Reinforcement Force Research Articles

Effect of soil-reinforcement interaction coefficient on reinforcement tension distribution of reinforced slopes

This paper examines the effect of the mobilized reinforcement tension within reinforced soil slope at a different level of soil-geosynthetic interaction. The mobilized reinforcement tension is assumed, in most design methods for the internal stability of reinforced slopes, to be equal to mobilized soil forces computed using a limit equilibrium method. However, comparison with the reinforcement tension force measured in the field has shown that this approach is conservative. This paper examines the effects of the soil-reinforcement interaction coefficient on the tensile redistribution of geosynthetics. The modified process of Bishop Method of slope stability analysis is used to locate the critical slip surface and to calculate the mobilized reinforcement tensile force. The reinforcement forces obtained from field data and on centrifuge model test results for a reinforced slope problem are used to examine the relationship between mobilized reinforcement tensile force and mobilized soil shear strength.

Разработка и исследование основных особенностей соединения пластмасс с металлами

This work examines a method of ultrasonic pressing of metal parts into a thermoplastic part using thermoplastic rivets and screws installed into the threaded holes obtained by ultrasound forming, welding metal parts through a pre-applied plastic layer, and welding metal and plastic parts through an intermediate plastic insert. It is shown that the introduction of metal fittings into plastic products using ultrasound is a progressive method of obtaining permanent joints of products from plastics and metals. It leads to an increase in labor productivity and ensures production of consistently high-quality and durable connections. The dependence of the holding force of the metal reinforcement in thermoplastic on the tightness is determined. The possibility of obtaining a metal-plastic welded joint using ultrasound is established. It was previously impossible to obtain such joints using classical methods of welding due to specific features of the metal-plastic material. The main technological modes of joining metal materials with thermoplastics are determined, namely static force, duration of ultrasonic action, waveguide oscillation amplitude.

Impact of Embedment Resistance on Required Reinforcement Force in MSE Walls

This paper presents a limit equilibrium (LE) method to quantify the impact of the embedment resistance on the maximum mobilization reinforcement force required for global stability of the mechanically stabilized earth wall. This LE method is based on the log spiral failure mechanism and is rigorous in the sense that it satisfies equilibrium at the limit state. The presented formulation yields required reinforcement force, not taking into consideration limitations of the stiffness of the facing. Results show that the reinforcement would be eliminated when having enough embedment depth from an analytical parametric study standpoint. However, when the embedment depth is shallow, more reinforcements should be required on account of insufficient embedment resistance.

Finite element modelling of unbonded post-tensioned simply supported beam

This paper describes an experience of designing of some finite element models of unbonded post-tensioned simply supported concrete beam. It was purposed to evaluate a bending moment capacity, crack resistance, increment of pre-stressing force in reinforcement and deflection of models. Their behaviour under gradual loading was in the spotlight as well. There is short information about preliminary performed experimental study of beams. Parameters of physical models of beams obtained from experiment were used as initial data while finite element models were being created. Discussion of results obtained is listed. Their comparison with an experimental data is done.

Approximation Method for Evaluation of Strains and Forces in LTP Reinforcement of Embankments on Columns

This article presents a method of approximate finding of forces and strains resulting from the so-called membrane effect in the reinforcement of the transmission layer of embankments located on a soft soil improved by columns (rigid inclusions). The model task needed to determine the characteristic values in geosynthetic reinforcement supported on rigid columns was formulated. The reinforcement is treated as an isotropic membrane, in which the strains are determined using the formula for the length of the curve, i.e. it deviates from the assumptions of the small strain theory. Spatial problems are reduced to equivalent one-dimensional static tasks for analysis using the isotropic membrane theory. The closed form solution of this task exists only in the case of uniform load. For other types of loads, it is necessary to approximate the formula for the length of the curve occurring in the expression defining the strains in the membrane, e.g. using the Taylor series, and then solving the strongly non-linear equation in which the membrane tension force is unknown. The article presents the analysis of the effect of the length curve approximation with usage of the Taylor series on the accuracy of the results obtained. The presented analysis is very important from the point of view of standard engineering calculations needed to design the reinforcement of the transmission layer in the case of embankments located on soft soil reinforced with rigid inclusions.

