Reinforcement Force Research Articles

Stability Analysis of Reinforced Embankments on Soft Soils

Recent advances in polymeric materials have opened up a new alternative of providing additional stability to embankments on soft soils by incorporating polymeric reinforcement in the form of sheet or grid at the base of embankments. A new approach to the analysis of rotational stability of reinforced embankments, based on the work of Low for unreinforced embankments, is presented in the paper. The equation for required reinforcement force for an arbitrary slip circle is set up. From this, the solutions for center of critical slip circle and maximum reinforcement force are obtained in the form of closed-form equations. The design of wide-crested reinforced embankments can be carried out quickly, using the equations and tabular values presented herein.

Computer aided design of geosynthetic reinforced soil walls

The computer aided design of geosynthetic reinforced soil walls is reported. The magnitude of tensile forces in the geosynthetic reinforcement has also been studied under external vertical and horizontal strip loads.

STABILITY EVALUATION OF A GEOGRID REINFORCED EMBANKMENT OF SOFT GROUND

In order to construct a geogrid reinforced embankment on soft ground, it is significant to forecast its deformation in terms of the function as well as to evaluate safety factor. For that purpose, pull-out resistance of an embedded geogrid must be grasped. Even if various geogrids have the same tensile strength, they seem to display the different reinforcement force depending on their geometrical forms and surface states. In this paper, firstly the interaction between soil and a geogrid which affects pull-out resistance was examined based on pull-out test results. Secondly, influence of the material properties on the stability of an embankment on soft ground was analyzed from two aspects of reinforcement force and embankment deformation. As a result, the importance of the material properties for the stability evaluation was shown.

Bearing capacity of reinforced horizontal sandy ground

In order to develop a method of predicting the bearing capacity of horizontal sandy ground reinforced with tensile-reinforcement layers horizontally placed beneath a footing, a series of plane strain model tests with a strip footing was performed. The effects of the length, the arrangements and the rigidity and rupture strength of reinforcement were examined systematically. The strain fields in sand, the tensile forces in reinforcement and the distribution of contact pressure on footing were measured. Even by means of reinforcement layers with a length similar to the footing width, the bearing capacity increased remarkably. Also, the portions of reinforcement layers located outside the footing width contributed to the increase in the bearing capacity only in a secondary way. The bearing capacity of reinforced sand was found equal to the smaller of the following two values; the one controlled by the failure of the reinforced zone immediately beneath the footing and the other by the failure of sand beneath the reinforced zone. Based on the test results, a method of stability analysis by the limit equilibrium method was developed, taking into account the effects of the arrangement and properties of reinforcement and the failure modes of reinforced sand. The predicted values were well in accordance with the measured ones.

INFLUENCE OF GEOGRID'S MATERIAL PROPERTIES ON THE STABILITY OF REINFORCED EMBANKMENT

In order to construct a geogrid reinforced embankment on soft ground, it is significant to forecast its deformation in terms of the function as well as to evaluate safety factor.In this paper, a stability analysis for geogrid reinforced embankments with various properties was carried out using the circular are method which can evaluate two aspects of reinforcement force and embankment deformation, As a result, it is concluded that the reinforcement effect by geogrids can be widely different even if they have the same tensile strength.

On the design of geosynthetic-reinforced walls

An important design aspect of a geosynthetic-reinforced wall is specifying the reinforcement length. A simple limit equilibrium analysis, which considers two possible extreme inclinations of a reinforcement's resistance force, shows that predictions based on the K a-analysis may not be safe. Although rules of thumb to determine embedment length are sometimes superimposed on the K a-analysis prediction in design, it is demonstrated that such ‘rules’ may not always be safe. Design charts for granular backfill illustrate the effects of the reinforcement's force inclination showing quantitatively that the horizontal inclination required slightly larger tensile resistance force, while underestimating the embedment length.

Bottom Slab Strength of PC-Barge while Alighting on Sea Bed

The strength of bottom slab of PC-barge under the operation of alighting on the sea bed was studied experimentally and theoretically. Large cone penetration tests were performed on three model slabs. The penetration-resistance curves were obtained. The initial destruction mode was the punching shear, and then the concrete crashed. Before crashing out of the concrete, the punching shear strength of JACE's formula was in good agreement with the resistance. After crashing out of the concrete, the resistance was generated from tensile forces of reinforcements and prestressing strands.The bottom slab strength against the local contact forces of the foundation soils, the side shell strength against the local ice pressure loads, and the strength against the ship collision were discussed. The local contact forces of the foundation soils were too small to cause damage to the bottom slab. However, the local ice pressure loads were very huge, so that it was almost impossible to design the side shell free from damage. The steel-concrete sandwich wall would be the better structural element against the local ice pressure loads than the PC-slab dealt with in this paper. The strength against the ship collision was evaluated with the energy absorption capability. The absorbed energy of the PC models were much more than that of the steel models.

