In most cases, the concrete wall panels are subjected to axial eccentric distributed loading; due to this type of loading, concrete wall panels behave and fail somehow. There are many parameters that affect the structural behavior of the concrete wall panels. This study presents experimental investigation the structural behavior of concrete wall panels subjected to axial eccentric distributed loading; also evaluates the effect of the parameters, slenderness ratio (H/t), aspect ratio (H/L) and concrete strength on the behavior of concrete wall panels. The experimental program includes testing fifteen concrete wall panels hinged at top and bottom with free sides, by applying the load axially with eccentricity equal to (t/6); these panels are divided into five groups, each group consists of three panels with slenderness ratio (H/t) equals to (20 , 25 , 30) for each panel, three groups of normal concrete strength with aspect ratio (H/L) equal to (1.0 , 1.5 . 2.0) for each group and the other two groups are of high strength concrete with aspect ratio (H/L) equal to 2.0 for both two groups. The deflections of concrete wall panels depend on the slenderness ratio (H/t), aspect ratio (H/L) and concrete strength. The failure mode of the concrete wall panels is greatly affected by the aspect ratio (H/L); the panels with low aspect ratio tend to fail by crushing, while panels with high aspect ratio tends to fail by buckling.
Concrete structures suffer from the impact of many harmful attacking materials that affect theproperties of the main material in them, which is concrete. These structures are also, exposedto the negative impact of many hostile environments such as soils containing harmful salts andharmful acids. A number of precautions should be considered in order to protect the concreteused in such structures. Adding polymer to concrete components as a percentages weight ofcement is one of the methods for producing polymer-modified concrete, which has lowpermeability, better mechanical properties and is more resistant to the negative effects ofharmful environmental factors. The utilization of polymers could help in protecting structuresand enhancing concrete strength. In this study, concrete mixes were prepared with inclusion ofstyrene butadiene rubber (SBR) polymer at four percentages (0%, 5%, 7% and 10% by cementweight). Co-polymers of butidine with styrene (styrene-butadine rubber (SBR)), are a group oflarge-volume synthetic rubbers. High adhesion occurs between the polymer films that formand cement hydrates. This action gives improves the properties of concrete such as flexuraland compressive strength and gives also a higher durability. The investigation was extended toevaluate the compressive strength of the SBR concrete mixes immersed in three types ofwaters: tap, drainage and ground water, at three different ages. The results showed that SBRpolymer enhanced the compressive strength of concrete significantly. A comparison betweenreduction in strength of concretes immersed in these three types of waters was also presented.Moreover, the presence of SBR polymer led to reduced loss in strength of concrete specimensimmersed in drainage and ground water. A proposed model to determine the compressivestrength of concrete specimens immersed in drainage and ground waters was deduced. Thismodel could be a helpful tool for rapid and easy estimation of the strength of concretespecimens immersed in drainage and ground water at different contents of SBR polymer. Theresults showed the highest improve in compressive strength to be associated with 7% SBRmixes at the three tested ages. The increases in this strength at days 7, 28 and 56 with inclusionof 7% SBR polymer were 112.8%, 113.9% and 116%, respectively, compared to OPC mix.
New composite reinforced concrete beams, in which reinforced concrete component is connected to steel T-section, are proposed. The shear connection between the two components, the reinforced concrete and the T-section, is provided by the stirrups that are required for the reinforced concrete component to resist the applied shear. Experimental tests in addition to numerical analysis were conducted to determine the behaviour and strength of such beams under pure torsion. Full scale one conventional reinforced concrete beam, T1, and two composite reinforced concrete ones, T2 and T3, were tested. The degree of shear connection between the two components of beams T2 and T3 was changed by varying the number of stirrups which are used as shear connectors. The experimental results revealed approximately same torsional stiffness for the three beams at the uncracked concrete stage. The torsional strength of the composite reinforced concrete beams was greater than that of ordinary reinforced concrete one by 11% and 27% for beams T2 and T3, respectively. Three-dimensional finite element analysis was conducted using program ABAQUS. To model the shear connection in composite reinforced concrete beam, the stirrups were connected to the web of the steel T-section by springs at the location of the stirrups. Good agreement is obtained between the results of the experimental tests and the finite element analysis. The ratios of experimental results to those of finite element analysis for torsional strength are approximately one. Under the pure torsion loading the degree of shear connection is found to have no effect on torsional capacity of beams.
The standard concrete mixing procedures indicate that during concrete mixing process, it is recommended to use fully saturated- dry surface course aggregates (FSDCA). It is clear that the exact application of this rule will produce a concrete of a good quality. But in practice, course aggregates are exposed to weather changes. This actual situation will lead to dry the course aggregates in summer and to over wet it during winter. To investigate the effect of using different moisture content course aggregates on concrete product in work site an experimental program had been done. This program consists of testing 54 concrete samples (27 cube +27 prism). The samples were divided into three groups (a, b, and c). The second group (b) was a concrete mix containing dry aggregates, while the third group (c) contained over wet aggregates and the first group (a) was the basic standard mix using (FSDCA). One third of the samples were tested in the age of 7 days, while the other third was tested in the age of 14 days and the rest after 28 days. Test results show that there are reduction in compression and flexural strengths of concrete due to the use of different moisture content course aggregates. Finally, new recommendations were concluded to be used in practice to overcome the mentioned repetitive error and to be more close to the theoretical recommendations in order to get better concrete properties.
This research paper is an attempt to reuse plastic waste fibre resulting from plastic sections industry as an additive to concrete matrix. The relationship between fibre volume fraction and mechanical properties of concrete and re-inforced concrete tiles was investigated. Three volume fractions of fibre ( 0.5 % , 1 % and 1.5 % - by volume of concrete ) were used through the experi-mental program. Tests’ results proved a slight decrease in concrete compres-sive strength as plastic fibre was added compared with the reference mix. Flexural behaviour of concrete tiles was enhanced as adding fibres. Adding fibre to Concrete results in a negligible reduction in concrete density. Fibre with high volume fractions improved Splitting tensile strength compared to the reference mix.
