Dissertations/Theses - Department of Civil Engineering

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1D nonlinear site response analysis of DMDP area, Bangladesh
(Department of Civil Engineering, 2023-06-17) Abul, Khair; Ansary, Dr. Mehedi Ahmed
The purpose of this research is to perform 1D site response analysis using Standard Penetration Test (SPT) and shear-wave velocity of the Dhaka Metropolitan Development Plan area (DMDP), Bangladesh. Additionally, the result obtained from the 1D analysis has been validated through microtremor analysis result. For this purpose, fifty locations were selected in the study area and the selected locations maintain approximately a uniform distribution within the whole DMDP area. Most of the locations are located on reclaimed areas with sand filling up to a depth of 10 to 15m or more. The depth of boreholes varies between 30 to 85.5m depending on the SPT-N value of 65 or more in the last consecutive 3 layers. After completing SPT a 100mm PVC pipe was installed in the same hole to obtain shear-wave velocity using the seismic downhole technique. The shear-wave velocity beyond the borehole depth has been taken from CDMP 2009 data applying the closest pair of points between the test borehole to the CDMP test point. For estimating site responses for those selected fifty locations, a computer program DEEPSOIL was used. Soil layer depth, unit weight, shear wave velocity (Vs) and soil shear strength as inputs, soil site responses were estimated by equivalent linear and non-linear analysis. Total ten input motions were used in these analyses, which were scaled to 0.13g value for bedrock in the Dhaka region. Besides, a microtremor recording has been carried out at every location of those fifty borehole locations. Microtremor data has been collected according to the guideline of SESAME. Finally, a Horizontal to Vertical spectral Ratio (HVR) curve has been obtained of the site to compare with the 1D response analysis. From the detailed site-specific analysis, it was observed that the amplification factor of the study area ranges 3.1 to 5.5 for nonlinear analysis and 3.8 to 8.5 for equivalent linear analysis and the amplification factor obtained from microtremor analysis ranges 1.3 to 6.6. In areas of thick and soft Holocene deposit the amplification is more than the areas where shallow valleys of Pleistocene deposits with artificially filled sand or any clay in top layer. The peak spectral acceleration (PSA) for 50 sites varies between 0.41g to 0.80g in the case of nonlinear analysis whereas the range of PSA is 0.50g to 1.12g for equivalent linear analysis. It also observed that, the peak ground acceleration (PGA) of the study points ranges 0.17g to 0.26g for non-linear analysis and 0.22g to 0.43g for equivalent linear analysis.
A statistical pattern recognition based damage identification of a bridge using time series modeling of vehicle induced dynamic responses
(Department of Civil Engineering(CE), BUET, 2024-02-25) Hossain Nadim, Md.; Shohel Rana, Dr.
The deterioration of bridge conditions over time is attributed to various degradation processes, including creep, corrosion, cyclic loading, and others. As bridges age and undergo deterioration, monitoring their structural health has emerged as a significant concern in recent decades. The primary focus in this regard is the detection of damage.This research proposes an output only data driven technique for damage identification which will not require any physical model of the structure nor any known input excitation. This study introduces a damage detection technique that relies on evaluating the dynamic acceleration response of a bridge when subjected to the passage of a vehicle.Finite Element Method (FEM) is used to simulate the structure of the bridge and a dynamic half a car model is employed to depict the vehicle and its suspension system.The Vehicle-Bridge Interaction (VBI) is formulated incorporatingthe dynamic models for bridge structure subsystem and vehicle subsystem, interaction constraints and road roughness modelling. Newmark’s-β method is utilized for solving the coupled VBI problem to extract the vehicle-induced acceleration responses.Through the reduction of structural stiffness of a specific element within the bridge, an artificially induced damage is incorporated. The dynamic acceleration responses are fitted to linear and stationary time series models. An automatic model selection method and model order selection method are demonstrated in this study. The appropriate model class and model orders are selected according to the response from undamaged structure using the proposed technique. The model residuals are used as the damage sensitive features. A damage assessing index is presented utilizing a statistical distance metric named Kullback-LeiblerDivergence (KLD). The proposed damage index is used to identify different simulated damage scenarios. An experimental study is also performed on a laboratory scale bridge specimenwitha vehicle model passing over the bridge. The results of the study demonstrate the method’s effectivenessin identifying damage atvarious position of the bridge spanfor different severity levels.
A study of drainiage systems for selected cities in Bangladesh
(Department of Civil Engineering, 1998-09) Ubaidur Rahman Quabili, Md.; Habibur Rahman, Dr. Md.
The planning and design of urban drainage system can not be successfully conducted without a variety of supporting data relating to the locality of the actual project as well as to the entire region that will be benefited or affected by the project. The drainage design should provide a balanced combination of natural and man-made drainage elements which offer an adequate flood protection for urban developments and minimize drainage impact on receiving waters. It has been noted that although there has been substantial progress made in development of design tools, the progress in the availability and acquisition of supporting data is lacking. Therefore, this study is concentrated on the acquisition of supporting data such as climatic condition, urbanization pattern, topography of land, surface water availability and socio-economic condition of Bangladesh. After conducting the survey on the existing drainage system in the selected towns, the problems were identified and summarized. Some probable solutions are also proposed to overcome the problems and difficulties. These will help in designing and taking decision in the field, in this regard. A new concept on the shape of drain has been suggested to construct the drains in flat areas which allows to flow sullage more efficiently. This shape provides better self cleansing velocity to the sullage flow. Run-off coefficient for some selected areas in Bangladesh have been determined, this may help in assuming run-off co-efficient for any area. Attempt is being made to identify the cost effective drain, over ditch or pond to minimize construction difficulties.
