Table of Contents (Department of Civil Engineering)

Sl # Name of Student Thesis Title
1 Sharmin Reza Chowdhury NUMERICAL MODELLING OF EDGE SUPPORTED SLAB RESPONSE
2 Shamsul Gafur Mahmud OPERATIONAL EFFICIENCY OF CONVENTIONAL IRON REMOVAL PLANT IN MUNICIPAL WATER WORKS OF BANGLADESH
3 Md. Rafiqul Islam DRINKING WATER QUALITY AND SANITATION CONDITION OF FLOOD SHELTERS IN DHAKA CITY
4 Fateh-Ul-Anam Muhammad Shafee Yusuf RAINWATER HARVESTING POTENTIAL IN BANGLADESH
5 Md. Asif Iqbal SOIL-STRUCTURE INTERACTION EFFECTS ON TALL BUILDINGS WITH MAT FOUNDATION
6 Nur Sadeque EFFECT OF INTERFACE ELEMENT TYPE ON SOIL-STRUCTURE INTERACTION
7 Nibedita Chowdhury REMOVAL OF ARSENIC FROM WATER BY FERRIC CHLORIDE
8 Roksana Mannan DEVELOPMENT OF AN INTERACTIVE DATABASE FOR SOIL STRENGTH PARAMETERS OF DHAKA CITY BASED ON ARTIFICIAL NEURAL NETWORKS
9 Md. Shamsul Islam SLOPE STABILITY AND SETTLEMENT ANALYSIS OF DHAKA FLOOD PROTECTION EMANKMENT
10 Md. Abdur Rashid SEISMIC MICROZONATION OF DHAKA CITY BASED ON SITE AMPLIFICATION AND LIQUEFACTION
11 Mohammad Sharfuddin EARTHQUAKE HAZARD ANALYSIS FOR BANGLADESH
12 Gazi Arif Iqbal STUDY OF VEHICLE ARRIVAL PATTERN AND FREE SPEED CHARACTERISTICS ON SELECTED NATIONAL HIGHWAYS
13 Md. Arifur Rahman A STUDY OF THE ELEMENTS OF DRIVER’S OVERTAKING SIGHT DISTANCE ON SELECTED NATIONAL HIGWAYS OF BANGLADESH
14 Md. Ashiqur Rahman CHARACTERISTICS OF MAJOR INDUSTRIAL LIQUID POLLUTANTS IN BANGLADESH
15 Sultana Naznin Afroze REMOVAL OF MICROORGANISM AND SUSPENDED MATERIAL BY COAGULATION AND FILTRATION
16 Sania Huq TREATMENT OF LIQUID WASTE FROM A TEXTILE INDUSTRY WITH WATER HYACINTH
17 Salma shahid REMOVAL OF IRON FROM GROUND WATER BY COAGULATION AND SEDIMENTATION
18 S. M. Zulkernine ENVIRONMENTAL IMPACT ASSESSMENT OF INTRODUCING LIGHT RAIL TRANSIT IN DHAKA CITY
19 Mst. Anjuman Ara CORRELATION OF ARSENIC AND IRON IN GROUNDWATER OF BANGLADESH
20 Misbah Uddin Khan INFLUENCE OF SALINITY ON THE PERFORMANCE OF A SLUDGE BLANKET CLARIFIER
21 Syed Md. Mymur Sultan A RATIONAL DESIGN OF SIMPLY SUPPORTED AND CONTINUOUS DEEP BEAMS
22 A. K. M. Jahangir Alam PUNCHING SHEAR BEHAVIOUR OF REINFORCED CONCRETE SLABS
23 Munaz Ahmed Noor REAPPRAISAL OF CODE PROVISIONS FOR STRUCTURES SUBJECTED TO SEISMIC LOADING
24 Md. Golam Mostafa PUNCHING BEHAVIOUR OF FOOTINGS
25 Bipradas Rajbongshi A STUDY ON CEMENT AND LIME STABILISED CHITTAGONG COASTAL SOILS FOR USE IN ROAD CONSTRUCTION
26 Md. Mokhlesur Rahman EFFECTS OF SAMPLING DISTURBANCE ON MECHANICAL PROPERTIES OF RECONSTITUTED NORMALLY CONSOLIDATED AND OVERCONSOLIDATED DHAKA CLAY
27 Md. Abul Bashar GEOTECHNICAL CHARACTERIZATION OF DHAKA METROPOLITAN AREA
28 Md. Zahid Hossain INFLUENCE OF STRUCTURE PARAMETERS ON PERIOD OF FRAME STRUCTURES FOR EARTHQUAKE RESISTANT DESIGN
29 Hafiz Ahmad COMPARATIVE STUDY OF COPPER CONTAMINATION IN THE WATER AND SEDIMENT COLUMN OF THE RAMNA LAKE AND DHANMONDI LAKE
30 Md. Naziruzzaman PERFORMANCE OF THE EXISTING SEWERAGE SYSTEM OF DHAKA CITY AND PAGLA SEWAGE TREATMENT PLANT
31 Khandaker Nurul Ashfaque ANALYSIS OF HEAVY METALS IN BED SEDIMENTS OF DHANMONDI LAKE

  

Table of Details

 

Thesis Title

NUMERICAL MODELLING OF EDGE SUPPORTED SLAB RESPONSE

 

Name of the Student

Sharmin Reza Chowdhury

 

Supervisor

Department

Dr. Bashir Ahmed

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     March, 2000

Abstract

Any satisfactory design requires the magnitude of deflection of structural components of roof system at the service load to be within acceptable limit. Excessive deflections of reinforced concrete roof structures can cause severe serviceability problems. Although deflection is an important parameter in the design of structure, enough emphasis is not usually given to the calculation of slab deflection. None of the several methods presently available for the calculation of deflection of slabs provides the designer any unified approach to readily estimate the slab deflection for any span ratio and support condition. This study briefly reviews the methods available in literature for calculation of slab deflection and attempts to develop a method to readily calculate the deflection and moments of different types of slabs with various edge conditions.

With the aforesaid objective in mind, a software analysis technique (Using a general purpose Fintie Element software , ANSYS) has been used to study the behaviour of different types of edge supported slabs. The results obtained from the Finite Element (FE) models have been compared with those of the ACI moment coefficient method in order to check the reliability of the method. The FE model has been used in the parametric studies of deflection of slab with various edge conditions and span-ratios. The results of parametric studies have been presented in tabular form that forms the basis of an unified method for calculating the slab deflection.

Moreover, the present study provides a method to compute the moment and deflection of slabs with opening. Results obtained from the FE model have been used to develop chart that relate the strip moments and deflection of such slabs with solid slabs. Using these charts it becomes possible to calculate the moments and the deflection of such slabs by simply multiplying the moments and deflections of the appropriate solid slab with a correction factor.

Finally, octagonal slabs with a few selected supporting states have been analysed. An attempt is made to identify the geometric dimensions of the slab when it can be treated as a rectangular slab for design purpose. Results are presented in tabular form so that deflection and moments of any octagonal slab with the selected support conditions can be computed.

 

Thesis Title

OPERATIONAL EFFICIENCY OF CONVENTIONAL IRON REMOVAL PLANT IN MUNICIPAL WATER WORKS OF BANGLADESH

 

Name of the Student

Shamsul Gafur Mahmud

 

Supervisor

Department

Dr. Farooque Ahmed

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     1999

Abstract

In Bangladesh about ninety percent of municipal water works are using ground water as a source of drinking water. The reason is this water requires no treatment for bacterial contamination and can be supplied directly. But ground water contains minerals like iron, manganese and arsenic etc. of which iron is most commonly present in ground water of this country.

The presence of iron in ground is generatingvarious complications in municipal water supply system. This complication is not limited to technical aspect but also to the management of municipal water works. The horizon of this complications due to this iron is increasing as the number of thana towns are upgraded to municipalities.

In the past, inadequate measures have been taken to minimize the iron problem through installation of limited number of iron removal plants. Due to resource constraints installation of IRPs in large number could not be made possible. But with the increasing number of municipalities the demand for removal of iron from water is growing. During eightees, the Netherlands government came forward to minimize the problem and installed a number of IRPs. But several operational difficulties showed up within short period after commissioning. In course of time the plant performances are reported to decline and their O & M cost stands so high that it becomes very difficult for the municipal authority to meet these cost out of their revenue income.

In this study the declining performances of the IRPs were investigated. The study also examined the effectiveness of various steps of the treatment process and their findings were analyzed along with observational, experimental and theoretical findings. During the study it was found that these IRPs were not designed on the basis of any pilot plant performance or on the basis of any laboratory model test.

The study also reveals that plant performances are declining due to some design faults. Design of Wash trough, filter underdrain and determination of backwash rate in accordance to grain size are worthwhile to mention.

Poor backwash creates a couple of problems: the impurities are not completely removed at one hand and on the other hand premature filter breakthrough occurs which means water quality deteriorates much before filter head loss reached to terminal head. It is found that no plants could meet neither the designed water quality nor WHO guideline value for drinking water.

In this study, a laboratory model test was performed in order to determine the unit processes of treatment that would require for the study area on the basis of the investigation. A unit process of treatment is selected and design outline is given on the basis of the model test.

Some operational procedures are suggested, as observed during the study. If these were implemented, plant performances would improve by 30 to 50% with respect to wash water requirement. Moreover some modifications are also suggested to improve the performances of the existing plants which can be made without disturbing whole process. These will reduce the operational cost of the plants.

For IRPs to be constructed in future it is recommended to carryout detailed water quality investigation and pilot plant/laboratory model study before construction of treatment plant in large a scale. It is also recommended to strengthen close monitoring of plant performance with special focus on day to day O & M.

 

Thesis Title

DRINKING WATER QUALITY AND SANITATION CONDITION OF FLOOD SHELTERS IN DHAKA CITY

 

Name of the Student

Md. Rafiqul Islam

 

Supervisor

Department

Dr. Md. Mafizur Rahman

Asst. Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     September, 1999

Abstract

Dhaka water supply and sewerage authority (DWASA) in responsible for supplying potable water, Dhaka City Corporation (DCC) is also responsible to make the city clean and to ensure safe environment for the city dwellers. For different managerial problems they could not serve these communal facilities. That is why city dwellers have to bear enormous sufferings regarding quantity and quality of potable water and solid waste disposal system. During natural disaster these problems become more acute. Safe and pure water become precious thing and the access regarding solid waste disposal becomes blocked. Hence it necessitates the study regarding the identification and to make a possible solution of the problem during disaster.

