Pollutant Dispersion Characteristics in Dhaka City, Bangladesh

Khandaker M. A. Hossain,Said M. Easa 한국기상학회 2012 Asia-Pacific Journal of Atmospheric Sciences Vol.48 No.1

Air pollution is a major environmental concern in major cities around the world. The major causes of air pollution include rapid industrialization/urbanization and increased non environmentfriendly energy production. This paper analyses the atmospheric pollutant such as carbon monoxide (CO) and particulate matter (PM)dispersion characteristics of Dhaka city. The yearly and diurnal variations of pollutant concentration are described by taking into consideration of both meteorological and emission source parameters highlighting washout effect due to rainfall and inversion phenomena. Concentration of PM (both PM2.5 and PM10) and CO in the ambient air are measured for a period of one year with Airmetric Minivol air samplers and Gas Chromatographic (GC) technique, respectively. The trend over the year shows an increase in the monthly average hourly PM and CO concentrations in winter months (November to March)when both PM10 and PM2.5 annual average concentrations (about 130 and 95 μgm−3, respectively) exhibit levels exceeding World Health Organization (WHO) guidelines as well as exceed more than twice the national standards of annual PM10 (50 μg m−3) and PM2.5 (15μg m−3) concentrations. Such high pollutant concentrations may have significant health implications for residents of Dhaka city. It is also found that the PM concentration increases with the increase of wind speed during dry winter season and is also influenced by transboundary air pollution. The data and subsequent recommendations can be useful in formulating air quality management strategies for the Dhaka city.

Computational optimisation of a concrete model to simulate membrane action in RC slabs

Khandaker M. A. Hossain,Olubayo O. Olufemi 한국계산역학회 2004 Computers and Concrete, An International Journal Vol.1 No.3

Slabs in buildings and bridge decks, which are restrained against lateral displacements at the edges, have ultimate strengths far in excess of those predicted by analytical methods based on yield line theory. The increase in strength has been attributed to membrane action, which is due to the in-plane forces developed at the supports. The benefits of compressive membrane action are usually not taken into account in currently available design methods developed based on plastic flow theories assuming concreteto be a rigid-plastic material. By extending the existing knowledge of compressive membrane action, it is possible to design slabs in building and bridge structures economically with less than normal reinforcement. Recent research on building and bridge structures reflects the importance of membrane action in design. This paper describes the finite element modelling of membrane action in reinforced concrete slabs through optimisation of a simple concrete model. Through a series of parametric studies using the simple concrete model in the finite element simulation of eight fully clamped concrete slabs with significant membrane action, a set of fixed numerical model parameter values is identified and computational conditions established, which would guarantee reliable strength prediction of arbitrary slabs. The reliability of the identified values to simulate membrane action (for prediction purposes) is further verified by the directsimulation of 42 other slabs, which gave an average value of 0.9698 for the ratio of experimental to predicted strengths and a standard deviation of 0.117. A ?eflection factor?is also established for the slabs, relating the predicted peak deflection to experimental values, which, (for the same level of fixity at the supports), can be used for accurate displacement determination. The proposed optimised concrete model and finite element procedure can be used as a tool to simulate membrane action in slabs in building and bridge structures having variable support and loading conditions including fire. Other practical applications of the developed finite element procedure and design process are also discussed.

The presence of carcinogenic radon in the Padma River water, adjacent to the Rooppur Nuclear Power Plant

Siraz M.M. Mahfuz,Alam M.S.,Jubair A.M.,Das S.C.,Ferdous J.,Hossain Z.,Das S.,Khandaker Mayeen Uddin,Bradley D.A.,Tokonami Shinji,Yeasmin S. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