In this research, the effect of adding fillings of steel resulting from factory of smithery was studied. The fiber was added with two different percentages to the ordinary and polymer concrete to study their effects on some of the properties of both type of concrete like compressive strength, flexural strength and density. Two different percentages of fiber by volume of concrete (0.5%, 1.0%) were added to concrete mixes. A reference mix was also made. The results showed that adding of fillings of steel with these percentages lead to improvements in both compressive strength and flexural strength of polymer concrete with the increase of its percentage while it's less effect on these properties of ordinary concrete. An improvement in flexural strength appeared more clearly in both type of concrete. Significant increase in density was noted in both types of concrete.
Deep beams with rectangular cross-sections are widely used in concrete structures. In the present study, reinforced concrete rectangular deep beams cast with self-compacted concrete (SCC) which contains recycled concrete as coarse aggregate (RCA) were tested under directly and indirectly loading conditions. In the experimental work, fifteen deep beams were investigated, the first parameter considered in this study was the shear span to effective depth (a/d) ratio. The other variable is the replacement ratio by which the normal coarse aggregate is replaced by RCA. The beams were cast without the use of shear reinforcement. During the tests, the response of the beams including the cracking load, the ultimate load, concrete strain, and mid-span deflection were recorded. Test results indicate that the presence of RCA caused a reduction in the values of cracking and ultimate loads. For instance, the cracking load was reduced by 9%, 23%, and 50% and the ultimate load was reduced by 2% , 23%, and 25% as RCA replacement increased by 25%, 50%, and 75% respectively for a/d ratio equals 1.0. Further, by increasing the a/d ratio, the ultimate load was decreased due to the lower contribution of arch action shear transfer in the beam with a higher (a/d) ratio.
This research, an attempt is carried to explain the use of new products of superplasticizers type (Glenium) locally recent period used in normal concrete strength,espeacailly in precast concrete. and the effect of medium hot weather climates on compressive strength of normal concrete made with various percentages of Glenium dosages , and to evaluate the dosages on workability of fresh concrete. Concrete mixes with two types containing of Glenium, G51 and G21. and different dosages of Gelnium, namely 0.8 and 1.2 liter per 100 kg of cement and reduction in water quantity about 25% Five mixes are made with 90 specimens, each mix contains 18 cubes ,half of specimens are cured by moist curing in normal condition, the other half of specimens are exposed to temperatures of 40oC.which is transferred to moist medium of hot water. The properties which are covered in this work consist of workability which represented by slump test, and strength represented by compressive strength and ultrasonic pulse velocity(UPV) tests. It is obtained that using the two types of Gelnium will improve the slump about (157% to 183%) compared with reference mix .The concrete cured at medium hot weather condition, show improves in compressive about (19.2 to38.12%) at 3 days age. The use Glenium type 51 is to be more suitable for normal concrete works in medium hot weather .
The presented work investigates the effect of addition admixtures (superplasticizer and polymer) to Chopped Worn-Out Tire concrete as a partial replacement of cement weight. Superpasticizer was addition by 4% and polymer (SBR) by 15%. The Chopped Worn-Out Tire (Ch.W.T.) addition to reference concrete with the three proportions as a Partial Replacement Ratio (PRR) of (25,25),(20,30),and (30,20) by volume of (sand and gravel) respectively. Three mixes were selected with above PRR for each type of admixture in additional to three mixes for Ch.W.T. concrete without admixtures and three reference mixes with admixtures without Ch.W.T. Thus, twelve mixes could be used in this investigation. Compressive strength and modulus of elasticity (static and dynamic) were tested. The test results indicated that the use of admixture led to significant improvement in concrete properties in general. Superplasticizer gave best results comparative with polymer, for example at 28 day the compressive strength of superplasticizer Ch.W.T. concrete Csp25,25 was 32.5 MPa, while compressive strength of polymer modified Ch.W.T. concrete CB25,25 was 28 MPa and compressive strength of Ch.W.T. concrete C25,25 was 21.2 MPa.
The concrete members several blessings over steel beam, like high resistance to prominent tem-perature, higher resistance to fatigue and buckling, high resistance to thermal shock, fire re-sistance, robust resistance against, and explosion. However there are some disadvantages as a result of exploitation totally different materials to product it. The most downside of structural concrete member is its deprived the strength to tensile stresses.The bond mechanism between steel bars and concrete is thought to be influenced by multiple parameters, like the strength of the encompassing media, the prevalence of cacophonous cracks within the concrete and therefore the yield stress of the reinforcement. However, properties of concrete mass has significantly effect when it was subjected to elevated temperature.The objective of this paper presents the results that allocating with the bond behavior of the rein-forcement of steel bar systems below static pull-out loading tests subjected to elevated tempera-tures. This numerical technique relies on relative slip and therefore the stress of bond distribu-tions done the embedded length and size of the bar within the concrete cylinder specimens. The obtained results square measure given and commented with the elemental characteristics of ferroconcrete members. The comparison showed smart agreement with experimental results
Since concrete is one of the most popularly utilized building mixtures in construction, a high demand of natural resources is significantly emerged. Therefore, a skyrocketed attention has been paid to create new opportunities for the use of recycle materials to develop a new construc-tion substance with more satisfactory properties. The use of waste products in concrete is not only economical, but it helps in solid waste management as well. Among various properties of concrete, thermal conductivity is a crucial factor that plays an important role in in building insu-lation by evaluating a material's capacity to transfer heat. This paper aims to review the potential application of waste materials in concrete as additive ingredients and investigate the effect of this waste material on thermal conductivity of concrete. The review of literature revealed that the application of most of the waste materials exhibited an obvious potential as thermal insulator. However, further investigated work is needed to highlight the advantages of utilizing waste mate-rials in concrete containing various type of waste materials
Scientists have recently started looking for new ecologically friendly and sustainable materials. Construction materials are among the numerous widely employed materials, and it is normally acknowledged that they have an apparent detrimental influence on the environment. Thus, the contribution of this paper is to describe the palm frond natural fibers' effect on concrete's mechanical characteristics. Since concrete is a brittle material, the goal of this research is to increase the tensile strength of concrete by using organic fibers (palm frond fibers), a waste product. In order to determine the ideal percentage of fibers, the following percentages were tested: 0.25, 0.5, 0.75, and 1% by volume of concrete. On dry density, compressive strength, and tensile strength, the impacts of fibers were investigated. The density of concrete decreased with increasing fiber ratios. The compressive strength slightly decreased, while the splitting strength significantly improved. According to the results, the best amount of palm frond fibers that can be add to concrete is 0.75% by volume.
