STR-942: PUNCHING SHEAR OF SELF-CONSOLIDATING TWO WAY SLABS

This paper presents an experimental program conducted to investigate the punching shear behaviour of self-consolidating (SCC) two-way slabs, and the influence of using different sizes of coarse aggregate and slab thickness on this behaviour. For this purpose, a total of six slabs were tested. Two groups of labs with targeted compressive strength of 30 MPa were used; for group A, 10 mm coarse aggregate size was used, and 20 mm coarse aggregate size was used for the slabs in group B. Each group consisted of three slabs with different thicknesses of 150, 200, and 250 mm. The results revealed a significant effect of slab thickness and size of coarse aggregate. The failure criterion proposed by (Muttoni 2008) based on the slab rotation was used to predict the tested slabs capacities. In addition, comparison with other codes of practice (CSA A23.3-04, ACI 318-11, BS8110-97, and EC2) was carried out. These codes except the EC2 can be safely used to check the punching shear capacity of SCC slabs without the need of any modification to the equations used

MAT-708: MONITORING THE CORROSION PROCESS OF REINFORCED CONCRETE FLAT SLAB-COLUMN CONNECTION

The corrosion of the steel reinforcement embedded in a two-way reinforced concrete flat slab around the column stub area was investigated in this study, which aimed to studying the effect of corrosion on the shear punching behavior. Two square flat slab-column connections were cast, the flat slab dimension was 1900 mm × 1900 mm × 150 mm, and the column dimensions was 250 mm × 250 mm. A specific delaminated area was corroded around the column stub to emphasize the effect of corrosion around punching area. The corrosion reached two levels of mass loss uniformly over that specified area: 0% and 26%. Corrosion process was monitored under an accelerated corrosion technique through the application of a constant potential of fifteen volts to reach the targeted uniform corrosion level. Then, the corrode slab-column connection was loaded until failure for each slab occurred. The corrosion performance of the slab was evaluated based on the results of the current measurement, half-cell potential tests, and mass loss. The test results show that the corrosion of reinforcement rebar around the column stub in flat slab causes a significant loss in punching shear capacity and affects the structural integrity by increasing crack widths

Models Development for Asphalt Pavement Performance Index in Different Climate Regions Using Soft Computing Techniques

The Pavement Condition Index (PCI) is one of the most critical pavement performance indicators and ride quality. This study aims to develop PCI models based on pavement distress parameters using conventional technique and artificial neural network (ANN) technique across two climate regions in the U.S. and Canada. The long-term pavement performance (LTPP) database was used to obtain pavement distress data, including pavement age, rutting, fatigue cracking, block cracking, longitudinal cracking, transverse cracking, potholes, patching, bleeding, and ravelling, as input variables for predicting PCI. Forty-three flexible pavement segments were considered with 333 observations. The type, severity, and extent of surface damage and the PCI were determined for each pavement segment. Two modelling techniques were conducted to predict the PCI, namely, multiple linear regression (MLR) and artificial neural network (ANN). The coefficient of determination (R2), Root mean squared error (RMSE), and mean absolute error (MAE) were used to examine the performance of the two techniques adopted in this study. The models' results determined that both ANN and MLR models could predict PCI with high accuracy; ANN models were more accurate and efficient. ANN provided the highest accuracy in predicting PCI of pavement for wet and wet no-freeze climate regions, with R2 values of 99.8%, 98.3 %: RMSE values of 0.44%, 1.413%, and MAE values of 0.44%, 1.022%, respectively. Whereas in the MLR method, R2 values of 86.8% and 89.4%: RMSE values of 7.195%, 7.324%, and MAE values of 5.616%, 5.79% for wet and wet no freeze climate regions, respectively

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Behaviour of high-strength concrete under biaxial loading conditions

