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Go to Editorial ManagerNew composite reinforced concrete beams, in which reinforced concrete component is connected to steel T-section, are proposed. The stirrups of the beam were utilized as shear connectors by passing them through drilled holes in the web of the steel T-section. Experimental test and numerical analysis were conducted to determine the behaviour of such beams when subjected to combined shear, torsion, and bending stresses. Full scale one conventional reinforced concrete curved in plan beam C1, and four composite reinforced concrete ones, C2 to C5, were tested. The degree of shear connection between the two components of beams C2 to C5 was changed by varying the number of stirrups which are used as shear connectors. The increase in load carrying capacity of the composite reinforced concrete beams reached 55 % for beam C4 as compared to that of ordinary reinforced concrete beam. The experimental results demonstrated that the stirrups are very effective in providing the interaction between the two components of the beams. The degree of shear connection emerged not to have effect on the behaviour of tested beams. Three-dimensional finite element analysis was conducted using commercial software 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.
Artificial Neural Networks (ANN) have been applied to structural engineering in recent years. Most of the researches are based on backpropagation neural networks due to its well-studied theory. A backpropagation neural network has been used to predict the ultimate torsional strength of reinforced concrete rectangular beams. The effects of the parameters, such as the number of nodes in the input, output and hidden layers and the pre-process of the training patterns, on the behaviour of the neural network have been investigated. The algorithm called 'resilient propagation algorithm' has been used to the performance of the neural network. After training, the generalization of the neural network was tested by the patterns not included in the training patterns. Once the neural network has been trained, the ultimate torsional strength of reinforced concrete is obtained very easily and efficiently. Based on the ANN results, a parametric analysis was carried out to study the influence of parameters affecting the ultimate torsional strength of reinforced concrete beams and these results are compared with the equations of ACI-code.
A large number of RC structures or at least some of their members need strengthening or rehabilitation. Among the typical failure modes, the shear failure is more dangerous and less predictable, because of usually brittle behavior and sudden collapse. Therefore, there are necessities for upgrading the shear capacity and the local ductility of reinforced concrete beams. In this study, four different techniques of concrete jacketing were used to improve the behaviors of the shear deficiencies beams. The four techniques used in this study to enhance the behavior of the beams were by using a Self-Compacted Fiber Reinforced Concrete jacket without stirrups (S.-J. + Steel Fiber), a concrete jacket of Self Compacted Concrete with stirrups (S.-J. + Stirrups), a concrete jacket of ferrocement jacket (S.-J. + Ferrocement), and a concrete jacket of ferrocement jacket with external steel reinforcing bars (S.-J. + Ferrocement + R). These techniques contributed to enhancing the load-carrying capacity and delaying the appearance of the first crack in tested beams compared with the control beam by a percentage of (35, 59, 30, 6) % and (18, 35, 81, 80) %, respectively. The specimen (S.-J. + Stirrups) showed the best performance in comparison with the other used strengthening techniques used in this study in terms of stiffness and the ultimate load-carrying capacity. The ferrocement jacket (S.-J. + Ferrocement) was found to be the most suitable jacketing system used to enhance the shear capacity in terms of cracking load.
This research concerns with the fracture behavior of reinforced concrete beams without shear reinforcement numerically. The software ABAQUS is adapted to simulate the crack propagation using the eXtended Finite Element Method (XFEM), taking into account materials nonlinearities using concrete damage plasticity CDP criteria. XFEM is used to solve the discontinuity problems in the simulation. The maximum principal stress failure criterion is selected for damage initiation, and an energy-based damage evolution law based on a model- independent fracture criterion is selected for damage propagation. The traditional nonlinear finite element analysis is used to specify the crack initiation position, which is required to specify the crack location in the analysis of beams using XFEM. Three-dimensional reinforced concrete beam models are investigated subjected to three and four-point loading tests. Simply supported beams under the effect of applied static load are investigated. An elastic perfectly plastic model is used for modeling the longitudinal steel bars. The main variables considered in the study are beam depth and the shear span with beam length. The numerical results are compared with the available experimental results to demonstrate the applicability of the model. The XFEM provides the capability to predict the concrete member fracture behavior.
