Ph.D.http://hdl.handle.net/20.500.12228/242024-03-29T12:50:55Z2024-03-29T12:50:55ZNon-Linear Finite Element Analysis of Wall-Beam StructuresHossain, Dr. Md. Monjurhttp://hdl.handle.net/20.500.12228/4452018-08-30T21:00:23Z1997-05-01T00:00:00ZNon-Linear Finite Element Analysis of Wall-Beam Structures
Hossain, Dr. Md. Monjur
The composite action between masonry wall and its supporting beam
concentrates the vertical loading applied on the top of wall close to the beam supports.
This produces bending moments much less than would be expected when the full load
is acting directly on the beam. The study of this composite action is of economic
importance since if the concept is utilised, a rational design of the beam will be
achieved.
This thesis presents a comprehensive material model and its incorporation into
non-linear finite element computer model for the analysis of wall-beam structures
made with brickwork of solid brick subjected to uniformly distributed load. The
program is incremental in nature and capable of reproducing the non-linear behaviour
caused by material non-linearity and progressive local cracking and crushing. The
program is thus capable of modelling the behaviour of wall-beam structures subjected
to non-linear load from first crack to final failure. The material model used in this
program is derived from tests on representative samples of brick, mortar and small
samples of brickwork.
In the finite element model brick, mortar, concrete and steel are treated as
separate materials along with the simulation of actual directional effects of mortar
joints. A series of failure criteria have been adopted to model the different modes of
failure experienced in the constituent materials. Due to the crack sensitive nature of
the problem, particular emphasis has been given to the modelling of cracking and the
post-cracking behaviour of the materials, especially the manner in which the local
stresses in the fractured region are redistributed.
The results of finite element model have been verified by comparison with
experiments on brick masonry wall-beam structures subjected to uniformly distributed
load applied at the top and extending over the full length and thickness of the wall.
Comparison with published literature reveals that the present method can provide a
more comprehensive prediction of behaviour of the wall-beam structure up to failure
load.
Sensitivity analyses of the various parameters defining the material model and
the boundary conditions have been canied out. With the important parameters thus
obtained, the finite element model has been used to carry out a comprehensive
parametric study of the behaviour of storey height wall-beams subjected to uniformly
distributed load. Based on the findings of this study, design recommendations have
been proposed. As the computer program developed can handle general cases with
arbitrary geometry, loading and boundary conditions, recommendations for
investigations of various other wall-beam structures have been made.
This thesis is submitted to the Department of Civil Engineering, Bangladesh University of Engineering and Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy, May 1997.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 248-257).
1997-05-01T00:00:00ZStress-Deformation Characteristics of Selected Coastal Soils of Bangladesh and their Sampling EffectsBashar, Md. Abulhttp://hdl.handle.net/20.500.12228/2702018-09-18T09:24:34Z2002-03-01T00:00:00ZStress-Deformation Characteristics of Selected Coastal Soils of Bangladesh and their Sampling Effects
Bashar, Md. Abul
A considerable development activity within the Coastal Region of Bangladesh has necessitated an understanding of the geotechnical behaviour of soils from this region. With this objective in view a study into strength-deformation, compressibility and intrinsic properties of reconstituted samples of Chittagong coastal soils were undertaken. This thesis presents stress-deformation characteristics of three selected coastal soils and their sampling effects. The soils were collected from Banskhali, Anwara and Chandanaish in Chittagong coastal belt of Bangladesh. The soils are low to medium plasticity (Liquid limit = 34 to 45 and Plasticity index = 10 to 20). Reconstituted samples of the three soils were prepared in the laboratory by K0- consolidation of slurry in a large cylindrical consolidation cell using a consolidation pressure of 150 kN/m2. Overconsolidated samples were prepared in the triaxial cell by releasing the maximum isotropic consolidation pressure of 150 kN/m2 to appropriate values to achieve overconsolidation ratios (OCR) of 1.5, 2, 5, 10, 20 and 30.
The stress-deformation-strength, stiffness and pore pressure characteristics of reconstituted isotropically normally consolidated and overconsolidated "block" samples of the three coastal soils were investigated in the laboratory by performing undrained triaxial compression tests. Models for the prediction of undrained shear strength of normally consolidated and overconsolidated samples have been developed. To develop intrinsic models of compressibility, intrinsic compression lines (ICL) for the three soils under K0 and isotropic stress conditions have been established which can be used to determine compressibility indices of soils at any depth of known overburden pressure. State boundary surfaces (Roscoe and Hvorslev state boundary surfaces) and critical state lines of the three coastal soils have been established. The critical state parameters of the soils have also been evaluated. Constitutive models relating critical state soil parameters and plasticity index of the soils have been proposed. Applications of these models to undisturbed naturaj clays will require further investigation. The experimentally observed stress-strain behaviour of reconstituted normally consolidated samples of the three coastal soils have been compared with those predicted using two critical state models, namely, "Cam clay model" and "Modified Cam clay model". It has been found that the results predicted by using "Modified Cam clay model" compared more favourably with the observed experimental results than "Cam clay model" for the three coastal soils.