THE EXPERIMENTAL RESEARCHES OF REINFORCED CONCRETE I-BEAM ELEMENTS WITH NORMAL CRACKS WHEN TURNING

The data of experimental researches of the rigidity of reinforced concrete I-beam elements with normal cracks at the action on them of the twisting moment have resulted in this paper. It is shown that the dependence "torque-twist angle" is almost linear. Significant nonlinear deformations appear in the last stages of loading before failure. Therefore at normative torques, it is recommended to consider the work of reinforced concrete elements of the I-beam cross-section with normal cracks linear. It is shown that the presence of longitudinal reinforcement affects the strength and rigidity of beams with normal cracks. Quite a large part of the external torque is perceived by the pin forces in the longitudinal reinforcement. The difference between the external torque and the moment of the pin forces in the armature is perceived by the upper shelf of the I-beam element. In the absence of longitudinal reinforcement, the upper shelf can collapse at loads much smaller than the destructive load of beams with longitudinal reinforcement.

Ultimate bearing capacity correlation of steel tube confined RC column under combined compression-bending-torsion load

Based on the completed experimental study, the structural response of steel tube confined RC (STRC) columns under pure torsion, bending-torsion and compression-bending-torsion load were investigated through the finite element method (FEM). Experimental results were used to verify the proposed finite element model and the verification results revealed that the assessment capability of the developed models was efficacious. The model considered the 3D equilibrium, compatibility, and constitutive laws of materials at the section and structural level. In addition, a parametric study was performed to visualize the influence of steel tube, section size, concrete, longitudinal reinforcement, stirrup, and axial force on the ultimate bearing capacity and the ultimate bearing capacity correlation of STRC columns. To this aim, a total of 72 STRC columns were modeled. It was noticed that the thickness of steel tube, the yield strength of longitudinal reinforcement, the diameter of longitudinal reinforcement (longitudinal reinforcement ratio) and axial force were the most crucial parameter, influencing the ultimate bearing capacity of STRC columns significantly. As well, it was overtly beheld from the study that the correlation curves of flexural and torsional capacity were similar under the influence of different parameters, and relevant equations of flexural and torsional capacity were proposed through curve fitting.

Extensional Stress-Induced Orientation and Crystallization can Regulate the Balance of Toughness and Stiffness of Polylactide Films: Interplay of Oriented Amorphous Chains and Crystallites

Polylactide (PLA) films with an excellent balance of toughness and stiffness were realized by extensional stress efficiently. For the relatively low extensional stress, gauche–gauche conformers that originated from the oriented amorphous chains lead to super-toughening behavior. Among higher extensional stress, strain-induced orientation and crystallization act as the driving force of reinforcement. This mechanism is evidenced by the pronounced enhancement in the elongation at break from 16.9 up to 294.9% accompanying the variation yield strength from 45.3 up to 135.5 MPa. The highest elongation at break results from the early stretching stages, whereas the highest yield strength is obtained from a high draw ratio. More impressively, PLA films show temperature-invariant super-ductility and reinforcement at low temperatures (0 and −20 °C). This work provides a preferable and scalable method to fabricate competitive PLA materials, expanding the practical application of sustainable polymers served at a wide temperature range or in harsh environments.

