http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/273 2026-04-21T22:00:47Z 2026-04-21T22:00:47Z HOQUE, MD. ASRAFUL http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/1048 2025-12-03T13:03:18Z 2024-03-01T00:00:00Z

STRENGTH, STIFFNESS AND FAILURE MECHANISM OF DOUBLE SHEAR WELDED CONNECTIONS BETWEEN COLD-FORMED AND HOT-ROLLED STEEL HOQUE, MD. ASRAFUL Cold-formed steel is widely used for routine structural steel design including portal frames composed of open and/or closed sections. Nowadays, cold rolled steel channel and Z sections are now used in structure as a structural member with the hot rolled steel by welding connection. The connection between hot rolled and cold rolled steel is very important in the structure. Structural behavior of steel structures generally depends on the rigidity of the connections and their force transfer mechanism. In the present study, an experimental investigation has been conducted on double shear welded connections made of ASTM A653 Gr.50 and ASTM A36 grades of cold-formed steel. Primarily a set of coupons extracted from the cold form steel of different thicknesses and steel grades are tested under uniaxial tension to understand their actual strength and modulus of elasticity. In addition, a total of 4 numbers of weld coupons are fabricated to determine different weld specifications used in this study. Finally, 24 test specimens of double shear welded connections are formed by overlapping two cold-formed steel plates of similar thickness with the two hot rolled steel plates and forming a double shear welded connection at the joint. The influence of weld strength, plate strength, and plate thickness on joint behavior is evaluated meticulously by employing standard data acquisition system. These weld connections are tested on tensile loading until failure. The response of the double shear welded connections for varying material properties is examined in terms of load-elongation plot, connection strength, failure mode, stiffness, and ductility. It is observed, that with the increase of plate thickness failure mode changes from net-section fracture to weld throat failure. Usually increasing weld strength, steel grade, and plate thickness shows a rise in joint capacity and stiffness. Current American design provisions are evaluated for these ASTM A653 Gr.50 and ASTM A36 grade samples. Research into the Heat Affected Zone (HAZ) strength resulting from joint welding reveals a reduction in joint capacity of 6 to 19% due to the Heat Affected Zone (HAZ) effect. Strength, Stiffness and Failure Mechanism of Double Shear Welded Connections Between Cold-Formed and Hot-Rolled Steel

2024-03-01T00:00:00Z MUNIRUZZAMAN, MD. http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/828 2024-06-11T06:31:55Z 2023-12-01T00:00:00Z

EFFECT OF CARBON FIBER REINFORCED POLYMER RETROFITTING ON RECYCLED BRICK AGGREGATE CONCRETE COLUMN MUNIRUZZAMAN, MD. Most old structures in Bangladesh are found to be made of poor-quality materials, lowstrength concrete (about 17 MPa), and brick aggregate because of the acute scarcity of natural stones in the early days. Moreover, some of them were constructed without proper compliance with the existing codes, and the updated building code demands a more stringent design philosophy. Hence, strengthening the structures to comply with the recent design guidelines becomes an issue of utmost significance. The study examined the feasibility of using CFRP jacketing to retrofit inferior-quality columns in Bangladesh. In this study, one-third scale columns made of low-strength recycled brick aggregate concrete (17 MPa and 10 MPa), with square and rectangular shapes having dimensions of 150 mm x 150 mm x 950 mm (kl/r = 21.94, l/h = 6.33) and 150 mm x 225 mm x 950 mm (kl/r = 14.63, l/h = 4.22), respectively are tested. Columns are evaluated to find out the effect on axial capacity, moment capacity, dilation, ductility, and toughness with discrete and continuous CFRP confinement under eccentric loading. Columns of similar sizes with no CFRP confinement are also tested under concentric and eccentric loading to compare their behavior. One square column having no transverse reinforcement was tested to observe the effect of confinement by tie bars. The results indicate that CFRP wrapping enhanced the axial capacity, moment capacity, deformation responses, ductility, and toughness of the columns. It is observed that the discrete and continuous wrapping increased the axial capacity of a column by at least 27% and 49%, respectively, and the corresponding moment capacity increased by at least 32% and 54%. The confined compressive strength (f’cc) of the concrete cylinders increased by a minimum of 41% and 91%, respectively, due to adding one and two CFRP layers. The ACI 440.2R-17 code is not recommended for FRP systems for concrete with compressive strength (f'c) less than 17 MPa, but a minimum of 65% higher compressive strength is found for a lower strength (10 MPa) concrete. Thus, the ACI 440.2R-17 code can be conservatively used to predict the capacity of a CFRP-confined recycled brick aggregate concrete column. First and foremost, I would like to thank Allah (SWT) with the blessings of Whom all the good deeds are fulfilled. I would like to express my deepest gratitude and most humbly enunciate my sincere appreciation to my supervisor, Lt Col Md Jahidul Islam, Ph.D., Engrs., Associate Professor, Department of Civil Engineering, Military Institute of Science & Technology (MIST), for his constant and acute supervision, continuous encouragement, suggestions, instructions, and compelling discussions. Without his relentless, kind, and diligent perseverance, this thesis would not have been able to be concluded by me alone. I would also like to thank Assistant Professor Md. Shahjalal and Research Assistant Tasnia Ahmed for their advice and assistance needed for the research. I acknowledge the generosity of the Head of the Department for the financial allocation that made this study possible. I would like to express my gratitude to all the lab assistants of the Civil Engineering Department of MIST for their constant technical access and help, without which it would have been difficult to conduct the experimental work of my study. Lastly, I am also indebted to the Department of Civil Engineering of MIST for allowing me to conduct the research successfully. I also acknowledge my family members for their loving support and encouragement, and I thank our friends and well-wishers for always supporting and helping me throughout the journey

