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For normal physiologic functions, Iodine is necessary in small amount. It sanctions the thyroid gland to creates thyroid hormones, which is essential for mature and enlargement of the brain, body structures and central nervous system (CNS). In developing countries mental impediment and insufficient commercial performance are one of the results of iodine insufficiency issue. Globally, universal salt iodization has been executed to eradicate iodine insufficiency. However, the sufficiency of iodine in salts needs close observing to match its deliberated target. From this study,we find the adequately iodized salt consumption is associated with some demographic features such as, education, region, wealth index, access to mass-media etc. These findings are important for policy makers and Government as they should take necessary steps to increase the accession to education and media and also take realistic plan to increase the availability of adequately salt in Bangladesh. Dhaka Univ. J. Sci. 70(2): 1-7, 2022 (July)

In recent decades, researchers have begun to investigate innovative sustainable construction materials for the development of greener and more environmentally friendly infrastructures. The main purpose of this article is to investigate the possibility of employing date palm tree waste as a natural fiber alternative for conventional steel and polypropylene fibers (PPFs) in concrete. Date palm fibers are a common agricultural waste in Middle Eastern nations, particularly Saudi Arabia. As a result, this research examined the engineering properties of high-strength concrete using date palm fibers, as well as the performance of traditional steel and PPF concrete. The concrete samples were made using 0.0%, 0.20%, 0.60%, and 1.0% by volume of date palm, steel, and polypropylene fibers. Ten concrete mixtures were made in total. Compressive strength, flexural strength, splitting tensile strength, density, ultrasonic pulse velocity (UPV), water absorption capability, and water permeability tests were performed on the fibrous-reinforced high-strength concrete. With a 1% proportion of date palm, steel, and polypropylene fibers, the splitting tensile strength improved by 17%, 43%, and 16%, respectively. By adding 1% fiber, flexural strength was increased by 60% to 85%, 67% to 165%, and 61% to 79%. In addition, date palm fibers outperformed steel and PPFs in terms of density, UPV, and water permeability. As a result, date palm fibers might potentially be employed in the present construction sector to improve the serviceability of structural elements.

To limit the cross-sectional size of concrete structures, high-strength, lightweight concrete is preferred for the design and construction of structural elements. However, the main drawback of high-strength, lightweight concrete is its brittleness over normal-weight concrete. The ductility of concrete is a crucial factor, which plays an important role when the concrete structures are subjected to extreme situations, such as earthquakes and wind. This study aims to improve the ductility of high-strength, lightweight concrete by incorporating steel fibers. The palm oil clinker (POC)-based, high-strength, lightweight concrete specimens reinforced with steel fibers were prepared and their ductility was systematically examined. POC was used as aggregates and supplementary cementitious materials. Steel fibers from 0–1.50% (by volume), with an increment of 0.5%, were used in the concrete mix. Compression ductility, displacement ductility and energy ductility were used as indicators to evaluate the enhancement of ductility. Moreover, the compressive strength, flexural strength, stress-strain behavior, modulus of elasticity, load-displacement characteristics, energy absorption capacity and deformability of the concrete samples were investigated. The compression ductility, displacement ductility and energy ductility indexes were found to be increased by up to 472%, 140% and 568% compared to the control specimens (concrete with 0% steel fibers), respectively. Moreover, the deformability and energy absorption capacity of the concrete were increased by up to 566% and 125%, respectively. Therefore, POC-based, high-strength, fibrous, lightweight concrete could perform better than conventional concrete under extreme loading conditions as it showed significantly higher ductility.

Bangladesh relies mainly on groundwater for irrigation and drinking purposes. Groundwater, however, continuously polluted, is a major obstacle. Nowadays, Bangladesh is moving towards industrial revolution in a considerable speed. As part of this paper's attempt to analyze the groundwater pollution scenario in Bangladesh, specifically in the past two decades, about 100 articles, conference papers, and reports published in national and international journals and books were reviewed, as well as issues concerning pollution sources, health impact assessment, and future perspectives were discussed. The groundwater is contaminated by different contaminants, such as physico-chemicals, trace metals, and microbes. Human health is at great risk from arsenic (As) contamination; it is one of the biggest threats. The cancer risk and non-cancer risk of ingesting water are increased. On the other hand, a large number of peoples were affected due to waterborne diseases governed by microbial contamination. Geophysical and anthropogenic sources, the depth of wells, and geographical factors may influence groundwater pollution. It is recommended that policy makers should address the issue immediately and precautions should be taken wherever necessary.

