ANCHORAGE OF HEADED REINFORCING BARS IN CONCRETE

Headed reinforcing bars serve as a viable alternative to hooked bars for anchorage in concrete because they provide a more efficient anchorage mechanism and limit congestion of the reinforcement. This study is part of a comprehensive study of the anchorage behavior of the headed bars. The work described in this report includes tests of 32 No. 8 headed bars anchored in simulated column-foundation joints represented by bars anchored in slabs, all but two with reinforcement in the plane of the slab, and six lapped-slplice specimens without confining reinforcement containing No. 6 headed bars and an analysis of these tests along with test results from 23 studies by other researchers of 84 exterior, seven roof-level interior, and seven knee beam-column joints subjected to reversed cyclic loading. The headed bars in the column-foundation joint specimens had net bearing areas ranging from 4 to 15 times the area of the bar Ab; some of the headed bars contained large obstructions adjacent to the bearing face of the head that exceeded the dimensional limits for HA heads in ASTM A970-16; embedment lengths ranged from 6 to 8.5 in.; reinforcement in a plane perpendicular to the headed bars included combinations of bars placed symmetrically about the headed bar, parallel and close to the long edges of the specimen, bars placed symmetrically about and close to the headed bar in the short direction of the specimen, and bars oriented in both the long and short directions of the specimen; concrete compressive strengths ranged from 4,200 to 8,620 psi; and stresses in the bars at failure ranged from 49,500 to 117,000 psi. The No. 6 headed bars had a net bearing area of 4Ab and a lap length of 12 in. The center-to-center spacing between the spliced bars was 1.67, 2.33, or 3.53 bar diameters db; clear concrete cover to the bars was 2 in.; concrete compressive strengths averaged 6,360 and 10,950 psi; and stresses in the bars at failure ranged from 75,010 to 83,560 psi. For the beam-column joints subjected to reversed cyclic loading, headed bar sizes ranged between D12 (No. 4) and D36 (No. 11), net bearing areas ranged from 1.7 to 11.4Ab, and embedment lengths ranged from 8 to 22.6db; concrete compressive strengths ranged from 3,480 to 21,520 psi and steel yield strengths ranged from 53,650 to 149,930 psi; all but four specimens contained hoops, spaced at 2.2 to 6.8db (1.8 to 5.9 in.), as confining reinforcement parallel to the headed bar within the joint region; clear cover and minimum center-to-center spacing between the bars ranged from 1.4 to 9.9db and from 2 to 11.2db, respectively. Experimental anchorage strengths are compared with values based on descriptive equations for anchorage strength and design provisions for development length of headed bars for members with concrete compressive strengths up to 16,000 psi and steel yield strengths up to 120,000 psi that recognize the contribution of confining reinforcement without specifying minimum limits on bar spacing or clear cover. The descriptive equations and design provisions were developed based on tests of simulated beam-column joints under monotonic loading as part of the comprehensive study. The comparisons are used to expand the applicability of the descriptive equations to members subjected to reversed cyclic loading and develop simplified design guidelines allowing for the use of headed reinforcing bars in wide range of reinforced concrete members. Changes in the provisions of ACI 318-14 for the development length of headed bars and in ASTM A970 for head dimension requirements are also proposed. The results of this study show that reinforcement perpendicular to headed bars in column-foundation joints does not improve the anchorage strength. Headed bars with obstructions exceeding the dimensional limits for HA heads in ASTM A970-16 provide adequate anchorage strength. Headed bars did not provide sufficient anchorage in knee beam-column joints subjected to reversed cyclic loading. The descriptive equations and proposed design provisions developed based on headed bars in beam-column joint specimens tested under monotonic loading, in which the anchorage strength of the headed bar is a function of embedment length, concrete compressive strength, bar spacing, bar diameter, and confining reinforcement within the joint region, are applicable to a wide range of reinforced concrete members, including beam-column joints subjected reversed cyclic loading, lap splices, and column-foundation joints, and allow the minimum clear spacing of 3db between headed bars permitted in joints in special moment frames in accordance with Section 18.8.5.2 of ACI 318-14 to be reduced to 1db, allowing for the use of more closely spaced headed bars. The anchorage strength of the headed bars calculated using anchorage provisions of Chapter 17 of ACI 318-14 with a strength reduction factor of 1.0 provides a very conservative and highly variable estimate of anchorage strength for headed bars compared to the proposed design provisions