Kinematic analysis of geosynthetics-reinforced steep slopes with curved sloping surfaces and under earthquake regions

A procedure of kinematic analysis is presented in this study to assess the reinforcement force of geosynthetics required under seismic loadings, particularly for steep slopes which are hardly able to maintain its stability. Note that curved sloping surfaces widely exist in natural slopes, but existing literatures were mainly focusing on a planar surface in theoretical derivation, due to complicated calculations. Moreover, the non-uniform soil properties cannot be accounted for in conventional upper bound analysis. Pseudo-dynamic approach is used to represent horizontal and vertical accelerations which vary with time and space. In an effort to resolve the above problems, the discretization technique is developed to generate a discretized failure mechanism, decomposing the whole failure block into various components. An elementary analysis permits calculations of rates of work done by external and internal forces. Finally, the upper bound solution of the required reinforcement force is formulated based on the work rate-based balance equation. A parametric study is carried out to give insights on the implication of influential factors on the performance of geosynthetic-reinforced steep slopes.

Effect of cohesion on internal stability of bilinear geosynthetic-reinforced slopes

This paper presents a limit equilibrium (LE) approach to analyze the internal stability of the bilinear geosynthetic-reinforced slopes comprised of cohesive reinforced fill. This LE analysis uses a top-down log spiral mechanism to formulate the resultant reinforcement force in the lower tier required for internal design of such reinorced slopes. The presented formulation considers both cohesion and depth of crack, and then the required unfactored reinforcement strength is defined and used for subsequent analysis. Results are presented in the form of stability charts, enabling quick assessment of reinforcement strength required for internal stability. In addition, the effect of cohesion and depth of crack on the critical slip surface is discussed, respectively.

Stability of Reinforced Retaining Wall under Seismic Loads

Based on the horizontal slice method (HSM) and assuming a log spiral slip surface, a method to analyze the stability of a reinforced retaining wall under seismic loads was established in this study by calculating the tensile force of the reinforcement. A parametric study was conducted on the normalized tensile force of the reinforcement, and it was observed that the normalized tensile force tends to increase with acceleration of the seismic load and the height of the backfill. Moreover, it also increases with soil unit weight, while it decreases with increased friction angle of the backfill soil, and the influence of soil cohesion on the normalized tensile force is not significant. The HSM method is proved to be suitable for analyzing the tensile force of reinforcement in retaining walls under seismic loads.

Analytical Model for Tensile Membrane Action in RC Beam-Slab Structures under Internal Column Removal

An analytical approach was developed at Nanyang Technological University, Singapore, to predict structural capacities of RC beam-slab structures under the internal column removal scenario, taking into account the contribution of tensile membrane action in the slab. The model considers both commonly used loading methods in the laboratory, namely, concentrated and uniformly distributed loads. Catenary action in internal beams is neglected for conservatism, and tensile membrane action is assumed to rely solely on the yielding force of the top reinforcement arranged along negative yielding lines in the slab. The failure criterion of the model is based on fracture of longitudinal bars in internal beams, either near the middle or near the edge of beam-column joints. The proposed approach is shown to be reasonable because it provides conservative estimates compared with actual tests, which had high rotational restraints at the slab perimeter, and still gives good predictions for cases of semirigid rotational restraints.

Tensile behaviour of geotextile reinforcement within the sandy soil supporting a strip footing

The available analytical equations in the literature for the bearing capacity of geosynthetic-reinforced foundation soils include the tensile force developed in reinforcement as a product of mobilised tensile strain and the tensile modulus of the reinforcement. These methods overlook the fact that the tensile modulus of a geotextile is a function of strain, and is usually given based on in-isolation testing of geotextile. This study focuses on strain distribution and the mobilisation of tensile modulus in geotextile reinforcement buried within the sandy soil by using the laboratory model strip footing tests. The strain distribution results reveal that the tensile strain in the geotextile is maximum in the centre of the footing and decreases along the width of the footing. The mobilised tensile modulus of geotextile is also calculated from the increased bearing capacity of the reinforced soil by using available equations in the literature. Results show that the tensile modulus of the geotextile is mobilised in the range of 3–7% of the nominal values that are used in theoretical solutions for the estimation of mobilised tensile force in geotextile reinforcement. This can be due to the in-isolation methods being used by standards to measure the tensile modulus of geosynthetics.