Makale, WOS:000927702300001, Sometimes civil engineering infrastructures have been constructed in hot and cold weathering regions such as desert areas. In such situations, the concrete is not only smashed by hot and cold processes but also spoiled by shrinkage cracking. Therefore, this study intends to examine the influence of heat-cool cycles on high-strength concrete comprising various fibers, such as natural date palm, polypropylene, and steel fibers, and their different volume percentages. The most popular technique for improving the structural behavior of concrete is fiber insertion. Fibers decrease cracking occurrences, enhance early strength under impact loads, and increase a structure's ability to absorb additional energy. The main goal is to examine the effects of three different types of fibers on regular concrete exposed to heat-cool cycles. For each type of fiber, three dosages of 0.2%, 0.6%, and 1% were used to create high-strength concrete. After 28 days of regular water curing and six months of exposure to heat-and-cold cycles, all specimens were tested. The heat-cool cycles entailed heating for two days at 60 degrees C in the oven and cooling for another two days at room temperature. The results of the experiment showed that fiber reinforcement in concrete improves its strength and durability. The flexural strength was substantially improved by increasing the date palm, polypropylene, and steel fibers into the high-strength concrete with and without heat-cool cycles. Adding increments of date palm, polypropylene, and steel fibers into high-strength concrete revealed a significant improvement in energy absorption capacity in both cases, i.e., with or without the implementation of heat-cool cycles. Therefore, the natural date palm fibers might be utilized to produce sustainable fibrous high-strength concrete and be applicable in severe weathering conditions., Deanship of Scientific Research at Najran University

Structural strengthening comprises modification of the structural elements to enhance their load bearing capability, stiffness, toughness, and ductility. The present study is an experimental investigation on the performance of reinforced concrete (RC) beam specimens strengthened by the side near surface mounted (SNSM) technique with reinforcement strengthening of glass fiber reinforced polymer (GFRP) bars in flexure. Sustainable palm oil fuel ash (POFA) mortar (PM) and normal mortar were used as bonding mediators between the concrete substrate and GFRP bars as a replacement for epoxy adhesive. A total of eight specimens, in which one was a control, one was strengthened by GFRP bars and full epoxy adhesive in grooves, and six specimens were strengthened by GFRP bars and partial replacement of epoxy adhesive by PM and NM, respectively. The specimens were tested in the static condition under four-point bending. During the test, the loads, deflection, and strains of the specimens were stored in a data logger and the failure modes of the specimens were observed. Critical discussions were made based on the flexural capacities, load-deflection, ductility, energy absorption, the influence of epoxy replacement and the type of mortars in the strengthened specimens as compared to the control specimen. ACI 440.2R-08 and ACI 318-11 were applied to predict the ultimate load-carrying capacity and deflection characteristic graphs of the tested specimens. The predicted results of the specimens were in close agreement with the experimental results. The test results also exhibited that the epoxy substituted by sustainable PM had superior flexural performance to the NM strengthened SNSM-GFRP bar specimens, particularly when considering the economic and eco-friendly viewpoint.

In recent decades, the application of carbon fibre-reinforced polymer (CFRP) composites for strengthening structural elements has become an efficient option to meet the increased cyclic loads, or repair due to fatigue cracking. The premature failure due to end-debonding is a key limitation to achieve high fatigue performance of strengthened steel beams with externally bonded CFRP plates. The objective of this study is to explore the reinforcing techniques using the CFRP in-plane end cutting shapes and the triangular spew fillet of adhesive at the tips of the plate to care for fatigue damaged of wide-flange steel I-beams due to end-debonding. Four in-plane CFRP end cutting shapes were chosen, namely: rectangular, semi-elliptical, semi-circular and trapezoidal. The application of the trapezoidal end shape was found to be the best configuration for delaying the end-debonding failure mode and high fatigue life compared to the other CFRP in-plane end cutting shapes. Applying the triangular spew fillets of adhesive significantly increased the end-debonding and steel beam fracture initiation life of the strengthened beams.

