A review of prefab home and relevant issues.

Having an easily built house has been always one of human wishes. Prefabricated home makes this wish come true because of its affordability and fast completion. This paper gives an overview of different types of prefab home and its terminology. This review sheds light on the characterisation of prefab home, which takes the aspects of off-site technology, mass customisation, and sustainability into consideration. This paper is confined to general review of prefab home without going through different systems utilised in off-site technology. In spite of the fact that prefab home has many advantages, which are discussed in this review, it suffers from a few drawbacks which should be considered by designers. Various exploitations in this field may merit further research in future, including finding the optimum prefabricated systems among the existing systems such as roof, wall, and floor systems for different applications of prefab homes. Nevertheless, there is still a universal design and practice code for prefab homes that emphasize on green technology and sustainability yet to be discovered

A Review for Characterization of Silica Fume and Its Effects on Concrete Properties

 Mineral additions which are also known as mineral admixtures have been used in Portland cement for many years. There are two types of additions which are commonly mixed into the Portland clinker or blended directly with cement these days. They are crystalline, also known as hydraulically inactive additions and pozzolanic, which are hydraulically active additions. Silica fume is very reactive pozzolan, while it is used in concrete because of its fine particles, large surface area and high SiO2 content. Silica fume is much fined separated silica obtained as a by-product in industry. It is used as an admixture in the concrete mix and it has significant effects on the properties of the resulting material. Simultaneously, silica fume can be also utilized in production of refectory and porcelain, to increase intensity and durability. In addition, it can improve the overall performance of the material as filler used in coating resin, paint, rubber and other high molecular materials. This review paper discusses the effects of silica fume on the concrete properties such as strength, modulus, ductility, permeability, chemical attack resistance, corrosion, freeze-thaw durability, creep rate. Characterisation of silica fume as well as its physical and chemical properties will also be reviewed in this paper.&nbsp

Behavior of high-strength concrete cylinders repaired with CFRP sheets

This study aims to investigate the behavior of damaged high-strength concrete cylinders repaired using carbon fiber reinforced polymer (CFRP) sheet. The experimental work on CFRP-wrapped concrete cylinders with various predamage levels indicated that CFRP can precisely resist the axial aggravated deformation of cylinders caused by damaging under uniaxial loading. The findings also revealed that the energy absorption of the damaged specimens confined with CFRP was restored approximately three times more than that of the undamaged specimens without confinement. Therefore, an empirical relationship exists between the pre-damage levels and the uniaxial compressive strength reduction of the concrete cylinders

FRP Sheets Contribution in Common Repair Techniques of Concrete Structures with Emphasis on Concrete Columns

The history of composites dates back to few thousand years ago. Actually, natural fibrous composites were used by ancient Egyptians to build small houses. Numerous studies have revealed that Fibre Reinforced Polymer (FRP) is a convenient material for repair and strengthening of concrete structures compared to the traditional materials. Since the presentation of fibre reinforced polymer (FRP) in the concrete structures, the need for practice codes containing FRP in field of strengthening and repair has emerged. Many parts of structures are usually replaced simply, instead of repair due to the lack of knowledge about the techniques of repair. Hence, in this review, advantages and disadvantages of FRP repair, different types of FRP repair systems, repair stages and principles of repair theory for concrete structures with FRP are reviewed. In addition, modern repair techniques are reviewed in detail for different damaged levels of concrete structures. Recent developments in the field of repair with FRP have highlighted the need for assessment of repaired concrete columns. Thus, in one part of this review, the authors emphasise different damaged concrete column repaired with CFRP. Finally, the recent needs for further researches in field of repair with FRP are discussed

FRP sheets contribution in common repair techniques of concrete structures with emphasis on concrete columns

The history of composites dates back to few thousand years ago. Actually, natural fibrous composites were used by ancient Egyptians to build small houses. Numerous studies have revealed that Fibre Reinforced Polymer (FRP) is a convenient material for repair and strengthening of concrete structures compared to the traditional materials. Since the presentation of fibre reinforced polymer (FRP) in the concrete structures, the need for practice codes containing FRP in field of strengthening and repair has emerged. Many parts of structures are usually replaced simply, instead of repair due to the lack of knowledge about the techniques of repair. Hence, in this review, advantages and disadvantages of FRP repair, different types of FRP repair systems, repair stages and principles of repair theory for concrete structures with FRP are reviewed. In addition, modern repair techniques are reviewed in detail for different damaged levels of concrete structures. Recent developments in the field of repair with FRP have highlighted the need for assessment of repaired concrete columns. Thus, in one part of this review, the authors emphasise different damaged concrete column repaired with CFRP. Finally, the recent needs for further researches in field of repair with FRP are discussed