The failure bond force of untreated and epoxy-treated reinforcement: An analytical study

This study proposes a prediction model to evaluate the failure bond strength of the untreated and epoxy-treated reinforcement bars having a wide range of bar diameter (Db), bar length (Lb), coating thickness (Cw) and the compressive strengths of concrete (f′c). In order to achieve the stated objective, a total of 462 records were collected, compiled, and prepared an extensive database from the past experimental studies. Various regression models were performed between the four independent variables Db, Lb, Cw and f′c and the response variable of the failure bond force of reinforcement (Pf). Using the statistical significance and the diagnostics of the validation of all models, the empirical equation that represented the best fit to the data points was proposed. The study revealed that the predicted bond strength showed a very good correlation with R2 of 94.45% and 93.35% with the experimental values for the training (304 data records) and validation (158 data records) datasets, respectively. Further rationalization of the model proposed herein was also investigated using the experimental data of three existing studies, and the results reconfirmed the similar conclusion; the proposed empirical equation was capable of predicting the failure bond force of untreated and epoxy treated reinforcement.

Crush simulation and optimisation study of power battery pack

In order to accurately simulate the crush process of power battery pack, ductility failure criterion was introduced. The ductility failure parameters of aluminium alloy materials were obtained by tensile test of aluminium alloy samples under different stress triaxialities and finite element simulation. To evaluate the crush resistance of profiles, the concept of specific crush force was proposed, the crush resistance of different sections of extruded aluminium profiles were compared, and the relationship between the angle and thickness of the reinforcement and crush force was summarised. The result shows that the form and thickness of the reinforcement have a great influence on the crush resistance of the section. The research provides a quantitative reference for the form of the stiffeners of aluminium section in the concept phase of power battery packs design.

Simplified solution to analyse seismic stability of reinforced soil wall

ABSTRACT The normalized tensile reinforcement force for the seismic stability of reinforced soil walls using some rigorous methods considering the pseudo-static seismic forces is mostly used by the earlier researchers in the design of retaining walls backfilled with cohesive soil. Few studies have been presented using horizontal slice method without taking effect of the seismic acceleration in vertical direction. In the present study, a simplified solution has been presented using the pseudo-static equilibrium of the reinforced soil wall taking the effect of seismic accelerations in the horizontal and in the vertical direction. The seismic stability analysis presented here accounts the required total reinforcement strength in terms of the maximum value of reinforcement force coefficient and the critical inclination of failure plane. Taking some geometrical values of retaining wall and soil characteristics based on the literature, a detailed and comparative parametric study presented here accounts the effect of cohesion of the backfill, angle of internal friction of soil, horizontal seismic coefficient, vertical seismic coefficient and surcharge loading.

Pseudo-static/dynamic solutions of required reinforcement force for steep slopes using discretization-based kinematic analysis

This paper presents a procedure for assessing the reinforcement force of geosynthetics required for maintaining dynamic stability of a steep soil slope. Such a procedure is achieved with the use of the discretization technique and kinematic analysis of plasticity theory, i.e. discretization-based kinematic analysis. The discretization technique allows discretization of the analyzed slope into various components and generation of a kinematically admissible failure mechanism based on an associated flow rule. Accordingly, variations in soil properties including soil cohesion, internal friction angle and unit weight are accounted for with ease, while the conventional kinematic analysis fails to consider the changes in soil properties. The spatial–temporal effects of dynamic accelerations represented by primary and shear seismic waves are considered using the pseudo-dynamic approach. In the presence of geosynthetic reinforcement, tensile failure is discussed providing that the geosynthetics are installed with sufficient length. Equating the total rates of work done by external forces to the internal rates of work yields the upper bound solution of required reinforcement force, below which slopes fail. The reinforcement force is sought by optimizing the objective function with regard to independent variables, and presented in a normalized form. Pseudo-static analysis is a special case and hence readily transformed from pseudo-dynamic analysis. Comparisons of the pseudo-static/dynamic solutions calculated in this study are highlighted. Although the pseudo-static approach yields a conservative solution, its ability to give a reasonable result is substantiated for steep slopes. In order to provide a more meaningful solution to a stability analysis, the pseudo-dynamic approach is recommended due to considerations of spatial–temporal effect of earthquake input.