Radon is a naturally occurring carcinogenic agent, poses a serious health hazard when inhaled or ingested in significant amounts. The water of the Padma river will be used as a tertiary coolant for the soon-to-be-commissioned ‘Rooppur Nuclear Power Plant’. Hence, it is important to assess the radiological status of the river prior to the commission of this power plant. Therefore, for the first time, 25 samples of water were collected from various locations of the Padma River and analyzed for radon concentration using the RAD H2O (DURRIDGE) radon monitoring device. The radon concentrations were found in the range from 0.077 ± 0.036 to 0.494 ± 0.211 Bq/L with a mean of 0.250 ± 0.093 Bq/L. All the concentrations were found to be below the recommended limits of WHO (100 Bq/L) and USEPA (11.1 Bq/ L). The mean annual effective dose due to the radon exposure via inhalation and ingestion pathways were 0.638 mSv/y and 0.629 mSv/y, respectively, which were all well below the annual effective dose recommended by WHO (0.1 mSv/y). Since Bangladesh lacks a national safety limit of radon in water, this pioneering study provides baseline data on radon levels for the environment around Rooppur Nuclear Power Plant.

Artificial neural network model for the strength prediction of fully restrained RC slabs subjected to membrane action

Khandaker M. A. Hossain,Mohamed Lachemi,Said M. Easa 한국계산역학회 2006 Computers and Concrete, An International Journal Vol.3 No.6

This paper develops an artificial neural network (ANN) model for uniformly loaded restrained reinforced concrete (RC) slabs incorporating membrane action. The development of membrane action in RC slabs restrained against lateral displacements at the edges in buildings and bridge structures significantly increases their load carrying capacity. The benefits of compressive membrane action are usually not taken into account in currently available design methods based on yield-line theory. By extending the existing knowledge of compressive membrane action, it is possible to design slabs in building and bridge decks economically with less than normal reinforcement. The processes involved in the development of ANN model such as the creation of a database of test results from previous research studies, the selection of architecture of the network from extensive trial and error procedure, and the training and performance validation of the model are presented. The ANN model was found to predict accurately the ultimate strength of fully restrained RC slabs. The model also was able to incorporate strength enhancement of RC slabs due to membrane action as confirmed from a comparative study of experimental and yield line-based predictions. Practical applications of the developed ANN model in the design process of RC slabs are also highlighted.

Lightweight Self-consolidating Concrete with Expanded Shale Aggregates

Abdurrahmaan Lotfy,Khandaker M. A. Hossain,Mohamed Lachemi 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.2

This paper presents statistical models developed to study the influence of key mix design parameters on the properties of lightweight self-consolidating concrete (LWSCC) with expanded shale (ESH) aggregates. Twenty LWSCC mixtures are designed and tested, where responses (properties) are evaluated to analyze influence of mix design parameters and develop the models. Such responses included slump flow diameter, V-funnel flow time, J-ring flow diameter, J-ring height difference, L-box ratio, filling capacity, sieve segregation, unit weight and compressive strength. The developed models are valid for mixes with 0.30?0.40 water-to-binder ratio, high range water reducing admixture of 0.3?1.2 % (by total content of binder) and total binder content of 410?550 kg/㎥. The models are able to identify the influential mix design parameters and their interactions which can be useful to reduce the test protocol needed for proportioning of LWSCCs. Three industrial class ESH?LWSCC mixtures are developed using statistical models and their performance is validated through test results with good agreement. The developed ESH?LWSCC mixtures are able to satisfy the European EFNARC criteria for self-consolidating concrete.

Effects of Milled Cut Steel Fibers on the Properties of Concrete

Okan Karahan,Erdogan Ozbay,Cengiz D. Atis,Mohamed Lachemi,Khandaker M. A. Hossain 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.7

This study presents the mechanical and transport properties of milled cut steel fiber reinforced concretes (MCSFRC). Properties studied include unit weight, workability, compressive strength, flexural strength, splitting tensile strength, bond strength, water absorption, water porosity, water sorptivity, rapid chloride ion permeability and drying shrinkage of concrete. Mixtures with a waterbinder ratio of 0.40, total binder content of 500 kg/m3 and milled cut steel fiber content of 0, 0.25, 0.50 and 1.00% by concrete volume were produced and tested. The laboratory results showed a slight reduction in compressive strength with the use of milled cut steel fiber. On the other hand milled cut steel fibers significantly improved the tensile strength and decreased the drying shrinkage. Although no significant increase was observed in the absorption, porosity and sorptivity, chloride ion permeability increased drastically with the increase of milled cut steel fiber content.