Entire Dhaka City runs and is expanding in the north-south direction. The western part of it is protected as the Dhaka embankment runs along the western periphery. During 1998 flood western part was affected much less than the eastern part. The study was conducted at the time when the entire eastern part was submerged by a devastating flood in 1998. Water supply in the study area has resumed. About 66% of drinking water supply lines in the flood shelters were under water. Sufferings regarding the potable water and solid waste were acute. An extensive survey for the water quality and solid waste management is done in the eastern part.

For this purpose extensive field investigations and a questionnaire survey among the affected people have been made. A laboratory test program was undertaken to observe the water quality of flood shelters. The important parameters those have been taken under consideration are pH, color, turbidity, total coliform and fecal coliform.

It was found that overall water quality of the flood shelters exceeds the acceptable limit. Positive consciousness was not observed among 93% of them regarding purification of the water. About 7% people got access to the solid waste disposal system.

 

 

Thesis Title

RAINWATER HARVESTING POTENTIAL IN BANGLADESH

 

Name of the Student

Fateh-Ul-Anam Muhammad Shafee Yusuf

 

Supervisor

Department

Dr. Md. Mafizur Rahman

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     August, 1999

Abstract

In Bangladesh, surface water was the principal source for drinking water ever upto recent past. However, during the recent decades, due to the intensive development programs, the ground water is utilized for drinking purpose in most rural areas. Unfortunately, recent investigations have demonstrated almost countrywide occurrence of high arsenic levels in the tubewell water. Today, Bangladesh seems to be one of the most arsenic affected countries in the world. Bangladesh is a tropical country and receives heavy rainfall during the rainy season. In the present context, rainwater harvesting is being seriously considered as an alternative option for water supply in Bangladesh.

The objective of this research is to study the potential of the rainwater harvesting system in Bangladesh. Ninety seven percent of rural population has access to tubewell water and ground water is still good for all type of uses except drinking. Therefore, the main emphasis is given on the rainwater harvesting as a source of drinking water. The research includes a literature review on rainwater harvesting systems, costs and water quality.

In performing the study, frequency analysis is undertaken on annual rainfall data from 25 stations of Bangladesh Meteorological Department (BMD). The most appropriate probability distribution for each location is determined and used to estimate the reliability of the system of that location. Based on this, design curves are developed to estimate the reliability of the system for any consumption rate at different areas in Bangladesh.

Mass curve analysis is used to determine required storage volumes for every location. Based on statistical analysis of required storage volumes, design curves are developed for estimation of storage tank volumes covering the need for dringing water of different household sizes. These curves can be applied at field level by non professionals.

 

Thesis Title

SOIL-STRUCTURE INTERACTION EFFECTS ON TALL BUILDINGS WITH MAT FOUNDATION

 

Name of the Student

Md. Asif Iqbal

 

Supervisor

Department

Dr. T. M. Al-Hussaini

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     July, 1999

Abstract

Finite element analysis is performed to study soil-structure interaction (SSI) effects on static and seismic response of tall buildings on mat foundations. Simplified numerical models consisting of beam-column elements and lumped masses are used to model building superstructure including mat. For the static analysis, the soil is represented by equivalent springs lumped at the foundation nodes. Results from the static analysis show that the mat can be modeled realistically with beam-column elements to represent the thick slab. It is also found that the superstructure rigidity has some effects on the overall settlements and bending moments in the mat.

For seismic analysis, the soil is modeled by frequency independent springs with viscous damping. Two and three-dimensional models for different building layouts are used. Building height is varied from six to ten stories. The influence of soil flexibility on the response of the mat and the superstructure is studied. Parametric studies are performed to evaluate the effects of different parameters on the behaviour of the building. It is observed that soil-structure interaction, in general, results in reduced base shear under seismic loading. SSI effects not only depend on building configuration, but also are very much influenced by ground motion characteristics. SSI effects are also found to be beneficial for building with mass eccentricity where torsional response is important.

 

Thesis Title

EFFECT OF INTERFACE ELEMENT TYPE ON SOIL-STRUCTURE INTERACTION

 

Name of the Student

Nur Sadeque

 

Supervisor

Department

Dr. Md. Saiful Alam Siddiquee

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     Feb. 1999

Abstract

A comprehensive literature survey and review of all interface elements so far developed and implemented within their limited scope of applications have been carried out in this study. From the literature survey, three major types of interface elements such as, Goodman (1968) Type, Katona (1983) Type and Desai (1984) Type have been selected for further study depending on their successful application to physical problems. These three most important interface elements are judged in an existing nonlinear incremental-itrative generalized elsto-plastic Finite Element Method (FEM) program.

The parameters controlling the main features of each interface elements have been identified. These parameters are examined critically in a typical problem setting of direct-shear box simulation. In order to investigate the evolution of different internal variables like deformation, strain or stresses, various types of figures have been drawn. Each case of analysis resulted in outputs of: (a) deformed mesh; (b) force-deformation and stress-strain relationship inside the interface; (c) shear strain contours; and (d) displacement fields. As most of the figures were drawn at different load steps in order to trace the progress of the variables, it was rather easy to identify the trouble spots for a particular type of interface.

The contrast between an analysis in direct-shear box without an interface element and with an interface element is very clear. Goodman (1968) type of interface performed well in direct shear simulation. The performance of this interface depends on the relative stiffness of the interface compared to the surrounding soil. Its behavior also depends on the thickness of the interface and load eccentricity from the interface. It shows distinct sign of mesh penetration at higher shear deformation. Katona (1983) type interface element is the simplest interface in terms of number of parameters required. It does not have any penetration or separation problem. The performance in slip mode is ideal although not realistic. The performance of Desai (1984) type interface element seems to be the most realistic although it showed tendency of mesh penetration. It also showed better convergence properties. Reduction in the thickness of the element improves the performance of the Desai type element.

Finally, it can be concluded that among the three interfaces studied in this research, Katona and Desai type of interface element are much better in accuracy and although, practically Goodman type of interface is easy to formulate and to implement.

 

Thesis Title

REMOVAL OF ARSENIC FROM WATER BY FERRIC CHLORIDE

 

Name of the Student

Nibedita Chowdhury

 

Supervisor

Department

Dr. M. Ashraf Ali

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     October, 1999

Abstract

Widespread arsenic contamination of groundwater has become a major public health concern in Bangladesh, where water supply is heavily dependent on groundwater. The present study focused on removal of arsenic from groundwater by coagulation with ferric chloride. Removal of both As (V) and As (III) was found to increase with increasing coagulant (ferric chloride) dose. For higher coagulant (ferric chloride) doses, removal efficiencies appear to be independent of initial arsenic concentration. Removal efficiency of As (III) by ferric chloride was found to be significantly lower than that of As (V). For example, 25mg/L of ferric chloride could bring down As (V) concentration to less than 10mg/L from an initial concentration of 0.25 mg/L; whereas in case of As (III) a ferric chloride dose as high as 125 mg/L resulted in a residual arsenic concentration of about 55mg/L, higher than the drinking water standard (50mg/L) set by the Bangladesh EQS. It was found that removal efficiency of As (III) pre-oxidized with bleaching powder was almost identical to that of As (V). For a sorbate/sorbent ratio (expresse as mg As/mg Fe) of about 50 or less, removal efficiencies exceeding 95 percent could be achieved, irrespective of the initial arsenic concentration. This can serve as a guideline value or thumb rule in determining required dose of ferric chloride for arsenic removal. A maximum adsorption density of about 353mg As/mg Fe was achieved with a As(III) (pre-oxidized) concentration of 2.0 mg/L and ferric chloride concentration of 25 mg/L. However, at optimum sorbate/sorbent ratios (i.e., 50 or less) maximum adsorption density achieved was much less, about 50mg As/L mgFe.

Since significant fraction of arsenic in the groundwater of Bangladesh can exist as As(III), it appears that arsenic removal technology based on ferric chloride coagulation must involve a pre-oxidation step for converting As(III) to As (V). In this study, good removal of As(III) was achieved in jar tests using a chlorine (bleaching powder) dose 3 to 4 times that calculated from stoichiometric consideration. However, the unstable nature of bleaching powder is a cause of concern in its use as an oxidant. Results obtained from this study enabled determination of ferric chloride dose required for achieving a particular removal goal for arsenic present at different initial concentrations. It was found that ferric chloride requirement for satisfying the WHO standard (10mg/L) was significantly higher than the required for satisfying the Bangladesh standard of 50mg/L. Thus, the cost of arsenic removal by ferric chloride would depend on the water quality standard it is designed for. This is important in view of the possible revision of the drinking water standard for arsenic in many countries. In Bangladesh, arsenic removal by coagulated flocs of ferric hydroxide could be a very effective technique, particularly in view of the presence of elevated levels of iron in many regions of the country.

Removal of As(V) appears to be maximum in the neutral pH range and slightly depressed at higher pH values, exceeding 8. Since pH of groundwater usually falls between 6 and 8 in Bangladesh, pH is not likely to play a major role in determining the removal of arsenic from groundwater by ferric chloride. Although pH has a more pronounced effect on As(III) removal, this may not be an important consideration for arsenic removal by ferric chloride involving pre-oxidation. Phosphate appears to have a dramatic effect on arsenic removal from groundwater. Removal of arsenic present at an initial concentration of 0.10 mg/L (and treated with 10 mg/L of ferric chloride) came down from 92 percent (in the absence of phosphate) to about 46 percent in the presence of 2mg/L of phosphate. Relatively high concentrations of phosphate, reaching as high as 5.8 mg/L, have been found in some places of Bangladesh and it appears that ferric chloride doses determined from laboratory batch studies (without the presence of phosphate) can significantly understimate the actual dose requirement. Effect of phosphate on arsenic removal by ferric chloride also suggest that phosphate ions can play an important role in the release of arsenic in the groundwater environment in Bangladesh.