The present study has also been carried out to investigate the effects of "perfect" sampling disturbance and tube sampling disturbances on engineering properties of reconstituted normally consolidated samples of the three coastal soils. Undrained triaxial compression tests were carried out on "in situ", "perfect" and "tube" samples. "In situ" samples were prepared by consolidating reconstituted specimens of 38 mm diameter by 76 mm high under K0-condition in the triaxial cell to its in situ stress state. "Perfect" samples were prepared from "in situ" samples by undrained release of the total stresses in the triaxial cell. "Tube" samples were prepared from the large diameter consolidated samples by inserting samplers of different area ratios, external diameter to thickness ratio (De/t) but of constant outside cutting edge angle (OCA) and internal diameter (Di). Area ratio, De/t ratio, OCA and Di of the samplers were 16.4% to 73.1%, 27.3 to 8.3, 5° and 38 mm, respectively. Undrained triaxial compression tests were carried out on reconsolidated "perfect" and "tube" samples of the three coastal soils to assess the suitability of various reconsolidation techniques to minimize sampling disturbance effects.
Experimental results indicate that disturbances due to perfect and tube sampling have significant influence on the mechanical properties of coastal soils. The nature of the effective stress paths and por' pressure responses of both "perfect" and "tube" samples are markedly different from those of the "in situ" samples. The "perfect" and "tube" samples adopted stress paths and showed pore pressure responses which are more typical of overconsolidated clays. Disturbances due to perfect sampling led to reduction in the values of undrained shear strength (se), Skempton's pore pressure parameter A at peak deviator stress (Ap), initial tangent modulus (Ei) and secant stiffiess at half the peak deviator stress (E50) whilr axial strain at peak deviator stress (εp) increased due to total stress relief. Due to total stress relief, the reduction Su, Ei and E50 increased with the decrease of plasticity while the increase in c. increased with the decrease of plasticity of the soils. It is also evident that the decrease in mean effective stress (p') due to perfect sampling increases with decreasing plasticity of the soils. The initial effective stress (σ՛i) of "tube" samples reduced considerably because of disturbance caused by penetration of tubes. Compared with the "in situ" samples, values of s, E1, E50 and A of the "tube" samples decreased while sp increased. The changes in measured soil parameters between the "in situ" and "tube" san )les have been found to depend significantly on the sampler characteristics, i.e., area ratio, De/t ratio, used for retrieving the "tube" samples. The values of σ՛i, su, Ei and E50 were decreased due to increase in area ratio (or reduction in De/t ratio). The values of εp, however, increased due to increasing area ratio. A quantitative increase in the degree of disturbance (Dd) has been obtained due to increase in area ratio, while the values of Dd increased with the decrease of De/t ratio of sampler. Disturbance due to tube sampling has been found to depend on the plasticity of the samples of the three coastal soils. The highest reductions in a', st,. Ei and E 0 occurred in the least plastic samples, whereas the minimum reduction in σ՛i, su, Ei and E50 occurred in the most plastic samples. Among the samples of the coastal soils, the least plastic sample produced higher degree of disturbance than the most plastic sample.
This thesis is submitted to the Department of Civil Engineering, Bangladesh University of Engineering & Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering, March 2002.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 309-320).
2002-03-01T00:00:00ZDevelopment of Sustainable Cement Mortar Incorporating Rice Husk AshRashid, Muhammad Harunurhttp://hdl.handle.net/20.500.12228/2552018-09-18T09:24:56Z2011-12-01T00:00:00ZDevelopment of Sustainable Cement Mortar Incorporating Rice Husk Ash
Rashid, Muhammad Harunur
The study for the development of sustainable cement mortar incorporating rice husk ash was conducted by several approaches. Several researchers have been conducting research to replace the ordinary Portland cement by new materials with pozzolanic and cementitious properties. The aim of this study was to investigate the performance of cement mortar with rice husk ash for its sustainable development. A detail investigation was conducted to produce the rice husk ash with appropriate properties by effective incineration process. The fineness of rice husk ash based on different incineration systems, retention time and grinding time was determined. Characterization of rice husk ash was performed with XRD, SEM and chemical composition analysis. The effect of rice husk ash on heat of hydration was examined. Eventually, the performance of cement mortar with different proportions of rice husk ash was evaluated based on strength, permeability, sorptivity, salt crystallization, resistance to sulphate attack and effect of elevated temperature ranging from 200 to 700°C. The result shows that the highest fineness of 6894 cm2/gm was obtained for rice husk ash produced in laboratory burning system with 60 hours retention and 180 minutes grinding. The result of XRD confirmed the amorphous state of rice husk ash produced in laboratory burning system at 663.6°C. The maximum compressive strength of 33.09 MPa at 28 days was found for control sample. The highest compressive strengths at later age of 90, 350, 600 and 900 days were found to be 38.08, 38.80, 39.09 and 39.23 MPa respectively for 20% replacement with rice husk ash. The highest permeability of 4905 columbs was found in case of control sample at 28 days age. The result indicates that the permeability is inversely proportional to rice husk ash and curing age of sample. The trend of sorptivity was found similar to permeability and the highest value of control sample was found to be 0.214 kg/m2-min0.5. It was found that the mortar samples with 15% and 20% rice husk ash sustained up to standard 20 cycles in salt crystallization. No crack or spalling was observed due to sulphate attack on the mortar samples with 15 and 20% replacement of OPC with rice husk ash. The control sample exhibits the highest strength of 44.47 and 23.85 MPa at 200 and 700°C respectively. The sample having 15% rice husk ash shows maximum strength of 48.26 and 43.52 MPa at 300°C and 400°C respectively while the highest strength was obtained at 500°C for sample with 20% rice husk ash. The findings of the present study would contribute to the sustainable development of cement mortar incorporating rice husk ash.
