One-sided Loading Research Articles

Numerical study of effective parameters on true triaxial test results in rigid type apparatus

Operational parameters in true triaxial loading devices (TTA), such as the loading rod dimensions, friction between the loading platens and sample faces, loading gap, and one-side loading may affect the test results. Knowledge of the effect of each parameter is very important to correctly interpret rock behavior and to optimize these devices. Employing the Flac3D finite difference software, a rigid type true triaxial systemdesigned and builtat Amirkabir University of Iran (AUT-TTA) was simulated andinvestigated in this study. The results indicate that increasing the ratio of the rod cross-section to the loading platen area leads to an increase in the sample confinement, so, more uniform stress distribution occurs in the rock sample. The loading gap reduces strength of the rock specimen and leads to concentration of tensile stresses at the sample edges. The end effect leads to an increase in the stress level and a pseudo-hardening behavior in the samples. Also, the end effect is intensified under one-side loading condition compared to two-side loading. Comparison between results of AUT-TTA numerical simulation and analytical analysis (ideal conditions without considering operational parameters) indicates that the slope of the stress–strain diagram has low sensitivity to operational parameters. The most important operational factor affecting the stress level and dilatation stress is the end effect and other operational parameters have little effect. All parameters lead to an increase in the dilation strain. The clear edge and one-sided loading under low intermediate principal stresses and the end effect under high intermediate principal stresses have the greatest effect on the dilation strain.

Bilateral differences in handgrip strength in Czech female tennis players aged 11–12 years and injury prevention

The term laterality refers to the preference or dominance of the lateral asymmetry of the human body. The prevalence of left-handedness is reported to be 10–13%, but in some sports (e.g. boxing, ice hockey, tennis), the proportion of left-handers is higher. The left-handedness is considered an advantage in tennis; however, the one-sided load can cause muscular dysbalances leading to injuries. The research aim was to assess bilateral differences in handgrip strength in top Czech female tennis players U12 as to injury prevention. The participants were tennis players (n = 165) aged 11.0–12.9 years taking part in the regular testing by the Czech Tennis Association using the TENDIAG1 test battery between 2000 and 2018. 87.3% of all players were right-handed (RH) and only 12.7% left-handed (LH). Bilateral differences between the right- and left-hand strength of all players were medium significant in favor of the right hand. The assessment of differences between RH and LH players showed only small differences in favor of LH players. There was a medium significant difference between RH and LH players in favor of the dominant hand (DH) over the non-dominant one (NDH). As to injury prevention, it is surprising that a difference between DH and NDH strength >15% was found in 40.91% of RH players and even in 40.06% of LH players. This predicts an increased risk of injury, so it is desirable to pay attention to both sides of the training load and to include compensatory or strengthening exercises.

Predicting Delaminations and Residual Strength of Carbon Fibre Reinforced Polymers (CFRP) After One-Sided Thermal Loading by Means of Infrared Spectroscopy

This study investigates the change of chemical, structural, and mechanical properties of carbon fibre reinforced polymers (CFRP) after one-sided thermal loading. Therefore, CFRP samples (HexPly® 8552/IM7) with varying thickness (4 and 8 mm) are irradiated at different heat fluxes (15, 30, and 50 kW/m2). For a depth-resolved view on matrix degradation inside the CFRP, infrared spectroscopy (ATR-FTIR) is applied along a ground incline plane. A change of structural properties in the form of developing delaminations is investigated with microfocused computed X-ray tomography (µCT). The loss of residual strength is determined by means of interlaminar shear strength testing (ILSS). The evaluation of the data shows that delaminations occur predominantly dependent on temperature and only beyond a certain level of matrix degradation traceable by IR spectroscopy. It is also shown that delaminations are mainly responsible for the loss of strength. Furthermore, linear discriminant analysis (LDA) is performed to predict the presence of delaminations. This information provides a basis for a reliable prediction of the residual strength by IR spectroscopy after one-sided thermal loading.

Body posture and competitive sport - a review of selected studies

Increased motor activity does not unequivocally affect the incidence rates of correct and incorrect postures and practising physical exercise does not ensure good posture. One-sided load that occurs in competitive sports affects the formation of physiological curves of the spine, most often causing their deepening. In disciplines characterised by asymmetry of movements, lateral curvatures of the spine occur more often than in others.In order to achieve a posture considered to be correct, in addition to general development and sports result-oriented exercises, it is necessary to consciously shape and correct it. This is especially important when working with children and youth. It should be remembered that the susceptibility of the spine to changes in the shape of curves is different and depends on age. Wolański studied the so-called critical periods of posturogenesis among Warsaw youth and stated that the most dangerous age is between 12 and 15 for boys and between 10 and 13 for girls.It is then that the thoracic and lumbar curves are characterised by the greatest lability. They are very often deepened, which the author explains, among others changes in body proportions, i.e. elongation of the lower limbs. The commencement of professional training often takes place during this period, therefore, compensatory exercises should be its permanent element.