 

Thesis Title

DEVELOPMENT OF AN INTERACTIVE DATABASE FOR SOIL STRENGTH PARAMETERS OF DHAKA CITY BASED ON ARTIFICIAL NEURAL NETWORKS

 

Name of the Student

Roksana Mannan

 

Supervisor

Department

Dr. Mehedi Ahmed Ansary

Asstt. Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     December, 1999

Abstract

This research presents the development of an Interactive Database for different soil parameters for different areas of Dhaka City based on Artificial Neural Networks (ANN). Since it is expensive to obtain extensive information regarding soil parameters of a region, ANN can be used to generalize soil data over three-dimensional space. Soil data from the existing soil reports are used to  train a hierarchy of artificial neural networks for this purpose. The study has been divided into two phases. In the first phase of the study, soil reports have been collected from different Government and Non-government organization to prepare a relational database based on Microsoft Access Software which is readily available in most of the Personal Computers. This database can be used effectively for the preliminary design of any geotechnical structures. Artificial neural network has the capacity to map a very complex relationship among different parameters of a complex phenomena. It can generalize and interpolate the missing data in any possible direction. Thereby a complete three dimensional geotechmical database of an area can be obtained. In the second phase of the study, back-propagation neural networks has been used to simulate soil strength parameters (SPT and Unconfined Compression Strength) in three dimension using the data from the geotechimcal database developed in the first phase of the study. The variable used in the models are Topographical Information, Depth, Specific Gravity (GS), Water Content, Dry Density, Percentage of Sand, Silt and Clay, Liquid Limit and Plastic Limit.

The Database contains 140 borehole data of Dhaka. The database can be updated easily and data of any place of Bangladesh can be added. The training of the ANN system is performed based on the available data of SPT, UCS and other available soil parameters stored in the database. The modeling approach has been found to be successful. The model predictions are convergent with the observed results. It has been observed that water content and dry density have significant effect on both SPT and UCS. The other soil parameters GS, %Sand, % Silt, %Clay. LL or PL do not have individual effect on SPT and UCS, but together with other variables they can be used to predict SPT and UCS up to a depth of 25ft. additionally, %Sand, %Silt and %Clay together with Topographical Information and Depth has been used for prediction of SPT up to a depth of 100ft.

The methodology and application developed in this research can be extended, in many directions. A framework that integrates spatially enhanced GIS systems with 3D graphics representation using a shared database can be developed. Also similar ANN models for predicting soil strength paramenters for other areas of Bangladesh can be developed.

 

Thesis Title

SLOPE STABILITY AND SETTLEMENT ANALYSIS OF DHAKA FLOOD PROTECTION EMANKMENT

 

Name of the Student

Md. Shamsul Islam

 

Supervisor

Department

Dr. Mehedi Ahmed Ansary

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg      January, 2000

Abstract

The severe flooding in 1987 led to the design and construction of about 30 km long flood control embankment on the Western side of Dhaka city. In some of the stretches, the embankment crossed silted up channel consisting of soft subsoils. Approximately 13 km of the embankment suffered some sort of failure immediately after construction, including slip failures and failure due to plastic lateral spread of the subsoils. Subsequent studies by local and foreign Consultants identified several failure zones. Based on those studies three locations of the embankment at Mirpur and two locations at Kellar Mohr site have been selected for this study. Detailed field and laboratory investigations were carried out. Based on the results of soil investigations, stability analysis using XSTABL at five critical sections (9500, 9900, 13925, 29930, 30000) of the embankment were performed compared with previous analysis. It has been found that stability of the embankment increased significantly within the last few years. This can be attributed to the fact that repeated dumping of soil at the top of the embankment and consequent settlement of the embankment has improved the properties of soil. The settlement analysis has been performed for three critical sections 9900, 13925, 29930 of the embankment. The analysis is based on the soil parameters obtained during the construction phase of the embankment. Finite Element program CRISP has been used for modeling settlement of the embankment. Consolidation analysis with elastic-anisotropic model ahs been used. The loading is due to the self-weight of the body of the embankment. Loading has been transferred on the foundation of the embankment in three stages using remove-add mechanism of CRISP, to simulate embankment construction sequence. Maximum settlement estimated for the embankment top at 9900, 13925 and 29930 are 4.07ft, 5.44ft and 3.49 ft respectively.

 

 

Thesis Title

SEISMIC MICROZONATION OF DHAKA CITY BASED ON SITE AMPLIFICATION AND LIQUEFACTION

 

Name of the Student

Md. Abdur Rashid

 

Supervisor

Department

Dr. Mehedi Ahmed Ansary

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     February, 2000

Abstract

Microzonation is a systematic way for the management of earthquake vulnerability, integrating for application the earth and engineering sciences. It can be achieved by inputting local site characteristics, ground shaking, liquefaction, slope stability, high ground water, fault rapture, economic involvement such as land cost, transportation costs, seismic damage etc. In the present study local site conditions and liquefaction potential of sites were used for mixrozonation of Dhaka city. Dhaka was first divided into small grids. At the grid points shear wave velocities were estimated by using SPT test results. More than two hundred bore hole data were collected and converted into shear wave velocities using empirical relations. All these data were used to estimate vibration characteristics at different grid points of the city employing one dimensional wave propagation program SHAKE. The computation were made in the frequency range of 0 to 20 Hz. At frequencies every 0.05 Hz interval. The loss of energy of seismic waves in the soil layers was also considered. The vibration characteristics of each site such as predominant frequency and amplification amplitudes were found. The predominant frequency (inverse of period) at the site is an important information in estimating the input force to a structure due to the earthquake. The amplification amplitude is the relative amplification of a seismic wave at ground surface level coming from baserock.

In this study, at each site of Dhaka city, liquefaction potential was analysed using maximum acceleration of 150 cm/s2. This maximum acceleration is based on 200 years Peak ground surface acceleration contour estimated from earthquake hazard analysis for Bangladesh based on National Oceanic and Atmospheric Administration (NOAA) earthquake data from 1900 to 1977. The liquefaction potential of different locations of Dhaka is estimated by two methods: The Seed et al. method (1983) where SPT data was used and Iwasaki et al. method (1982) based on topographical information.

The results of the amplification and liquefaction analysis were transformed into microzonation maps depicting : (i) zones showing quantitative estimates of site amplification; (ii) zones showing the natural frequency of the soils; (iii) zones showing qualitative estimates of liquefaction potential; (iv) zones showing quantitative estimates of liquefaction potential. These maps will be useful for preliminary selection of a project site, land use planning zoning ordinances, pre-disaster planning, capital investment planning etc.

 

Thesis Title

EARTHQUAKE HAZARD ANALYSIS FOR BANGLADESH

 

Name of the Student

Mohammad Sharfuddin

 

Supervisor

Department

Dr. Mehedi Ahmed Ansary

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     Aprin, 2001

Abstract

As a first step in earthquake disaster mitigation, this study aims to identify and evaluate the seismic hazards in Bangladesh. The seismic environment of Bangladesh is first studied. This includes geological and seismotectonic setup in Bangladesh, probable major seismic sources, existing zoning maps etc.

Due to the lack of a proper seismotectionic map in the region under consideration, the insufficiency of data and high uncertainties in seismic source parameters, a simple model for earthquake occurrence using a newly developed earthquake catalogue is used. Initially a detailed earthquake catalogue analysis is carried out to understand the nature of seismicity. For the development of the catalogue, earthquake data are collected from various sources, such as ISC, ISS, USGS, RRLJ and other independent researchers. Different correlations are developed using the collected data to homogenize earthquake magnitudes. The data completeness of the earthquake catalogue is examined and the time periods in which the data are complete are identified for each magnitude. For the maximum use of the available data, the data of the large earthquakes are taken from the long time period while the data of small earthquakes are taken from the shorter time period in which they are complete.

Using the simple catalogue based model; the seismic hazard at 42 points in Bangladesh is estimated. The seismic hazard maps are presented as contour maps in terms of horizontal Peak Ground Acceleration (PGA) based on 50, 100, 200 years return period and 10% probability of exceedance in a design life of 50 years. A return period seismic hazard map for PGA³150 cm/s2 is also presented. In addition expected Ms values for 34 points are estimated for 50,100 and 200 years return period.

By comparing the seismic base shear coefficients with the values of the hazard maps, a new seismic zoning map for short period structures are proposed based on the 200 year PGA. Similar to the BNBC 1993 seismic zoning map, the proposed map has three seismic zones. It assigns higher seismicity to Bandarban, Faridpur, Kustia, Natore, Nilphamari, Panchogarh, Rajshahi, Sandwip and significant part of Bogra, Cox’sbazar, Khargrachari, Noakhali, Rangamati and Rangpur. These areas have been assigned low seismicity in the seismic zoning map of BNBC 1993.

The finding of this study shows that considerable seismic hazard exists for major parts of the country. Based on the 1991 Census data and proposed seismic zoning map, about 42 million people, representing one third of the total population live in Zone 3 (38% area), i.e. areas which may be classified as “liable to severe damage”, another 52 million (i.e. approx. 46% of the population) live in Zone 2 (39% area), i.e. areas “liable to moderate damage” and the rest 19 million population live in Zone 1(23% area), i.e. areas “liable to slight damage”. The outcome of this study, coupled with vulnerability studies, must guide, stimulate and facilitate the efforts of the respective government, the earthquake engineering and the disaster mitigation planning communities to take specific practical preventive measures to reduce seismic risk of Bangladesh.

 

 

 

Thesis Title

STUDY OF VEHICLE ARRIVAL PATTERN AND FREE SPEED CHARACTERISTICS ON SELECTED NATIONAL HIGHWAYS

 

Name of the Student

Gazi Arif Iqbal

 

Supervisor

Department

Dr. Moazzem Hossain

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     August, 1998

Abstract

Analysis and interpretation of traffic operations on national highways require a sound understanding of the traffic flow parameters. Such traffic flow parameters are traffic arrival headways, free speed of vehicles, operating speed and speed-flow-density relationship. No significant study has yet been made to investigate these traffic parameters of Bangladeshi national highways. In this study, effort has been given to investigate the traffic arrival pattern and free speed characteristics of vehicles on two-lane two-way national highways of Bangladesh. The research study has been based on field data. Both video and manual data on the traffic flow of selected national highways have been collected for a net period of approximately twenty five hours. The analysis of collected data has been made using different statistical softwares. Analysis of traffic arrival pattern using the vehicular time headway data has revealed that the pattern follows more than one statistical distribution models for all the highways. Generally, it has been observed that the vehicles maintain close headways when they are in following situation. It has been observed that the traffic arrival pattern on selected Bangladeshi national highways can be described by one or more of the two statistical distributions, namely, exponential and lognormal. The relevant parameters of the corresponding arrival headway distributions have been estimated. Analysis of free speed of the commonly found vehicles (bus, minibus, truck, passenger-car, nonmotorised vehicles) follow normal distribution pattern. Corresponding parameters of the normal distribution have also been estimated. From regression analysis, it has been found that free speed of vehicles depends on the pavement and shoulder width. In a pavement width range of 5.8m to 7.5m, free speed of commonly found motorized vehicles increases with the increase in shoulder width except for the case of bus (the reason of which has been identified as a local phenomenon on a particular highway).