Mathematical programming techniques have been used to minimize the cost of reinforced concrete counterfort retaining wall.The study presents a formulation based on elastic analysis and the ultimate strength method of design as per ACI-M318code. A computer program is generated to handle the considered problem. The formulation of optimization problem has been made by utilizing the interior penalty function method as an optimization method with the purpose of minimizing the objective function representing the cost of one-meter length of the counterfort retaining wall. This includes cost of concrete, reinforcement, and formwork. The design variables considered in this study are the dimensions and the amounts of reinforcement. It is found that the optimal spacing of counterforts equals about (0.214 to 0.366) of total height of wall. The optimum width of the base is found in the range (0.50 to 0.78) of the total height of the wall. Also the thickness of the stem is in the range(0.0284 to 0.0377) of the total height and it is less than half thickness of the base.
The study investigates the behavior of reinforced concrete cylindrical shells under monotonically increasing loads. Three-dimensional models of six small-scale experimental shells with length-to-radius ratios ranging from short (0.84) to long (5.0) are implemented within the context of the finite element method, through use of the ANSYS computer code, and the nonlinear response is traced throughout the entire load range up to failure. Cracking occurs at working load levels, with subsequent reduction in shell stiffness. Increasing loads lead to failure modes varying from a beam failure in long shells, combined longitudinal and transverse cracking in intermediate length shells, and abrupt diagonal with limited transverse cracking in short shells. Ultimate load capacities range from 5.0 kPa to 60.0 kPa increasing with decreasing length-to-radius ratios.
This numerical study aimed to investigate the torsional behaviour of hollow cross section reinforced concrete members strengthened with steel fibers (end hooked and corrugated), subjected to pure torsion. The numerical results were compared with experimental results and show good agreement. The experimental study was conducted on ten steel fiber reinforced concrete specimens with low longitudinal reinforcement ratio to investigate the torsional behavior under pure torsion. For this analysis, a computer program (ANSYS 18.2) was used. The brick elements 8-nodes (SOLID65) were used to concrete simulation, while the steel bars simulated as axial members (link 180). The steel fibre was represented theoretically by the stress-strain relationship. The theoretical results indicated that the adopted smeared crack model is capable of making relatively acceptable estimations of cracking and ultimate torsional capacity of the members.
This study is to investigate the effect of partially replacement of coarse aggregate by waste plastic and using the paper sludge as additive material at concrete, on the hardened concrete properties and its impact on structural behavior of the reinforced concrete members (slab, column, and beam). Plastics and paper are widely used in daily life in huge amounts. Both incineration and landfilling are options for disposing of plastic and paper waste, but either one could be harmful to the environment. Therefore, reducing waste or increasing its value can reduce pollution and reduce disposal costs. The variables of the experimental program include the ratio of waste plastic and paper sludge, the used ratios for plastic and paper were (5%, 10%, and 15%) by volume. Hardened concrete properties were investigated for concrete include: flexural strength, modulus of elasticity, and splitting tensile strength. For each structural reinforced member, the (Load – Deflection) curve has been extracted. The study shows that the plastic waste negatively affects most of concrete properties. The research indicates that using waste plastic in reinforced concrete members with percentage of (5% and 10%) by volume as a partially replacement of coarse aggregate giving acceptable results. However, when adding (5%) by mixture volume of waste paper in reinforced concrete members, the load-deflection behavior and ultimate load-bearing capacity have been improved. In general, using waste plastic and paper sludge in concrete mixtures lead to reduction in ultimate load ranging between (4.62%-10.82%) for slab under point load, (4.85-18.99%) slab under distributed load, (3.72%-12.21%) column, and (1.78%-7.16%) beam specimens respectively.
