and 7 beam-column connections. Some of the preliminary results and observations are presented and discussed

Evaluation of FRAX® score use in Maltese osteoporosis management guidelines

Objectives: Recent years have brought a shift towards evidence-based fracture risk engines. Fracture Risk Assessment Tool (FRAX®) is one such diagnostic tool used to evaluate the ten-year probability of osteoporotic fracture risk. The aim of this study was to evaluate the Maltese FRAX® score-based osteoporosis management guidelines and identify the suitability of using such a risk factor engine-based protocol. Study design: Data from 702 patients presenting for bone mineral density (BMD) estimation in 2010- 2011 were collected. In this period, local guidelines were devised but not yet put into practice so all referred patients underwent BMD estimation. These patients were below 65 years of age and above the minimum age for FRAX® use: 40 years. Data included Age, Weight, Height, BMI and the presence of any risk factor components of the FRAX® score tool. BMD was assessed using Norland/Hologic densitometers. FRAX® scores (excluding BMD) for each patient were calculated using the online tool www.shef.ac.uk/FRAX as accessed in 2014. The resulting major osteoporotic fracture risk was compared to age-specific assessment thresholds as set by Kanis et al. (2013). Thus the appropriateness (or otherwise) of densitometry measurements as dictated by local guidelines was determined. Main outcome measures: The main outcome measures in this study were the femoral neck and vertebral body BMD. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of using the FRAX®-based guidelines in under 65 year olds were calculated. Results: Local guidelines for managing <65 year olds were found to have a PPV of 11.26% and a NPV of 94.38 % Conclusion: FRAX®-guided local guidelines are well suited at excluding non-osteoporotic patients (False omission rate of 5.62 %). Positive likelihood ratio for the protocol was found to be 1.27. This means that 1 in every 8.8 patients that would have been referred for BMD estimation were actually osteoporotic.peer-reviewe

Equation of State and Isentropic Releasem of Aluminum Foam and Fluoropolymer Composites

There is considerable interest in developing a better understanding of the dynamic behavior of heterogeneous materials. This study investigates and compares the dynamic response of 20 and 47% dense aluminum foam systems with and without a polytetrafluoroethylene (PTFE or Teflon) fill. Experiments on 47% foam were conduced in a 60 mm bore gun in a reverse ballistic configuration at velocities ranging from 350 m/s to 2.5 km/s. The particle velocity of the backside of the anvil was monitored with a VISAR system. Mesoscale simulations are in good agreement with the available experimental data. Both the experimental and simulated data are in good agreement with an analytic release isentrope when released from Hugoniot stress levels less than 5 GPa. However there is significant deviation from the analytic isentrope as the Hugoniot stress level is increased

Production rates of neon xenon isotopes by energetic neutrons

As a first step in an experimental program to study the behavior of noble gases produced in situ in minerals, a suite of minerals and pure chemicals were irradiated with 14.5 MeV neutrons at LLNL's Rotating Target Neutron Source (RTNS-II) and production rates for noble gases were determined. While neutron effects in meteorites and lunar samples are dominated by low-energy neutron capture, more energetic cosmic-ray secondary neutrons can provide significant depth-dependent contributions to production of cosmogenic nuclides through endothermic reactions such as (n,2n), (n,np), (n,d) and (n,alpha). Production rates for nuclides produced by cosmic-ray secondary neutrons are therefore useful in interpreting shielding histories from the relative abundances of cosmogenic nuclides. Absolute production cross sections were calculated from isotope dilution analyses of NaCl, Mg, CsCl, and Ba(NO3)2 samples, assuming purity, stoichiometry, and quantitative noble gas retention and extraction. Relative production cross sections determined from neon isotopic ratios in the mineral samples were also considered in evaluating the neon production cross sections. Results are presented

Future mangement arrangements for Western Australia\u27s temperate shark fisheries.

This paper provides a summary of the attributes of these temperate shark fisheries, and sets out the proposed objectives and the measures available to achieve them. In summary, primary measures are aimed at the sustainability of dusky and whiskery sharks, with dusky sharks being of greater concern as their status is more critical. The final decision on management of these fisheries cannot compromise sustainability, not only because of the Department’s obligations under the Fish Resources Management Act, 1994, but also: • national and international obligations associated with ecologically sustainable development; • export accreditation under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act); and • the National Plan of Action for shar

Mean first passage time analysis reveals rate-limiting steps, parallel pathways and dead ends in a simple model of protein folding

We have analyzed dynamics on the complex free energy landscape of protein folding in the FOLD-X model, by calculating for each state of the system the mean first passage time to the folded state. The resulting kinetic map of the folding process shows that it proceeds in jumps between well-defined, local free energy minima. Closer analysis of the different local minima allows us to reveal secondary, parallel pathways as well as dead ends.Comment: 7 page

Scale Free Cluster Distributions from Conserving Merging-Fragmentation Processes

We propose a dynamical scheme for the combined processes of fragmentation and merging as a model system for cluster dynamics in nature and society displaying scale invariant properties. The clusters merge and fragment with rates proportional to their sizes, conserving the total mass. The total number of clusters grows continuously but the full time-dependent distribution can be rescaled over at least 15 decades onto a universal curve which we derive analytically. This curve includes a scale free solution with a scaling exponent of -3/2 for the cluster sizes.Comment: 4 pages, 3 figure

VLA Observations of the Infrared Dark Cloud G19.30+0.07

We present Very Large Array observations of ammonia (NH3) (1,1), (2,2), and CCS (2_1-1_0) emission toward the Infrared Dark Cloud (IRDC) G19.30+0.07 at ~22GHz. The NH3 emission closely follows the 8 micron extinction. The NH3 (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of ~10 to 20K and NH3 column densities of ~10^15 cm^-2. The estimated total mass of G19.30+0.07 is ~1130 Msun. The cloud comprises four compact NH3 clumps of mass ~30 to 160 Msun. Two coincide with 24 micron emission, indicating heating by protostars, and show evidence of outflow in the NH3 emission. We report a water maser associated with a third clump; the fourth clump is apparently starless. A non-detection of 8.4GHz emission suggests that the IRDC contains no bright HII regions, and places a limit on the spectral type of an embedded ZAMS star to early-B or later. From the NH3 emission we find G19.30+0.07 is composed of three distinct velocity components, or "subclouds." One velocity component contains the two 24 micron sources and the starless clump, another contains the clump with the water maser, while the third velocity component is diffuse, with no significant high-density peaks. The spatial distribution of NH3 and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH3 predominantly in the high-density clumps, and the CCS tracing lower-density envelopes around those clumps. This spatial distribution is consistent with theories of evolution for chemically young low-mass cores, in which CCS has not yet been processed to other species and/or depleted in high-density regions.Comment: 29 pages, 9 figures, accepted for publication by ApJ. Please contact the authors for higher resolution versions of the figure