CUT SLOPE STABILIZATION BY USING ROCK BOLTS OF COMPARATIVELY SHORT LENGTH

Many reinforcing methods and stabilization techniques of in-situ cut slope are fundamentally based on the statical conception, in which the internal forces of reinforcements at the place of crossing the (assumed) slip surface secure the stabilization of the cut slope, even when deformation of the slope is permitted.In this paper, in order to clarify the mechanism of cut slope stabilization using comparatively short rock bolts which are same length and arrayed regularly, small scall laboratory tests of a vertical cut in a granular cohesionless soil and its simple analysis are studied. As a result, rock bolts make the soil around each of them perform almost a monolithic mass, and form the quasi-retaining wall made of in-situ soil.This mechanism of rock bolts is the same of NATM which is a tunnelling method.

Direct shear tests on reinforced sand

New data are presented from internal measurements in direct shear tests on sand. An interpretation is given for the plane strain angle of friction and the angle of dilation of sand in a direct shear test. The direct shear angle of friction deduced from the conventional analysis is shown to under-estimate the frictional shearing resistance of sand by about 20%. Results are presented from direct shear tests on reinforced samples and these are fitted by a limit equilibrium analysis in which all the parameters are independently measured. Plastic incremental strains cause dilation in dense sand and dominate the deformation with increasing stress ratio. The rate of increase of the reinforcement force in shearing sand is shown to depend on the angle of dilation. The maximum bond angle of friction between sand and the rough surface of reinforcement is also determined by plastic deformation in the sand. A theoretical analysis for the bond is supported by the test results which show that the maximum bond angle of friction for rough reinforcement equals the direct shear angle of friction. Thus the modified direct shear test is a good way to measure bond strength parameters for design. L'article présente de nouvelles données obtenues à partir des mesures internes effectuées au cours de quelques essais de cisaillement direct dans le sable. Une interprétation est donnée à l'égard de l'angle de frottement en déformation plane et de l'angle de dilatance du sable dans un essai de cisaillement direct. L'angle de frottement du cisaillement direct déduit de l'analyse normale sousestime la résistance au cisaillement à friction du sable d'environ 20%. Des résultats de quelques essais de cisaillement direct effectués sur des échantillons renforcés sont présentés. Des déformations plastiques incrémentielles sont la cause de la dilatance du sable dense et dominent la déformation au fur et à mesure que le rapport des contraintes s'accroît. La vitesse d'accroissement de la force de renforcement dans du sable soumis au cisaillement dépend de l'angle de dilatance. L'angle de liaison maximal de frottement entre le sable et la surface rugueuse de renforcement est déterminé aussi par la déformation plastique dans le sable. Une analyse théorique de la liaison est confirmée par les résultats des essais qui indiquent que l'angle de liaison maximal de frottement pour le renforcement rugueux est égal à l'angle de cisaillement de la frottement. L'essai de cisaillement direct modifié est une bonne méthode pour mesurer les paramètres de résistance des liaisons.

Effects of pimozide on emitted force, duration and rate of operant response maintained at low and high levels of required force.

The behavioral effects of pimozide (0.25, 0.5, and 1.0 mg/kg) were assessed in two separate experiments in which session mean peak force, maximum peak force, and response duration served as the dependent variables complementing operant response rate. In the first experiment, two groups of water-deprived rats were trained on a continuous reinforcement (CRF) schedule for reaching out and pressing downward on a force transducer with peak forces of at least 4 g (low-force group) or 40 g (high-force group). In the second experiment a pull-type response topography and fixed ratio 20 were used, and force requirements were 4 g for the low-force group and 100 g for the high-force condition. Under these conditions pimozide decreased response rate and increased response duration irrespective of response topography, required force, or schedule of reinforcement. Neither mean peak force nor maximum peak force were significantly decreased by the drug, and in the low-force CRF condition a small but significant dose-related rise in mean peak force was observed. It was hypothesized that neuroleptics exert their motor-impairing effects primarily in the temporal domain of behavior but do not appreciably affect the force dimension of performance capacity. And these temporal domain effects may be reflected in differences in the kinetic requirements for the overall behavior and not just the response itself. Additionally, the possibility that some of the observed effects could be accounted for by "anhedonia" was addressed.