The corrosion of reinforcement iron is one of the dangerous problems in middle and west of Iraq and Arabian gulf which is needed to large investigations because of increasing of chloride salts in soil and ground water and rising of temperature at summer which encourage of finding the shrinkage cracks in their two types : Plastic and drying shrinkage . cracks are easy way for harmful ions present at soil and ground water to enter through reinforced concrete making damage for protection film a rounding rein forced iron and led to rust with cracks in concrete cover a rounding rein forced iron added to its may be to cause structural damage in members of rein forced concrete because of absence of a adhesive between concrete and steel leading to structural failure . This research presents study for this problem and knowing their causes and methods to reduce it. Experimental work show that the concrete exposed to chlorides leads to decreasing in density with ratio (1.5%) and decreasing in flextural strength with ratio (138%) at age (28) day .
During the last years, several researches have been studying the final disposal of tyres wastes, due to the great volume generated worldwide, as well as the difficulty for discarding the disposal sites which become a serious environmental problem. In spite of this, recycling appears as the best solution for disposing tyres residues, due to its economical and ecological advantages. This research carried out to assess the feasibility of using crumb rubber (the product of shredding used rubber tyres) as a partial sand replacement in foamed concrete, and investigates the effect of it on some properties of foamed concrete such as, density, water absorption, compressive strength, tensile strength, flexural strength and impact resistance. Crumb rubber of tyres ranging from (0.7 to 5mm) in size was used in this research. Three proportioned mixes were designed in this research, have the same cement content, water-cement ratio, and foam content. The first mix represents a typical reference formulation of foamed concrete without crumb rubber (FC). In the others mixes (FCR-1 and FCR-2), respectively, 20 and 30% of volume of sand were replaced by crumb tyres rubber waste. Tests carried out to assess the behaviour of final product. The results obtained were demonstrated decreasing in foamed concrete strength (compressive, tensile, flexural, and impact) with the increasing of crumb tyres rubber content in the mixture and rubberized foamed concrete specimens (FCR-1 and FCR-2) show a cohesive behaviour than the specimens of reference mix (FC), especially in tensile strength. Comparing with the reference mix (FC), at an age of (28 days), the decreasing of compressive strength was (20.85%) for (FCR-1) and it for (FCR-2) was (37.76%).
The main purpose of this search is to study the punching shear behavior of fourteen specimens of Reactive Powder Concrete (RPC) two-way flat plate slabs, half of these slabs have been exposed to a high temperature up to 400 C° by using an electric oven. All slabs have dimensions of (400x400x60) mm, with steel reinforcement mesh of (Ø6mm) diameter. Laboratory tests show that there is an increase in the value of First Crack Loading (FCL) and Ultimate Load (UL) by (208, and 216.67) % and a decrease in deflection by (56.85) % due using slab with complete reactive powder relative to a slap made of normal concrete. The use of the (RPC)mixture in layers in slabs gave results close to the slab which consists of full (RPC) this gives the benefit of more than the use of a slab that contains full reactive powder concrete in terms of cost, the increase was in FCL and UL by (130.8, 169.23, 102.7 and 135.135) % and a decrease in the value of deflection by (37.17, 47.64) %. The use of a partial reactive powder mixture also showed good results, and by increasing the dimensions of the RPC area, the results were better. the increase in FCL and UL by (54, 116, and 185) % and (53, 116.67, and 166.67) % and a decrease in value of deflection by (36.12, 42.4, and 50.26) % from reference slab. When slabs are subjected to high temperatures, there may be a decrease in the value of the FCL and UL and an increase in the value of deflection when compared to models not exposed to high temperature. But when compared to the reference slab with the same circumstance showed an increase in the value of the FCL and the rate ranged between (50- 200) % and the UL was the ratio ranged between (51.35-208.1) % and a decrease in the value of the deflection where the ratio ranged (21-46) %
The purpose of this paper is to developing a mathematical relationship between the Ultrasonic Pulse Velocity (UPV) and the compressive strength for concrete specimens subjected to different amounts of exposure of sulfate attack. The experimental data were collected from a research work by the author using concrete subjected to sulfate exposure and form a literature used an extensive concrete work without sulfate exposure. The sulfate exposures studied were 0%, 3%, and 6% of fine aggregate. It is found that with the same amount of sulfate exposure a clear relationship curve can be drawn to describe the UPV and compressive strength. This paper proposes the UPV-strength mathematical expression suitable for prediction of the concrete strengths when subjected to sulfate attack.
This research work includes study of sound insulation property of concrete samples with different densities. This study intended to present a proposed empirical formula to determine the sound insulation of concrete walls using the ultrasonic instrument. Experimental tests on concrete samples were made using the ultrasonic instrument, the sound insulation of concrete walls calculated according to a proposed empirical formula made in this work. This formula takes into consideration pulse velocity, wall width, and frequency .This formula is supported on a statistical criteria. The results are evaluated and compared with the values that computed using the most well-known formula, the comparison show compatibility of the results with tolerance of (3%).
This research work includes production of polymer modified polystyrene concrete and studies the mechanical properties. Several proportions of raw materials were used to produce this type of concrete. This study is intended to improve the mechanical properties of light weight polystyrene concrete using styrene butadiene rubber(SBR) with rate of (5,10,15and20)% of cement weight. Compressive strength, flexural strength, impact strength and dry density tests were made on more than 150 specimen at age of 28 days. The results show that the addition of (SBR) with range of (5-20)%of cement weight is improve the flexural strength with range (3.74-18)%, and improve the impact strength with range (39-163)%. Also the results show that it is possible to produce polystyrene concrete with density (1680,1433 and 1147) kg/m3 replacing light weight Polystyrene aggregate with volume fraction (30,50 and70)%of sand.
The aim of this paper is to study experimentally the effect of steel fibers content on the modulus of elasticity of High Performance concrete HPC in different curing age. The results showed that adding steel fibers to HPC led to a considerable improvement in static and dynamic modulus of elasticity where at 90 day water curing the percentages of increasing in static modulus of elasticity of High Performance Steel Fiber Concrete HPSFC relative to HPC were 8.2%, 9.98%, and 11.88% at 0.5%, 1%, and 1.5% steel fibers by total concrete volume, respectively. While, the improvement of dynamic modulus of elasticity of HPSFC relative to HPC at 28 day were 8.09%, 10.7%, and 11.07% % at 0.5 %, 1 %, and 1.5 % respectively.