 

 

Thesis Title

A STUDY OF THE ELEMENTS OF DRIVER’S OVERTAKING SIGHT DISTANCE ON SELECTED NATIONAL HIGWAYS OF BANGLADESH

 

Name of the Student

Md. Arifur Rahman

 

Supervisor

Department

Dr. Moazzem Hossain

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     August, 1998

Abstract

In case of two-lane two-way highways, drivers’ overtaking manoeuvres has significant bearings on the design and control measures. Parameter related to drivers’ overtaking is, therefore, useful to the highway engineers in setting geometric design criteria and implementing traffic control measures on the highways. This research study has been undertaken with the objective of comprehensive understanding of the drivers’ overtaking process on the national highways, (which are basically two-lane two-way type) of Bangladesh. An empirical approach based on extensive real field data has been adopted for the present study. Both video and manual data on the traffic operation of national highways have been collected for a period of over two months. Then the relevant data items have been transformed in use-able format. The collected data items have been analysed using different statistical computer softwares. It has been observed that the whole overtaking manoeuvre can be divided into four clearly identifiable distance elements as suggested by earlier studies of AASHTO. These are trailing distance (d1), overtaking distance (d2), clear distance (d3) and lag time distance (d4). However, these elements in the case of national highways of Bangladesh have been estimated and analysed in this research study. The analysis reveals that all the four components of overtaking process follow normal distribution model. But there are variations in the values of these elements depending on the vehicle size (larger/smaller) and type (motorized/non-motorised). Total overtaking sight distance required for the drivers’ overtaking manoeuvre has been estimated from the four distance elements. This total distance has also been compared with the AASHTO design criteria. It has been found that the total sight distance required for overtaking vehicle on the selected national highway is smaller im comparison to that suggested by ASSHTO for the same speed group. Regression analysis of overtaking distance and speed difference of vehicles involved reveals that there is a linear relationship between the two. Generally, overtaking time and distances decrease with the increase of speed difference when other conditions remain same. It has also been observed that there is a strong relationship between the overtaking of vehicles and actual pavement width and shoulder condition of the highway. Generally, on wider highways with stable shoulder the number of successful overtakings are higher than the corresponding number in case of narrow pavement with unstable shoulder.

 

Thesis Title

CHARACTERISTICS OF MAJOR INDUSTRIAL LIQUID POLLUTANTS IN BANGLADESH

 

Name of the Student

Md. Ashiqur Rahman

 

Supervisor

Department

Dr. Md. Delwar Hossain

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     October, 1997

Abstract

Bangladesh is promoting rapid industrial development and on the other hand industries contribute to serious pollution problems, since a large number of industries discharge their wastes, including potentially toxic substances, without treatment directly into the environment. The characterization of this raw waste is an essential component of the overall planning for effective and economical methods of industrial liquid waste pollution control. The treatment units for different types of industries can be designed with due consideration to the varying nature of industrial waste characteristics. Therefore, characterization of industrial liquid wastes prior to a treatment plant design is very important.

 On the basis of pollution effect on the environment, the major industries in Bangladesh are categorized as textile, tannery, pharmaceutical, fertilizer, paper and pulp, vegetable oil, sugar, cement, steel, paint and chemical industry. Most of the industries under these categories do not have any type of treatment facilities and they routinely discharge their raw wastes; which contains various toxic and hazardous substances directly or through the local storm drainage system to nearby khal, lake or river. To quantify the characteristics of major industrial liquid pollutants in Bangladesh, the important parameters those have been taken under consideration are pH, BOD5,COD, SS,TS, inorganic substances (Nitrogen, Phosphorous, Chlorides), sulphate, sulphide, heavy metals (Cu,ZN, Hg, Cr, Pb), colour and turbidity. The study was conducted through collecting different industrial effluent test results from the Environmental Engineering Laboratory, BUET and then analysed by using computer software (EXCEL). The study reveals that in most cases, the concentration of these parameters exceed the respective EQS for discharge into a surface water body. Since river water is largely used for drinking, washing, irrigation and fisheries purposes; serious adverse economic, environmental and human health effects occur due to the discharge of industrial liquid pollutants in surface water bodies.

A wide variation of the range of characteristics of different parameters has been observed in the same categorized industries. The characteristics of industrial liquid wastes in our country vary from place to place and depend on various factors like raw materials used, manufacturing process, condition of machinery, water supply position, weather condition of the locality etc. With due Consideration of these factors and from laboratory analyses of wastes a general characteristics of major industrial liquid pollutants has been proposed in this study. Results of this study suggest that the effluents from different categorized industries need to be properly treated before discharge into a surface water body.

 

Thesis Title

REMOVAL OF MICROORGANISM AND SUSPENDED MATERIAL BY COAGULATION AND FILTRATION

 

Name of the Student

Sultana Naznin Afroze

 

Supervisor

Department

Dr. Md. Delwar Hossain

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     Apruil, 1998

Abstract

The quality of water is of vital concern for mankind since it is directly linked with human welfare. But majority of people are still not aware of it. People use surface water for various domestic purposes. Surface water is often physically and bacteriologically contaminated due to unhygienic practices. During floods the water quality deteriorates and treatement is required to make water potable.

The study was devoted to acquire a better understanding of the effectiveness of alum for removal of faecal coliform as well as kaolin particles. Different parameters affecting removal of faecal coliform and kaolin particles were investigated in this study such as alum dosage, pH, sedimentation time and mixing. Filtration with filter paper was performed after coagulation. Removal of faecal coliform was observed at different pH and sedimentation time.

Alum dosage was found effective for reduction of faecal coliform and kaolin particles. With increasing alum dosage faecal coliform and turbidity removal rate were found increasing pH and sedimentation time also significantly affected the removal of faecal coliform and turbidity. Most of the experiments were performed at pH 4.5 and 6.0. It was observed that the removal efficiency at pH 6.0 was higher than that of pH 4.5.

At any alum dosage, removal of faecal coliform was found to increase with increasing sedimentation time. Moreover for the same removal of microorganism less sedimentation time was required for increased alum dosage. With increasing sedimentation time settlement rate was found to decrease. It was found that with increasing alum dosage potable water could be obtained within a short period of sedimentation.

 

Thesis Title

TREATMENT OF LIQUID WASTE FROM A TEXTILE INDUSTRY WITH WATER HYACINTH

 

Name of the Student

Sania Huq

 

Supervisor

Department

Dr. Md. Delwar Hossain

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     September, 1998

Abstract

Waste water treatment using aquatic plants is gradually gaining importance. The aquatic treatment system consists of one or more shallow ponds in which one or more species of aquatic macrophytes are grown. Waterhyacinth is one of the most promising aquatic plant which has been successfully used all over the world in industrial waste water treatment. In this study an experimental investigation has been carried out to find the effectiveness of water hyacinth in control of pollution by textile liquid waste.

This study focuses on the characteristics of liquid waste of existing textile industries in Bangladesh. In our country very small efforts are made for the treatment of industrial waste. Most of the existing industries dispose off liquid waste having pollution indication parameters exceeding the respective environmental quality standard. This study shows that the effluents from these industries can be effectively treated by water hyacinth ponds as an alternate low cost treatment method before discharge of raw liquid waste into a surface waterbody.

In this study different experiments have been conducted to determine the removal rate of pollutants with giving importance to colour, turbidity, suspended solids from textile liquid waste at different concentrations of waste water and at different pH. Ignoring the effect of different types of water hyacinth in the treatment of waste water, in this study plants having long and extensive root system are used. Representative samples of Beximco Textile Industry were collected and polluting parameters were analysed in the Environmental Engineering laboratory of BUET. Water hyacinth was used to treat this liquid waste at different concentrations in some plastic buckets. Samples from these buckets were collected at regular interval and pollutant contents were determined. This process was repeated to determine the removal of pollutants by water hyacinth at different pH of raw effluent.

This study reveals that water hyacinth could be positively used in the treatment of waste water. It has found that removal rate of pollutants by water hyacinth are excellent if the waste water is diluted fifty percent. Test results also show that removal rate of pollutants at pH 4.8 are much better than at pH 6.8 of the waste water.

Treatment of textile liquid waste by coagulation and sedimentation process gives a better understanding of the effectiveness of alum for removal of pollutant. An attempt was made to remove pollutants from textile liquid waste by sludge blanket and coal filter method.

 

Thesis Title

REMOVAL OF IRON FROM GROUND WATER BY COAGULATION AND SEDIMENTATION

 

Name of the Student

Salma shahid

 

Supervisor

Department

Dr. Md. Delwar Hossain

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     December, 1998

Abstract

Ground water is a major source of safe water for drinking and other domestic purposes for the rural/urban population of Bangladesh which may have iron content in excess of 5 mg/L. This study is an experimental investigation to observe the effect of different factors in iron removal and also to develop simple and cost effective iron removal method.

Relevant literature on chemistry of iron content water and unit processes of iron removal have been reviewed, and water use pattern and distribution of iron in ground water have also been focused.

Investigations were made at laboratory condition on artificial iron content water and natural ground water collected from tubewells of iron prone areas to find out effect of different unit processes and other related factors on iron removal Experimental results shows that filtration is an effective mode of iron removal. However, considering the frequent cleaning of the filter bed and low yield, in this study emphasis have been given on sedimentation, for effective and efficient iron removal. As an aid in improving settling characteristics of the precipitated iron, coagulation is observed to be an important tool.

Aeration, coagulation and 30 min sedimentation can reduce iron concentration to allowable limit of 1 mg/L. However, the analysis also shows that iron removal increases with an increase in anion concentration. More pronounced effect is observed when the added anion is common to the anion already in solution, due to common ion effect. Alum used as coagulant is observed to be more effective than lime in iron removal. Whereas, the coagulant cost involved using alum as coagulant is 191.7% higher than lime.

 

Thesis Title

ENVIRONMENTAL IMPACT ASSESSMENT OF INTRODUCING LIGHT RAIL TRANSIT IN DHAKA CITY

 

Name of the Student

S. M. Zulkernine

 

Supervisor

Department

Dr. Md. Delwar Hossain

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     August, 1999

Abstract

Dhaka, the capital of Bangladesh, is a large city, which is going to be one of the mega cities of the world within the early next century. Among other problems of a mega city, Dhaka is being faced with the environmental degradation of the city. The population of Dhaka has increased substantially since the independence of the country and eventually the number of motorized transport has increased to meet the increasing demand of the city dwellers. The harmful gases emitted from these vehicles are polluting the air of the city and has put the health of the city dwellers in danger. Besides this, accident rate has increased and traffic congestion has become a regular phenomena. To cope with this problems an alternative transportation system has become imperative which will be environment friendly and have the potential to meet the demand of the city. Light Rail Transit, which is a modern version of the traditional tramway, can be a probable solution to this problem.