This work deals with the effect of using Recycled Concrete Aggregate (RCA) as a partial replacement of coarse aggregate in Self-Compacting Concrete (SCC), on the structural behavior (flexure and shear) of reinforced concrete one-way slabs. To the authors’ knowledge, this study is one of limited studies concerning the behavior of recycled aggregate concrete one-way slabs subjected to line loading with significant replacement of conventional aggregates by recycled concrete aggregate (up to 75 %). Three replacement ratios were considered: 25 %, 50 %, and 75 %. The mixes (with natural stone coarse aggregate, NCA) have an averaged compressive strength of ($F_{cu} = 42 \text{ MPa}$) at the age of 28 days with a tolerance of ($\pm 1.5 \text{ MPa}$). While, the mixes (with RCA) have an averaged compressive strength of ($38.5, 36.5, \text{ and } 34 \text{ MPa}$) for the three replacement ratios respectively, at the age of 28 days with a tolerance of ($\pm 2 \text{ MPa}$). All the slabs were cast with length of ($1600 \text{ mm}$), width of ($600 \text{ mm}$), while the thickness was variable. For this purpose, sixteen reinforced concrete one-way slabs were cast and divided into five groups (G1 to G5). Different parameters that affect the behavior of one-way slabs were studied and include type of failure, replacement ratios of NCA by RCA, amount of main reinforcement, thickness and locations of line loadings along the span. Hardened concrete specimens results show that the **compressive strength** $F_{cu}$, **tensile strength** $F_t$, **modulus of rupture** $F_r$, and **modulus of elasticity** $E$ were decreased as the RCA replacement increased. The experimental results of slabs show that the **ultimate capacity** of slabs decreased as the RCA replacement increased, the **deflection** and **strain** increase as the RCA replacement increases and the **crack width** increases as the RCA replacement increases. From the results of ultimate capacity, cracking load and moment, deflections, crack width and pattern and concrete surface strains, it can be concluded that the recycled concrete aggregate can be used as a partial replacement of natural coarse aggregate to produce self-compacting concrete mixes. Also, the behavior of one way slabs cast with SCC containing RCA is acceptable.
This paper deals with the behavior of reinforced concrete anchor blocks for underground steel pipelines.~ under the effect of loads caused by internal pressure and temperature variation due to the transportation of hydrocarbon products. The finite element method is used to carry out the analysis using the ANSYS 5.4 program. To study the effect of oil, it is represented by springs with different values for the modulus of subgrade reaction in normal and tangential reactions. It is concluded that increasing the values of the modulus of subgrade reactions, kn and ks of the soil surrounding the reinforced concrete anchor block causes an increase in the failure loads of the block. But at high values of these modules, the rate of this increase in the failure load will decrease. The area of the passive face of the concrete anchor block is found to have the main effect on the failure load as compared to the length of that block. The failure load of the concrete anchor blocks that have square cross sections is 1.33 times larger compared to that of rectangular sections. It is also concluded that locating the steel flange at the middle of the block leads to a larger resistance of anchor blocks as compared to any other position.
In this investigation, the bond stresses between the reinforcement and concrete was studied by using non-material interface elements that are able to produce the bond stresses for the reinforced concrete beam gradually loaded from zero to failure. Depending on (Jawad) program, which is a non-linear analysis program of plain and reinforced concrete beams through a discrete-crack approach by using the finite element method. The stiffness matrix derivation of the interface element and the way of non-linear treatment were explained. The distribution of bond stress drawings along the steel reinforcement for different values of loading was achieved before and after cracking.
The present study deals with the analysis of short reinforced concrete columns subjected to axial load. One of the efficient techniques is applied, known as artificial neural networks. The descent gradient backpropagation algorithm is employed for analysis. The optimum topology (which gives the least mean square error for both training and testing with a fewer number of epochs) is presented. The effects of the number of nodes in input and hidden layer(s), and selecting of leaming rate and momentum coefficient, on the behavior of the neural network, have been investigated. Due to the slow convergence of results when using descent gradient backpropagation, the faster algorithm called "resilient backpropagation algorithm" has been used to improve the performance of the neural network and the results have been compared with those obtained using the descent gradient backpropagation algorithm.