This research investigates the impact resistace of reinforced high strength concrete slabs with steel meshes (BRC) modified by styrene butadiene rubber (SBR) with different weight ratios of polymer to cement as follows: 3%, 5% and 7%. Reference mix was produced for comparison of results. For all selected mixes, cubes (100×100×100mm) were made for compressive strength test at (365) days. In conducting low-velocity impact test, method of repeated falling mass was used: 1400gm steel ball falling freely from height of 2400mm on reinforced panels of (50×50×800 mm) reinforced with one layer of (BRC). The number of blows causing first crack and final perforation (failure) were calculated, according to the former results, the energy of each case was found. Results showed an improvement in compressive strength of polymer modified high strength concrete (PMHSC) over reference mix; the maximum increase being of it were (3.93%-11.96%) at age of (365) days. There is significant improvement in low-velocity impact resistance of all polymer modified mixes over reference mix. Results illustrated that polymer modified mix of (3%) give the its higher impact resistance than others, the increase of its impact resistance at failure over reference mix was (154.76%) while, for polymer modified mix (5%) it was (30.95%) and it was (14.28%) for polymer modified mix of (7%).
The presented work investigates the effect of addition admixture (cement kiln dust) to concrete as a partial replacement of cement weight. Cement kiln dust was added by (10,30,50)% of cement weight.Four mixes were selected, three of them contain cement kiln dust (CKD) and one reference mix without any admixture for ages (7,28,90) days. Compressive strength ,flexural strength, ultra-sound velocity (UPV), slump, splitting tensile strength and static modulus of elasticity were tested.The test results indicated that the use of (CKD) led to significant decreasing in concrete strength in general and this decreasing increases with the increasing of (CKD), for example at 28 day the compressive strength of reference concrete (A) was 35 MPa, while the compressive strength of (B,C,D) contain (10,30,50)%CKD were (28,25,22) MPa respectively.
The behaviour of high-strength fiber reinforced concrete columns was observed with a testing program of 7 columns, loaded eccentrically. The theory was analyzed by modifying the stress block diagram of concrete. The experimental results show that using high-strength fiber reinforced concrete with fiber volume fraction of 1.0%, increased the column ultimate capacity up to 40% in addition to increasing its ductility and toughness, significantly. The proposed theoretical analysis gave a good estimation of experimental results.
This study aims to improve different properties of sustainable self-compacting concrete SCC containing treated and modified polyethylene terephthalate PET fibers. For this purpose, gamma ray surface treatment and geometric modification were utilized for the used PET fibers. Concrete fresh properties include slump flow, T500mm, L-box and sieve segregation while mechanical properties include compressive, split tensile strength, flexural strength, static modulus of elasticity and impact strength. Further, physical properties and related durability properties comprise dry density, ultrasonic pulse velocity, porosity and water absorption. The results obtained demonstrated that the treatment and the modification used for the PET fibers slightly reduced the fresh properties of produced sustainable SCC (slump flow, T500 mm, L-Box and sieve segregation). However, they were within the limits of the SCC specification as reported in EFNERC guidelines. Further, concrete hardened properties in terms of compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, impact strength, ultrasonic pulse velocity, decrease in the dry density, decrease in porosity and water absorption increased significantly.
The demand for strengthening structures becomes necessary when an increase in load is inevitable. For instance very little information is available on the time-dependent behaviour of strengthened concrete columns. Also, this is a primary factor hindering the widespread uses of FRP strengthening technologies in the construction implementations. This paper investigates the behaviour of strengthened concrete columns with FRP sheets subjected to long-term loading by non linear finite element analysis using ANSYS computer package. A three-dimensional finite element model has been used in this investigation. This study achieved a good agreement between numerical and experimental results, it was found that the percentage of error of specimens do not pass (5%) for creep strain. In addition, a parametric study was performed to study the effect of different factors on the behaviour of FRP strengthened concrete columns.
The nonlinear finite element analysis has become an important tool, for the structural design and assessment of prestressed reinforced concrete members. However, design and assessment of torsion are still done with simplified analytical or empirical design methods. This paper pre-sents results from a numerical analysis using the ANSYS finite element program to simulate a prestressed concrete beams subjected to static and cyclic torque. The eight- node brick ele-ments SOLID65 are used for the idealization of concrete while the reinforcements are idealized by using 3D spar element LINK8. The steel plates are idealized by using three dimensional solid elements SOLID45. The results showed that the general behavior of the finite element models represented by torque- twist angle relationships show good agreement with the experimental results from the Abdullah's beams.
In General, original reactive powder concrete (RPC) consists of a superplasticized cement mixture with silica fumes, steel fiber and ground fine sand (150-600 ىm). The main purpose of the present work is to produce and study some mechanical properties of lightweight reactive powder concrete using a superplasticized cement mixture with high reactivity metakaolin (HRM) instead of silica fume, steel fiber (with different ratios ) with ground fine sand (150-600 ىm) and light weight material called (Perlite ) also with different ratios .This investigation was carried out using several tests, these tests were compressive strength, modulus of rupture, modulus of elasticity, density and absorption, and performed for specimens at ages of 3, 7, 28 days, respectively. The tests results were compared with a reference mix. The experimental results shows that , with different ages, (for constant Perlit ratio for 0% to 10% as additional cementtitious materials) addition of 1% steel fiber will improve about (8.3%-10% , 3.2%-11%and 0.25%- 8%) for compressive strength , modulus of rupture, and modulus of elasticity respectively, and increase density, absorption about (0.8%-1.8%,4.5%-8.2%) respectively. Also an increase of steel fiber ratio to 2% will improve about (16.5%-20.3%, 9.0%-17%, and 1.7%-11.5%) for compressive strength , modulus of rupture and modulus of elasticity respectively, and increase density, absorption about (1.7%-2.3% , 7.3%-8.3%) respectively. For same steel fiber ratio about 0% to 2%, increasing Perlite ratio to 2.5% will decrease about (17.3%-18.8%, 9.5%-15.5%, 4.4%-16.6%, and 4.98% - 6.9%) for compressive strength, modulus of rupture, modulus of elasticity and density respectively and increase absorption to about (55.5% - 66.5%). Increasing the ratio to 5% will also make a decrease of about (36%-36.77%, 33.7%-37%, 16.5%- 21.88%and 15.91%-19.74%) for compressive strength, modulus of rupture, modulus of elasticity and density respectively and increase absorption for about (106%- 110.5%) . Increasing the ratio to 10% will also decrease about (45.98%-47.2%, 46.5-54.2%, 30.6%- 35.57%and 19.4%-23.36%) for compressive strength, modulus of rupture, modulus of elasticity and density respectively and increase absorption about(183%- 192.6%). To produce structural lightweight concrete, the tests results show that the optimum steel fiber is 1% by volume and optimum Perlite ratio is 2.5% by weight of cement as additional materials.