Influence of the Structure of the Cross-section of Load-bearing Structures on Their Deformation during Emergency Actions

The paper deals with the issues of destructure modeling for constructive systems of reinforced concrete framing buildings. It is considered the widely using in practice framework of interspecific appliance for multi-storey buildings and structures on the basis of protection against progressive collapse. The results of dynamic additional loading analysis for girders of considering reinforced concrete framework at sudden structural transformation of constructive system are presented. It is obtained that at accidental impact and fragile destruction of tensiled concrete the coefficient of dynamic increasing of internal forces in tensiled reinforcement of reinforced concrete elements depends on the percent of reinforcement in cross section, prestressing level and topology of structure. It is proposed to calculate without of structural dynamic methods on the energetic basis the coefficient of dynamic increasing of internal forces in structures at sudden removal of a bearing element and cracking.

A new analytical approach to estimate the seismic tensile force of geosynthetic reinforcement respect to the uniform surcharge of slopes

This paper investigates the pseudo-static analysis of reinforced slopes with geosynthetics under the influence of the uniform surcharge to evaluate the maximum tensile force of reinforcements. The analytical approach has basically been used to develop the new practical procedure to estimate both tensile force and its distribution in the height of the slope. The base of developed relationships has been adapted from the conventional horizontal slice method. The limit equilibrium framework and the assumptions of log-spiral failure surface have directly been used for proposed analytical approach. A new analytical approach considering a single layer of non-cohesion soil and the influence of uniform surcharge has been extracted from the 5n equation and 5n unknown parameters. Results of the proposed method illustrated that the location of the surcharge, amount of internal friction and the seismic coefficient have the remarkable effect on the tensile force of reinforcement and might be 2 times increasing on it. Furthermore, outcomes show that the amount of tensile force has directly until 2 times related to the amount of slope angle and its height range. Likewise, it is observed that the highest value of the tensile force in case of slope degree more than 60-degree is observed on the lower layers. While in case of less degree the highest amount of tensile force has been reported on the middle layers and extremely depended to the seismic coefficient. Hence, it has been shown that the tensile force has increased more than 6 times compared with the static condition. The obtained results of the developed procedure were compared with the outcomes of the previous research. A good agreement has been illustrated between the amount results of developed relationships and outcomes of previous research. Maximum 20 and 25 percent difference have been reported in cases of static and seismic condition respectively.

Static Performance of Geosynthetic Reinforced Soil Walls with Peripheral Soil–Cement Mixtures

Recently, much effort has been devoted to improving the performance of geosynthetic reinforced walls under various stress conditions. In this research, the effect of using cemented mixed soil as a backfill material is studied on the static response of geosynthetic reinforced soil (GRS) walls. For this, numerical models based on a finite-difference code are made according to one of the Royal Military College’s (RMC) full scale test walls with a segmental facing. Different arrangements of soil reinforcement are considered in the presence of cemented sandy soil and sandy soil alone. In the cement-treated approach, each reinforcement layer is surrounded by a 30 cm cemented sand soil. The results show that using cement-treated sandy soil decreases the maximum deformation of the wall by as much as 75% compared with the case where untreated sandy soil is used. Moreover, by using cemented soil around reinforcements, the reinforcement forces reduce considerably. Therefore, increasing the number of reinforcement layers in the backfill will decrease the face wall deformation as well as the reinforcement forces, which are not cost-effective in many situations. It is also suggested that using the cement-treated technique can be an efficient cost-saving method compared with common GRS walls.