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Go to Editorial ManagerReinforced concrete slab with plastic voids (Bubbled Deck system) is a new type of slabs which has two-dimensional arrangement of voids within the slab that is developed to decrease the slab self-weight while maintaining approximately the same load carrying capacity as compared with the solid slabs. Plastic voided slabs have the ability to reduce concrete amount by about 30 percent and this reduction is so important in terms of cost saving and enhancement the structural performance. In this research paper investigation is carried out to study the shear strength behavior of one-way bubble deck slab using self-compacting reinforced concrete. The experimental program consists of testing thirteen one-way slabs with dimensions of (1700 length, 700 width and 150 thick) mm. One of the tested slabs is a solid slab (without balls) is used as a reference, the remaining twelve bubbled slabs with ball diameter (73, 60) mm are divided into five groups according to the parameters of the experimental work, the parameters of the experimental work include: type of slab (bubble and solid slabs), ball diameter (73, 60) mm, shear reinforcement and spacing between balls. The experimental results showed that the bubbled slabs without shear reinforcement have a decrease in the ultimate load as compared to solid slab by about 3.7% to 14.3% and an increase in the deflection at ultimate load by about 10% to 22%, at the same time the first crack load decreases by about 15.3% to 42.4% as compared to solid slab due to decreases of moment of inertia of bubble slab compared to solid slab. Also, the results showed that the bubbled slabs withe shear reinforcement (multi-leg) have an increase in the ultimate load as compared to solid slab by about 35.4% to 57.3% and an increase in the deflection at ultimate load by about 1% to 15%, at the same time the first crack load decreases by about 2.8% to 27.4% as compared to solid slab.
This paper presents a simple strut and tie model to calculate the shear strength of reinforced concrete deep beams. The proposed model assumes that the shear strength is the algebraic sum of three strength components: concrete diagonal strut, vertical stirrups, and horizontal web reinforcements. The contribution of each strength components was calibrated with the test results of 305 deep beams compiled from previous studies with wide range of geometrical and material properties. The predictions of the proposed model were compared with those of the current codes of practice (ACI-318-14 and ASHTOO 2014) and those of existing model in the literature. Comparisons revealed that the proposed model provided better predictions than other models. The mean of predicted strength to test of the proposed model, the ACI-318-14 model, the ASHTOO 2014 model were 0.98, 0.79, and 0.75, respectively. The corresponding standard deviations were 0.17, 0.28, and 0.49, respectively.
In this vast world after an earthquake lessons are learned; many strategies have been considered in order to achieve a proper seismic strength capacity.The aim of this paper is studying the seismic behavior of a typical reinforced concrete bridge pier in Iraq and implementing a proper technique of strengthening in order to fix any damage that had happened.Structure of a full scale three-dimensional finite element model was used in order to simulate a reinforced concrete pier via the computer software ABAQUS/CAE 2017 using concrete plasticity damage model (CDP).Under the action of Halabja earthquake, which was recorded at city of Halabja in Iraq on 12 November 2017, the behavior of model was traced, analyzed and the resulted damages were managed.The finite element analysis results indicated that the proposed configuration of carbon fiber reinforced polymers laminates substantially increases the lateral load strength and deformation capacity of the bridge pier
Real-life strategies are applied to assess pavement functionality, high-quality performance, and durability throughout its service life. Estimating pavement maintenance and sustainability is difficult. High-performance continuous reinforced concrete pavement (CRCP) structural design and Jordanian natural zeolite (JNZ) as a sustainable supplementary cementitious material (SCM) and unique mixed cement for green manufacturing are researched in this paper. The results obtained from this study showed that replacing cement with JNZ powder at 0%, 10%, 15%, and 20% improved concrete performance. Natural zeolite-mixed cement preserved concrete quality and reduced the need for ordinary Portland cement (OPC) and sulfate-resistant cement (SRC) clinker. After that, slab universal testing equipment and Jordanian zeolite-blended cement-reinforced concrete slabs were developed for CRCP performance. Therefore, fresh concrete was tested for partial cement substitution and standard mixture workability. Compressive, tensile, and flexural strength tests on 7 and 28 days and durability test (water absorption) were utilized to assess concrete strength and natural zeolite's potential to reduce resource consumption and carbon footprint while maintaining structural integrity using Open LCA. Sustainable CRCP structure development improved performance, resource conservation, and carbon footprint over the prior mix, according to EIA (Environmental Impact Assessment) software and chemical tests. This research improves materials and supports global sustainability goals.