Mathematical programming techniques have been used to minimize the cost of reinforced concrete T-beam floor. The floor system consists of one way continuous slab and simply supported T-beams. The study presents a formulation based on elastic analysis followed by the ultimate strength method of design with the consideration of serviceability constraints as per ACI Code. The formulation of optimization problem has been made by utilizing the interior penalty function method as an optimization method with the purpose of minimizing the objective function representing the cost of one-meter length of the floor system. The cost includes cost of concrete, reinforcement, and formwork. The design variables considered in this study are the dimensions and the amounts of reinforcement for the slab and beams, in addition to the spacing of the beams. Many examples are solved to show the effect of these design variables on the optimum solution of the floor system. The effect on the optimum design of the compressive strength of concrete, yield strength of steel, concrete cost ratios, and formwork cost ratios has also been studied.
A spandrel beam is a structural member lies at the edge of a frame and is connected by a joint to the floor beam extending into the slab. The spandrel beams are primarily responsible for transferring forces from a slab to the supporting edge columns. This work investigates the possibility of using the artificial neural networks to model the complicated nonlinear relationship between the various input parameters associated with reinforced concrete spandrel beams and the actual ultimate strength of them. The descent gradient backpropagation algorithm was employed for predicting the ultimate strength of the reinforced concrete spandrel beams. The optimum topology (which gives least mean square error for both training and testing with fewer number of epochs) is presented. Effects of parameters such as, number of hidden layer(s), number of nodes in the input layer, output layer and hidden layer(s), initialization weight factors and selection of the learning rate and momentum coefficient on the behaviour of the neural network have been investigated. Because of the slow convergence of results when using descent gradient backpropagation, another algorithm which is faster called "resilient backpropagation algorithm" has been used. The neural network trained with the resilient backpropagation RPROP algorithm gives better results than that trained with the steepest descent algorithm with momentum GDM algorithm.
This numerical study was conducted to simulate and analyze the pushout test for the new shear connector in a new steel-concrete composite system. In this system, the shear stirrups of the reinforced concrete beam are used as shear connectors when passed through holes drilled in the web of inverted steel T-section. The numerical analysis was performed by creating a three-dimensional finite element model using the finite element program ANSYS 21 student version to simulate the behavior of the new innovative shear connectors. The pushout specimens analyzed in this study have been tested experimentally by the same researchers earlier. A total of fifty-six push-out specimens were modeled and analyzed to investigate the effect of many parameters on the shear strength and slip capacity of the shear connector. The parameters studied in this investigation were the specimen dimensions (length and width), the diameter of stirrups (shear connector), the number of connectors per specimen, concrete strength, size of T-section, and shape of the specimen. The finite element analysis using ANSYS gave a good prediction of the effect of studied parameters on connector strength, the failure modes, the form and intensity of deformations in the model, and the load-slip response. The maximum difference in connector strength which was observed between the numerical and experimental results was 15 %.
The study aimed to investigate the structural behavior of indirectly loaded flanged deep reinforced concrete beams. Twenty-one flanged deep beams were tested. The behavior of beams under loading was observed. Cracking and ultimate loads were recorded.
The study investigates the behaviour of reinforced concrete corner joints under monotonically increasing loads which tend to increase the right angle between the two joint members. The experimental results for two case studies are considered, and the ANSYS computer code is employed to create three-dimensional models for corner joints within the context of the finite element method. The effect of reinforcement details at the corner joint is studied for commonly used detailing systems, and the nonlinear response is traced throughout the entire load range up to failure. The results obtained are generally in good agreement with the experiments, and show that the detailing system has a significant effect on corner joint behaviour, with efficiencies ranging from as low as 54% up to 147%.