Ten simply supported deep beams with high strength concrete (C55 MPa) have been casted and subjected to a four-point loading test. Different parameters were examined for their influence on specimen behavior. These parameters were the shear span to overall depth ratio (a/h), the overall depth of deep beams (h), and additional anchorage length beyond the centerline of support (la). The experimental results show that the beam capacity decreases as the shear span to the overall depth ratio increases, and the overall depth and embedment length decrease. The major effect of anchorage length on the shear strength is studied. Different failure modes were observed which do not match strut-and-tie failure modes. The shear compression and anchorage failures were con-trolled in the high compressive concrete deep beams due to bottom steel yielding. Finally, the ex-perimental test results are compared with predictions of the strut-and-tie method according to the ACI 318-14 and a good agreement was found.
Prefabricated schools are educational structures of great significance and utility, especially given our country's current challenges. They expedite construction, reduce environmental impacts, and enhance educational activities with strong structural integrity and comfortable, flexible, and healthy design. A compelling comparison can be made with traditional concrete schools. With advancements in technology and information in engineering and the construction industry, Building Information Modeling (BIM) technology has emerged, playing a vital role in prefabricated concrete engineering through 3D modeling simulations.Numerous challenges are encountered, such as meeting client requirements, project delays, cost overruns, quality issues, stakeholder conflicts, labor shortages, safety concerns, increased change orders, material wastage, and project complexity. Developed countries utilize BIM to mitigate these challenges and profoundly improve the AEC industry's performance. BIM tools provide a comprehensive building visualization, empowering stakeholders to make informed decisions that ensure efficiency, sustainability, and cost savings. These features motivate engineers and contractors to rely on them as essential engineering applications.This research involves modeling a school building in the Revit program, studying work flow between Revit and ETABS program, and conducting a dynamic analysis of the model from Revit. It also emphasizes the benefits of prefabricated construction and BIM technology, facilitated by Revit. The study emphasizes how important it is to visualize the building's actual form before beginning the design and decision-making processes.in summery, this study provides the possibility of growth and application in the industrialization of the construction industry and raise the project's overall quality. The development of tools and plugins programmed to reduce interoperability problems between various software packages allows for integrating all design activities.
Designing large structures like dams requires carefully selecting various geometric, hydraulic, and structural characteristics. The required structural design and performance criteria are considered when selecting these characteristics. In order to find the best solution, a variety of restrictions must simultaneously be carefully taken into account. This study presents an effective method for determining the optimal shape design for concrete buttress dams. The research was divided into two crucial phases. The dam's initial design and subsequent modeling were mostly done using DIANA FEA and traditional design and stability analysis. After that, a genetic algorithm was used on the MATLAB platform to control optimizing the dam's shape. Three design factors were used in this phase to alter the goal function and to reduce the amount of Concrete used, which decreased project costs. These variables covered three areas of the buttress's cross-section. Two important limitations were scrutinized during this optimization process: establishing a safety margin against overtopping and preventing sliding. The analysis included a detailed assessment of Shear friction stability to complete a thorough stability study. The optimization efforts had a spectacular result, resulting in a significant 52.365% reduction in the total volume of Concrete used, dropping from 19147.5 cubic meters to 9122.55 cubic meters. This decrease was made possible by reducing three distinct components (X1, X2, X3), with respective proportions of 37.5%, 13.33%, and 30%, including two segments related to the buttress and the final segment linked (slab) to the strip footing.
Thousands of tons of marble waste can be reused every year in Iraq. Few investigations are made to study the effect of marble as a filler on hot mix asphalt concrete.. This big amount of waste has a bad effect on the environment and needs a lot of money and effort for recycling or disposal. Lime stone dust was used as a control filler. The laboratory tests have been conducted in order to evaluate the properties of each type of filler, which consist of the grain size distribution, the specific gravity (Gs), specific surface area (SA), pore volume(PV), mineral composition, pH and chemical composition.To study the effect of SM on the performance of HMA mixture, several tests were made consist of Marshall stiffness, Indirect tensile strength, Moisture susceptibility and Creep tests. Many conclusions were achieved referring the importance of using Sulaimania Marble waste (SM) in the enhancing most of the properties of HMA concrete.
The goal of the current investigation is to construct an artificial neural network (ANN) to estimate the ultimate capacity of the composite columns consisting of a rectangular steel tube filled with concrete (RSTFC) under concentric loads. The experimental results of (222) samples collected from previous researches were used in constructing the proposed network. Totally (45) specimens were randomly chosen for network testing while the remaining (177) speci-mens were used to train the network. The information used to create the ANN model is ar-ranged into (6) variables represents the different dimensions and properties of the RSTFC col-umns. Based on the input information, a formulated network was used to estimate the columns' ultimate capacity. Results obtained from the formulated network, available laboratory tests, and Eurocode 4 and AISC equations were compared. The network values were closer to the laboratory values than the calculated values according to the specifications of the mentioned codes. It has been shown that the formulated ANN model has a high ability to estimate the RCFST ultimate capacity under concentric loads
This study aims to investigate the impact of various construction methods on labor productivity in Iraq, focusing on traditional, prefabricated steel structures, precast concrete, and mechanical or self-build construction techniques. The research employs a descriptive-analytical methodology, utilizing a structured survey distributed to 200 participants from different construction industry sectors, including engineers, contractors, and field workers. The survey examines key indicators of labor productivity, such as task completion speed, work quality, labor costs, safety, and project cost.The findings reveal significant differences in labor productivity across the construction methods. Traditional construction methods moderately impacted task completion speed and work quality but were less efficient in terms of cost reduction and safety. On the other hand, prefabricated and precast concrete methods demonstrated improvements in work quality, safety, and cost efficiency, although with some limitations regarding flexibility. Steel structures offered enhanced durability and faster construction times, while mechanical and self-build methods utilizing automation significantly reduced labor costs and accelerated the construction process.Based on these results, the study recommends incorporating modern construction methods, such as prefabricated and mechanical techniques, to improve overall productivity in the Iraqi construction sector. Additionally, it emphasizes the importance of training and adapting to these advanced methods to ensure long-term efficiency, safety, and cost-effectiveness in construction projects.