Side Near Surface Mounted (SNSM) strengthening technique is among the latest technique introduced recently. In this paper, SNSM carbon fiber reinforced polymer (CFRP) strips strengthening technique is proposed for enhancing the flexural performance of reinforced concrete (RC) beams. A total of seven RC beam specimens were tested: one un-strengthened control specimen, and six specimens strengthened by SNSM-CFRP strips. All beam specimens were tested under four-point bending. Analytical prediction methods were used to verify the experimental results. The load, mid-span, deflection, and strains data were recorded until failure of the specimens. The ductility, stiffness, and energy absorption capacity of the strengthened specimens by CFRP strips were enhanced due to SNSM technique. The results also showed that the SNSM-CFRP strips strengthening technique significantly enhanced the first cracking, yield, and ultimate load capacities up to 153%, 108%, and 147% respectively, compared with that of the control beam. Further, the comparison between the experimental and predicted values shows good agreement.

Recent trend is to use the lightweight concrete in the construction industry because it has several advantages over normal weight concrete. The Lightweight concrete can be produced from the industrial waste materials. In South East Asian region, researchers are very keen to use the waste materials such as oil palm shell (OPS) and palm oil clinker (POC) from the palm oil producing industries. Extensive research has been done on lightweight concrete using OPS or POC over the last three decades. In this paper the aggregate properties of OPS and POC are plotted in conjunction with mechanical and structural behavior of OPS concrete (OPSC) and POC concrete (POCC). Recent investigation on the use of crushed OPS shows that OPSC can be produced to medium and high strength concrete. The density of OPSC and POCC is around 20-25% lower than normal weight concrete. Generally, mechanical properties of OPSC and POCC are comparable with other types of lightweight aggregate concrete. It can be concluded from the previous study that OPSC and POCC have the noteworthy potential as a structural lightweight concrete.

Reinforced concrete (RC) structures necessitate strengthening for various reasons. These include ageing, deterioration of materials due to environmental effects, trivial initial design and construction, deficiency of maintenance, the advancement of design loads, and functional changes. RC structures strengthening with the carbon fiber reinforced polymer (CFRP) has been used extensively during the last few decades due to their advantages over steel reinforcement. This paper introduces an experimental approach for flexural strengthening of RC beams with Externally-Side Bonded Reinforcement (E-SBR) using CFRP fabrics. The experimental program comprises eight full-scale RC beams tested under a four-point flexural test up to failure. The parameters investigated include the main tensile steel reinforcing ratio and the width of CFRP fabrics. The experimental outcomes show that an increase in the tensile reinforcement ratio and width of the CFRP laminates enhanced the first cracking and ultimate load-bearing capacities of the strengthened beams up to 141 and 174%, respectively, compared to the control beam. The strengthened RC beams exhibited superior energy absorption capacity, stiffness, and ductile response. The comparison of the experimental and predicted values shows that these two are in good agreement.

In a sustainable approach, it is essential to reduce waste materials for improving the urban environmental performance leads to development in the livable, sustainable, and greener city. In pursuit of this goal, iron lathe waste was used in this study as a replacement of fine aggregate to produce sustainable concrete. Iron lathe waste is generally a waste material from the lathe machine, which is abundantly available to an extent. These waste materials may lead to environmental and health concerns. Therefore, the main goal of this study is to experimentally examine the physio-mechanical characteristics of sustainable concrete incorporating lathe iron waste. The lathe iron waste dusts (LIWD) were used as a partial replacement of fine aggregate in different levels by weight (5%, 10%, 15%, and 20%) to fabricate the sustainable concrete. The mechanical and physical properties of sustainable concrete were investigated by conducting tests, such as workability, ultrasonic pulse velocity, compressive strength, splitting tensile strength, and flexural strength to investigate the properties of the alternative concrete comparing with that of conventional concrete. The experimental results showed that the LIWD significantly enhanced the tensile, flexural, and compressive strength of the concrete up to 13%, 19%, and 38%, respectively. Therefore, LIWD can potentially improve the serviceability of the structural elements.