This study was designed to find out the environmental impact of the introduction of Light Rail Transit in Dhaka city. In doing this relevant literature have been reviewed. A route for LRT has been proposed and data collected through sample survey. However the feasibility to establish a track for LRT was not carried out purposely as that was out of the scope of the study.

Through the study, it appears that because of the introduction of Light Rail Transit, a substantial number of people will be diverted to LRT from other modes of transport and as a result emission of harmful gases like SOx, NOx and COx will be reduced by about 40%.

 

Thesis Title

CORRELATION OF ARSENIC AND IRON IN GROUNDWATER OF BANGLADESH

 

Name of the Student

Mst. Anjuman Ara

 

Supervisor

Department

Dr. Md. Delwar Hossain

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     August, 2000

Abstract

Water is a basic necessity of man along with food and air. In Bangladesh groundwater is a major source of safe water for drinking and other domestic purposes for the rural and ruban population. Groundwater contains dissolved minerals such as iron, arsenic, manganese, nitrate, fluoride, chloride, calcium, sodium etc. Presence of elevated levels of arsenic in groundwater has become a major concern in Bangladesh and elevated levels of iron are also present in many regions of the country. This study is an attempt to evaluate the possible correlation between the presence of Arsenic and Iron in groundwater.

In order to assess possible correction between arsinic and irom concentration in groundwater, 760 tubewell water samples were analyzed. These tubewells covers the north-eastern zome of Bangladesh, and the districts of Manikgonj and Noakhali. About 64% of the tubewells contain iron above 1.0 mg/1 and exceed Bangladesh standard and about 34% of the tubewells contain iron exceeding 5.0 mg/1. About 34% of the tubewells contain arsenic above 0.05 mg/1 which is the Bangladesh standard for Arsenic. These tubewells are a  potential threat to public health.

The overall correlation between arsenic and iron concentration of tubewell water in the study-area in Bangladesh is poor. But in some districts a positive correlation has been observed and in some than as the positive correlation is very strong. Arsenic concentration analysis of groundwater form 3912 tubewell water samples were performed and it was found that about 31% of the tubewells in Bangladesh have arsenic concentration above 0.05 mg/1 which poses a potential threat to public health.

In general if Arsenic concentration is higher, Iron concentration is also higher.

 

Thesis Title

INFLUENCE OF SALINITY ON THE PERFORMANCE OF A SLUDGE BLANKET CLARIFIER

 

Name of the Student

Misbah Uddin Khan

 

Supervisor

Department

Dr. Md. Delwar Hossain

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     April, 2000

Abstract

Coagulation is an important technique in water treatment to remove colloidal and non-settlable fine particle successfully. These particles are forced to settle as floc with the help of chemicals and particle transport mechanism. Common coagulant does is slum [Al2(SO4)3. 14 H2O], readily dissolves in water, is used in the pH range of 5.5 to 7.8. One of the limitations of coagulation is influence of salinity. Additon of salts interferes in the coagulation and, alum floc breaks in presence of salinity in water CWASA faced the salinity problem in 1991 for cyclone tide and in 1995 for backwater effect of sea. To review CWASA’s problem during saline intrusion and improve the situation, a physical model of sludge blanket clarifier which angle is same to Mohara Treatment Plant’s clarifier has been set-up for this study. Both the clarifiers work in the same method, hence, clarifier used in the laboratory can be considered similar to Mohara’s clarifier. It was found that saline intrusion problem could be minimized by controlling flow.

Performance Study for different units of the plant for selected parameters, i.e., pH, turbidity, colour, Total Dissolved Solid (TDS), Total Solid (TS), alkalinity and chloride have been done for each unit of the plant and for the whole plant taking samples at inlet and outlet of each unit. The study reveals that sedimentation unit of the plant is good in removing turbidity and Total Suspended Solid (TSS). Coagulation unit’s Flash mixer and Clarifier unit) performance in removing colour and turbidity is about 75-95%. Mohara Treatment Plant is performing well in removing turbidity, colour and TS. Alkalinity, pH and chloride of finished water were always in the range comparing World Health Organisation (WHO) guideline. This study has been done at low flow (winter season) condition of river Halda. Further study of the plant is required at high flow condition and during saline instrusion. The study shows that performance of clarifier depends on discharge, angle of clarifier with horizontal and depth of sludge. Critical discharge for the clarifier used in the study when sludge blanket disintegrates initially due to concentrated force was about 936 cm3/s/m3 of sludge. Clarifier’s performance decreases when salt is added at any flow. Increased salt increases density of water, hence concentrated force increases at the inlet of clarifier. Increased concentrated force increases initial dispersion of floc in the clarifier. But 134-535 cm3/s/m3 of sludge is the optimum discharge range for the clarifier used when performance is good at optimum salt value. Limiting chloride was found 1000 mg/1 from limiting concentrated force of 24764 c.g.s. unit. Unit at 17.5 cm sludge depth for the clarifier used in the laboratory. Maximum tolerable discharge for the clarifier used during salinity was about 893 cm3/s/m3 of sludge at minimum 500 mg/1 of chloride, while maximum tolerable chloride was about 3400 mg/1 at minimum discharge of 80 cm3/s/m3 of sludge. Again, maximum tolerable discharge for clarifier of Mohara during salinity was about 2219 cm3/s/m3 of sludge at minimum 500 mg/1 of chloride, while maximum tolerable chloride was about 6800 mg/1 at minimum discharge of 80 cm3/s/m3 of sludge. Upto 3400 mg/1 of chloride and at minimum discharge of 80 cm3/s/m3 of sludge, clarifier’s performance can be considered similar to slow mixing coagulation. CWASA could control both discharge and chloride at the flash mixer during salinity intrusion.

 

Thesis Title

A RATIONAL DESIGN OF SIMPLY SUPPORTED AND CONTINUOUS DEEP BEAMS

 

Name of the Student

Syed Md. Mymur Sultan

 

Supervisor

Department

Dr. Salek M. Seraj

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     September, 2000

Abstract

Deep beam is a very important structural element in various types of concrete structures such as pile cap, transfer girder, panel beams, foundation walls of rectangular tanks and bins, shear walls, folded Plate roof structures, etc. Analysis of deep beams under shear is quite complex’ and because of the complexities involved, exact theoretical basis for the analysis of deep beams in shear has not yet developed. Current design rules for deep beams are largely based on the provisions of American Concrete Institute (ACI) Code, Construction Industry Research and Information Association (CIRIA) Guide, and other codes and design methods. The present-day design provisions for deep beams are usually based on test result conducted on simply supported model deep beams, although deep beams are often continuous. Again, some of the provisions for the design of deep beams are essentially those for slender beams and are not applicable to deep beams.

In the absence of an exact and simplified basis for the design of deep beams, several new lines of thinking have developed in the recent past in order to unify the design of various structural concrete members. One of these new approaches is the concept of Compressive Force Path (CFP). However, a very limited number of tests have been conducted to verify the applicability of this method in the design of deep beams.

One of the primary purposes of this study is to try to understand the behaviour of deep beams with the help of tests conducted by various researchers. Again, available test results have been used, in conjunction with results from the limited tests conducted by the investigator on simply supported as well as continuous deep beams, in finding out the suitability of CFP method in the design of deep beams.

In the present study, test data of about 175 deep beams have been collected, analysed and employed in understanding the behaviour and predicting the strength of such members using ACI, CFP and CIRIA Guide methods. In addition, five simply supported and five two span deep beams were designed, fabricated and load tested to failure in an effort to enrich the data base of deep beam test results as well as to ascertain the applicability of CFP method in the design of deep beams.

From the investigation it has been found that shear failure is common in all the cases of deep beams. Whereas, clear span-to-effective depth ratio has demonstrated insignificant effect, shear span-to-effective depth ratio has been found to be a governing parameter in controlling the shear strength. Vertical web reinforcement, strength of concrete and amount of flexural steel have shown some influence on the shear strength of concrete and amount of flexural steel have shown some influence on the shear strength. It also appeared that the effect of horizontal steel is much less than what is usually considered. Again, inclined cracking strength has little  influence on the shear strength of such type of beams. The ACI code and CIRIA guide have failed in predicting the ultimate strength of deep beams. Although, in most cases, the CFP method predicted such strengths of deep beams more closely, as the shear span-to depth ratio gradually decreases from 1.0, this method becomes progressively conservative. Among other findings, it has been gathered that the results obtained from tests of simply supported beams may not be applied to continuous deep beams and that further tests on multi-span beams are essential.

 

 

Thesis Title

PUNCHING SHEAR BEHAVIOUR OF REINFORCED CONCRETE SLABS

 

Name of the Student

A. K. M. Jahangir Alam

 

Supervisor

Department

Dr. Salek M. Seraj

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     September, 1997

Abstract

Punching shear is an important consideration in the design of reinforced concrete flat plates, flat slabs and column footings. Present design rules for punching shear failure of reinforced concretes slabs, given in various Codes of practice, are largely based on studies of the behaviour and strength of simply-supported, conventional specimens extending to the nominal line of contraflexure. As punching shear provisions incorporated in various Codes of practice are a direct result of the empirical procedures, they do not usually provide anaccurate estimate of the ultimate punching load capacity of a slab with its edges restrained against rotation. This is because no direct account is taken of the significant enhancement of punching capacity due to the in-plane restraint in many types of reinforced concrete slab systems.

The present study describes punching tests conducted on reinforced concrete slabs with their edges restrained as well as unrestrained. Here, edge restraint has been provided, by means of edge beams of various dimensions, to mimic the behaviour of continuous slabs. A total of 16 model slabs have been tested in an effort to ascertain the influence of the degree of boundary restraint, percentage of steel reinforcement, and slab thickness of the slab models on their structureal behaviour and punching load-carrying capacity. The cracking pattern and load-deflection behaviour of the slabs tested have also been monitored closely. The test program was carried out to provide basic information on the real punching behaviour of restrained slabs subjected to concentrated loading and may also be usefully applied in the assessment of existing structures with laterally restrained slab construction.