A STUDY ON SOIL AND WATER CONTAMINATION OF AMIN BAZAR SOLID WASTE DISPOSAL SITE
(Department of Civil Engineering (CE), BUET, 2024-03-23) Saifuddin Manik, Md.; Dr. Rowshan, Mamtaz
In developing countries like Bangladesh, waste management faces significant challenges, including low collection coverage, inadequate transport services, and insufficient treatment facilities, leading to widespread pollution. Dhaka, the capital of Bangladesh, generates a substantial amount of solid waste daily, approximately 6756 tons, managed by two disposal sites. The Amin Bazar site, 17 km west of DNCC headquarters (Gulshan-2), handles solid waste for Dhaka North City Corporation. Despite concerns about soil and water contamination due to poorly managed landfills, studies investigating such contamination, especially at Amin Bazar, still need to be included. This study aims to fill this gap by examining potential soil and water contamination near the disposal site. A comprehensive study assessed soil and water contamination near the Amin Bazar disposal site, collecting samples from various sources during dry and monsoon seasons. The analysis included soil contaminants, treated leachate performance evaluation, and in-depth investigations through boreholes and monitoring wells. The Leachate Pollution Index (LPI) was calculated to understand the combined health impact, contributing to a comprehensive understanding of the landfill's environmental impact. Analysis of inland surface water on the south side reveals heightened levels of contaminants, with an LPI of 12.44, attributed to open dumping practices. During both dry and monsoon seasons, inland surface water bodies and nearby river water exhibit critically low dissolved oxygen levels, posing risks to aquatic life. Soil data within 450 meters of the disposal site shows significantly higher organic content, especially within the south side of the disposal site, and elevated heavy metal concentrations, surpassing USEPA guidelines. Among all heavy metals, the higher value of Lead (Pb) is found in surface water, groundwater, and soil samples. Monitoring well analysis results confirm groundwater contamination, and borehole data highlights increased heavy metal levels. The treated leachate satisfies Solid Waste Management (SWM) Rule 2021 standards, and during the monsoon season, lower concentrations were observed, attributed to rainwater dilution and mixing with river water. Treated leachate meets standards, with lower concentrations during the monsoon attributed to dilution. However, LPI values indicate a significant environmental impact, especially on the south side, suggesting potential contamination. Despite groundwater parameters complying with standard limits except Pb, elevated Health Risk Index (HRI) values for arsenic in groundwater samples indicate a potential health risk, emphasizing urgent waste management and environmental preservation interventions.
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Accident black spots identification for safety improvement on a section of Dhaka-Chittagong highway
(Department of Civil Engineering (CE), 2003-01) Abdus Samad, Mohammed; Jobair Bin Alam, Dr. Md.
This thesis presents the findings of the study concerned with accident blackspot identification for improvement of safety on the Jatrabari-Kanchpur Bridge section of Dhaka-Chitlagong highway. The selected section of Dhaka-Chitlagong highway is composed of three intersections and nine links. The study examines the trends and characteristics of the accident problem for identifying the dominant accident types which need to be addressed in future initiatives. A total of 356 Accidents oecurred on this highway section in a time period of 4 years from January 1998 to December 200 I. Out of total 356 reported accidents, 34% occurred at or near intersections and remaining 66% occurred on links of selected section of highway. The accidents occurring in the study area are classified as 49% fatal, 39% injury, 12% property damaged. The involvement of pedestrian in the accidents occurring in the study area is significant comprising 54.21 percent amongst the various classes of road users. Rear end accident is also identified as a dominant problem. In the study area, occurrence of accident is higher during day time than night time and the frequency of the occurrence of accident is the highest between 8 AM to 12 at Noon. Buses are involved in 40 percent of total accidents, followed by tmcks and mini buses with 30 and 9 percent, respectively. Detailed investigation of black spots are made using available accident data, field investigations and video data. For the purpose of the analysis, inforrnation availablc Ii'om FIR. Accident Report Forms and Register books is coded into a number of variables to correlate occurrence of accident with traffic system variables. Eight relevant. variables are extracted and used in subsequent analysis. As "- blackspots are related with roadway environment related variables, on the basis of the variables mentioned above the involvement of road environment is analyzed by using 'Principal Component Analysis (peA)' method. The aggregate factor weight of roadway environment in the total number of accidents occurring at a location is graphed onto the roadway section. The locations where the aggregate weight of roadway environment factor is more than the average is identified as black spot. From the analysis, five locations are identified as accident black spots. The locations arc Jatrabari intersection, Dania College. ICMII at Matuil, Saddam market and Kanchpur Bridge (western part). The highest number of accident occurred at Jatrabari intersection which is followed by Kanehpur Bridge, ICMII at Maluil, Dania College and Saddam marke!. In order to reduce the risk of accidents at the hlack spots, the study recommends construction of underpasses at the level of approaching road, grade separation for non-motorized traffic, construction of footpath for pedestrian movement, grade separated bus stops and channelization of traffic at intersections in the study area.