2023-12-01T00:00:00Z TALUKDER RANA, MD. LUTFAR RAHMAN http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/827 2024-06-11T06:27:47Z 2023-09-01T00:00:00Z

PROPERTIES OF CONCRETE CONTAINING RECYCLED AGGREGATE AND WASTE GLASS POWDER TALUKDER RANA, MD. LUTFAR RAHMAN The coarse aggregate and fine aggregate are replaced by the RBA and WG, respectively. A mix design of a total of fifteen different mixtures is planned with a comprehensive test matrix. Fundamental tests of concrete such as density, gradations, air content, slump, as well as the mechanical properties i.e. compressive strength, splitting tensile strength, and flexural strength of RBA-based WG concrete at different ages are investigated following ASTM standards. Subsequently, a non-destructive test method ultrasonic pulse velocity is also examined to understand the pulse conductivity through produced concrete. For further investigation, a microstructural analysis is also performed using scanning electron microscopy. It is observed that the compressive strength diminishes with a higher amount of reclaimed brick aggregate. In contrast, a 12.5% higher strength can be achieved with the addition of 20% glass content though the strength falls if further glass is added as fine content. Similar trends are observed for the split tensile and flexural strength properties of this RCG. In the SEM, it is observed that up to 20% glass content RCG becomes denser formation with lesser voids; however, the larger voids and fissures are observed as glass content increases. The research has been extended to investigate the flexural behaviour of the RCG in the reinforced concrete beam. Load-deformation of the beam and stress-strain response of the used rebar’s were recorded by a standard data acquisition system including LVDT, strain gauges with a 20-channel data logger. The flexural capacity of RCG-made beams is very much comparable with control beams as the deviation is only in a range of 1%-8% for adding glass content up to 20% replacement. The experimental results are compared with the established codes such as ACI-318-14. The experimental value is near to the theoretical value calculated through the ACI-318-14 code.The outcome of this study may contribute to the application of RBA and WG as ingredients of normal and reinforced concrete. First and foremost, all praise and profound gratitude goes to the almighty Allah, who is the most beneficent and the most merciful, for allowing the author a great opportunity and the ability to bring this effort to fruition safely and peacefully. The author conveys his heartiest gratitude to his supervisor, Lt Col Khondaker Sakil Ahmed, Ph.D., PEng., CEng. Associate Professor, CE Dept., MIST for his systematic support and supervision of the dissertation. His guidance and suggestions worked as inspiration to unlock different new avenues for research. The author would like to thank Dr. Ataur Rahman, Professor, CE Dept., KUET for the useful comments, remarks, and valuable suggestions. The author is grateful for the technical support provided by the Center for Advisory & Testing Services of the Civil Engineering Department (CATS-CE) of MIST, Dhaka, Bangladesh. The author would also like to acknowledge the contribution of lab technicians of the Concrete and SM lab of the Civil Engineering Department of MIST.

2023-09-01T00:00:00Z RAHMAN, MUHAMMAD SAIFUR http://dspace.mist.ac.bd:8080/xmlui/handle/123456789/825 2024-06-11T06:15:52Z 2022-10-01T00:00:00Z