The significant positive effect of edge restraint on the punching failure load, resulting in enhancing the ultimate punching strength, has been noticed. The code-specified strength of the specimens was calculated in accordance with the American, British, Canadian and European codes. It became apparent that no code-specified method predicts an enhancement in the punching shear strength of a restrained reinforced concrete slab with an increase in the degree of such restraints. Present Codes do not recongnize the role of percentage of longitudinal steel on the punching strength effectively either. It has been understood that inclusion of the findings of the study in the design Codes will result in a rational design of structural systems where punching phenomenon plays a vital role.

  

Thesis Title

REAPPRAISAL OF CODE PROVISIONS FOR STRUCTURES SUBJECTED TO SEISMIC LOADING

 

Name of the Student

Munaz Ahmed Noor

 

Supervisor

Department

Dr. Salek M. Seraj

Associate Professor

Department of Civil Engineering, BUET, Dhaka

And

Dr. Mehedi A. Ansary

Assistant Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     September, 1997

Abstract

Seismic code provides criteria for the design and construction of new buildings subjected to earthquakes in order to minimize the hazard to life for all buildings, to increase the expected performance of higher occupancy structures as compared to ordinary structures, and to improve the capability of essential facilities to function after an earthquake. In the present study, efforts have been made to critically evaluate seismic code provisions and identify areas in which investigations could be carried out to update the code provisions. Efforts have been made to formulate response spectra, which may be used in dynamic analysis. A suitable numerical coefficient have been derived from these response spectra for using in equivalent static analysis. Response spectra have been formulated using four soil types from rock to soft. For the development of the response spectra, several recent free field earthquake records have been used. In absence of free field earthquake records, earthquakes are simulated taking the appropriate properties of soils into consideration. To incorporate the effect of soil and the effect of attenuation in simulated earthquakes Kanai-Tajimi power spectra and Shinozuka-Sato (1967) envelope have been incorporated in the available subroutines. Performance of the developed spectra have been tested against Uniform Building Code (1994) spectra by analyzing various moderately high moment resisting framed structures. Additionally, a limited study has been conducted to calculate the predominant time period for Dhaka City soil to validate the applicability of the proposed simulated response spectra for Dhaka City soils.

It has been found that for calculating the base shear in the equivalent static method, almost all codes of practice adopt similar definitions for the various numerical coefficient of the base shear formula. It appears that further improvement in the equations pertaining to the calculation of time period of the buildings may not be rewarding. It has been found that the maximum amplitude of the acceleration spectra decreases as the soil changes from rock to soft type. It has been observed that largest amplification occurs at the vicinity of natural time period of soil. It has also been noticed that the rate of attenuation of rock spectra was faster than stiff soil spectra. Rate of attenuation of the spectra developed on the basis of recent free field earthquake records has been found to be faster than the spectra embodied in the present day codes. It is understood that efforts should be made to increase the value of structural damping so that amplification of seismic forces is less. It is imperative to install suitable number of seismic stations in Bangladesh so that local spectra based on site specific real earthquake records can be developed.

 

 

Thesis Title

PUNCHING BEHAVIOUR OF FOOTINGS

 

Name of the Student

Md. Golam Mostafa

 

Supervisor

Department

Dr. Salek M. Seraj

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     1997

Abstract

Punching shear is an important consideration in the design of flat plates, bridge decks, column footings and mat foundations. Present design rules for punching shear failure of reinforced concrete slabs and footings, given in various codes of practice, are largely based on studies of the behaviour and strength of simply supported, conventional specimens extending to the nominal line of contraflexure. As punching shear provisions incorporated in various Codes of practice are a direct result of the empirical procedures, they do not usually provide an accurate estimate of the punching load capacity of a slab with lateral restraint. Again, present codes indiscriminately use equations, base on punching test conducted on slabs, for the design of footings and mat foundations. More importantly, a majority of the present codes usually represent punching shear strength merely as a function of concrete strength  and ignores the possible effects of percentage of steel, span to depth ratio, etc.

The present study describes punching tests conducted on eighteen footings, seventeen of which rested on sand. During tests, percentage of steel reinforcement, depth, size and concrete strength of model footings, as well as punching area were varied. Again, the rate of loading as well as the degree of saturation of sand have been varied. The test program was carried out to provide basic information on real punching behaviour of footings subjected to concentrated loading.

The punching strength of footings resting on sand have been found to be significantly higher than the predictions of present design provisions. The code-specified strengths of the specimens were calculated in accordance with ACI 318-95, BS 8110-85, CAN3-A23.3-M84, CEB-FIB and BNBC codes. It appears that no code specified method adequately caters for the effect of the upward soil pressure on the punching strength of footings. Most of the codes do not recognize the role of percentage of longitudinal steel, on the punching strength either. The overall footing size has been found to have very little effect on the punching strength of footings. Since pressure distribution under a footing is expected to vary depending upon soil type, the code provisons for footings should address this issue faithfully to arrive at a realistic prognosis. During the course of the investigations it became apparent that the concrete strength has a very positive influence on punching strength of footings, as has already been recognized in the codes. The effect of concrete strength, however, becomes almost insignificant as the compressive strenth of concrete reaches high values. The present series of tests confirmed, albeit tentatively, that the presently adopted code methodology, where thickness has been considered to have a linear contribution towards the punching strength, may be considered to be valid. Rapid load tests conducted on footings resting on saturated sand demonstrated that the difference between experimental failure load and code predictions narrows down as the punching loads are applied at a very fast rate, in comparison to its normal rate counterpart. It has been understood that inclusion of the tenets of the thesis in the design Codes will result in an economic and rational design of footings where punching phenomenon plays a vital role.

 

Thesis Title

A STUDY ON CEMENT AND LIME STABILISED CHITTAGONG COASTAL SOILS FOR USE IN ROAD CONSTRUCTION

 

Name of the Student

Bipradas Rajbongshi

 

Supervisor

Department

Dr. Abu Siddique

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     December, 1997

Abstract

In the present study, cement stabilization of two selected soils (collected from Anwara and Banshkhali) and lime stabilization of a soil (collected from Banshkhali) of Chittagong coastal region were carried out in order to assess their suitability for use in road construction. The soils from Anwara and Basnkhali were respectively a clayey silt of low plasticity (LL = 30, PI = 7) and a silty clay of medium plasticity (LL = 44, PI = 19). As additives, ordinary Portland cement was used in percentages of 1, 3 and 5 while slaked lime was used in 3%, 5% and 7%. Analytical works using CIRCLY computer program were also undertaken in order to determine the thickness of cement stabilised bases and lime stabilised sub-bases of rural roads in the coastal region.

Index tests indicated that compared with the untreated samples, plasticity index and linear shrinkage of the cement and lime stabilised samples of the soils reduced. Shrinkage limit, however, reduced for cement-treated samples while it increased for lime-treated samples. For the cement and lime stabilised samples, maximum dry density increased and reduced respectively, while optimum moisture content reduced and increased for cement and lime stabilized samples respectively with the increase in additive content.

For samples of both the coastal soils, compared with the untreated samples, unconfined compressive strength (qu) of cement and lime treated samples increased significantly, depending on the additive content and curing age. It was found that compressive strength of samples treated with 3% and 5% cement and cured for 14 and 28 days satisfied the requirements of PCA (1956) for the compressive strength of soil-cement mix and that for all cement contents and all curing ages, compressive strength of the stabilised samples fulfilled the requirements of soil-cement mix for use in road sub-base and base subjected to light traffic, as proposed by Ingles and Metcalf (1972). It was also found that the compressive strength of samples treated with 5% and 7% lime met the requirements for upgrading heavy clays to sub-base material quality type, as proposed by Ingles and Metcalf (1972). In an attempt to investigate the effect of moulding water content on qu, it appeared that in order to achieve maximum compressive strength, the cement and lime stabilized samples should be compacted at their optimum moisture content respectively. Compared with the untreated samples, CBR of the cement and lime stabilized samples increased considerably. It was found that CBR-values of cement and lime stabilised samples increased up to about 5 times and 3 times respectively. CBR-values of samples of both the soils, treated with 3% and 5% cement, fulfilled the requirements of soil-cement road sub-base for light traffic while CBR of sample stabilised with 7% lime did not satisfy the criteria of the minimum CBR for soil-lime mix for improvement of base material in road construction, as proposed by Ingles and Metcalf (1972).

The flexural stress versus deflection curves have been found to be approximately linear for both cement and lime stabilised samples. Compared with the untreated samples, flexural strength and flexural modulus of the cement and lime stabilised samples increased considerably, depending on the additive content. Compared with the untreated sample, the flexural strength and flexural modulus of cement-treated samples increased up to about 6 times and 4.3 times while for lime-treated samples the respective increases were about 2 times and 2.25 times. The loss in soil-cement of cement-treated samples reduced with the increase in cement content. Although, the cement-treated samples did not meet the PCA (1956) durability requirements, the samples treated with 3% and 5% cement, however, fulfilled the requirements as suggested by Compendium 8 (1979).

It was found from comparisons that the values of qu, CBR, flexural strength and flexural modulus of the cement-treated samples of Banshkhali were significantly higher than those of the lime-treated samples. Moreover, it is expected that compared with soil-lime mix, soil-cement mix would be much more durable in the weather conditions of tropical regions. It could be concluded that cement stabilisation of the coastal soils studied would be more suitable than lime stabilisation for their use in road construction.

Analytical results indicated that at a particular modulus and CBR, the thicknesses of soil-cement base (for both unpaved and paved road) and soil-lime sub-base increased with increasing allowable number of load repetitions to fatigue (N) and that for any particular value of N, the values of thicknesses of soil-cement base (for both unpaved and paved road) and soil-lime sub-base reduced as modulus of soil-cement base and soil-lime sub-base increased. Design charts have been developed for the three types of roads analysed and it has been found that, in general, at any CBR and N, the thickness of cemented layer reduced as modulus of the cemented layer increased.

