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Go to Editorial ManagerDouble skin composite (DSC) construction or Steel/concrete/steel sandwich construction (SCSS) is an innovative and relatively new form of composite construction that can be used in submerged tube tunnels, bridges deck, nuclear structures, liquid and gas containment structures, offshore and onshore structures, military shelters, and shear walls in buildings. The system consists of a plain concrete core sandwiched between two steel plates interconnected together by various types of mechanical shear connectors. The DSC construction perceives advantages that the external steel plates act as both formwork and primary reinforcement, and also as impermeable, blast and impact resistant membranes. The major duty of the shear connectors is to withstand longitudinal shear force and beam/slab separation, while in the bi-steel type where shear connectors are friction welded at both their two ends to two parallel steel plates, the longitudinal and transverse shear force, as well as plate buckling are resisted. The present paper highlights the previous prime researches concerning the subjects of SCSS composite construction, specifically on the conducted tests (push-out tests, tensile, direct shear tests, and bending tests) in which the components of partial interaction (uplift and slip forces) are resisted by various types of shear connectors.
In this study, the analytic model (Azmi Model) had been considered for computation the load capacities of the composite open web steel joists and compared them with those obtained from experimental tests. The capacities of seven joists had been studied, each including one of the following variables (distribution of headed studs, connection degree of the connectors, inclination of the web, shape of the web, density of slab concrete, length of connectors).Theoretically, according to the Analytic model, the referenced joist of (45° web inclination , uniformly distributed ,over connected ,short headed studs) exhibited maximum load capacity of (18.45) ton, while the joist of (45° web inclination, uniformly distributed, under connected, short headed studs) exhibited minimum load capacity of (16.23) ton at yield point of bottom chord. Experimentally, the referenced joist exhibited maximum load capacity of (15.51) ton, while the joist of (34° web inclination, uniformly distributed, over connected, short headed studs) exhibited (12.49) ton load capacity. The load capacities values of the tested joists ranged between (67%-85%) of the predicted values according to the analytic model.
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.
This article provides a general up to date review of the investigation on performances and resistances of plain and fiber containing concrete structures under periodical loadings of long endurance up to fatigue failure. Structures are almost, under the frequent influences of repeated loadings such as vibrations of rotary machines, sea /river waves, wind, earthquakes and moving vehicles. Long term application of cyclic loading leads to continually slow rate degradation of the structure rigidity leading to fatigue damage. In spite of the dominant usage of concrete, worldwide, as a building material, its fatigue behavior is not straight forward. In addition, this lack of comparison is confronted for fiber fortified concrete. The article also presently a survey of the available techniques for monitoring and measurement of fatigue impressions in concrete structures founded both their impact within the treatise domain and the non-destructive inspection. Those technical means are classified into, at least, two designations, specifically, the monitoring of fatigue induced cracking and the detection of fatigue charged damage. Those techniques parameters, evaluate the changes in the mechanical and physical materials properties during the fatigue endurance, are distantly reviewed in concern of the mechanism creating the change, shortcomings, constraints, etc. The merits, dependency, feasibility, disadvantages and limitations of each technique are assessed and compared to make an index to select the appropriated e technique for fatigues fracture or failure inspection of the type fibered or not of structural concrete
Behavior of composite beams with headed stud shear connectors subjected to monotonous and displacement controlled non-reversible repeated loadings has been evaluated through studying influences of the cross-sectional proportioning, the degree of partial interaction, and the level of ductile deformability in the post-yielding stage, in addition to the state of loading (whether monotonous or repeated). Eleven one- third scaled composite beams (with their push-out segments) were manufactured and tested in five pairs (each comprising the two loading cases representing one varying studied parameter) beside the single standard composite beam dedicated to verify accuracy of the test results by comparing them to the prototype ones (three authorized experimental and analytical investigations) where no distinction (other than 7 % difference) between the results of the three authorized refereed investigations (experimental, analytical and Eurocode) and the present one.Regarding the flexural resistance in repeatedly loaded composite beams, it has been found that lowering the neutral axis (by adding bottom steel plate) has significantly increased the beam flexural resistance by an average of 24.7 %. Meanwhile, the intensity of headed studs distribution in stiffened repeatedly loaded composite beams has revealed a vital role in controlling the severity of the post-ultimate flexural weakening, where decreasing number of the headed studs to the half has increased the value of that unfavorite parameter by 160.58%. Furthermore, that specified decrease of headed stud intensity has lowered the advantageous residual cyclic flexural ductility by 19.37 % and 11.48 % without and with stiffening bottom steel plates, respectively. Regarding the effect of the lengthening the headed stud on behaviour of the repeatedly loaded composite beams it has been found that lengthening the medium-length headed studs by 72% has raised the flexural stiffness by 41.1 %, while it has decreased the residual cyclic slippage index by 54.3 %.
The composite opened web steel joist supported floor systems have been common for many years. It is economic and has light weight and can embed the electrical conduit, ductwork and piping, eliminating the need for these to pass under the member, consequently eliminate the height between floors. In order to study the joist strength capacity under the various conditions, it had been fabricated seven joists composed of the steel and concrete slab connected to the top chord by shear connectors (headed studs). These joist have 2820 mm length c/c of the supports and 235 mm overall depth. In the present study, six variable parameters are adopted (Studs distribution, Degree of shear connection, Degree of the web inclination, Shape of the web, Density of concrete for slab and length of the shear connector). The test results exhibited that minimum strength capacity was 160kN for light weight joist and maximum capacity was 225kN for joist of long shear connectors at failure. The results were compared by ultimate flexural model by Azmi.
CFDSST Concrete Filled Double-skinned steel tubular columns are composite columns consisting of two concentric circular steel tubes with concrete filler in between. Finite elements method is considered through the use of the computer program ABAQUS to model CFDSST columns numerically under cyclic axial compression. Damage plasticity model was considered to model the concrete while elastic-plastic model used to model the steel tubes. six CFDSST specimens and three ordinary Concrete Filled Steel Tubular (CFST) specimens were analyzed under static axial compression, while three CFDSST specimens were considered for analysis under cyclic axial compression. The numerical results were presented in terms of axial load axial strain displacement curves. It was found that the ultimate axial load carrying capacity calculated numerically in good agreement with that of the experimentally tested specimens. Also it was concluded that Damage plasticity model used for simulating the behavior of concrete and metal plasticity model used for simulating the behavior of steel produced accurate results as compared to the experimental results.