Accumulation of arsenic in agricultural soil and selected crops
(Department of Civil Engineering, 2006-02) Ganesh Chandra Saha; Ali, Dr. M. Ashraf
Groundwater from arsenic contaminated shallow aquifers is widely used for irrigation in Bangladesh. In 2004, groundwater irrigation through shallow tubewells covered about 60% of the total irrigated area. Considering I m of irrigation for bora rice, the amount of As cycled each year through irrigation water is estimated to be about 1000 metric tons. In this study, twelve bora (dry season paddy) fields in four arsenic affected and two unaffected areas have been monitored during 2003 for assessing As status in irrigation water, soil and paddy plant. Irrigation with arsenic-bearing groundwater is definitely causing an increase of arsenic content of paddy field soils. Arsenic contents of paddy field soils, irrigated with high arsenic-bearing irrigation water, have been found to vary significantly over a paddy field, with depth and with time. In general, arsenic concentrations in the top soil layers (up to ISOmm) increased significantly at the end of the irrigation season. In general, higher increase in soil arsenic content was observed for sampling points located close to the entry points of water into different sub-areas of the paddy fields. For example, for a paddy field in Munshiganj, average arsenic concentration in the top 0-75 mm of soil increased from about 8.4 mg/kg in March 2003 to 14.8 mglkg right at the end of the irrigation season in May 2003. During the same period, it increased from about 4.7 to 8.0 mg/kg for a field in Comilla, 6.7 to 10.3 mg/kg in Brahmanbaria, and 5.7 to 7.2 mg/kg in Faridpur. Arsenic contents in the top soil layers at the end of the irrigation season have been found to be strongly correlated to the arsenic content of irrigation water. In the unaffected areas of Bogra and Naogaon, where arsenic concentration in the irrigation water was below I I-lg/I,arsenic levels in irrigated soils have been found to be comparatively low (varying from about 1.5 to 3.1 mg/kg) and did not vary significantly either with depth or sampling time. Arsenic concentrations in the paddy field soils have been found to be quite dynamic. After the rainy season (which immediately follow the bora season), arsenic concentration in the top soil layer (0-150 mm) of paddy fields in the arsenic affected areas decreased significantly and came down to levels comparable to those found at the beginning of the bora season. Since the majority of the As in the top 0-75 mm segment of soil layer is rassociated with iron oxyhydroxides, this is most likely due to partitioning of As from soil into the aqueous phase during inundation by reductive dissolution of iron oxyhydroxides and desorption. Thus, long-term As accumulation in agricultural soil appears to be counteracted by bio geochemical pathways leading to arsenic removal from soil. In both arsenic affected and unaffected study areas, the roots of paddy plants accumulated the maximum level of arsenic, followed by leaf and stem. Paddy grain and husk accumulated the least amount of arsenic. The arsenic content in top soil was found to be strongly correlated with arsenic concentration in root, moderately correlated with arsenic concentration in leaf and stem, and poorly correlated with husk and grain. Arsenic concentrations in grain and husk of samples from affected and unaffected areas did not differ significantly, although arsenic concentrations in both grain and husk have been found to be statistically higher in samples from the affected areas. Irrigation with arsenic bearing groundwater appears to be causing a minor increase in human exposure to arsenic. Considering average arsenic contents of rice grains from affected and unaffected areas and average rice consumption of 450 gm/person/day, daily As intake in affected areas is estimated to be slightly higher (233 I-lg)compared to that in unaffected areas (176 I-lg).Since As toxicity is strongly dependent on its chemical form and reported values for
Accumulation of arsenic in rice plant from arsenic contaminated irrigation water and its effect on nutrient content
(Department of Civil Engineering (CE), 2005-04) Zahangir Alam, Md.; Mujibur Rahman, Dr. Md.
To achieve self-sufficiency in food grain production, the HYV rice varieties are widely produced in Bangladesh, particularly in the dry season, and this requires a large volume of groundwater for irrigation. Groundwater of many areas of our country is severely contaminated with arsenic. So, there is a possibility of arsenic .accumulation in rice plants from arsenic contaminated irrigation water. Generally, consumption of protein is not adequate for our people due to insufficient production of major protein sources like fish, meat, milk, eggs, etc. and also due to economic constraints. Any adverse effect on protein content in rice due to use of arsenic contaminated irrigation water may, therefore, aggravate the malnutrition problem of our people. Similarly any adverse effect on amylose content, which is about one forth portion of rice grain by weight, would cause deficiencies in calorie supply. This study aims at assessing the accumulation of arsenic in rice plants and its possible effect on nutrient (protein and amylose) content of rice grains. Arsenic contents in different parts of rice plants were tested using hydride generation Atomic Absorption Spectrophotometry (Shimadzu, AA6800). For assessing nutrient contents (protein and amylose), rice samples were tested at the Laboratory of Grain Quality and Nutrition Division of Bangladesh Rice Research Institute (BRRI), Gazipur. Results from this study show that arsenic accumulates in different parts of rice plants, though the accumulation varies from variety to variety. Highest arsenic concentration was found in root hair with a mean 16.7 mglkg and maximum 38.5 mglkg, and least in grain with a mean 0.32 mglkg and maximum 1.1 mglkg. Mean arsenic concentrations in husk, leaf and stem were found to be 1.06 mglkg, 3.98 mglkg and 3.32 mglkg, respectively. Presence of arsenic in straw (leaf and stem) at moderately high concentration poses risks for cattle and human health. Arsenic concentration in top soil samples of study fields were found to be up to 12 mg/kg. From linear regression analysis only a moderate correlation (R2 = 0.45) was found between arsenic in water and arsenic in root hair. Measured nutrient contents were compared with the standard values. Test results for protein content show rice grain contain less protein than standard values. Similarly, for most samples, amylose content was found to be less than standard value. More studies are needed to better understand these phenomena.