 

Thesis Title

EFFECTS OF SAMPLING DISTURBANCE ON MECHANICAL PROPERTIES OF RECONSTITUTED NORMALLY CONSOLIDATED AND OVERCONSOLIDATED DHAKA CLAY

 

Name of the Student

Md. Mokhlesur Rahman

 

Supervisor

Department

Dr. Abu Siddique

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     September, 2000

Abstract

The present study has been carried out to investigate the effect of sampling disturbance on mechanical behaviour  of reconstituted  normally consolidated and overconsolidated Dhaka clay (OCR values of 2, 5 and 10).. Disturbed Dhaka clay samples were collected from Rupnagar Housing Project, Mirput-11, Dhaka. The clays were low to medium plasticity (LL= 47, PI= 26). Reconstituted normally consolidated samples of Dhaka clay were prepared in the laboratory by K0-consolidation of slurry in a large cylindrical consolidation cell using a consolidation pressure of 150kN/m2 while overconsolidated samples having OCR values of  2, 5 and 10 were prepared by reducing the maxmimum pressure of 150 kN/m2 to 75 kN/m2, 30 kN/m2 and 15 kN/m2 respectively. “In situ” samples were prepared (by consolidating 38 mm diameter by 76 mm high specimens under K0-conditions in the triaxial cell) to its “in situ” stress state. “Tube” samples of various OCR values were prepared from the large diameter consolidated sample by inserting samplers of different area ratio, external diameter to thickness ratio (De/t) and outside cutting edge angle (OCA). The area ratio, De/t ratio and OCA of the samplers varied from 16.4% to 73.1%, 27.3 to 8.3 and 5° to 20° respectively. Normally consolidated and overconsolidated “perfect” samples were prepared from respective “in situ” samples by undrained release of the total stress in the triaxial cell. Undrained triaxial compression tests were carried out on “in situ” “tube” and “perfect” samples. “Tube” and “perfect” samples having OCR values of 2 and 10 were also reconsolidated isotropically and anisotropically under K0-condition using BjerrUM (CKoU-1.0s¢vc) and SHANSEP (CKoU -1.5s¢vc and (CKoU -2.5s¢vc) procedures.

Disturbance due to perfect and tube sampling have significant influence on the mechanical properties of normally consolidated and over consolidated Dhaka clay. Disturbance due to perfect sampling led to reduction in the value of su and Ap while Ei, E50 and ep increased caused due to total stress relief. Because of perfect sampling undrained strength (su) reduced up to 8.2% while, axial strain at peak deviator stress (ep) increased up to 20.9% for samples of OCR value of 10. Due to perfect sampling pore pressure parameter at peak deviator stress (Ap) reduced up to 90% while, initial tangent modulus (Ei) and secant stiffness at peak half deviator stress E50) increased up to 14.0% and 19% respectively for normally consolidated sample. Due to total stress relief for perfect sampling disturbance, the reduction in su increases with increase in OCR while, the increase in Ei, E50 reduce with increase in OCR.

The initial effective stress (s¢i) of “tube” samples reduced considerably because of disturbance caused by penetration of tubes. Compared with “in situ” samples, values of su, Ei, E50 and Ap of the “tube” samples reduced while ep  increased. Changes in measured soil parameter between the “in situ” and “tube” samples have been found to depend significantly on the sampler characteristics (area ratio, De/t ratio and OCA) used for retrieving the “tube” samples. The values of s¢i, su, and Ei were reduced up to 26.2%, 43% and 62% respectively for normally consolidated sample due to increase in area ratio from 16.4% to 73.1% (or reduction in De/t ratio from 27.3 to 8.3). The respective reductions for normally consolidated sample due to increase in OCA from 4° to 15° are 21.9%, 38% and 60%. Values of ep for OCR values of 1 and 5, increased up to 57.7% and 52.6% due to increase in area ratio and OCA respectively. A quantitative increase in the degree of disturbance (Dd) has been obtained due to increase in area ratio and OCA. The results indicate that compared with normally consolidated reconstituted Dhaka Clay, tube sampling causes relatively little degree of disturbance in overconsolidated reconstituted Dhaka Clay. The reduction in initial effective stress due to tube sampling reduces with increase in OCR. The increase in value of ep due tube sampling reduce with increasing OCR. For tube sampling disturbance, trend of small decrease in the reduction of su/s¢vc, E i/s¢vc and E 50/s¢vc was obtained with increasing OCR. However, significant increase in reduction of Ap with increasing OCR also been observed.

It appeared that for good quality sampling, a sampler ought to have a well combination of area ratio and OCA. In order to reduce disturbance due to sampling in soft Dhaka clay, are ratio and OCA of sampler should be kept practically as low as possible. A correction curve has been provided from the plot of strength ratio versus overconsolidation ratio for samples of Dhaka clay. This correction curve can be used to find the perfectly undisturbed strength of the tube samples of Dhaka clay for use in analyses and designs.

Isotropic reconsolidation (CIU-1.0s¢vc) has the effect of gross overestimation of “in situ” strength, ep and Ei for the “tube” and “perfect” samples. It has been found that compared with SHANSEP procedures reconsolidation using Bjerrum procedure (CKoU-1.0s¢vc) for both “tube” and “perfect” samples of overconsolidated Dhaka clay, produced the best overall estimate of the “in situ” properties in terms of undrained strength, stiffness, strain and pore pressure response.

 

Thesis Title

GEOTECHNICAL CHARACTERIZATION OF DHAKA METROPOLITAN AREA

 

Name of the Student

Md. Abul Bashar

 

Supervisor

Department

Dr. Abu Siddique

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     July, 2000

Abstract

The present study has been carried out to develop generalized soil profiles of Dhaka Metropolitan area. Attempt has been made to investigate the variation of the soil properties with depth and to establish approximate correlation among different geotechnical properties of the sub-soil of the Dhaka Metropolitan Area. Attempt has also been made to verify the existing soil data by drilling a number of test bore holes.

About 300 sub-soil investigation reports consisting of data of 674 boreholes were collected from different drilling companies, civil consulting firms and other organizations of different places of Dhaka Metropolitan Area. Majority of the borings were drilled up to depth of 50ft to 60ft and a feew borings were drilled up to 100ft. Dhaka city map, bounded by longitude 90°20¢ to 90°27¢E and 23°41¢ to 23°53¢N, has been divided into grids by four by longitudinal grid lines long North-South direction and five cross grid lines along East-West direction. These grid lines were spaced at 2 minutes interval. All borehole site location points were inserted on the Dhaka city map. One site location point consists of multiple number of boreholes. Under the scheme of the  research, seven test borings of 100 ft depth were drilled in the vicinity of the grid points.

Soil profiles established for Dhaka Metropolitan area, in general, showed soft to very stiff cohesive layers at the top strata up to depth of 20 ft. At large depths, the soil layers have been found to consist of loose to very dense sandy soils. In some areas of the eastern region of Dhaka Metropolitan, However, cohesive layers up to depth of 100ft have been encountered. Range of the values of different soil parameters near the locations of sixteen grid points of Dhaka Metropolitan area has been summarized. The soil parameters considered are N-value, liquid limit, plasticity index, natural moisture content, grain size fractions (percentages of sand, silt and clay), unconfined compressive strength, compression index (Cc) and initial void ratio. Geotechnical properties of the sub-soil of Dhaka metropolitan area were found to vary with depth. In general, water content, liquid limit and plasticity index decrease with the increase in soil depth. The percentage of coarser material increases with the increase in soil depth.

The relationship between unconfined compressive strength (qu) and standard penetration resistance (N) can be expressed as qu = N/2.77 ksf. It has been found that the proposed relation between qu and N for Dhaka clay samples compared favourable with the correlation proposed by other researchers. The relation between plasticity index and liquid limit for the cohesive soil samples of Dhaka Metropolitan area showed that majority of the samples are clays of low to medium and medium to high plasticity. A few samples were, however, cohesive silts. A trend of decrease in unconfined compressive strength with the increase in natural water content has been observed while an increase in the value of compression index with the increase in initial void ratio (e0) was found for samples of Dhaka Metropolitan area. A trend of increase in the value of the ratio Cc/(1+e0) with the increase in natural moisture content value has been observed for samples of Dhaka Metropolitan area. No conclusive relation could not be found between compression index and plasticity index for samples of Dhaka Metropolitan area.

The collected soil data were compared with those obtained from the test boreholes in order to verify the available type of strata and N-values. In a number of locations, the soil profile and N-values obtained from the test boreholes compared favourably with those obtained from the available borehole data drilled in the vicinity of the test boreholes. In some locations, however, the soil profile and N-values obtained from the test boreholes were different from those obtained from the available boreholde data drilled adjacent the location of test boreholes.

 

Thesis Title

INFLUENCE OF STRUCTURE PARAMETERS ON PERIOD OF FRAME STRUCTURES FOR EARTHQUAKE RESISTANT DESIGN

 

Name of the Student

Md. Zahid Hossain

 

Supervisor

Department

Dr. A. M. M. Taufiqul Anwar

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     January, 1997

Abstract

Codes of practice suggest equivalent static force method for earthquake resistant design of frame structures of moderate height. For regular frames, the codes propose approximate formulae for fundamental period required for the evaluation of base shear. These formulae describe period either as a function of height of the structure or number of stories. Lack of reflection of other structure parameters makes them grossly approximate. An investigation is conducted in this work to assess the influence of different structure parameters on the period of regular frame structures. Model frames, divided into six major groups are subjected to modal analysis to evaluate the fundamental frequency and corresponding period. General purpose finite element package ANSYS, Revision 5.2, has been employed to conduct the analyses. The analysis tool assumes constant stiffiness and mass effects and neglects damping. Appropriate elements are selected from ANSYS element library to model the frames. ANSYS option of lumped mass approach has been used for mesh elements. Masses of secondary structures are added as point mass elements at nodal points. Modal analysis has been used as analysis type and reduced method as analysis option. The extracted eigenvaleus and the corresponding eigenvectors represent the frequencies and mode shapes respectively. The fundamental period is obtained from the lowest frequency.

An extensive parametric study is conducted to identify influence of parameters like numbers and width of bays, numbers and height of stories, stiffiness of columns and beams and strength and density of concrete on fundamental period. Effect of inclusion of floor slabs and masses of secondary structural elements in the analysis is also studied. The period has been found to increase with decreasing number of bays along the direction of motion or increasing number of bays transverse to the direction of motion. An increase of bay width, story height  or number of stories leads to an increase of period. Approximate code formulae are found to become increasingly conservative with increasing structure height in evaluation of earthquake forces.

Use of stiffer columns and beams or concrete of higher strength has a reducing effect on period. It has been revealed that application of approximate code formulae in cases of low rise structures with stocky columns and beams or with concrete of higher strength may lead to an understimation of earthquake forces. A reduction in beam height or column dimension in the direction of earthquake forces or choice of low strength concrete are found to reduce design earthquake forces. In most practical cases, the approximate code formulae lead to a conservative estimation of earthquake forces.