VULNERABILITY ASSESSMENT OF MOTORCYCLE RIDING IN DHAKA CITY BY STRUCTURAL EQUATION MODELLING RAHMAN, MUHAMMAD SAIFUR In recent years, motorcycles have become one of the preferred modes of transport for commuters of Dhaka city as an alternative to car travel and public transports for its affordability and easy accessibility to reach any destination. This massive raise of the number of motorcycles has increased accidents and consequent casualties which is a growing problem for the urban dwellers of Dhaka metropolitan city. It is quite evident that motorcyclists are being forced to share the road with mixed traffic due to absence of separate motorcycle lane in road infrastructure. Thus, it has an associated safety concerns as well as psycho-social impacts on motorcyclists and other road users in Dhaka city. In view of the mixed traffic situation, the study has been intended to assess the overall vulnerability of motorcycle riding within the existing roadway characteristics and traffic management system of Dhaka city from the two-folded safety perceptions and reported behaviours of motorcyclists as well as other road users by Structural Equation Modelling (SEM). The research methodology has been designed into three-steps procedures to develop and analyze the models. In the first step, a set of 26 and another set of 24 perceived safety concerns variables have been selected for Motorcyclists as well as Other Road Users respectively. Secondly, two sets of stated preference survey questionnaire have been administered among motorcyclists including service riders as well as other road users including pedestrians, car and public transport drivers in the Dhaka city by both field and online questionnaire survey. Then, two Structural Equation Models on the safety concerns of motorcycle riding have been generated by carrying out by 1 st and 2nd Order Confirmatory Factor Analysis (CFA) method using the Stata software. Finally, both the models have been analyzed basing on the ranking values of standardized factor loading of all the latent and observed variables to determine the Most Significant/Important and Significant/Important factors related to the overall vulnerability/ safety concerns of motorcycle riding in Dhaka city. The study has unveiled that comparing both models, all the perceived safety concerns of motorcycle riding in Dhaka city are being recognized by both Motorcyclists as well as Other Road Users. Only there are differences of perception from both ends in prioritizing or ranking the safety factors in different safety aspects. As such, in the mixed traffic iii situation of Dhaka city, the five safety aspects like Road Infrastructures (n1), Traffic Management System (n2), Traffic Rules Violation by Motorcyclists (n3), Psycho-social aspects influencing riding of Motorcyclists (n4) and Traffic Rules Violation by Other Road Users (n5) are the determinant safety concerns and mutually influencing for the overall vulnerability assessment of Motorcycle Riding in Dhaka City. Amongst the 05 safety aspects, Traffic Rules Violation by Motorcyclists (0.87) is identified by both Motorcyclists and Other Road Users as the most significant safety concerns for vulnerable motorcycle riding in Dhaka city. In regards to Traffic Rules Violation by Motorcyclists, the result shows that frequent changing the lane by zig-zag driving (0.89), disregarding the speed limit by motorcycle drivers (0.89), uncertain movement of roadside parked motorcycles (0.89), using footpath by motorcyclists while stuck in traffic on main road (0.86) and overtaking any vehicle without proper precautions (0.82) are the most significant priority concerns as exhibited by the reported behaviours of motorcyclists. It is revealed in the analysis that motorcyclists’ attitudes and aggressive behavioural issues are influenced by various family and psycho-social issues which lead to commit an accident. The most significant psycho-social factors are riding aggressively during social or family crisis (0.96), breaking traffic rules to reach the destination at the earliest (0.89), violating the traffic rules during office time (0.89), ‘maximum income within shortest possible time’ by the service riders (0.87), driving fatigue for overstressed riding time by service riders (0.87). The certain traffic rules violation by other road users (public transport drivers, private cars drivers and pedestrians) also has a significant contributing impact on vulnerability of motorcycle riding in Dhaka city. The reported behaviour of other road users like not wearing helmet or other safety gears properly by the passengers (0.89) is identified as most significant safety concerns by both Motorcyclists and other road users. The study shows that road geometry and infrastructures of Dhaka city are not user-friendly and great safety concerns of motorcycle riding. The most significant safety concerns are absence of separate lane for motorcycle in mixed traffic flow (0.88 which is rated as top priority concern by both Motorcyclists and Other Road Users) and no footpath for walking or occupied footpath for other purpose (0.81). The study also reveals that absence of road signage / non-functional signal at a junction (0.78) and presence of unmarked elevated speed breaker (0.67) are the significant safety concerns in respect of traffic management system of Dhaka city. The outcome of this research can be a good instrumental tool for formulation of safety programs and policies for a safe motorcycle riding in Dhaka city. All praise to Almighty Allah for His graciousness, unlimited kindness and the blessings for the successful accomplishment of entire thesis work. The author would like to express my deepest sincere gratitude to my supervisor Lieutenant Colonel Mohammed Russedul Islam, PhD, for giving me an opportunity to work on such an important topic. His continuous guidance, invaluable suggestion, affectionate encouragement, generous help and invaluable acumen are greatly acknowledged. His keen interest on this topic and enthusiastic support on my effort was a source of inspiration for me to carry out the study. The author considers myself fortunate to work under his dynamic supervision. The author deeply acknowledges the expert observations and guidance of his Research Assistant, Md Hazrat Ali. He with his scholarly approach and continuous guidelines enabled him to conduct proper research. The author is truly obliged to him. The author would like to thank all who have extended their helping hands both directly and indirectly and regretful for not mentioning their names individually. Finally, the author is grateful to his family for their continuous encouragement and support during the study.

2022-10-01T00:00:00Z