Development of strut-and tie model for carbon fibre reinforced polymer strengthened deep beams

Deep beams are commonly used in tall building, offshore structures and foundations. According to many codes and standards, strut-and-tie models (STM) are recommended as a rational approach to analyse discontinuity regions (D-regions) and consequently deep beams. Since the last decade, strengthening of reinforced concrete (RC) beams with carbon fibre reinforced polymer (CFRP) has become a topic of interest among researchers. However, STM is not able to predict shear strength of deep beams strengthened with CFRP sheet. There is a need for a rational model to predict the ultimate strength of CFRP strengthened deep beams is the significance of this research problem. This thesis elaborates on the STM recommended by ACI 318-11 and AASHTO LRFD using experimental results to point the way toward modifying a strut effectiveness factor in STM for CFRP strengthened RC deep beams. It addresses several ways to enhance our understanding of strut performance in the STM. The purpose of this research is to modify the STM for prediction of shear strength of RC deep beams strengthened with CFRP. Hence, the main objective of this research is to propose an empirical relationship to predict the strut effectiveness factor in STM for CFRP strengthened RC deep beams. Besides, the issue of energy absorption of CFRP strengthened RC deep beams is also discussed in this research. Twelve RC deep beams comprising six ordinary deep beams and six CFRP strengthened deep beams with shear span to the effective depth ratio of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were tested till failure in a fourpoint bending set up. The values of principal tensile strain perpendicular to strut centreline were measured using demountable mechanical strain gauge (DEMEC). Finally, a modified STM using an empirical relationship was proposed to predict the ultimate shear strength of CFRP strengthened RC deep beams. The modification of STM was made by proposing an empirical equation to predict the strut effectiveness factor in STM for CFRP strengthened RC deep beams. According to the experimental results the growth of energy absorption of CFRP strengthened RC deep beams varies from approximately 45% to 80% for shear span to effective depth ratio of 0.75 to 2.00 respectively. This research is confined to RC deep beams strengthened with one layer of CFRP sheet installed using two-side wet lay-up system

Refinement of Strut-and-Tie Model for Reinforced Concrete Deep Beams.

Deep beams are commonly used in tall buildings, offshore structures, and foundations. According to many codes and standards, strut-and-tie model (STM) is recommended as a rational approach for deep beam analyses. This research focuses on the STM recommended by ACI 318-11 and AASHTO LRFD and uses experimental results to modify the strut effectiveness factor in STM for reinforced concrete (RC) deep beams. This study aims to refine STM through the strut effectiveness factor and increase result accuracy. Six RC deep beams with different shear span to effective-depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were experimentally tested under a four-point bending set-up. The ultimate shear strength of deep beams obtained from non-linear finite element modeling and STM recommended by ACI 318-11 as well as AASHTO LRFD (2012) were compared with the experimental results. An empirical equation was proposed to modify the principal tensile strain value in the bottle-shaped strut of deep beams. The equation of the strut effectiveness factor from AASHTTO LRFD was then modified through the aforementioned empirical equation. An investigation on the failure mode and crack propagation in RC deep beams subjected to load was also conducted

Strut Deformation in CFRP-Strengthened Reinforced Concrete Deep Beams

Strut-and-tie model (STM) method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions). It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP) as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level

Test set-up.

<p>Test set-up.</p

Experimental and numerical study of temperature field and molten pool dimensions in dissimilar thickness laser welding of Ti6Al4V alloy

2019 The Society of Manufacturing Engineers Laser study is an important consideration in the present century with advances in laser technology. Titanium alloys are of great importance to the defense industry, aerospace and other industries due to its properties, including strength to weight. In this research, experimental and numerical study are investigated for laser welding on sheets of Ti6Al4V alloy with different thicknesses. Analysis of the temperature distribution around the molten pool and dimensions of the depth and width of the molten pool are performed by changing the parameters of laser such as focal length, speed of laser welding and power. The results show that the heat affected zone (HAZ) and molten pool is diverted to the thinner sheet. Also, by decreasing the focal length, the temperature of the workpiece and the dimensions of depth and width of the molten pool are increased. In addition, with enhancing the laser speed, the laser beam contact time with the workpiece surface reduces and the temperature decreases, resulting in a decrease in the dimensions of the depth and width of the molten pool. Eventually, as the power increases, the dimension of the melt pool increase and at both 180 W and 240 W powers, the thinner sheet experiences higher temperatures compared to the thicker sheet. In this study, the results of numerical simulation are matched with the experimental results and can be applied to obtain the temperature and geometry of the melt pool in other cases to reduce the cost and time