Prestressing of strengthening materials can enhance the performance of strengthened structures as the materials become more efficient as a greater portion of their tensile capacity is employed. Prestressed concrete beams are widely used in the construction field, however, there is a lack of studies on the strengthening of these structural elements. This paper presents an experimental study on strengthening prestressed beams using near surface mounted (NSM) prestressed steel strands. A total of seven prestressed beams were constructed for static testing, with one unstrengthened control beam, one beam strengthened with a non-prestressed NSM steel strand, and five beams strengthened with NSM steel strands prestressed to varying levels of their nominal tensile strength. The structural behavior and failure modes of these specimens were investigated and the differences in performance due to the effect of the prestressing force in the NSM strands were analyzed. Based on the results, applying prestress force provides an increase in load carrying capacity with corresponding higher concrete cracking and steel yielding initiations when compared to beams strengthened with no added prestress force. The influence of various prestress levels on the deflection of the tested beams was also assessed, and the relevant results were presented and discussed. The test results showed that the strengthened prestressed beam with a 70% prestressed steel strand performed better compared to the other strengthened beams. The first crack load, yield load and ultimate load of the prestressed beam strengthened with a 70% prestressed steel strand increased by 40%, 57% and 40%, respectively, compared to the control beam.

The side near-surface mounted (SNSM) method is an alternative method used for applying fibre reinforced polymer (FRP) flexural strengthening on reinforced concrete (RC) beams. The SNSM method places the FRP grooves at the sides of the beam, rather than at the bottom in the normal near surface mounted (NSM) method. This research focuses on studying the performance of precracked RC beams when strengthened with the SNSM method. Six RC beams strengthened with the side-NSM (SNSM) method were tested in flexure. Precracked SNSM strengthened beams have reduced ultimate load by up to 3.3% and higher stiffness by up to 28.4% compared to non-precracked SNSM strengthened beams. The modes of failure for SNSM strengthened beams was identical for the precracked beams and the equivalent non-precracked beams. A simulation method based on the moment-rotation approach was also presented and was found to be reasonably accurate and able to simulate the change in stiffness caused by precracking.

This paper presents the experimental behavior of reinforcement concrete beams strengthened with near surface mounted (NSM) steel bar. Several researchers have used NSM fiber reinforced polymer (FPR) bar or strip for strengthening reinforced concrete beams. Though FRP has a number advantages like high strength, light weight and corrosion resistance it doesn’t show any ductile behavior, still highly expensive and not easily available in market. On the other hand, steel bar is less expensive, readily available in the market and shows good ductility. In order to get rapid and economic strengthening solution, strengthening with near surface mounted steel bar may become a potential alternative to retrofit reinforced concrete members. Therefore, the main purpose of this paper to investigate the experimental behavior of reinforced concrete beam strengthened with near surface mounted steel bar. Seven full-size beams (one control beams and six strengthened beams) were tested. Steel bars were used for strengthening. The failure load, mode of failure, deflection, and strain behavior are discussed. The study reveals that the near surface mounted technique with steel bars and cement mortar is the most economical strengthening solution to increase the flexural performance of RC beams.

In this paper, the effectiveness of cement mortar as bonding materials in the strengthening of reinforcements and concrete surface for flexural improvement of reinforced concrete (RC) beams were investigated. Recently, side near surface mounted (SNSM) and existing near surface mounted (NSM) techniques with glass fiber reinforced polymer (GFRP) bars are adopted as the strengthening methods for RC beams in which varieties of epoxy adhesive were replaced with cement mortar. In this study, one control and seven strengthened beams were tested under four-point loading in a static condition. The load-carrying capacities, failure modes, deflection, strains characteristic, parametric study and energy absorption capacities are addressed through laboratory experiments. The results revealed that the flexural performance was successfully achieved by using cement mortar as a replacement for adhesive. The SNSM strengthening technique exhibited better structural performance compared with the existing NSM technique in all aspects.