 

Thesis Title

COMPARATIVE STUDY OF COPPER CONTAMINATION IN THE WATER AND SEDIMENT COLUMN OF THE RAMNA LAKE AND DHANMONDI LAKE

 

Name of the Student

Hafiz Ahmad

 

Supervisor

Department

Dr. A. B. M. Badruzzaman

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     February, 1998

Abstract

The primary objective of this study was to assess the level of copper contamination in the lake water and sediment of Dhanmondi and Ramna Lakes. The other major objectives were determination of equilibrium speciation of copper in lake water in order to assess its toxic effects, determination of spatial distribution of major copper species, evaluation of copper adsorption characteristic on different sizes of bed sediment particles of both the lakes and assessment of gross bioaccumulation of copper in fish.

Water and sediment samples of Dhanmondi and Ramna lakes were collected from different sampling locations for laboratory analysis during three different periods of the year namely, dry period (April to May), wet period (June-July) and intermediate period (August-January). Sediment samples were collected to assess the nature of copper adsorption on the bed sediment particles. In addition, bioaccumulation of copper in fish of the lake was assessed by determining copper concentrations in various parts including gill, stomach etc. of a fish (Nilotica) of Dhanmondi lake.

Both the Dhanmondi and Ramna lake water and sediment layers were found to be heavily contaminated with copper. Maximum and minimum concentrations of copper in the water of Dhanmondi lake was 0.2913 mg/1 and 0.062mg/1 and in Ramna lake 0.2047 mg/1 and 0.0723mg/1, respectively. Major aqueous copper species found in both the Dhanmondi and Ramna lakes were Cu(OH)2, Cu2+, CuCO3, concentration of Cu(OH)2 was maximum. Cu2+, the free and most toxic form of copper species was also present in considerable amounts. pH was found to be the major controlling factor for copper speciation. With a decrease in pH, ionic copper (Cu2+) concentration increase thus increasing the toxicity of water. Conversely, with an increase in pH, ionic copper concentration decreases with increased adsorption reducing toxicity.

Analysis of sediment samples suggest that maximum amount of copper was adsorbed on particles retained on sieve # 30, # 40, # 50 (i.e. size <1.19mm to >0.297mm). In most cases, copper absorption increased with the decrease in particle size upto a certain level (0.42mm). After that particular particle size copper absorption decreased with the decrease in particle size. From the analysis of bed sediment it was found that maximum copper concentrations in top and bottom layers of Dhanmondi lake were 59.45 mg/kg and 52.28 mg/kg, respectively. In Ramna lake copper concentration in top and bottom layers were 47.77 mg/kg and 46.21 mg/kg respectively.

Study of bioaccumulation of copper revealed that copper is present in excessive amount in the different parts of fish in Dhanmondi lake. Maximum copper concentration was found in the stomach (7.442 mg/kg) of fish. Thus, human consumption of the fishes from Dhanmondi lake may be harmful.

At persent renovation work is underway at the Dhanmondi lake. It seems that the lake is dredgedbridged indiscriminately and the dredged spoils are being piled along the shore. If not done upto a proper depth this dredging process is likely to expose the soil layer heavily contaminated with copper. (The ovelying fresh water way be contanuinated through)diffusion and desorption from the newly exposed bed. In addition, the dredged spoils piled along the shore may release copper following rainfall into the lake and surrounding areas.

 

Thesis Title

PERFORMANCE OF THE EXISTING SEWERAGE SYSTEM OF DHAKA CITY AND PAGLA SEWAGE TREATMENT PLANT

 

Name of the Student

Md. Naziruzzaman

 

Supervisor

Department

Dr. A. B. M. Badruzzaman

Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     July, 1999

Abstract

The sewerage system of Dhaka city was initiated in 1923 with about 50 km sewer lines and an imhoff tank type treatment plant. Till to date about 531 km sewerage network, 20 sewage lift stations have been developed in different phases at different times to keep pace with the expansion of the city. The first conventional sewage treatment plant with 4 facultative lagoons built at Pagla in 1968 was renovated in 1977. The present sewage treatment plant at Pagla was rehabilited and expanded in 1992 to treat a capacity of 120,000 m3/day sewage with influent BOD5 of 200 mg/1 and effluent BOD5 of 50 mg/1.

About 150,000m3/day wastewater is presently being generated within the sewerage covered area of which only 28% find it’s way to reach Pagla sewage treatment plant. Remaining 72% of sewage generated is discharged to the environment through leakages, overflows, etc. of the network, creating tremendous pollution, hence affecting the human health. From the study it is found that under present situation about 50% of the city sewerage network is undersized, a large portion of the trunk mains are in low lying areas without service road. Some portion of the sewer mains is under the roads or even under structures. In addition, the sewer mains have construction defects like frequent improper sewer gradients, syphones, etc. Due to the defective construction of sewers manholes always remain flooded with several feet of wastewater. In this study, it is also observed that there are several leakages in the sewerage network including completely blocked manholes. The outlet sewer of the Dhaka Medical College sewage lift station is broken and sewage is being pumped into the nearby surface drain. Most of the sewage lift stations were constructed or designed in such way that the back-flow/submersion of intake frequently takes place with subsequent septic condition in the sewage. This is one of the major reasons for high BOD5 value. Pumps of the sewage lift stations are very old and needs frequent repair.

An average of 28% (43,000 m3/day) of generated wastewater is being treated by the Pagla Sewage Treatment Plant (PSTP) at present. From the study it is found that the performance of the primary sedimentation tanks are acceptable and that of facultative lagoons are not satisfactory. The influent BOD5 value of the sewage treatment plant is as high as 4,100 mg/1, which was designed for a influent BOD5 value of 200 mg/1. The effluent BOD5 value is much higher, some 240 mg/1 instead of designed value of 50 mg/1. The observed effective sewage depths of the lagoon are around 1.0m though these were designed for an effective sewage depth of 2.0m. On the bottom of the lagoons about 0.30m height of suspended solids found to have settled. The laboratory of the treatment plant is not well equipped to conduct regular monitoring. The sludge lagoons are functioning well and are in good condition. There exists a liquid chlorination system at the outlet of the plant with a dosing of 3.0 ppm and performing twice a day from 6 A.M. to 9 A. M. and 2 P. M. to 4 P. M.

For the improvement of the sewerage system, rearrangement and redesign is recommended. Moreover, the entire Dhaka City should be covered under sewerage system. It is also recommended to specifically identify the reasons of the high BOD5 value in the sewage including a proper inventory of effluent quality, discharge points, etc. of different industries. Change of old pumps of the sewage lift stations with suitable new ones like variable speed pumps may be introduced to overcome the problems of the lift stations.

 

Thesis Title

ANALYSIS OF HEAVY METALS IN BED SEDIMENTS OF DHANMONDI LAKE

 

Name of the Student

Khandaker Nurul Ashfaque

 

Supervisor

Department

Dr. A. B. M Badruzzaman

Associate Professor

Department of Civil Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     November, 1999

Abstract

The Dhanmond Lake, the largest urban lake of the Dhaka City, has been receiving domestic as well as industrial sewate for a long time. The primary objective of the study was to assess the heavy metal contamination of the sediment column of Dhanmondi Lake at different locations. Secondary objectives include the determination of any possible relationship between metal concentration with particle size, vertical distribution of metal, assessment of association of metal with the organic and inoraganic fractions and estimation of partition coefficient of a specific heavy metal.

Sediment samples from ten locations of Dhanmondi Lake were collected from various depths. Locations were selected considering the probable sources of contamination from sewer lines connected to the Lake. In general, the soil samples were found to be grayish to black in color indicating high organic content. This can be attributed to disposal of domestic and industrial sewage. However, at greater depths reddish silty clay soil’ were distinctly visible which represent the original bed soil of the Lake. Samples were oven dried, ground and sieved. Then the samples were digested and the concentrations of different heavy metals (copper, lead, cadmium, chromium and mercury) at different depths were determined for each particle size using an Atomic Adsorption Spectrometer.

The general trend of copper distribution associated with particle sizes indicates that the copper concentration increases with the decrease of particle size up to 0.30mm, then it decreases with the decrease in particle size ranging between 0.30mm to 0.15mm. This trend changes again and the copper concentration increases with decrease in particle size. In case of lead, the concentration increases with the decrease in particle size upto 0.15mm. Then it decreases with the decrease in particle size of 0.15-0.075mm. Finally, it increases slightly with the decrease in particle size. No general pattern of cadmium distribution with particle size has been observed. However, test results indicate that higher cadmium concentration is associated with particle size between 0.6-0.3mm at all locations irrespective of depth. Concentration distribution of chromium with particle sizes generally followed two distinct patterns: (a) chromium concentration increases upto 0.15mm particle size, then decrease for particle sizes 0.15-0.075mm and then increases again; (b) chromium concentration decreases upto 0.075mm particle size and then increases. However, in both of the patterns the lowest cadmium concentration was found to be associated with particle sizes of 0.075mm.

Mercury is probably the most toxic metal available in the environment even at very low concentrations. But due to lack of resources very limited number of samples were tested for the presence of mercury. Vertical distribution of mercury concentration as well as those of other metals indicated a higher level near the bed surface, which subsequently decreased as the depth increased. Samples collected from near the Pikhana BDR Gate exhibited highest concentration for all metals among all the locations. However, the average concentration level throughout the lake sediment is alarming.

The laboratory results indicate that the major fractions of the heavy metals are associated with the organic fraction of the soil. However, it should be noted that during washing of the samples to separate organic fraction using NaOH, a significant portion of iron (oxy) hydroxides (and probably some other oxide particles as well), which provides the surface for adsorption of heavy metals on sediments, might have been washed out from the inorganic fraction. In general, the heavy metal concentration was found to increase with the increase in organic content. In order to estimate the partition coefficient of a specific heavy metal, a synthetic sample was prepared in the laboratory and was dosed with different metal solutions. The analysis of the synthetic sample does not provide any conclusive evidence. This may be attributed to the fact that the synthetic samples were analyzed only 72 hours after dosing which might not have given enough time to allow proper adsorption of all metals. Also, the chemical composition of the synthetic soil sample might have been different than that of bed sediment of Dhanmondi Lake.

At present, the restoration work of the Dhanmondi Lake is in progress. A massive excavation campaign was conducted to remove the contaminated bottm  sediment. At some locations the excavation was carried out to reveal the original formation. However, at most of the places this was conducted to partially remove the contaminated soil leaving the highly contaminated soild layer exposed to the fresh water to be introduced. This will definitely pollute the overlying water layer. In addition, these excavated contaminated soils were used for landfilling purposes within the city areas leaving the population and aquatic biota susceptible to heavy metal pollution.