Adsorption-desorption characteristics of arsenic on agricultural soil
(Department of Civil Engineering (CE), BUET, 2006-12-27) Sultana Rebeka Akhter; Ali, Dr. M. Ashraf
Accumulation of As on paddy field soils as a result of irrigation with As contaminated groundwater and its introduction into the food chain are major concerns. Adsorption is the principal mechanism by which As is accumulated on soils. [n this study, adsorption characteristics of arsenic on paddy field soils from three As affected areas (Munshiganj, Faridpur and Brahmanbaria) and one unaffected area (Naogaon) were assessed in laboratory batch experiments. As adsorption on paddy field soils has been found to increase with increasing oxalateextractable iron content (as well as total iron content) of soil; thus amorphous iron oxyhydroxides appear to be the principal adsorbent of As. [ron content of paddy field soil, in turn, has been found to increase with increasing dissolved Fe content in irrigation water. Thus, As adsorption onto paddy field soil depends not only on the characteristics of soil, but also on the characteristics of (e.g., iron content) of irrigation water. For some paddy field soils, very high adsorption densities, approaching 200 mg/kg, have been recorded under thc laboratory experimental conditions. [f As is present in such high concentrations in paddy field soils throughout the year, it could have significant adverse effects on growth and yield of crops. On thc other hand, As adsorption by soil may play an important role in reducing As availability to plant and its introduction into the food chain. The high adsorption capacity of soils could reduce the bioavailability of arsenic to plant and also retard its transport through the subsurface. Arsenate adsorbs much more strongly onto soil than arsenite. For same initial concentration of arsenic, arsenate adsorption is almost 3 times greater than arsenite adsorption. Phosphate was found to adsorb quite strongly on paddy field soils and, like As, its adsorption appear to increase with increasing iron content of soil. Arsenite adsorption was found to decrease with increasing phosphate concentrations due to its higher affinity for sorption sites than As; but since the batch experiments were carried out with low sorbate to sorbent ratios, the effects were apparent only when concentrations of both As and phosphate were high. Effect of pH on adsorption of both arsenate and arsenite appear to follow the same trend; adsorption as a function of pH followed a concave downward profile with the maximum adsorption occurring at pH between 4 & 6. Some recent studies suggest that significant amount of As (that is accumulated in the paddy tield soils during the irrigation season) is mobilized/released from paddy field soil in the wet scason (that immediately follow the irrigation season) during inundation with flood/rain water. Desorption from soil and reductive dissolution of iron oxyhydroxides, the principal adsorbent is the soil matrix, are thought to be responsible for the phenomenon. Results obtained from this study confirm that significant amount of As could be mobilized from paddy field soils by desorption, especially over longer time periods, and through reductive dissolution. Desorption of As from paddy field soils have been found to be a strong function of time. Under the experimental conditions, about [0% of As initially present in soil was desorbed within a period of about one month. Since paddy fields are often inundated under a significant depth of water for about three months during the wet season, As release/mobilization from soil by desorption could be significant. Significant As release from As-rich paddy field soils was recorded under reducing condition created by addition of a carbon source (glucose) and nutrients. Such mobilization of As through reductive dissolution of iron oxyhydroxides has also been found to be a strong function of time. Both desorption and reductive dissolution of iron oxyhydroxides appears to be important processes that govern the fate of As in irrigated paddy fields. Results from this study suggest that these natural processes playa major role in preventing As concentration in soil to reach toxic levels.
Air quality assessment and the health effects of air pollution in Dhaka city through impact-pathway model
(Department of Civil Engineering, 2010-09) Mokhlesur Rahman, Sheikh; Ali, Dr. M. Ashraf
Dhaka, the capital city of Bangladesh, with a population density of around 20,000 per square kilometer is at the risk of experiencing significant health impacts from poor air quality, especially during the dry season. The economic cost associated with urban air pollution is estimated to be around 1.1% of national GDP. Recently, the Government introduced a number of initiatives such as banning of twostroke engine vehicles, promoting the use of alternative fuels like CNG, banning of old vehicles from plying on streets, in order to curb the growing air pollution problem. Though some improvements have been observed, such policy decisions are taken on adhoc basis and there is a lack of benefit modeling to support these decisions due to limited monitoring and limited analysis of the options. Currently, the institutions lack an integrated policy analysis tool to help the decision makers evaluate alternate air pollution management strategies and analyze costs and benefits. This research aims to fill this gap, by developing a policy analysis tool for Dhaka to better understand the impact of various abatement measures and potential for environmental benefits. The tool is designed to follow the impact pathway approach linking the changes in emissions with changes in ambient concentration, especially particulate matter (PM) and related health impacts - mortality effects and the associated monetized benefits. A grid based source-receptor matrix over Dhaka has been developed using an atmospheric dispersion model, considering temporal variations in emissions and weather parameters round the year. The contributions from major sources (vehicles, and brick kilns) have been considered in determining the ambient PM concentrations; both spatial and temporal variations of PM have been estimated. In the Dhaka city the PM10 concentrations in dry season has been estimated to be less than 50 μg/m3 to about 150 μg/m3. The range of PM2.5 concentration in the city has been estimated in between 25 μg/m3 and about 65 μg/m3. Near the National Parliament Building, where CAMS (air quality monitoring station) is located, brick kiln has been found to be the major source of particulate pollution with 43% contribution to PM10 concentration and 21% contribution to PM2.5 concentration. Traffic pollution contributes 10% to PM10 concentration and 13% to PM2.5 concentration at that specific site. However, the sourcereceptor matrix could be easily utilized to obtain ambient concentrations as new sources are added/removed from the domain. Particulate related health impacts have been evaluated utilizing established concentration-response functions for mortality due to pollution exposure. Moreover, the monetary value of these health impacts due to traffic and brick kiln emissions are estimated. Finally, the study presents case studies under “what-if” scenarios for multiple policy alternatives using the developed policy assessment tool for Dhaka. It has been found that significant health and economic benefits could be achieved with policy interventions aimed at improving air quality.
Alternative approach of estimating vehicle trajectory for heterogeneous traffic condition considering dynamic capacity
(Department of Civil Engineering (CE), 2016-04) Shantana Sheikh; Hadiuzzaman, Dr. Md.