With the increasing applications of high strength concrete in the construction industry, the understanding of its behaviour under multiaxial loading is essential for reliable analysis and safe design. This thesis encompasses an investigation of the behaviour of high strength concrete under biaxial loading conditions, and a constitutive modelling study to enable numerical prediction, through the finite element method, of such a behaviour. -- The experimental phase included the evaluation and design of the loading platens. The test set-up and supports are very crucial to this type of testing due to the friction that exists between the testing platens and the specimen. A theoretical study using the finite element approach was conducted to investigate the effect of confinement on the displacement field in addition to the stress distribution in the loading direction. Three types of loading platens were examined: the dry solid platens, the brush support and teflon friction reducing pads. The results of the simulation indicated that the most homogeneous stress and displacement field are achieved through the brush platens. Based on the finite element investigation, the size and dimensions of the brush platens were recommended. They were used in the experimental study. -- A test set-up was designed and manufactured. Modern control schemes and highspeed data acquisition system were be used to monitor the material response and collect the experimental results. Four different types of high strength concrete plate specimens were tested under different biaxial load combinations. The principal deformations in the specimen were recorded and the crack patterns and failure modes were examined. Based on the strength data, failure envelopes were developed for each type of concrete. The test results revealed that the failure envelopes of concrete depends on the concrete strength and on the type of aggregates. A pronounced difference was found between the high strength light weight and the high strength normal weight concrete. The deformation characteristics indicated that high strength concrete shows a linear behaviour up to a higher stress than normal strength concrete. It also has a higher discontinuity limits. The observed failure modes showed that there is no fundamental difference in the crack patterns and failure modes due to the increase in the compressive strength of the concrete or due to the use of light weight aggregates under different biaxial loading combinations. -- The test results were used to modify and calibrate a fracture energy-based non-associated model for high-strength concrete. The model was implemented in a general purpose finite element program and was verified against the test results. Using the proposed constitutive model, a finite element study was carried out to analyze the standard compression test on a concrete cylinder. The effects of the compressive strength, cylinder size, loading platens and sulphur capping were investigated. The study confirmed that a triaxial compressive stress state exists at the cylinder end, and a large stress concentration occurs at the corner. The simulation results revealed that the use of a standard bearing block is essential in testing high strength concrete. Moreover, in some cases, the use of a non standard bearing block can result in a lower strength, which was observed experimentally. The simulation provided an explanation for such a behaviour. Finally, the finite element analysis demonstrated that the use of soft materials, as friction reducers, could create drastic changes in the state of stress in the specimen as well as its compressive strength. The use of soft materials should, therefore, be carried out with caution

Behaviour of reinforced concrete slabs made with high-strength concrete

The present research investigation deals with the structural behaviour of two-way slabs made with high-strength concrete subjected to punching shear. -- A high-strength concrete mix, suitable for offshore applications, was developed using conventional cement and aggregates available in Newfoundland. The incorporation of silica fume and high-range water reducing agent made it possible to achieve high strengths at early ages. A compressive strength of 70 MPa at 28 days was achieved for concrete mix incorporating 12% class F fly ash, 8% condensed silica fume and a high-range water reducing agent of naphthalene formaldehyde base. The relevant rheological and mechanical properties of the mix were examined. In addition, an experimental program was carried out to study the effect of cold ocean water, simulated under laboratory conditions, on the mechanical properties of green high-strength concrete containing silica fume and fly ash. -- Seventeen slabs were tested in the structural laboratory at M.U.N. The effect of the reinforcement ratio, concrete strength, slab depth and column size on the behaviour of the slabs was investigated. The structural behaviour of the tested slabs with regard to deformations, strains, ultimate capacity, and modes of failure was examined. Test results revealed that the present North American Codes are unsafe for high-strength concrete slabs, since they overestimate the influence of the concrete strength, as a factor, on the ultimate capacity of two-way slabs. -- Based on the test results, a mechanical model was adopted. The formulation takes into account the actual behaviour of the high-strength concrete and steel. The proposed model gave a fairly good agreement between the predicted and experimental punching loads