This study investigates the effect of the shear span-to-effective depth ratio (a/d) on the behavior of high-strength steel fiber–reinforced concrete deep beams without stirrups containing circular web openings. A circular opening of 12.6 cm diameter was positioned at the center of the shear span, and beam performance was evaluated in terms of crack patterns, load–deflection response, and stress–strain behavior. Four specimens were tested experimentally. The control specimen consisted of a solid deep beam without openings and without steel fibers, while the remaining three specimens were reinforced with 1% steel fibers and included circular openings. All specimens were reinforced with 2Ø12 mm top bars, 3Ø16 mm bottom bars, and two stirrups at the supports to prevent local failure. The beams had different shear span ratios (a/d = 0.75, 1.0, and 1.5) and corresponding total lengths of 1025 mm, 1200 mm, and 1550 mm, respectively. All specimens were simply supported and subjected to two-point loading. The experimental results revealed that the optimal shear span ratio for maximum performance was a/d = 0.75 when combined with 1% steel fiber reinforcement. In addition, the ultimate strength of beams with circular openings decreased as a/d increased, with a strength increase of approximately 5.48% at a/d = 0.75 compared with a/d = 1.0.
A computer program has been generated to calculate the optimum dimensions and the amount of reinforcements for open reinforced concrete circular cylindrical tanks rest on ground. The design is based on limit state method for both ultimate and serviceability limit states in accordance with the British Standards B.S. 8110 and B.S. 5337. The cost of concrete, steel, and formwork are considered. The procedure is based on the interior penalty method to find the optimum solution for the non-linear programming problem. The tank consists of cylindrical wall and circular base and the joint between them was considered as partially fixed. The design variables consist of tank geometric variables in addition to steel content in seven positions. The effect of the design capacity of the tank, bearing capacity of the soil, unit price of steel and concrete, and finally unit cost of formwork was studied. It is found that the reduction of the bearing capacity of the soil linearly increases the cost of the tank. The increase of concrete and steel unit costs leads to increasing the tank height while the increase of formwork unit cost enhances the tank diameter, to reach the optimal design.
This study investigates the shear strength behavior of two-layer reinforced concrete beams consisting of two different types of concrete. One of the layers made of lightweight concrete (LWC) and the other was normal weight concrete (NWC). A total of 16 shear deficient reinforced concrete beams were fabricated and cast with NWC, LWC, and two-layer beam of both material with different configuration. All the beams were tested under four-point loading after 28 days. The variables of the experimental program include the ratio of thickness of the lightweight concrete layer to the overall depth of beam ( h LW / h ), and concrete compressive strength. Experimental results which include load-deflection response curves along with failure modes for NWC, LWC and two-layer beams. The results showed that all beams failed in a similar mode, due to diagonal tension shear crack. Based on the experimental results it can be also concluded that the shear load is governed by compressive strength of lower layer of the concrete when the shear span to overall depth ( a / h ) of the beams is 2.75 or more. While for the a / h 2.375 and 2.00 the two-layer beam has a significant reduction in the shear capacity compared to the NWC beams and increasing compared to LWC beam. The ratio of experimental shear stress divided by the root square of concrete compressive strength (vexp √f c ' ) , which demonstrates the diagonally cracked concrete's ability to transfer strain and shear was maintained for all configurations greater than 0.17, which is the minimal value recommended by ACI318-19.
This research is devoted to investigate the effect of Carbon Fibre Reinforced Polymer (CFRP) strips on the behaviour and load carrying capacity of strengthened and repaired reinforced concrete corbels. Experimental investigation were carried. The experimental program variables include location, direction, amount of CFRP strips and effect of shear span to effective depth (a/d) ratio on the behaviour of strengthened corbels. All corbels had the same dimensions and flexural reinforcement and they were without horizontal shear steel reinforcement. The experimental results obtained from the adopted strengthening and repairing CFRP techniques showed a significant improvement in the behaviour and carrying capacity of the tested corbels. An increase of about (44.5 - 60) % in the ultimate load has been obtained for specimens strengthening by inclined technique compared to the ultimate load of control corbel and (14.7 - 31.2)% for specimens strengthening horizontal technique. For corbels repaired with CFRP strips, an increase of (56%) with respect to the ultimate load of control corbel is achieved. Also the strengthened corbels show stiffer load deflection response than corresponding control corbels (unstrengthened corbels).
