Small Amount Of Reinforcement Research Articles

The axial compression mechanical properties and factors influencing spiral-ribbed thin-walled square concrete-filled steel tube composite members

Thin-walled concrete-filled steel tubular members have significant economic advantages, but are prone to local buckling, which has a great impact on structural safety. Therefore, this paper proposes a new spiral stiffened thin-walled CFST composite column to solve the above problems. The axial compression test found that spiral stiffeners can significantly improve the buckling resistance of thin-walled steel tubes, with the ultimate bearing capacity increased by 18 % and the ductility coefficient reaching about 2.0. Through the study of the mechanical mechanism, it is found that the spiral rib has little contribution to the vertical stiffness of the component, mainly by restricting the transverse deformation of the steel pipe to improve the mechanical performance of the component. At the same time, it is also found that the spiral rib can also play a strong constraint on the external concrete, and with a small amount of reinforcement, it can ensure the synergistic force of each part of the component. Based on the test, a parametric analysis was conducted on the pitch, the width-thickness ratio of the spiral rib and the influence law were quantified, and the design suggestions were provided. Finally, based on the fitting method, a formula for calculating the bearing capacity of this superimposed member was proposed. The new composite member has the advantages of less steel consumption, good mechanical properties, strong fire resistance, corrosion resistance, and good engineering application prospects.

Artificial neural network model for prediction of viscoelastic behaviour of polycarbonate composites

Polymer composites are the result of incorporation of nanoparticles into the polymers and can lead to improvements even with a very small amount of reinforcement which can be tuned according to the applications. In order to understand the behaviour of these polymer composites we need to perform a number of characterizations and analyses which in turn requires investment of money and time. Thus, to reduce the number of characterizations and analyses for developing polymer composites, computational techniques can prove helpful. By means of a computational technique known as artificial neural network (ANN), prediction of the thermo-mechanical properties was made possible. Here dynamic mechanical analysis (DMA) data set was used for characterization of polycarbonate / calcium carbonate-SiO2 core shell composites (polycarbonate composites). Using the dataset, the selected ANN model consisted of a network of [3-10-1]. The prediction accuracy achieved using ANN method, was around 90%. Applicability and performance of ANN to the existing system was also confirmed by mean squared error (MSE), which is favourably small for this case, in the range of 10-5. The output predicted by ANN had a coefficient of correlation of 0.999. Furthermore, sensitivity analysis confirmed the importance of various input variables in relation with output. An optimization of the variables facilitated to maximize the conditions thus predicting glass transition temperature.

The Effects of Magnitude-Based Differential Reinforcement on the Skill Acquisition of Children with Autism

A common recommendation for teaching skills to children with autism is to apply differential reinforcement by reserving high-quality reinforcement for unprompted responses (Sundberg and Partington in Teaching language to children with autism or other developmental disabilities, Behavior Analysts Inc., Pleasant Hill, 1998). Earlier research focuses primarily on schedules or quality of reinforcement, rather than magnitude of reinforcement, when evaluating the use of differential reinforcement in practice. The utility of magnitude-based differential reinforcement may be dependent upon evidence that a learner responds differentially to large and small amounts of reinforcement such that he or she selects the large amount of reinforcement over the small amount of reinforcement and engages in more responses that produce the relatively larger magnitude reinforcement. Three individuals with autism participated in a treatment comparison of differential reinforcement. The manipulation of magnitude of differential reinforcement in a skill acquisition program did not have an appreciable effect on the rate of acquisition for any of the three participants.

Centrifuge modelling of soil slopes reinforced with vegetation

This paper reports a series of geotechnical centrifuge model tests conducted to investigate the mechanical reinforcement of slopes by vegetation. Some of the model slopes contained young willow trees, which were grown in controlled conditions to provide different root distributions and mechanical properties. Slopes were brought to failure in the centrifuge by increasing water pressures. The failure mechanisms were investigated photographically and using post-test excavation. By measuring the soil properties and pore pressures in each test when failure occurred, slope stability calculations could be performed for each slope failure. These back-calculations of stability suggest that only a small amount of reinforcement was provided by the root system even when it was grown for 290 days before testing. In contrast, the use of the measured root properties and a commonly used root reinforcement model suggests that significant reinforcement should have been provided by the roots. This disparity is probably due to either inappropriate assumptions made in the root reinforcement model or soil alteration produced by root growth. Such disparities may exist in the application of root reinforcement models to full-scale slopes and therefore require additional study. The modelling technique outlined in this paper is suitable for further investigation of root mechanical interactions with slopes.