Using statistical tools of quality help in identifying the daily production problems.Collecting data will enable the management to diagnose problems affecting the work and correcting the defects in the products and reduce its percentage; such defects cost the organization too much and influence its profits. Histograms were used in presenting the collected data from Amanat Baghdad. The data related to asphaltic concrete produced by its plants . Control charts were used to evaluate these tests. The research indicates differences in the results of mechanical analysis tests also in the asphalt percentage in the asphaltic concrete samples and air voids ratio as in Marshall samples. The results indicated that management of plants has no benefits gained from results tests carried out by the quality control department which indicate and diagnose the variances of the product and recommend the required corrections.
The impact resistances of concrete slabs have a different volume fraction replacement of waste plastic aggregate has been examined in this study as a fine aggregate as: 0% (reference), 10%, 20% and 30%. These tests include the splitting tensile, density, compressive strength. Also, the (ultrasonic pulse velocity tests) was carried out. Repeated falling mass was used in order to carry out the low-velocity impact test in which a 1300 gm steel ball was utilized. From a height of 2400mm, the ball falls freely on concrete panels of (500×500×50 mm) with a network of waste plastic aggregate. As per the results, a prominent development was seen in the mechanical properties for mixes involving polyethylene aggregate up to 20% as compared to the reference mix. A significant development was seen in low-velocity impact resistance of all mixes involving waste plastic fine aggregate as compared to reference mix. As per the results, the greater impact resistance at failure is offered by the mix with (20%) waste plastic aggregate by volume of sand than others. The reference mix increased by (712.5%).
The White Cement Kiln Dust (WCKD) is a byproduct material, formed in cement factory during the operation of cement production. In highway construction, the WCKD can be used in different ways such as stabilizing the subgrade of highway embankment and as mineral filler in Hot Mix Asphalt (HMA); the latter usage will give clean and healthy environment in addition to more economy. In Iraq, there are two common types of fillers, Portland cement and lime stone powder. In this research, WCKD taken from Fallujah cement plant used as mineral filler in addition to two common types. Various percentages , such as 100%WCKD, 50%WCKD + 50%Cement(C) ,100%C , 50%WCKD+50%Limestone (L), and 100% L, were used to prepare asphaltic concrete mixes. In general, five tests were used to evaluate the performance of these mixes. Standard Marshall Test procedure was applied under three different conditions, two of them at two temperatures at 60 OC and 70 OC and in the third one it was used to test samples immersed in water, at room temperature(24 OC), for four days. Indirect Tensile Strength Test (ITST) was used to evaluate conditioning and un-conditioning samples. All test results, when compared with controlled asphalt concrete sample (Sample contained 100% limestone as filler), were acceptable and within the AASHTO and Iraqi Standard Specifications of Roads & Bridges 2003. Stability values, at standard condition test, of samples containing 100% WCKD, 50%WCKD+50%C, and 50%WCKD+50%L are 11.9kN, 13.2kN, and 14.0kN respectively, while for controlled sample was 9.0kN. The Marshall stiffness values showed similar trends, for samples having 100% WCKD, 50%WCKD+50%C, and 50%WCKD+50%L giving 3.22kN/mm, 3.38kN/mm, 3.5kN/mm respectively but for controlled sample was 2.43 kN/mm. Same trends of results gained in ITST .The results showed the beneficial using of WCKD as filler that will conserve the environment and encourage the HMA producers to use this inexpensive material in their works.
Progressive collapse is a partial or total failure of a building that mostly occurs when the build-ing loses primary structural elements (typically columns) due to accidental or natural hazards. The failure of structures due to an earthquake is one of the most important and frequent types of progressive collapse. In this study, the finite element method is used to assess the response of multistory reinforced concrete buildings subjected to column loss during an earthquake. Three-dimensional nonlinear dynamic analyses are carried out using SAP2000 V.20 program. The ef-fects of different parameters on the progressive collapse behavior are investigated, namely: the location of the removed column within the ground floor; the method of column removal (sudden, in two-steps, and in four-steps) and the removal timing during the earthquake. It is demonstrated that the collapse occurs when all or most of the hinges at the bases of the ground floor columns reach their collapse level. The chosen column removal timing and policy affect the structural behavior considerably. It is realized that, the risk of building collapse increases when the removal timing harmonizes with the peak ground acceleration timing. Based on the adopted earthquake characteristics and building configurations, it is found that, the two steps removal scenario is the most dangerous one.Keywords:Progressive collapse, Concrete buildings, Seismic load, Nonlinear dynamic analysis, Plastic hinge.© 2014
This study aims to examine the relationship between the corrosion rate of longitudinal tensile steel bars and the maximum flexural strength of reinforced concrete RC beams. The study's methodology is designed to show the structural behavior of corroded and non-corroded RC beams, such as ultimate load, deflection, stiffness, crack patterns, and failure mode. Three rectangular beams were cast with dimensions (150× 200 ×1200) mm, and all specimens have the same amount of longitudinal and transverse reinforcement and the same concrete strength. The major parameter is the theoretical mass loss level due to corrosion (0, 10, 15) %. Electrochemical technique was used to accelerate the corrosion in the longitudinal tensile bars. All RC beams were tested under four-point monotonic loading. The test results confirm that the cracking load in corroded beams decreased by 25% comparative to the non- corroded beam. The increase of the percent of corrosion experimental mass loss by 8.25 and 14.15 % decreased the ultimate load by about 14 % and 27%, respectively. This reduction coincided with the decrease in deflection values in mid-span for the ultimate load, which decreased by 53.9% and 46.3%. However, the flexural stiffness was reduced by 13.4 and 15.6% for corroded beams with mass loss (8.25 and 14.15), respectively, compared to the control beam (non-corroded RC beam).