In recent decades, the need for strengthening and repairing reinforced concrete structures has increasingly arisen. One common method is the use of concrete jackets. Slurry Infiltrated Fiber Concrete (SIFCON), a newly developed material, offers superior mechanical properties, making it a preferred choice for strengthening and repairing concrete structures. However, there is limited understanding of its bonding performance when used as an overlay on a Normal Strength Concrete (NSC) substrate. This study conducted a direct Shear Test (DST) to evaluate the bond performance using reinforced NSC cubes externally bonded with SIFCON jackets subjected to direct shear. Eighteen reinforced cubes were strengthened with various bonding systems to investigate how different factors affect the bond performance between the NSC substrate and SIFCON overlay. The parameters studied included surface preparation methods, binder types, jacket configurations, bonding conditions (fresh overlay on hardened substrate and hardened overlay on hardened substrate), dowel placement, and bonding mechanisms. The results show that using bonding agents significantly improved bond strength, with epoxy proving more effective than latex. Specimens prepared by chipping showed better bonding performance compared to those prepared through diamond cutting. Chipping increased bond strength by 8.91% to 13.84% over diamond cutting in the case of fresh SIFCON overlay on hardened substrate. Using dowels in the bonding systems also improved bond performance by 10.89% to 16.97%. Applying jackets to three sides instead of two increased the ultimate failure load by 31.76% when dowels were used in both the two-sided and three-sided strengthened samples, and by 35.45% in the absence of dowels in both types of strengthened specimens. The cast-in-situ specimens demonstrated superiority over those strengthened with precast jacket layers.
The objective of the present paper is to evaluate the effects of the soil-structure interaction on the seismic evaluation in the building when a framed building is supported on raft foundation. Also the foundation-soil interaction effect has been considered by replacing it with equivalent springs. Nonlinear static pushover analyses of eight-storey reinforced concrete hospital building located at Delhi-India has been performed using the Capacity Spectrum Method of ATC-40. The deformations define the state of damage in the structure through three limit states of the NEHRP Guidelines and the FEMA-356 have been used to evaluate the performance level of the building for drift, the plastic hinge stage of the crack and shear under the condition of the fixed base and the effect of the soil-structure interaction. The performance of the building and individual components has been estimated for Design Basis Earthquake and Maximum Considered Earthquake. The weight of the slab was distributed as triangular and trapezoidal loads to the surrounding beams as per IS 456:2000. The weight of the brick masonry was distributed uniformly on the beams. The results show that the soil structure interaction has marked effect on the roof displacement, storey drift, design base shear, effective damping and crack pattern for beams and columns while there is a minor effect on the torsional behavior of the building. The building is more critical in the performance level when considering the soil flexibility.
The effect of different dosages of the high range water reducing admixture–additive- (HRWRA), the commercially polymeric material (Plastocrete-N), on the corrosion resistance of embedded steel in concrete exposed to chloride solution in the absence and presence of sulfate ions was studied. In the present study, four levels of polymeric material (Plastocrete-N) (0.125%, 0.250%, 0.375%, and 0.500% by weight of cement) were used to prepare HRWRA treated concrete. The concrete specimens exposed to chloride and chloride–sulfate solutions at concentrations of (3.5% NaCl and 5% Na2SO4), at ambient temperature. The electrochemical behavior of steel in both reference and HRWRA concretes was studied under the effect of corrosive environments using corrosion measurement systems such as: a) half – cell potentials measurement system and b) accelerated corrosion test system. The results showed that a longer time of corrosion initiation (180 day) observed with 0.500% HRWRA containing concrete compared to other different HRWRA percentage including the reference concrete. It was concluded that the use of 0.500% HRWRA provided superior protection to steel reinforcement in concrete that subjected to corrosive environments. Furthermore, the steel with 0.500% HRWRA was subjected to corrosion test by mass loss, it is evident that a reduction in mass loss by about 90.2% and 85.2% in both solutions, respectively.