Shaking Table Tests of Lightly RC Walls: Numerical Simulations

In the framework of the European consortium ECOLEADER, a seismic research project has been performed on specimens tested on a shaking table. The specimens were representative of reinforced concrete buildings with bearing walls. The mock-up studied in particular in this article is composed of two parallel walls linked with a perpendicular one that has openings. The walls are reinforced according to the current design practice in France with a small amount of reinforcement. Two kinds of finite element simulations have been performed: a refined one using a detailed 3D description of the specimen and a simplified one, based on multifiber beams. The comparison between the experimental and numerical results not only demonstrates the accuracy of the time-history analysis models, but also allows obtaining more detailed information about the behavior of the specimen for more complex seismic excitations. It is shown that both models are able to describe quantitatively the global and qualitatively the local behavior of the structure. The simplified model is furthermore used to investigate the behavior of the specimen under a 3D earthquake loading.

Theory of delayed fracture of composites in compression

Introduction. Composite materials fail as a result of different mechanisms, some of which were described in [8-10] and several other publications. One of the most common mechanisms in the case of compression is loss of stability by the structure of the composite. This is the main mechanism responsible for failure in the compression of unidirectional composites or composites with a small amount of reinforcement in the transverse direction.

Choice in humans: Functional properties of reinforcers established by instruction

Adult human subjects chose between schedules containing stimuli (indicator lights) that the subjects were instructed to consider pleasurable. The schedules differed in amount of reinforcement (period of illumination) or delay (interval between a choice response and light onset). Although subjects preferred large to small amounts of reinforcement, they were essentially indifferent between immediate and delayed reinforcement. In contrast, previous data on video game reinforcement demonstrated preferences for both immediate and large amounts of reinforcement. The instructed reinforcer was thus partially effective in controlling choice but was not equivalent to a reinforcer that presumably had intrinsic value.

Jute-Glass Sandwich Composites

The effect of surface layer reinforcement with glass fibres of unidirectional jute-rein forced epoxy composite on the flexural properties has been investigated. Substantial increase in flexural modulus and strength with small amounts of reinforcement (for reinforcement ratio (t/d) < 0.3, where "t" and "d" are the respective thicknesses of glass reinforced plastic (GRP) shell and JRP core) were achieved. In addition, studies on the effect of moisture absorption of flexural properties revealed a significant im provement in moisture resistance of jute reinforced epoxy with hybridization. Though density analyses of these hybrids indicate an increase in density with hybridization, the considerable improvement of the normalized properties of jute-glass hybrids make them candidate materials for cost-effective applications. The work has also shown that the reinforcement (t/d) is more useful a parameter in the case of sandwich-type hybrid fibre composites. Analysis of failure modes of these composites loaded in flexure is also presented.

Stability of parallel cracks in solids reinforced by bars

Investigated is the effect of one layer of steel reinforcement on the instability of a system of parallel equidistant shrinkage or cooling cracks in a concrete halfspace or parallel equidistant cracks due to bending of a beam. The cracks are assumed to propagate along straight lines normal to halfspace surface. The instability mode consists in the closing of every other crack at the expense of an extension and increase of the width of the remaining cracks. The previous formulation of stability conditions in terms of the derivatives of the stress intensity factors with respect to the crack lengths is used and numerical results are obtained by finite elements. It is found that instabilities of cracks in reinforced concrete do exist and are profoundly affected by the presence of reinforcement. Assuming a relatively limited length of bond slip near the crack, one finds that the presence of a reinforcement layer greatly increases the penetration depth of cooling or drying at which the instability occurs, but does not prevent the instability from occurring deeper beneath the reinforcement. A small amount of reinforcement, smaller than that required by the building codes, is sufficient to achieve this effect while a further increase of the reinforcement amount has relatively little effect.

Extinction in the Pigeon after Continuous Reinforcement: Effect of Number of Reinforced Responses

Number of responses and time to extinction were measured after 3, 10, 1000, 3000, 5000, and 10,000 reinforced key-peck responses during conditioning. Each response was reinforced with a 045-gm. food pellet. The number of responses in extinction was a monotonically increasing function which became asymptotic beyond 1000 reinforced responses. Number of reinforced responses during conditioning significantly affected the number of responses in extinction ( p < .001) but not the time to extinction. The results support the findings of previous free-operant bar-press studies with rats. Free-operant animal studies of extinction after continuous reinforcement have consistently produced monotonically increasing functions and have typically employed relatively small amounts of reinforcement. Amount of reward may be an important parameter determining the shape of the extinction function in the free-operant studies.

Resistance to extinction as a function of amount of reinforcement and reinforcement schedule

Sixty rats were run in an experimental design that factorially combined large and small amounts of reinforcement with 0, 12, 24, and 56 partial-reinforcement trials given after 28 continuous-reinforcement trials in a runway. Resistance to extinction was an increasing function of number of partial-reinforcement trials under large reinforcement; under small reinforcement, the partial-reinforcement groups did not differ in extinction. The results were discussed within the framework of frustration theory.