Technical efficiency of wheat growing farmers of Nepal

Wheat is a major staple food crop of Nepal, so it is necessary to increase its productivity. However, the national average wheat productivity of Nepal is low as compared to other neighboring countries. This study employed a Cobb-Douglas stochastic production frontier model to examine the technical efficiency and its determinants using randomly selected household data from 343 wheat farmers from four districts of Nepal. Maximum likelihood estimation results showed that wheat production responded positively to an increase in the quantity of inorganic fertilizer, whereas it was detrimental to seed rate. Likewise, the study found that farmers were not technically efficient with a mean technical efficiency of 81%. The result showed irrigation, herbicides, sowing time, Farm Yard Manure (FYM), and wheat varieties were statistically significant factors that affect the technical efficiency of wheat farmers. Furthermore, to increase wheat productivity, farmers should use better irrigation, appropriate weed management practices, optimum sowing time, and adoption of recent improved varieties. Findings suggest that the technical efficiency of wheat farmers could be enhanced by practicing optimum use of inputs and improving the inefficiency factor

Economics of production and marketing of wheat in Rupandehi district of Nepal

Wheat is the third most important cereal crop of Nepal after rice and maize in terms of area. The study on profitability and marketing of wheat was conducted in the Rupandehi district in 2019. The household survey, focus group discussion, interview with the individual market actors such as input suppliers, producers, collectors, wholesalers, millers, and retailers in selected clusters was carried out. The study showed that the Benefit-Cost Ratio of wheat production (BCR) was 1.87. The marketing margins at three different levels of marketing farm-wholesale, wholesale-retail, and farm-retail were also analyzed. The farm-retail marketing margin was found highest (31.42%) and the farm-wholesale marketing margins were less (15.78%). The producers’ share in consumer price was 68.5% and the total gross margin was 56.36%.  This showed if value-added activities are absent in the chain, the shorter chain can provide a higher margin to farmers by bypassing the intermediaries

Fabrication of UV sensing transistor based on transparent polycrystalline zinc oxide thin film using polymeric electrolyte gate dielectric

The fabrication of electric double layer thin film transistors (EDLTFTs) using polymeric electrolyte as gate dielectric on chemically grown polycrystalline ZnO thin film channel has the lower threshold voltage at 0.4 V and the saturation current at 3 µA in the dark. The lower threshold voltage is -1 V and the saturation current is 10 µA in the UV illumination. In the dark and under UV light, the off state ID is 1 nA and 0.3 µA respectively and under gate and UV illumination the on current shows more than 3 times enhancement. This improvement in photocurrent is due to the combined effect of gate and UV illumination. The field effect mobility of the TFT is 0.06 cm2/Vs in the dark and 0.16 cm2/Vs under UV illumination. This increase in mobility under illumination and gate bias is due to the increase in carrier concentration and reduction of charged defects in the channel length

Credit’s use performance and its determinants on farm household: A case of Chitwan district of Nepal