This paper investigates the possibility of recycled aggregate use in concrete slabs with hollow cores. The main variables considered in the experimental study for the slabs were the recycled aggregate percentage and the hollow core number. Six slabs with dimensions of (1000 × 500 × 120) mm was fabricated and tested. The results showed that the addition of recycled aggregate in the concrete slabs affected the ultimate strength, ductility, and energy absorption of the concrete members. An increase of the recycled aggregate percentage to 25 % decreased the ultimate strength capacity by 3.54 %, but the increase of recycled aggregate to 50 % led to a decrease in the ultimate strength of about 6.64%. The existence of a hollow core reduced the cracking and ultimate load capacity of the RCA slabs, and this reduction was according to the core number which the fabrication of more cores caused more decrement. The ductility and energy absorption were decreased when the replacement ratio of the recycled aggregate increased. Also, the core number affected the ductility and energy absorption. The energy absorption was the most property affected by the core number increase which caused an average reduction of 71.5 % when the core number increased from two to three hollow cores.
The choice of aggregate type in producing reinforced concrete depends on the availability of the source sometimes and the intended concrete requirements like lightweight or normal aggregate concrete or high strength concrete. The punching shear resistance is being considered to be influenced by numbers of parameters including aggregate size and types. These parameters have not accounted in most of codes of design and have given a little attention by researchers. Most of available knowledge are based on outcomes from experimental works on beams. In this paper, the considerable slab tests without shear reinforcement are collected from literature in which aggregate types and sizes are given and they were failed in punching. The test results are compared to those calculated by ACI, EC2 and CSCT. The deficits of shear resistance are found clear where high compressive strength is combined with reinforcement ratio.
The main objective of this study is to investigate the effect of repeated load on the strength and behavior of the spandrel beam by considering eight specimens divided into four groups based on the design methods; type of cross-section of the spandrel beam and the type of loading. Two design methods, two types of loading and two types of cross sel.1ions for spandrel beam are considered, the first is a solid rectangular section, while the other is a hollow rectangular section. The effect of repeated loads on the crack's width, deflections, torque, and angle of twist is studied using two stages of loading, the first stage is at the soft-cracking stage after the occurring of cracks in the spandrel beam and the second stage is the yielding of the bottom longitudinal reinforcement of the floor beam.
A composite beam is an accumulation of different materials so as to form a single unit to exploit the prominent quality of these materials according to their position within the cross-section of the composite beam. The present study investigates the structural behavior of six simply supported composite beams, in which a reinforced concrete T-beam is connected together with a steel channel located at the bottom of a T-beam by means of headed stud shear connectors. The used degrees of shear connection are (100%, 75%, 50%, and 38%). Three dimensional nonlinear finite element analysis has been used to conduct the numerical investigation for the general behavior of beams which are subjected to central point load. ANSYS 12.1 program code was used to estimate the ultimate loads, deflections, stresses, strains, end slip. Concrete was modeled by brick element (SOLID65), while the steel channel was modeled as brick element (SOLID45). Two-node discrete elements (LINK8) are used to represent the steel reinforcement and shear connectors. Perfect bond between the reinforcing rebars and the concrete was assumed. The load on beams was applied monotonically in increments up to failure. The reduction of the degree of shear connection from 100% to 38% causes increasing of strain, mid span deflection and end slip with an average of 3.95%, 13%, and 111% respectively, while the ultimate load decreases with an average of 7.3%. In order to observe the efficiency of the 3-D model, a comparison was made with available experimental work. Good agreement was obtained throughout this work between the finite element and available test results.