Application of fixed sensor and probe vehicle to collect traffic data has become popular over the years. Probe data provide spatial traffic information and direct measurements of travel time. However, their frequency is restricted with GPS reception errors in the probe data. On the other hand, video sensors record traffic data continuously at fixed locations only. So, the limitation of probe sensor in temporal domain and fixed senor in spatial domain tends to combine probe sensor with fixed sensor. Considering different characteristics of these traffic data from various sources, recently combination techniques are applied to reconstruct vehicle trajectories. This technique has become an advanced research area for intelligent transportation systems (ITS). Making an allowance for all-around limitations and advantages of different data sources, the combination technique is being developed to generate more reliable and continuous traffic information. Still, almost all the literature explore and improve over conventional lane based traffic condition. This may be due to the difficulty and high cost involved in data extraction, and complexities associated with non-lane based heterogeneous traffic movement. Addressing such shortage, this study deals with the development of a trajectory estimation method to reconstruct vehicle trajectories combining video sensor and probe data on urban arterial and freeway for non-lane based heterogeneous traffic condition. The combination technique involves extra equipment installation difficulties when the road segment becomes non-homogeneous due to traffic operations or lane configurations. Particularly, in developing countries, chaotic traffic pattern and absence of fixed sensor in the roadway create the trajectory reconstruction technique even more challenging. Video sensor (as well as other fixed sensors) based trajectory reconstruction technique requires sensors for each non-homogenous road segment and needs separate fundamental diagram (FD) to estimate required traffic parameters. This difficulty can be overcome through probe sensors alone. Thus, this research proposes an alternative approach of estimating traffic parameters only from probe data considering variable road capacity. Those parameters are used as input to reconstruct vehicle trajectories through lopsided network. The alternative method improves the Root mean square error (RMSE) of estimated travel time around 38.0% compared to that of original method where traffic parameters are obtained from FD, with respect to ground truth travel time. This method is found to be very appropriate, economical and reliable especially where required numbers of fixed sensors are unavailable.
Ambient vibrations of unreinforced masonry buildings in Dhaka city
(Department of Civil Engineering (CE), 2015-06) Romeo Nowreen Khan, Muhammad; Ahsan, Dr. Raquib
The ambient vibration investigations are performed for use in structural health monitoring and in structural control studies within the technical assessment of different kinds of structures. The ambient vibration tests define the linear behavior of structures, since the amplitudes of vibration are small. The actual responsive behaviour of structures under an earthquake is similar to the ambient vibration behaviour. It was shown that the dynamic behaviour of the masonry building, even if not regular and with deformable floors, can be effectively represented. Considering the above fact the main objectives of this research was to identify the pre-dominant or natural periods of the targeted unreinforced masonry (URM) buildings by performing ambient vibration tests, to compare the obtained structural pre-dominant period with the structural period calculated by the formula given in Bangladesh National Building Codes (BNBC) and to develop a relationship of structural period with different structural parameters of the URM buildings. This paper presents evaluation of ambient vibrations and the identification of the pre-dominant frequencies of seventeen low-rise URM buildings by ambient vibration tests. The buildings are of different stories from single storey up to five stories with regular and irregular shape in plans and elevations located in Dhaka, the capital city of Bangladesh. These masonry buildings were built in between 1960 to 1990 without any seismic guidelines. Attempt was made to correlate structural periods with heights and structural periods with total length of walls of structures by curve fittings and regression models. The multivariate linear regression analysis was selected for model development. Total three approaches were followed where structural period was the dependent variable. Approach 1was taken to find out an empirical model with the consideration that the dependent variable i.e. structural period is a cubic function of both the independent variables i.e. height of structures and total length of walls. Again Approach 2 was taken for the same with the consideration that the structural period is a quadratic function of both height of structures and total length of walls. Lastly Approach 3 considered that the structural period is a quadratic function of height of structures and a linear function of total length of walls, separately. Total four methods, namely the enter method, stepwise method, backward method and forward method, for each approach were used one after another as to check which one work better and provide realistic solution. Finally both forward selection and stepwise methods of Approach 1 and Approach 2 provided similar and the best possible statistical result combining height and total length of walls of structures. However analyzing all the findings of the regressions the parabolic curve fitting equation was selected for calculating structural periods of URM buildings. The endeavours of identifying the correlations through regressions were successful. The study suggested an insertion of the finding in the form of a formula in the BNBC in future.
Ammonia removal from tannery wastewater using calcined eggshell
(Department of Civil Engineering, 2022-02-26) Abdul Momen, Md.; Hossain, Dr. Md. Delwar
Ammonia pollution has become a severe problem for aquatic livestock. A high concentration of ammonia content causes life risks for fishes and animals in the water bodies. Ammonia is introduced in wet lands from different anthropogenic activities like leather manufacturing, paper pulp etc. In this study calcined eggshells were used to remove ammonia from tannery wastewater. Raw eggshells contain 97.50 % CaCO3 which is converted into 97.40 % CaO via calcination at 900 °C for 3 hours of heat. Physical, chemical, and morphological properties of raw, calcined, and ammonia loaded treated eggshells are studied. Off-white, odorless raw eggshell regained bright white color and converted to soft powder in calcined phase. Thermal characteristics were studied by Differential Scanning Calorimeter (DSC) and Thermo Gravimetric Analysis (TGA). The STA analysis indicated the phase transformation from raw eggshell (RES) to calcined eggshell (CES) with gradual increases in temperature and beyond 680 °C to 880 °C (̴ 900 °C) temperature CaCO3 turned into CaO. Furrier Transform Infrared Spectroscopy (FTIR) reflected group generated in calcined eggshell (CES) which is occupied after treatment of tannery wastewater. Ammonia loaded eggshell powder showed a sharp, medium N-H bond at wavenumber 2934.79 cm-1. Morphological structure of RES, CES, and loaded eggshell are analyzed by scanning electron microscope (SEM) and X-Ray Fluorescence Spectroscopy (XRF) studied to detect chemical composition among the different three phases of eggshells. 97.40 % CaO reduced to 87.84 % after reduction of different pollution loads from tannery wastewater and XRF result said that 3.54 % SO3 increased in loaded eggshell. Physicochemical parameters of tannery wastewater were studied before and after treatment by CES and compared with the allowable limit. Different three wastewater samples were tested with an adsorbent dose of 4 gm/L. BOD5, COD, TSS were reduced whereas EC, TDS, pH, and turbidity were increased due to the use of calcined eggshells. Initial ammonia content was 242.5 mg/L which was decreased to 57 mg/L at pH 12.47. 99.9 % chromium reduction has been achieved by CES through the adsorption process. Adsorbent dose 4 gm/L and maximum removal efficiency have achieved 76.29% within only 10 minutes of reaction time. Reaction kinetics were calculated using a linear line graph reaction coefficient. Pseudo first order and pseudo-second-order reaction kinetics give heterogeneity and unoccupied sites of CES. Langmuir isotherm declared physical adsorption of ammonia occurred with CES and RL of this isotherm model is greater than 0 and less than 1. Therefore adsorption is favorable on the other hand, n values of Freundlich isotherm model have calculated less than 1 thus poor multilayer adsorption has occurred. The favorable pH for the ammonia removal was 12.47, which was achieved using the aforementioned amount of CES. Therefore, pH is one of the parameters which influence ammonia removal. The performance and potentiality of CES would be an invention for the treatment of ammonia removal and reduced pollution load from the tannery wastewater.