Credit has been considered to play a pivotal role in the agricultural development of Nepal. A large number of institutions are involved in the disbursement of credit to agriculture. In this backdrop, the present study has examined the performance of agricultural credit and has identified the determinants of increased use of credit at the farm household level in Nepal. The study was based on survey data consisting of 107 samples collected randomly from the Chitwan district. The study has revealed that the quantum of credit availed by the farming households is affected by several socio-demographic factors which include caste, economically active population, food sufficiency, and membership in an organization. The research revealed that if the household is Brahmin/ Chettri, the probability of borrowing loans decreased by 32% as compared to other castes. Similarly, if the household’s economically active population increased by one unit, the probability of taking a loan increased by 16%. The results also show that, if household food sufficiency increased by one month the probability of taking loans decreased by 4 % but if the household head is a member of an organization, the probability of taking a loan increased by 28%. The congenial environment to increase the involvement of the household head to an organization like cooperative and farmers group, increasing the food self-sufficiency through productivity enhancement program and creating awareness on credit utilization helps to increase credit use performance in Agriculture

Issues in rice marketing system: a case of central terai

This study was conducted to understand the challenges and prospects of ricemarketing by taking case of central Nepal. Two focus group discussionsalong with eight key informants’ interviewswere conductedinBara and Parsa districts of Nepal.Also, secondary information was collected by reviewing the related literatures.The study revealed that the consumer price of rice is almost double than the farm gate price, possibly due to the presence of several intermediaries in different nodes of the supply chain.Key market actors like large collectors, millers and wholesalers have a dominating role in price negotiation and supply of rice in the market. The rice value chain is not strong enough, which might be due to poor vertical and horizontal as well as backward and forward linkages among the key players. The demand of fine and aromatic rice is gradually increasing due to changing food habits of the consumers and their access to purchasing capacity as well.The high yielding short duration varieties of fine and aromatic rice need to be identified and developed to meet the growing demand of consumers.In addition, to boost productivity and profitability of rice, a better investment climate, risk sharing mechanism and strengthened value chain with efficient research and extension services are required

Approaches and advantages of increased crop genetic diversity in the fields

Field trials of rice and bean dynamic mixtures were carried out in low input and hill farming systems of Nepal from 2019 to 2021 to improve productivity and resilience. The rice trials were conducted in two locations (Jumla and Lamjung) and those on bean in Jumla, using a randomized complete block design with three replications. Dynamic mixtures were constructed from landraces, improved varieties and breeding lines for both crops. A total of 48 bean entries were used in Jumla, whereas 56 and 66 rice entries were used to make location-specific dynamic mixtures in Lamjung and Jumla, respectively. They were formed by mixing diverse varieties as a strategy to maintain a broad genetic base. Farmers (men and women) and technicians selected from the most complex mixture and the selections were added to the trials starting from second year. In rice, some mixtures and selections from the mixtures gave grain yield comparable to the improved check and higher than the local checks. In the case of bean, differences between entries were not significant but some of the selections received a high preference score. Overall, the dynamic mixtures appear as a reliable material for sustainable increase in yield in the low input and hill farming system of Nepal

Farmers’ preferences and agronomic evaluation of dynamic mixtures of rice and bean in Nepal

Field trials of rice and bean dynamic mixtures were carried out in low input and hill farming systems of Nepal from 2019 to 2021 to improve productivity and resilience. The rice trials were conducted in two locations (Jumla and Lamjung) and those on bean in Jumla, using a randomized complete block design with three replications. Dynamic mixtures were constructed from landraces, improved varieties and breeding lines for both crops. A total of 48 bean entries were used in Jumla, whereas 56 and 66 rice entries were used to make location-specific dynamic mixtures in Lamjung and Jumla, respectively. They were formed by mixing diverse varieties as a strategy to maintain a broad genetic base. Farmers (men and women) and technicians selected from the most complex mixture and the selections were added to the trials starting from second year. In rice, some mixtures and selections from the mixtures gave grain yield comparable to the improved check and higher than the local checks. In the case of bean, differences between entries were not significant but some of the selections received a high preference score. Overall, the dynamic mixtures appear as a reliable material for sustainable increase in yield in the low input and hill farming system of Nepal

Alcohol use and burden for 195 countries and territories, 1990-2016 : a systematic analysis for the Global Burden of Disease Study 2016