Openings in reinforced concrete (RC) slabs are usually created as a result of variations in construction function, architectural or mechanical necessities. Heavy equipment loads resulting from mechanical system of any building are often carried by RC slabs. Even the static analysis and design of RC slabs with opening is not clearly stated in the available international Codes, dynamic analytical solution for such structure is complex._x000D_ In this paper, numerical analysis based on finite element approach is utilized to implement the modal analysis of RC slabs. Opening size and position was parametrically studied. Slab natural frequency or periods in addition to, the mode shape were registered. The results showed that the opening size and position involved in RC slab had a significant change in the value of natural frequency and period for the high level modes. The material nonlinearity affect on free vibration analysis of RC opening slab with different levels of stiffness modifiers was taken into account. The dynamic characteristics of RC opening slab as a function of stiffness modifier degree was numerically measured for six mode shapes. The paper found that a reduction in stiffness modifier value greatly reduce the .natural frequency of RC opening slab.
This paper presents experimental investigations to study the behavior of High Strength Reinforced Concrete (HSRC) deep beams with web openings under monotonic and static repeated loading conditions. The experimental work procedure consisted of testing eighteen simply supported HSRC deep beams both with and without web openings. The numerical work procedure consisted of testing ten simply supported HSRC deep beams both with web openings. All beams had the same dimensions and flexural reinforcement. They had an overall length of 1400 mm, a width of 150 mm and a height of 400 mm. The investigated test parameters were concrete compressive strength, shape and size of openings, vertical and horizontal reinforcement ratios, shear span to effective depth ratio (a/d ratio) and loading history. The experimental results reveal that the ultimate load capacities for specimens tested under four different repeated loading regimes decrease in the range between 2% and 19% in regards to the control specimens which were tested under monotonic loading regime. The results indicated that the increase in the severity of loading history leads to a decrease in the ultimate shear strength of the deep beams and causes increases in their ductility ratio. The ultimate loads of HSRC deep beams with square web openings size of (50*50mm, 60*60mm and 70*70mm) tested under the repeated loading history (HS-1) which consisting of five phases decreased by (11.4 %, 24.1% and 26.3 %, respectively) compared to that of identical solid deep beam. The ultimate load of HSCR deep beam with circular web openings shape tested under repeated loading history (HS-1) increases by 8.6 % compared to the equivalent square web openings shape. For numerically analyzed beams under repeated loading history (HS-1), the ultimate load increases by 16% when using area of 2500mm2 of circular web openings shape (equal in area to square web opening size 50mm*50mm) and by 13.5% when using rhombus web openings shape of the dimensions 50*50mm in comparison with the case of 60-mm size square web openings.
Action of applied external loads, early thermal by hydration of cement in reinforced concrete (RC) structures, creep and shrinkage and seasonal effects due to environmental conditions are the main causes of inducing cracks in RC members. Most Design Codes of RC structures have underestimated the distribution steel requirements based on stating nominal or minimum requirements for early thermal and moisture movement especially in watertight continuous constructions. Three dimensional finite element analysis for a verification problem was carried out on a continuous reinforced concrete members with different bar diameter subjected to different applied temperatures values which represent the early-age and seasonal effects. The results of this analysis were compared with the available BS Code equations for crack control for early thermal movements. The comparison between the Code equation and finite element analysis was met in a good agreement. The resulted data was used to study parametrically the crack characteristics in terms of crack width and spacing of RC members in term of the effects of three different construction exposures (Class A, B and C), three values of temperatures with three different bar size diameter (10mm, 12, 16) for each one. The present work was indicated as the bar diameter increases, the required steel ratio increases proportionality to match the assumed crack width. So, to get the minimum steel ratio this is the target. It must use smallest bar diameter. But unfortunately this is limited by minimum practical bar spacing. The overall of present study was indicated that the continuous construction required high steel area especially for class A exposure.