Anaerobic digestion of tannery solid waste by mixing with different substrates
(Department of Civil Engineering, 2012-03) Basak, Shilpy Rani; Hossain, Dr. Md. Delwar
Leather is one of the most prospective industries in Bangladesh .Out of the total 206 tanneries in Bangladesh 192 of them are located in Hazaribagh of Dhaka city. A large amount of solid waste (even in lean season 69.1 ton/day according to 2006 survey of UNIDO) is generated daily by leather manufacturing process in this area and crude disposal of this waste are creating serious hazard to the environment. An attempt has been made to analyze the present status of Hazaribagh in terms of solid waste management. Now it is prerequisite to develop an appropriate waste management system of the tannery waste and for this it is obvious to manage each fraction of the waste in a cost effective and environment friendly way. With rapid depletion of conventional energy sources, the need to find an alternative, preferably renewable, source of energy from waste is becoming increasingly important for the sustainable development. A major portion of the solid wastes from leather industry is fleshing, originates from animal tissue, which contains mainly fat and protein, and residual chemicals such as lime and sulphide used in the unhairing process of beam house operation. Experimental results showed that fleshing contains a significant quantity of volatile solids (including non-biodegradable fraction of volatile matter such as lignin, 82.57%VS) amenable for biodegradation. Further the characterization of fleshing showed that it contains low C/N ratio (2.64) and high pH (10.99), these characteristics were not suitable for using fleshing alone as substrate for anaerobic digestion,for this reason different proportion of cowdung and domestic sewage were used as co-substrate for optimum results. The study was carried out by using different proportions of waste fleshing, cowdung and domestic sewage in four different laboratory scale reactors carrying 6% total solid concentration. In all the reactors fleshing and domestic sewage were mixed in 1:1ratio. Anaerobicdigestion was carried out for 60 days of digestion period at room temperature 30°c ±3 and the pH of the slurry was maintained by the process itself. The inoculums were synthesized by the cowdung and water in the laboratory in the same environmental condition taken for the study and sufficient active biomass was present there.For thatthe start-up of the reactor was achieved easily. The reactors were subjected to anaerobic digestion with an aim of developing an appropriate technology for recovery of bioenergy from the tannery solid waste fleshing. From the study it was observed thatamended fleshing with domestic sewage when mixed with cowdung, the significant increase of gas production was remarkable. The performances of the reactors were analyzed on the basis of volatile solids destruction efficiency, specific gas yield, COD reduction rate and on methane yield. Within four reactors the percentages of volatile solid destruction were between 42% to 52%, specific gas production were 0.401, 0.476, 0.239 and 0.288 l/g respectively according to volatile solids fed and methane yieldwere achieved72%, 73%, 70% and 72% by volume respectively.COD reduction achieved in the test reactors 48.02% 50.67%, 44.80% and 44.61% respectively. Further, the kinetic analysis of the data revealed that first order kinetic model is adequate to describe the co-digestion of animal tissue with cowdung and domestic sewage. On the basis of analysis of the performance of the reactors, it was evident that amended fleshing is highly potential substrate for biogas generation and it was also found that R2 reactor, where on the total solids (6%TS) of the slurry 75% of fleshing with domestic sewage and 25% of cowdung were used, showed the optimum results in terms of VS reduction (52%), specific gas yield (0.476 l/g) and methane yield (73% by volume). For this reason, the standards of the reactor R2 were chosen as optimum condition for gas generation from fleshing. The criteria of the reactor R2 can be used for further study or design purposes. Based on the principles of R2 reactor, the economic feasibility of a fleshing based pilot scale biogas plant was also studied. The economic return was found to be 3.5 years for that type of plant.
Analysis and design of geosynthetics reinforced unpaved roads on clay subgrades
(Department of Civil Engineering, 1994-07) Kabir Uddin Ahmed; Kabir, Dr. Muhammed Humayun
A new non linear approach to analysis and design of unreinforced and reinforced unpaved roads on clay subgrade is developed. These are based on the non-linear stress strain behaviour generally exhibited hy the clay suhgrade soils as well as geosynthetic and natural f1hre reinforcing elements. The newly developed design method is based on closed form solution of the plane strain analysis of the deformation track produced under wheel loading, which consider the compatibility of deformation (rutting) between the constituent materials, clay subgrade and reinforcing element. Appropriate constitutive laws, for montonic and repeated loading conditions, for the subgrade clay and reinforcing elements are developed and used to predict the behaviour under quasi-static and traffic loading conditions. The equivalent material approach is used to simulate the weakening of the system under traffic loading condition. Special test set up are fabricated and installed to estahlish these constitutive relations. The settlement behaviour of clay subgrade is analysed using the fundamental approach suggested by Prakash, Sharan and Saran (1984), using non-linear constitutive relation. The out of the plane load deformation behaviour of reinforcing elements are determined by assuming the deformation track to be of parabolic shape. Design charts are produced to show the applicability of the new methodology for a silty clay subgrade and a woven tape polypropylene geotextile reinforcing element. A comparison of the proposed method with the conventional Giroud and Noiray (1981) method is also produced which show the latter method to yield unsafe results specially under low deformation (rutting) conditions.