Background Alcohol use is a leading risk factor for death and disability, but its overall association with health remains complex given the possible protective effects of moderate alcohol consumption on some conditions. With our comprehensive approach to health accounting within the Global Burden of Diseases, Injuries, and Risk Factors Study 2016, we generated improved estimates of alcohol use and alcohol-attributable deaths and disability-adjusted life-years (DALYs) for 195 locations from 1990 to 2016, for both sexes and for 5-year age groups between the ages of 15 years and 95 years and older. Methods Using 694 data sources of individual and population-level alcohol consumption, along with 592 prospective and retrospective studies on the risk of alcohol use, we produced estimates of the prevalence of current drinking, abstention, the distribution of alcohol consumption among current drinkers in standard drinks daily (defined as 10 g of pure ethyl alcohol), and alcohol-attributable deaths and DALYs. We made several methodological improvements compared with previous estimates: first, we adjusted alcohol sales estimates to take into account tourist and unrecorded consumption; second, we did a new meta-analysis of relative risks for 23 health outcomes associated with alcohol use; and third, we developed a new method to quantify the level of alcohol consumption that minimises the overall risk to individual health. Findings Globally, alcohol use was the seventh leading risk factor for both deaths and DALYs in 2016, accounting for 2.2% (95% uncertainty interval [UI] 1.5-3.0) of age-standardised female deaths and 6.8% (5.8-8.0) of age-standardised male deaths. Among the population aged 15-49 years, alcohol use was the leading risk factor globally in 2016, with 3.8% (95% UI 3.2-4-3) of female deaths and 12.2% (10.8-13-6) of male deaths attributable to alcohol use. For the population aged 15-49 years, female attributable DALYs were 2.3% (95% UI 2.0-2.6) and male attributable DALYs were 8.9% (7.8-9.9). The three leading causes of attributable deaths in this age group were tuberculosis (1.4% [95% UI 1. 0-1. 7] of total deaths), road injuries (1.2% [0.7-1.9]), and self-harm (1.1% [0.6-1.5]). For populations aged 50 years and older, cancers accounted for a large proportion of total alcohol-attributable deaths in 2016, constituting 27.1% (95% UI 21.2-33.3) of total alcohol-attributable female deaths and 18.9% (15.3-22.6) of male deaths. The level of alcohol consumption that minimised harm across health outcomes was zero (95% UI 0.0-0.8) standard drinks per week. Interpretation Alcohol use is a leading risk factor for global disease burden and causes substantial health loss. We found that the risk of all-cause mortality, and of cancers specifically, rises with increasing levels of consumption, and the level of consumption that minimises health loss is zero. These results suggest that alcohol control policies might need to be revised worldwide, refocusing on efforts to lower overall population-level consumption.Peer reviewe

Population and fertility by age and sex for 195 countries and territories, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017