This research submits theoretical and experimental realization of shear behavior of RC I-beams with polypropylene fiber with different volume fraction of plastic fiber as additive. The enhance of the sustainability of structural elements through the development of its mechanical performance by adding new materials such as plastic raw materials has become more important in the current period , particularly I- beams that was used in the long spans structure to become more environmentally-friendly. Seven specimens were tested in this study and only the amount of fiber volume fraction was varied. Experimental results showed that the ultimate strengths are increased in range (4.4% to 35.27%) that of control IB-1 for the tested beams containing Polypropylene Fiber Reinforced Concrete (PPFRC) with varied amount percentage of fiber material. Crack arrest mechanism of polypropylene fibers, and compressive strength of concrete increased in range (7.42% to 29.3%) that of plain concrete, and improved the tensile response in range (8.36% to 92.7%) that of plain concrete, limited crack propagation. So, improved behavior was obtained._x000D_ ANSYS 11, Finite Element models software are used to emulate two tested I-beams. 3D - nonlinear solid elements was utilized to model the concrete, while, the steel reinforcement was demonstrated by spar element. It was found that the general practices of the FE models demonstrated acceptable concurrence with perceptions and information from the experimental tests.
Numerical analysis of the performance of reinforced concrete (RC) deep beam subjected to static and fixed-point pulsating loading at the midpoint has been investigated. Three-dimensional nonlinear finite element model using the Strut and Tie approach was adopted. The damage level under the influence of the applied fixed pulsating loading is higher than the static applied loading, hence early crack was observed because of the stepwise loading in the form of vibration. Although the Strut and Tie approach gave a good estimation of the resistance capacity of the beam, the beam undergo high shear damage when subjected to these two types of loading. Material strength properties, applied loadings and cross-sections adopted are some of the factors that affect the performance of the deep beam.
Eight RC circular hollow columns (external diameter = 220 mm, internal diameter = 100 mm, length = 1000 mm and the hollow part = 700mm) casted and strengthened with ferrocement fibers composites to illustrate the behavior of these columns under concentric and eccentric axial compression force. Two columns where used as reference columns, which were repaired after failure to be tested as retrofitted columns. Six specimens were strengthened with one and two WWM layers as required. The variables considered included number of the WWM layers (N), the loading configuration and the eccentricity value (e) of loading. The ferrocement thickness was constant at 20 mm in all retrofitted and strengthened specimens.The test results revealed that the maximum increase in the ultimate concentric loads were 67% by strengthening the reference column with two layers of WWM, and the maximum increase in the ultimate eccentric load of columns was 78% by increasing of the WWM from one to two layers. For a constant number of WWM layers, the change from concentric to eccentric force caused a decrease in the ultimate load value attaining 73.5% for one- layer WWM strengthened columns. The failure of columns occurred by yielding of steel reinforcement followed by concrete crushing (i.e. tension failure).
This paper studies the effect of different design spectral response acceleration parameters as suggested by the uniform building code (UBC), unified facilities criteria (UFC), and Iraqi seismic code(1997) (ISC 97) on the seismic response of reinforced concrete multi-story framed building located in Baghdad city, Iraq. These parameters are: (a) spectral response accelerations Ss, at short periods, and S1 at a 1-second period in accordance with international building code (IBC), (b) seismic zone factor (Z) according to UBC, (c) Seismic hazard zoning coefficient (Z) according to ISC 97. In this paper, first, the elastic seismic responses for significant modes of vibration for chosen building under design response spectrum that obtained from the above mentioned codes are calculated, and then a comparison was made among different design spectral response acceleration parameters. The intent of this study is to review the seismic provisions of the current edition of Iraqi seismic code (1997) to determine whether it provides an equivalent level of safety to that contained in other international codes. Design base shears, lateral seismic forces, inter story drifts, response spectrum modal, effective seismic modification, floors acceleration and story shears are comparatively presented.