The term "fire safety engineering" refers to the process of applying scientific and engineering principles to the effects of fire in order to lessen the number of deaths and property damage caused by fire. This is done by determining the risks that are involved and providing the most effective method for implementing measures of prevention or protection. The paper showing experimental results of ordinary concrete columns made of "NSC" subjected to axial load and cyclic firing is presented in this study. the bearing capacity of the column decreased. all samples have been loading an eccentric load with "e = 75 mm" ,"e / h = 0.50," and the ratio Celsius (30%Pu) continuously through the burning period. The first column(C1) was the sample control with out exposure cyclic fire , and the second column was subjected to four burning cycles over the course of four days, with a duration specific of "45 minutes" for each cycle, at a temperature of "400 °C", and the third column was subjected to four burning cycles over the course of four days, with a duration longer amount of "75 minutes" for each cycle, at a temperature of "400 °C, ", the four column was subjected to four burning cycles over the course of an of four days, with a duration specific of "45 minutes" for each cycle, at a temperature of "600 °C " , the bearing capacity of the column decreased. that to be amount losses (C2,C3 and C4) comparison to (C1) equile ( 27.20 , 29.12, and 36.40)% respectively. the fracture load of the experimental columns varied by decreasing with these variables. Additionally, the depth and spread of the cracks increased with the increase in burning duration and target temperature.
Some mechanical properties of mortar (compressive strength and hardness) with sawdust replacement of sand were investigated. Cubes of 50 mm × 50 mm were prepared, the compressive strength tests were done for a replacement levels ranging (5, 10, 15, 25, 50, 75) % by volume a reference mix were also prepared for comparison this test was done after 7, 14, and 28 days while hardness test were done after 28 day for a replacement levels (0, 5, 10, 15, 25) % by volume. Result showed that the compressive strength of the specimen were decreased with higher sawdust content, hardness values were decreased slightly in the replacement levels 0, 5, 10 % while the values began to decrease noticeably in the replacement levels 15 and 25 % the hardness values were (59, 57.5, 56, 47.77 , 45.2) N/mm2 respectively A cost analysis was done, this analysis was based on a unit of mortar (1.0 m3) made from conventional materials and a modified concrete made by substituting materials with sand using sawdust
This paper investigates the possibility of strengthening Reinforced Concrete (RC) beams under pure torsion loadings. The torsional behaviour of strengthened RC beams with near-surface mounted steel and CFRP bars was investigated. The verification with the experimental work was performed to ensure the validity and accuracy which revealed a good agreement through the torque-rotation relationship, ultimate torque, and rotation, and crack pattern. This numerical study included testing of thirteen specimens (one of them was control beams while the remaining 12 were strengthened beams) with several parameters such as mounting spacing and configuration. The analytical results revealed that the addition of NSM rebar redistributed the internal stresses and enhanced the ultimate torsional strength, torque-rotation capacity, ductility, and energy absorption of the concrete beams. Most of the strengthened beams revealed the appearance of the cracks at a phase less than the reference beam by an average of (9%). Concerning the NSM strengthening, the CFRP bars provided a higher enhancement ratio when compared with the beams that strengthened with NSM steel rebar especially for the strengthening space equal to 130 mm and more. The ultimate torsional strength increased by (3.5%) and rotation decreased by (4%) approximately when the steel rebar was replaced by the carbon bar. The ductility and energy absorption of the analysed beams showed that the strengthening enhanced the ductility of the twisted beams. The ductility values varied according to the method of strengthening used, as it showed the highest values of the beam that was strengthened small spacing.
This paper presents a nonlinear finite element analysis of reinforced concrete beams subjected to pure torsion. A verification procedure was performed on three specimens by finite element analysis using ANSYS software. The verification with the experimental work revealed a good agreement through the torque-rotation relationship, ultimate torque, rotation, and crack pattern. The studied parameters of strengthening by CFRP sheets included strengthening configurations and number of CFRP layers. The confinement configuration methods included full wrapping sheet around the beam, U-shaped sheet, ring strips spaced at either 65 or 130 mm, longitudinal strips at the top and bottom faces, U-shaped strips in addition to the number of layers variable. It was found that the performance of the beam for resisting a torsional force was improved by (33-49%) depending on the method of coating with CFRP sheets and the number of used layers. A change in the angle of twist, as well as the shape of the spread of cracks, was also noticed from the predicted results.
This study aims to investigate the durability properties and microstructural changes of self-compacting concrete (SCC) incorporating waste polyethylene terephthalate (PET) as fibers and as fine aggregate replacement. This is after exposed to saline environment (Alkalies, Sulphates, and Chlorides). PET effect into two forms was also evaluated for routine rheological properties of SCC and mechanical strength before and after exposure to sulphate salt. Five proportions of each form of PET incorporation in SCC mixtures were utilized. The volume fractions considered for PET as fibers were (0.25, 0.5, 0.75, 1.0, and 1.25)% by volume, with aspect ratio of 28%, and (2, 4, 6, 8, and 10)% by volume for fine aggregate replacements. Results indicated that the inclusion of PET adversely affected fresh propertis especially high proportions of PET as fine aggregate. Alkali silica reaction (ASR) outcomes illustrated an enhancement in the mix containing PET fibers, while fine-PET mix was slightly enhanced. Magnesium sulphate reduced mass and compressive strength of all mixes in percentages ranging from (0.18-0.90) % for mass loss and from (0.47-55.13) % for compressive strength loss. Ultrasonic pulse velocity (UPV) and dynamic modulus of elasticity (Ed) increased due to the sulphate impact except for M0.5 and M10 which decreased in both tests. Chloride's theoretical and modelled results illustrated higher diffusion coefficients and lower surface chloride content of fiber-PET mixes as compared to fine-PET mixes. The predicted SCC cover depths for fiber-PET mixes were lower than those predicted for fine-PET mixes for 20 and 50 years of service life design.