Background: Population estimates underpin demographic and epidemiological research and are used to track progress on numerous international indicators of health and development. To date, internationally available estimates of population and fertility, although useful, have not been produced with transparent and replicable methods and do not use standardised estimates of mortality. We present single-calendar year and single-year of age estimates of fertility and population by sex with standardised and replicable methods. Methods: We estimated population in 195 locations by single year of age and single calendar year from 1950 to 2017 with standardised and replicable methods. We based the estimates on the demographic balancing equation, with inputs of fertility, mortality, population, and migration data. Fertility data came from 7817 location-years of vital registration data, 429 surveys reporting complete birth histories, and 977 surveys and censuses reporting summary birth histories. We estimated age-specific fertility rates (ASFRs; the annual number of livebirths to women of a specified age group per 1000 women in that age group) by use of spatiotemporal Gaussian process regression and used the ASFRs to estimate total fertility rates (TFRs; the average number of children a woman would bear if she survived through the end of the reproductive age span [age 10–54 years] and experienced at each age a particular set of ASFRs observed in the year of interest). Because of sparse data, fertility at ages 10–14 years and 50–54 years was estimated from data on fertility in women aged 15–19 years and 45–49 years, through use of linear regression. Age-specific mortality data came from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 estimates. Data on population came from 1257 censuses and 761 population registry location-years and were adjusted for underenumeration and age misreporting with standard demographic methods. Migration was estimated with the GBD Bayesian demographic balancing model, after incorporating information about refugee migration into the model prior. Final population estimates used the cohort-component method of population projection, with inputs of fertility, mortality, and migration data. Population uncertainty was estimated by use of out-of-sample predictive validity testing. With these data, we estimated the trends in population by age and sex and in fertility by age between 1950 and 2017 in 195 countries and territories. Findings: From 1950 to 2017, TFRs decreased by 49\ub74% (95% uncertainty interval [UI] 46\ub74–52\ub70). The TFR decreased from 4\ub77 livebirths (4\ub75–4\ub79) to 2\ub74 livebirths (2\ub72–2\ub75), and the ASFR of mothers aged 10–19 years decreased from 37 livebirths (34–40) to 22 livebirths (19–24) per 1000 women. Despite reductions in the TFR, the global population has been increasing by an average of 83\ub78 million people per year since 1985. The global population increased by 197\ub72% (193\ub73–200\ub78) since 1950, from 2\ub76 billion (2\ub75–2\ub76) to 7\ub76 billion (7\ub74–7\ub79) people in 2017; much of this increase was in the proportion of the global population in south Asia and sub-Saharan Africa. The global annual rate of population growth increased between 1950 and 1964, when it peaked at 2\ub70%; this rate then remained nearly constant until 1970 and then decreased to 1\ub71% in 2017. Population growth rates in the southeast Asia, east Asia, and Oceania GBD super-region decreased from 2\ub75% in 1963 to 0\ub77% in 2017, whereas in sub-Saharan Africa, population growth rates were almost at the highest reported levels ever in 2017, when they were at 2\ub77%. The global average age increased from 26\ub76 years in 1950 to 32\ub71 years in 2017, and the proportion of the population that is of working age (age 15–64 years) increased from 59\ub79% to 65\ub73%. At the national level, the TFR decreased in all countries and territories between 1950 and 2017; in 2017, TFRs ranged from a low of 1\ub70 livebirths (95% UI 0\ub79–1\ub72) in Cyprus to a high of 7\ub71 livebirths (6\ub78–7\ub74) in Niger. The TFR under age 25 years (TFU25; number of livebirths expected by age 25 years for a hypothetical woman who survived the age group and was exposed to current ASFRs) in 2017 ranged from 0\ub708 livebirths (0\ub707–0\ub709) in South Korea to 2\ub74 livebirths (2\ub72–2\ub76) in Niger, and the TFR over age 30 years (TFO30; number of livebirths expected for a hypothetical woman ageing from 30 to 54 years who survived the age group and was exposed to current ASFRs) ranged from a low of 0\ub73 livebirths (0\ub73–0\ub74) in Puerto Rico to a high of 3\ub71 livebirths (3\ub70–3\ub72) in Niger. TFO30 was higher than TFU25 in 145 countries and territories in 2017. 33 countries had a negative population growth rate from 2010 to 2017, most of which were located in central, eastern, and western Europe, whereas population growth rates of more than 2\ub70% were seen in 33 of 46 countries in sub-Saharan Africa. In 2017, less than 65% of the national population was of working age in 12 of 34 high-income countries, and less than 50% of the national population was of working age in Mali, Chad, and Niger. Interpretation: Population trends create demographic dividends and headwinds (ie, economic benefits and detriments) that affect national economies and determine national planning needs. Although TFRs are decreasing, the global population continues to grow as mortality declines, with diverse patterns at the national level and across age groups. To our knowledge, this is the first study to provide transparent and replicable estimates of population and fertility, which can be used to inform decision making and to monitor progress. Funding: Bill & Melinda Gates Foundation