Traditionally, multi-story buildings are designed to provide stiffer structural support to withstand lateral earthquake loading. Introducing flexible elements at the base of a structure and providing sufficient damping is an alternative way to mitigate seismic hazards. These features can be achieved with a device known as an isolator. This paper covers the design of base isolators for multi-story buildings in medium-risk seismicity regions and evaluates the structural responses of such isolators. The well-known tower building for police personnel built in Dhaka, Bangladesh by the Public Works Department (PWD) has been used as a case study to justify the viability of incorporating base isolators. The objective of this research was to establish a simplified model of the building that can be effectively used for dynamic analysis, to evaluate the structural status, and to suggest an alternative option to handle the lateral seismic load. A finite element model was incorporated to understand the structural responses. Rubber-steel bearing (RSB) isolators such as Lead rubber bearing (LRB) and high damping rubber bearing (HDRB) were used in the model to insert an isolator link element in the structural base. The nonlinearities of rubber-steel bearings were considered in detail. Linear static, linear dynamic, and nonlinear dynamic analyses were performed for both fixed-based (FB) and base isolated (BI) buildings considering the earthquake accelerograms, histories, and response spectra of the geological sites. Both the time-domain and frequency-domain approaches were used for dynamic solutions. The results indicated that for existing multi-story buildings, RSB diminishes the muscular amount of structural response compared to conventional non-isolated structures. The device also allows for higher horizontal displacement and greater structural flexibility. The suggested isolation technique is able to mitigate the structural hazard under even strong earthquake vulnerability.

Reinforced concrete (RC) structures require strengthening for numerous factors, such as increased load, modification of the structural systems, structural upgrade or errors in the design and construction stages. The side near-surface mounted (SNSM) strengthening technique with glass fiber-reinforced polymer (GFRP) bars is a relatively new emerging technique for enhancing the flexural capacities of existing RC elements. Nine RC rectangular beams were flexurally strengthened with this technique and tested under four-point bending loads until failure. The main goal of this study is to optimize the structural capacity of the RC beams by varying the amount of strengthening reinforcement and bond length. The experimental test results showed that strengthening with SNSM GFRP bars significantly enhanced the flexural responses of the specimens compared with the control specimen. The first cracking and ultimate loads, energy absorption capacities, ductility and stiffness were remarkably enhanced by the SNSM technique. It was also confirmed that the bond length of the strengthened reinforcement greatly influences the energy absorption capacities, ductility and stiffness. The effect of the bond length on these properties is more significant compared to the amount of strengthening reinforcement.

The strengthening reinforcement is glued to the soffit of the reinforced concrete (RC) beams in the mainstream externally bonded reinforcement (EBR) technique for flexural strengthening. However, the soffit of RC beams could be inaccessible for strengthening due to limited or no space at the soffit because of walls or doors, or the spalling of concrete. To overcome such difficulties, this paper investigates the feasibility of the flexural strengthening of lightweight non-pre-cracked and pre-cracked reinforced concrete (RC) beams using the side externally bonded reinforcement (S-EBR) technique with carbon fiber reinforced polymer (CFRP) fabric. A total of eight full-sized RC specimens were fabricated, strengthened, and tested under four-point loading until failure. The test variables were the internal reinforcement ratio, percentage of pre-cracking loads, and the effect of cracking loads on the flexural performance. The loads, deflection, and ultimate failure of the specimens were recorded and the types of modes of failure were also observed. The S-EBR strengthening technique with CFRP fabric significantly enhanced the flexural capacity of non-pre-cracked and pre-cracked lightweight RC beams compared to the control specimen. An analytical model in accordance with ACI 440.2R-08 was developed to verify the experimental results. The flexural capacity predicted by the model was in reasonable agreement with the experimental results.