Enhancing the hydrothermal performance of plate-fin microchannels heat sink (PFMCHS) promises smaller size and lighter weight, and then improve the heat removal in consequently increase the speed of electronic devices. In this numerical study, an innovative hydrothermal design of PFMCHS is suggested by inserting elliptic pins inside microchannels in different; aspect ratio (AR) of pin, pin number ratio (ψ) in order to optimize the hydrothermal design of this kind of heat sinks. The main objectives of this study are; investigating the effect of pins on the performance of PFMCHS by investigating the best geometry in the pinned-fin MCHS and which is higher, thermal or hydraulic performance of this kind of heat sinks and what is the optimal number of pins numerically and what about the pressure drop penalty in the proposed design, little, modest or high increase. It is seen that the thermal resistance of the pinned fin MCHS is about 50% lower, and pressure drop of it is much higher than that of the (PFMCHS) under the condition of equal wind velocity. Maximum mechanical fan power reduction obtained is about 57% for the pinned fin MCHS with ψ = 1 and Dh = 1 ×10-3 m compared to the corresponding original channel heat sink. To show the overall performance of the two parameters; aspect ratio (AR), pin number ratio (ψ), the overall JF factor is estimated and the concrete findings shows that the best hydrothermal performance is obtained at the greater aspect ratio which is around overall JF = 1.2. In addition, the trend of overall JF is going down with the pin number ratio, starting from 1.2 to 1.15. And the concrete findings show that pinned fin MCHS provides thermal performance of 1.42 times greater than the smooth one under the corresponding conditions when one pin is used in each channel
This investigation provides experimental results and nonlinear analysis by using finite element model of thick hollow core slab made from recycled lightweight material. Four hollow core slabs specimens were cast and tested in this investigation with dimensions (1200mm length, 450mm width and 250mm thickness). The crushed clay brick was used as a coarse aggregate instead of gravel. The iron powder waste and silica fume were used in order to increase the compressive strength of concrete. The techniques reduction hollow length and use shear reinforcement were used to improve shear strength and avoid shear failure. The specimens were tested by applying two-line load up to failure. The experimental results were showed these techniques were resisted the shear failure significantly and works to change failure mode from shear to flexural failure. Finite element computer software program (ANSYS) was used to analysis hollow core slabs specimens and compare the experimental results with the theoretical results. Good agreement have been obtained between experimental and numerical results.
In The present work, a thermal analysis of two different chimneys by studying the effect of the flue gases on the chimney shell structure was presented. A computer program was constructing using Fortran language to estimate the thermal stresses that: radial, circumferential and longitudinal thermal stresses which will induced as a result of thermal gradient across the chimney wall structure. The results show, the radial thermal stresses has the minimum value at the middle of the concrete layer in the unlined chimney. The circumferential and longitudinal thermal stresses are transferred from the negative value to the positive value. The maximum value of stresses is found in the inner surface negative value and on the outer surface positive value of the chimney.
The status of the infrastructure of the transport system and then mobility in the governorate of Anbar is deplorable. Therefore, it requires two types of solutions in two phases. This study concerned with the first phase, which is represented by solving the problem of the inadequacy infrastructure in terms of availability between the cities, and work to develop it toward being maximally connected. So, generally speaking this study aimed to facilitate mobility through this network, by improving the accessibility in term of connectivity. The analysis process in this study, have twin objectives: first, to determine how much new linkages we need for our network to be maximally connected as a first stage? Second, Building a legislative framework lends the weight for decision makers in transport agency to take tough decision built up on ranking the new proposed linkages according to their relative values in providing access to the network, and the increment in comparable nodal accessibility due to the new additions. So, there is need for more sensible decisions based on more accurate analysis for deciding the optimum priorities for the new linkages to take place in the stage of development implementation via legislative framework. Therefore, the analysis will deal with topological characteristics for a number of aspects by expressing the simple graph of the network in a matrix format. These aspects are simulated and measured through the matrices powering process and the principles of graph theory. However, in addition to reducing the time the vehicles stays on the road, the study results will assist to divert a large proportion of the traffic volumes concurrently with the implementation process, and this in turn will pave the way to precede the solution of the second phase inside the cities. Not to mention, the legislative framework will bases for the financial framework of the transport agency. Keywords: infrastructure inadequacy& development, accessibility and connectivity, graph theory, matrix representation &powering, new linkage, nodal accessibility , relative value ,optimum priorities (ranking) and Decision making(legislation).
This paper presents the experimental results of composite slabs under static and impact loading. Total of six specimens classified one specimen test under static loading and the remaining five were tests under impact dynamic loading with different parameters as type of connections and degree of interaction of composite slab. Low - velocity impact test was adopted by select the falling mass (4 kg) made from steel material and formed as ball shape without nose. The ball dropped freely from height of (2.4 m) and strikes the top of composite slab. The designed dimensions of specimens is (500×500×60 mm) as reinforced concrete slab that reinforced by mesh of (RBC) and the steel plate is (3 mm) in thickness. Deflection due to first crack is recorded, number of blows caused first crack and failure were counted. The test results showed that the welded stud connectors gives high strength capacity and resistance under static and impact dynamic loadings than other than type of connections, also, full interaction as degree of interaction is better than others
In this study an attempt is made to develop a method of analysis dealing with a multi-layer composite continuous beam , for linear material and shear connector behavior in which the slip (horizontal displacement) and uplift force (vertical displacement) are taken into consideration. The cross-sectional area for the beam consists of three layers varying in thickness and shear stiffness. The analysis is based on a approach presented by Roberts[1], basically for two layer simply supported beam, under uniform and point loads , which takes into consideration horizontal and vertical displacement in interfaces. The analysis led to a set of eight differential equations containing derivatives of the fourth and third order. A program based on the present analysis is built using finite difference method using boundary conditions. A comparison between the present analytical solution and previous studies shows close agreement. Continuous composite beams are very important element in construction of high rise buildings , multi-story frames and bridges, due to great advantages that can be obtained by using this sort of structural elements, such as reducing the beam moments, suitable reduction in deflections. The model deals with continuous beam consisting from three layers as a cross-sectional area with inter-layer slip. The cross-sectional area consist of composite material including intermediate layer from concrete and an upper and lower material with high strength in tension and compression ( i.e. steel plates or steel beams )