Analysis and design of plain and jacketed stone column in clays
(Department of Civil Engineering, 1989-12) Alamgir, Md.; Kabir, Dr. Muhammed Humayun
A novel approach on the analysis and design methods and" newly envisaged jacketed stone columns in clay presented in this thesis. It considers nonlinear for plain media is mechanical behaviour of the constituent materials as well as compatibility of deformation amongst these. To characterise the nonlinear mechanical behaviour of the constituent materials, the hyperbolic model forwarded by Kondner (1963) was used. The cavity expansion theory presented by Ladanyi (1963) is used here to formulate the desired equations for prediction of lateral resistance mobilized in the clay media. A new suction triaxial test was developed to characterise the mechanical behaviour of the aggregates which was proved to be very beneficial especially in case of large size specimens. As a part of these studies a literature review is presented to depict the state of the art as well as to identify the limitations of the existing design methods. To depict the applicability of the proposed analysis and design methods, illustration examples are presented. In the examples, the constituent materials include stone aggregates, a geogrid jacket liner and a soft clay from the south-east region of Bangladesh. A comparative study revealed that the existing methods may lead to unsafe designs. Moreover, the jacketed column was seen to provide a considerably stiffer foundation than its plain counterpart.
Analysis and design of solid waste management system for a residential zone of Dhaka City
(Department of Civil Engineering, 2001-04) Abdus Salam, Md.; Badruzzaman, Dr. A. B. M.
Dhaka, the capital of Bangladesh, with an inhabitant close to 10 million, undergoes regular environmental problems, which are linked to inefficient solid waste management system. The objective of the study was to establish the waste generation rate of Banani, Gulshan Baridhara and lJttara Model Town area to plan an efficient solid waste management system. The other major objectives were analysis and design of solid waste management system with an emphasis on collection and disposal and to determine appropriate methods and means to Improve collection and minimization of cost of collection, transport and disposal of solid waste. Domestic waste generation rate was estimated from Sector-4 of lJttara Model Town through house to house collection by rickshaw van. Population of each household was also determined from questionnaire survey. Commercial waste from five Chinese restaurant of lJttara model town. Hospital wastes from one private medical college hospital and three clinics were also collected. Street sweepings, a significant waste volume were also determined from different locations of lJttara model town. Domestic waste generation rate was found to be 0.60 kg/cap/day, commercial wastes 0.55 kg/cap/day, clinical wastes 1.75 kg/cap/day and street sweeping wastes 0.16 kg/ meter/day. Due to resource constraint in collecting samples from door to door, and due to constraints in analyzing the samples in the laboratory the sample size was kept purposefully small and may not be statistically representative of the study area. Thus, the results obtained on generation rate should be used with caution remembering that these data will be more applicable for the areas and the communities having same characteristics as the study area. Physical composition analysis of domestic waste shows that major portion is food waste (72.5%) and polythene is the second largest fraction(l3.70%). Waste stream analysis shows 58.70% domestic, 7.90%. commercial, 0.32% clinical and 33.08% street waste. Monitoring well were installed at Matuail and Mugdha landfill. Leachate samples were collected and analyzed at Environmental Engineering Laboratory. Analysis of ground water near landfill site (about 300m average) found to be free from contamination. It may be concluded that the presence of natural clay under the fill acts as a sealer and protects the aquifer. From cost analysis it was found that transportation cost is about 49%, primary collection is about 31%, disposal is about 20%. DCC's 75% cleaners are engaged in street sweeping actives who are under utilized and consuming major portion of yearly allocation. Street sweeping waste collection cost is 8 times higher than the primary collection cost. It was also found that house to house domestic waste collection and street sweeping by private contractor were less costly, than the present practices of DCC. Demountable container carrying trucks were underutilized in zones 1,2,3,4 and 5. This indicates that transportation by 5 ton capacity open truck may be cheaper than 3 ton capacity demountable container trucks. Installation of modified transfer station at Gulshan area may be economical compared to the present operation of transporting each truckload of waste to the Matuaillandfill area. It was also found that formal practice of resource recovery and recycling could earn approximately Tk. 71.91/ton of solid waste.
Analysis of aerobic digestion process of domestic solid waste
(Department of Civil Engineering, 2005-03) Abdullah AI-Muyeed; Habibur Rahman, Dr. Md.
Compo sting is generally achieved by converting solid waste into stable humus like materials via biodegradation of putrescible organic .materials generally in presence of oxygen. The microorganisms involved in solid waste composting include facultative and strict aerobic bacteria, fungi and actinomycetes. The end product, the compost, can be used as soil conditioner. It can divert a significant portion of organic waste from municipal collection services and from final disposal site, and therefore, enhances both economic and environmental sustainability of waste management system. In this work, barrel type composting was carried out to identify the proper range of operating conditions for thermophilic composting of domestic solid waste consisting of moisture content, temperature and time. A perforated pipe is inserted in the barrels to make the digestion process aerobic. Then the various environmental parameters of composting are observed during the aerobic digestion processes to assess the parameters. Hence, the effects of operating conditions on thermophilic composting of domestic waste be determined and compared with the information from literature survey. Thereafter, an empirical model of thermophilic composting also be derived by fitting in experimental data. The regression values of different parametric studies are determined using a software SPSS for Windows 10.0.5 and analyzed statistically to fit the empirical model. Furthermore the derived model is confirmed by F-test. The empirical model developed, can be effectively used to predict and assess thc operating conditions for thermophilic composting of domestic waste in a natural environment for designing a composting plant.