This study investigates the flexural behaviour of reinforced concrete (RC) beams strengthened through the combined externally bonded and near-surface mounted (CEBNSM) technique. The externally bonded reinforcement (EBR) and near-surface mounted (NSM) techniques are popular strengthening solutions, although these methods often demonstrate premature debonding failure. The proposed CEBNSM technique increases the bond area of the concrete–carbon fibre reinforced polymer (CFRP) interface, which can delay the debonding failure. This technique is appropriate when any structure has a narrow cross-sectional width or is in need of additional flexural capacity that an individual technique or material cannot attain. An experimental test matrix was designed with one control and five strengthened RC beams to verify the performance of the proposed technique. The strengthening materials were CFRP bar as NSM reinforcement combined with CFRP fabric as EBR material. The test variables were the diameter of the NSM bars (8 and 10 mm), the thickness of the CFRP fabrics (one and two layers) and the U-wrap anchorage. The strengthened beams showed enhancement of ultimate load capacity, stiffness, cracking behaviour, and strain compatibility. The ultimate capacity of the CEBNSM-strengthened beams increased from 71% to 105% compared to that of the control beam. A simulation method based on the moment-rotation approach was also presented to predict the behaviour of CEBNSM-strengthened RC beams.

Existing structural components require strengthening after a certain period of time due to increases in service loads, errors in design, mechanical damage, and the need to extend the service period. Externally-bonded reinforcement (EBR) and near-surface mounted (NSM) reinforcement are two preferred strengthening approach. This paper presents a NSM technique incorporating NSM composites, namely steel and carbon fiber-reinforced polymer (CFRP) bars, as reinforcement. Experimental and analytical studies carried out to explore the performance of reinforced concrete (RC) members strengthened with the NSM composites. Analytical models were developed in predicting the maximum crack spacing and width, concrete cover separation failure loads, and deflection. A four-point bending test was applied on beams strengthened with different types and ratios of NSM reinforcement. The failure characteristics, yield, and ultimate capacities, deflection, strain, and cracking behavior of the beams were evaluated based on the experimental output. The test results indicate an increase in the cracking load of 69% and an increase in the ultimate load of 92% compared with the control beam. The predicted result from the analytical model shows good agreement with the experimental result, which ensures the competent implementation of the present NSM-steel and CFRP technique.

An optimization procedural method for designing fiber reinforced polymer (FRP) plate for strengthening reinforced concrete beam is presented. The optimization procedure is formulated to find the design variables leading to the minimum cost of structural strengthening system using CFRP plate with constraints imposed based on TR55 code provisions. Genetic algorithm based approach is utilized to solve the optimization task. The cost of FRP plate and epoxy adhesive is included in the formulation of the objective function. The ultimate limit states and the serviceability limit states are included in formulation of constraints. A numerical example is given to show the validity of the proposed optimization method.

Upgrading or strengthening of existing reinforced concrete (RC) infrastructure is an emerging demand nowadays. Near Surface Mounted (NSM) technique is very promising approach for flexural strengthening of RC members. However, premature failure such as concrete cover separation failure have been a main concern in utilizing this technique. In this study, U-wrap end anchorage with carbon fiber reinforced polymer (CFRP) fabrics is proposed to eliminate the concrete cover separation failure. Experimental programs were conducted to the consequence of U-wrap end anchorage on the flexurally strengthened RC beams with NSM-steel. A total of eight RC rectangular beam specimens were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM-steel bars and the remaining four specimens were strengthened with NSM-steel bars and U-wrap end anchorage using CFRP fabrics. A 3D non-linear finite element model (FEM) was developed to simulate the flexural response of the tested specimens. It is revealed that NSM-steel (with and without end-anchors) significantly improved the flexural strength; moreover decreased deflection and strains compared with reference specimen. Furthermore, NSM-steel with end anchorage strengthened specimens revealed the greater flexural strength and improve failure modes (premature to flexure) compared with the NSM-steel without end anchorage specimens. The results also ensured that the U-wrap end anchorage completely eliminate the concrete cover separation failure.