This thesis is submitted to the Department of Civil Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering, December 2011.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 139-160).
2011-12-01T00:00:00ZEvaluation of Contamination Potential and Treatment Techniques of Leachate Generated from Landfill LysimeterIslam, Md. Rafizulhttp://hdl.handle.net/20.500.12228/2542018-09-18T09:25:14Z2014-08-01T00:00:00ZEvaluation of Contamination Potential and Treatment Techniques of Leachate Generated from Landfill Lysimeter
Islam, Md. Rafizul
In this study one open dump lysimeter with leachate detection and collection system as well as two sanitary lysimeter having two different types of cap liner were simulated. After designing a reference cell, construction of landfill lysimeter was started in January 2008 and completed in July 2008. In all construction process locally available civil construction materials were used. The municipal solid waste (MSW) of 2800 to 2985 Kg having the total volume of 2.60 m3 (diameter 1.48 m; height 1 .6m)
as well as moisture and organic content of 65, 52 %, respectively, was deposited in each lysimeter by applying required compaction energy. This study endeavors to characterize leachate and investigate the tropical climatic influence on leachate characteristics under different seasonal variation. The leachate characteristics, leachate generation and climatic influence parameter had been monitored since June 2008 to Dec. 2010. These periods covered both the dry and rainy season. The leachate generation followed the rainfall pattern and open dump lysimeter-A without top cover demonstrated more leachate generation due to percolation of rainfall than that of sanitary lysimeter-B and C.
Open dump lysimeter-A showed lower concentration of TKN and NH4-N as well as TKN load, while both the concentration and load of COD higher in compared to sanitary lysimeter-B and C. Sanitary lysimeter-B, not only revealed lower leachate generation, but also produced reasonable lower concentration and load of COD in compared with open dump lysimeter-A. Result depicted that lysimeter operational mode had direct effect on leachate quality. In contrary, sanitary lysimeter-C showed higher composition of LFG in compared to sanitary lysimeter-B due to the providing of lower compaction of cap liner in sanitary lysimeter-C. in absence of compacted clay liner (CCL) and hence percolation of rainwater that facilitated rapid degradation of MSW in open dump lysimeter-A and resulted in higher settlement than that of sanitary lysimeter-B and C. In sanitary lysimeter-B and C, leachate generation showed lesser amount than that of open dump lysimeter-A due to the providing of cap liner in lysimeter-B and C, played an important role to reduce the percolation of rainwater. Study revealed leachate pollution index (LPI) and sub-pollution indices (sub-LPI) for lysimeter significantly higher and proper treatment to be necessary before discharging the leachate into the water bodies.
To meet the standard discharge condition lysimeter leachate was treated in the laboratory through the phytoremediation treatment process by using aquatic reactors of duckweed, snail, helencha and topapana, but the removal efficiency was not satisfactory. Then the leachate was treated through the chemical coagulation process by using FeCl3, PAC, FeSO4 and Al2(SO4)3 in various dosages and pH. Result revealed that FeCl3 more effective for removing pollutant. In the laboratory, leachate was further treated by using FeCl3 at optimum dosage and the concentration and consequently the values of LPI of treated leachate were found within the limit of maximum discharge standards. Finally, it can be concluded that leachate generated from lysimeter may be discharge after required level of chemical treatment into the natural streams to maintain the limit of maximum discharge standards.
This thesis is submitted to the Department of Civil Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering, August 2014.; Cataloged from PDF Version of Thesis.; Includes bibliographical references (pages 246-269).
2014-08-01T00:00:00Z