Analysis of anchored earth wall supporting soft backfill
(Department of Civil Engineering, 2002-08) Jahangir Alam, Md.; Saiful Alam Siddiquee, Dr. Md.
A parametric study using a finite element method of analysis is undertaken to investigate the behavior of a new type of anchored earth wall system supporting simultaneously constructed roadway. Although the elasto-plastic strain hardening softening constitutive models are more appropriate for soil, but for simplicity elastoperfectly plastic Mohr-Coulomb constitutive model is used in this study. The emphasis of the study is placed on the effect of various components of proposed wall system to the deformation patterns and other associated behavior. The parameters studied are (1) stiffne'ss of reinforcement, (2) elastic modulus of soft backfill, (3) elastic modulus of retained soil, (4) elastic modulus of granular soil in between backfill and retained soil, (5) rigidity of facing (6) anchor size and (7) anchor position. A 4.5 m high vertically faced anchored earth wall supporting a simultaneously constructed roadway is designed as per BS 8006 (1995). Starting from facing to centerline of roadway, the wall system consists of (i) facing wall, (ii) thin vertical layer of uncompacted coarse sand as filter and drainage, (iv) thick vertical layer of moderately compacted soft backfill, (v) thin vertical layer of compacted granular backfill (vi) anchor plates or blocks and (vii) retained soil of roadway. Anchor sizes are designed according to RajagopaJ and Hari (1996) for a surcharge loading of 100 kN/m2 on the roadway. Horizontal spacing of reinforcement is 1.0 m and length of anchor is also taken as 1.0 m so that it become a plane strain anchor of length 1.0 m and height 0.12 m in the finite element model. Large factor of safety for anchors is used for standard wall configuration to minimize the effect of anchor size during study of other parameters. Lightly steel reinforced concrete wall with a small pad below wall is used as continuous rigid facing to reduce lateral deformation of wall and hence vertical deforination of top surface of roadway. It is observed that deformation of wall decreases with increasing stiffness of reinforcement and after certain value of stiffness it has no effect on deformation. On the other hand, anchor force increases with increasing stiffness of reinforcement and after certain value of stiffness it has no effect on anchor force. Deformation decreases with increasing stiffness of backfill and retained soil. Anchor force also decreases with increasing stiffness of backfill but remain constant with variation of stiffness of retained soil. Facing rigidity has significant effect on wall deformations. Deformation decreases' with increasing facing rigidity and after certain value of facing rigidity its effect become negligible. From the study it may be concluded that locally available silty clay soil may be used in the reinforced zone as well as in the retained soil mass of roadway. Moderately compacted fill of which elastic modulus is greater than or equal to 10 MPa is sufficient for reinforced zone, provided that stiffness of reinforcement is greater than 5.0x106 N/m and F.S. for anchor size is greater than or equal to 2.0. Moderately compacted fill of which elastic modulus is greater than or equal to 20 MPa is sufficient for retained soil mass of road embankment. Continuous rigid facing must be used for the proposed wall system. To avoid differential settlement of roadway, reinforced soil and retained soil should have same stiffness and strength properties and in no case should stiffness of retained soil be less than that of reinforced soil. Formula given by Rajagopal and Han (1996) is found to be more acceptable to estimate ultimate pull out capacity of vertical anchor used in anchored earth wall. Greater length of anchorage improves the serviceability of the retained structures in addition to ensuring stability.
Analysis of bridge soil interaction under seismic loading
(Department of Civil Engineering, 2001-09) Mozammel Hoque, Md.; Ansary, Dr. Mehedi Ahmed
Deformation of soil due to seismic load imposed by the structures above can result in the change in stresses and deformation of the structures. Considering the interaction between soil and structure is important especially for the design of large structures with embodiment such as nuclear power plant containment and foundations of bridges. Engineering experience has shown that under dynamic loading and particularly during earthquakes the bridge-soil systems undergo significant alterations. These alternations cannot be taken into account using the classical methods of design. Consequently, to prevent major disasters and material loss it is imperative to perform adequate soil structure interaction analysis. Furthermore, as some interaction phenomena have favorable effect on the structural resistance, their consideration enables design and construction with economy and elegance. Three multiple span simply supported bridges, representative of typical bridges in Bangladesh, has been analyzed. Soil supports are explicitly modeled with equivalent springs. Radiation damping associated with wave propagation between the masses of the superstructure and foundation-soil is one form of energy dissipation due to soil-structure interaction(SSI). In this study, damping due to material nonlinearly in the foundation-soil is explicitly modeled, while the radiation damping is implicitly accounted for through equivalent viscous damping. Beam column elements are used to model the columns and simple connection elements are employed in modeling bearings and soil-structure springs. Extensive parametric studies are also performed to show the influence of soil shear modulus (400 psi, 4000 psi and 40000 psi), backwall condition (intact and broken), bearing performances (intact and failed with two different coefficient of friction equal to 0.2 and 0.6). Results are presented in terms of time histories of shear force at pier columns, top displacement of pier, gap width of abutment, plastic rotation at base of pier column and deck displacements due to variation of bearing performances, SSI models, boundary conditions of the pier column footings and soil conditions. Time history analysis of bridges has considered both the fixity and flexibility of the supports using 5% damping. Push over analysis and nonlinear time history analyses of bridges have also been performed using both 2-D and 3-D computer models by DRAIN-2DX and DRAIN-3DX. Raleigh's damping proportional to both stiffness and mass matrices is used. Under peak ground acceleration (PGA) of 0.18g and O.4g bridges were analyzed under three different earthquake records (Parkfield, EI-Centro and Nahanni).