Normal concrete is weak against tensile strength, has low ductility and also insignificant resistance to cracking. The addition of diverse types of fibers at specific proportions can enhance the mechanical properties as well as the durability. Discrete fiber, which is commonly used, have many disadvantages such as balling the fiber, random distribution, and limitation of the used Vf ratio. Based on this vision, a new technique was discovered, enhancing concrete by textile-fiber to avoid all the problems mentioned above. This paper presents all important consequence and conclusions obtained from previous studies on how to strengthen concrete with two-dimensional and three-dimensional textile-fibers, and focuses on the flexural behavior of concrete members. The results indicate that there was an improvement in flexural strength, deformation capacity, and toughness with different load conditions when using different types of textile-fiber. It was observed that the effect of textile-fibers would increase when this fiber was coated by epoxy. In TRC system, there is a significant impact on the number of textile-fiber layers used.
In this paper, the cross section behavior of reinforced concrete columns made of normal and hybrid reactive powder concrete (hybrid by steel and polypropylene fibers) under concentric and eccentric vertical load was study. The casted columns were cured in two different type tap water for 28 days and chloride water for six months. Chloride salts with concentration was 8341.6 mg/l. Three variables were adopted in the experimental program; concrete type, curing type and the eccentricity of vertical load. Twenty (120x120x1200) mm columns were casted and tested depending on these variables. The different eccentricities were (0, 50,100 and 150) mm and where (e/h) were (0, 0.42, 0.83 and 1.25) respectively from the center of column, the other types of loading are tested the specimens as beam._x000D_ The experimental results showed increasing in ultimate load capacity and higher chlorides resisting for hybrid reactive powder concrete in comparison with normal concrete in both types of curing (tap and chloride water). Through studying load deflection, test results for Normal Strength Concrete (NSC) and Hybrid Fiber Reactive Powder Concrete (HFRPC) columns that deflection for columns cured in chloride water more than tap water when compared at the same load that also by increase eccentricity leads to an increase in deflection for both cured and The neutral axis depth for HFRPC columns is more than NSC at the same load also when eccentricity increases, the compression zone decreases and neutral axis also decrease by increase eccentricity. These results occur when columns are cured in tap and chloride water._x000D_
Structural elements. This means the structural behavior can be quantified by considering the behavior of each structural element in each load path. Concrete is a material known for its great strength. Regardless, there are a few weaknesses, which must be taken in consideration in the design of concrete structural elements. Basically, concrete is made of three main ingredients: Portland cement, water, and aggregates (sand and stone).In order to improve tensile strength and ductility (capacity to stretch and deform prior to failure) in concrete, so this paper discus some types of concrete and record the effect on beams. Reactive powder concrete (RPC) is an actual concrete mixture, it is a special type of concrete because mix concrete (coarse and fine aggregate ) replaced by fine sand size (150-400)µm. In the experimental comparison the mechanical properties( compressive , splitting tensile and flexural )strength of plain RPC and high and normal strength concrete. Each set consisted of (4) cubes of (100×100×100_mm, (8) cylinder of (150×300mm) and (4) prism of (100x100x500) mm and consisted of (4) beam of (1000×100×400)mm. The results shown that the maximum compressive strength is 107 MPa and the maximum splitting tensile 9 MPa of RPC comparison high and normal strength concrete. The result of the second part shown increased RPC reinforced concrete the firstcrack288 MPa and ultimate crack 380MPa comparison high and normal strength concrete and the mode of failure of RPC (flexural-shear).
This study concerns utilization of nonlinear finite element method for to evaluate the role of longitudinal soffit-bonded CFRP strips in elevating the shear behavior of RC beams without stirrups. All beams cross-sections were of 150 mm breadth and 200 mm depth, the overall length was 1500 mm with clear span 1300 mm. One beam was provided by minimum web reinforcement according to the ACI 318M-14, while the other five were without web reinforcement but externally strengthened by a variety of CFRP-strip combinations consisting of longitudinal soffit-bonded strips. The predictions of a proposed ANSYS (version 14.5) model for six of the test beams including modeling of concrete, steel rebars, CFRP strips and supports and loading steel plates, by SOLID65, LINK180, SHELL41 and SOLID185 elements, respectively, show high agreements with experimental evidence, which stands as a definite witness to the efficiency and reliability of the present numerical model.