Material properties for the design of geotextile reinforced slopes

The subject of the long-term reinforcement of soils with woven geotextiles and polymer grids is considered in this paper, with particular reference to the measurement of reinforcement stiffness and strength data for design. The robust nature of earthworks construction is likely to make material damage a more significant factor for soil reinforcement than for other applications of polymer materials. A clear distinction between the ideal behaviour relevant to the factory-produced material, and the expected changes from the ideal behaviour due to environmental factors and damage is recommended. A separation of the required reinforcement forces which depend on soil mechanics aspects and the available reinforcement forces which depend on reinforcement properties is recommended for calculation purposes. The aim is to clarify the selection of appropriate material properties and safety factors for design.

Punching Shear Load Equation of Reinforced Concrete Slabs

The major failure mode of reinforced concrete slabs subjected to a concentrated load on the small loading area is governed by punching shear. After the first study of Talbot in 1913, many research works have been carried out to investigate the mechanism and to derive a punching shear load equation. In Japan, the empirical equation analyzed statistically by Kakuta et al. has been used to be the most appropriate one to explain test results. However, it seems to be unappropriate to explain the punching shear load of one-way slabs using a rectangular loading pad. The authors have derived an equation applicable to one-way slabs also, which is composed of the ultimate shear strength in compression zone along the perimeter of the loaded area and the splitting strength of bottom covers induced by the dowel force of reinforcement.

The good productivity game: increasing work performance in a rehabilitation setting.

Simple reinforcement systems have been used to improve performance in a broad range of settings. For example, in classrooms, the “Good Behavior Game” has been shown to be very effective (Barrish, Saunders, and Wolf, Journal of Applied Behavior Analysis, 1969, 2, 119–124). In industry, small bonuses were used to increase the punctuality of workers (Hermann, deMontes, Dominquez, Montes, and Hopkins, Journal of Applied Behavior Analysis, 1973, 6, 503–572). In a sheltered workshop setting, Shroeder (Journal of Applied Behavior Analysis, 1972, 5, 45–52) examined work rates under varying frequencies and amounts of reinforcement and response force. The present study involved the utilization of simple group contingencies to increase productivity in a rehabilitation industry. Four state hospital residents who were trainees at a rehabilitation industry participated in the study which examined the effects of feedback, and feedback plus the “Good Productivity Game” to improve work output. The task, for which the employees were paid a wage, involved sorting boards by size. When the employees were provided with feedback on the number of boards sorted during the observation period, productivity increased slightly over baseline. After a return to baseline, the “Good Productivity Game” was played. For performance, the game afforded the employees pseudo‐competition (in that teams were paired against each other, but both teams always “won”) and simple rewards such as candy and early work termination. The game improved performance by 104% over the second baseline and by 64% over the third baseline. Data gathered on rates of on‐task behavior by the employees correlate with the productivity rates. Data gathered on rates of staff attention paid to employees show little difference across conditions, thus corroborating the function of the “Good Productivity Game” in increasing work output. Although no formal data were collected, the staff continued to use the game with considerable success after the formal termination of the study. The “Good Productivity Game” appears useful in increasing work output in a rehabilitation setting. Further research should concentrate on the utility of the game throughout longer periods of the workday and over extended periods of time.

Reinforcement rate and force proportional reinforcement

The research examines the consequences of making two reinforcement contingencies simultaneously available for the same bar-pressing response. Specifically, two experiments are described which concern the effects of reinforcement rate upon force proportional reinforcement (FPR). In Experiment 1, reinforcement rate was constrained by combining differential reinforcement of low rate with a force-proportional reinforcement contingency. The group of rats exposed to this regimen eventually showed a significant increase in response force compared to control groups. Experimental vs control response rates were not significantly different. In Experiment 2, reinforcement rate was affected through the expedient of relating the probability of obtaining a single pellet to the response force. The group for which the probability-force relationship was discontinuous came to exert higher forces than either a group for which the relationship was fairly continuous or an ordinary variable ratio control group. Response rate was significantly higher for the control group.

Frustrative nonreinforcement of operant responding: Magnitude of reinforcement and response force effects

Intermittent nonreinforcement between two successive reinforcement schedule components was shown to facilitate the performance of rats in the second component. The strength of the effect appeared to be directly related to the magnitude of reinforcement but unaffected by, a threefold increase in the operating force of the response lever.

Force of Response during Ratio Reinforcement

Sharp decline in response force after reinforcement and progressive force elevation over a sequence of unreinforced responses were observed for subjects in a fixed ratio lever-press situation. It is suggested that these systematic variations in force level may provide, through feedback, discriminable cues for behavioral regulation.