Rolls Geometry Calculating Mathematical Model for Rotational Bar Surface Drawing

The problem of round-rolled surface products improving quality by reducing roughness and waviness is solved. Traditionally, grinding is used to improve the surface quality, but at the same time new defects appear in the form of cracks, tinge colours and the abrasive particles in-filtration into the surface layer. Surface pressure processing instead of grinding is not associated with such defects, therefore, it is proposed to use a transverse rolling. Rolling rational profile for transverse rolling on round-rolled surface was theoretically determined. Analytical dependences were obtained for rolls in cage with support rings calibration calculations. Such calibration use ensures uniform deterioration of roll and rings bearing surfaces, as well as the rolls balance with their one-sided load during rolling. A parametric analysis of the deformation conditions effect on the rolls geometry was performed. The conditions under which rolls profile can be limited to a circle or a straight line were considered. The obtained results were used in rolls profiling for drawing the rolling surface in laboratory and industrial conditions.

The instrument geometrical parameters calculation theory for the pressure processing of the round-rolled surface

The problem of round-rolled surface products improving quality by reducing roughness and waviness is solved. Traditionally, grinding is used to improve the surface quality, but at the same time new defects appear in the form of cracks, tinge colours and the abrasive particles infiltration into the surface layer. Surface pressure processing instead of grinding is not associated with such defects, therefore, it is proposed to use a transverse rolling. Rolling rational profile for transverse rolling of round-rolled surface was theoretically determined. Analytical dependences were obtained for rolls in cage with support rings calibration calculations. Such calibration use ensures uniform deterioration of rolls and rings bearing surfaces, as well as the rolls balance with their one-sided load during rolling. A parametric analysis of the deformation conditions effect on the rolls geometry was performed. The conditions when rolls profile can be limited to a circle or a straight line were considered. The obtained results were used in rolls profiling for drawing the rolling surface in laboratory and industrial conditions.

Experimental assessment of the static stiffness of machine parts and structures by changing the magnitude of the hysteresis as a function of loading

Abstract Static stiffness is determined by one-sided loading and unloading of machine parts relative to the selected base. For each structure, there will be some loss of potential energy due to the dissipative forces that occur during the loading inside the structure. This loss is manifested in hysteresis in the stiffness diagram. A new approach to the assessment of static stiffness consists in gradual, bilateral loading and unloading of the structure through the effect of static forces of different magnitude. In this process, the stiffness hysteresis varies, depending on the intrinsic nature of the dissipative forces, a specific property suitable for assessing the condition of machines.

Loading of the Musculoskeletal System of a Person While Driving in a Passenger Car

The damping of these dynamic effects is solved by the vehicle suspension system. All this is then reflected in the safety of driving, the driving characteristics of the vehicle, but also in the response to the locomotive apparatus of the vehicle crew. Cervical injuries are usually caused by the inertia of the head. Although the product of speed and weight (kinetic energy) are proportional to the values that increase the likelihood of neck or head injury. It is surprising that significantly more injuries occur at slow speeds. The force effects transmitted to the cockpit always affect the body of the person controlling the vehicle. In the long term, one-sided loading of the organism negative impact on human health, in rare cases can lead to death. The main aim of the article was to measure the dynamic effects that are transmitted to the driver (co-driver) when driving in a passenger car over obstacles. The measurement was carried out experimentally in a real environment on a designated road at different driving speeds and different distribution of obstacles on the road. Acceleration sizes generated on the driver/co-driver seat structure, under the buttocks, head and cervical vertebrae C7 were sensed by acceleration sensors. The result of the work was to find out how much dynamic effects are transmitted from the vehicle structure to the driver/co-driver body, respectively. the head and vertebra of the cervical spine C7 (vertebrae cervicales) as the vehicle crosses obstacles.

Dynamic analysis of rectangular tank using response spectra

. Reinforced concrete tanks are currently used to store various substances and products. Most often they serve as drinking water reservoirs, to sewage treatment or to store various technical fluids. Although rectangular tanks are less used, they have advantages, such as less sensitivity to one-sided loading and better utilization of space when using a group of tanks. Rectangular tank which is the matter of interest in this paper is for the purposes of analysis considered as fulfilled with water. Dynamic analysis of the tank considering fluid-structure interaction (FSI) was the matter of interest here. Deformations and bending moments of walls were obtained.

Development of express method of microgravimetric determination of actual resins in petrols

A new approach is proposed for a quick, simple assessment of one of the quality indicators of gasoline - the concentration of actual pitches. Separate standard quality indicators for the gasoline samples (with octane number 92), which are associated with the content of the components of petroleum fractions and other non-volatile compounds, were measured. The method of piezoquartz micro-weighting with one-sided loading of the resonant electrode of the resonator, sensitive on mass (OAB-type) with a limiting contour, is used. The correlation between the results obtained by piezoquartz micro-weighing and by the standard method was studied. Critical points of the developed method are determined - the stage of applying the exact volume of samples to the resonator electrode with a micro syringe. The method of molecular absorption spectroscopy in the middle UV region relative to hexane revealed differences in the composition of the components of the petroleum fraction of gasoline samples. The principle of comparing "fingerprints" is used to compare and establish the degree of identity of spectra and composition for gasoline samples from several characteristic points on the spectra. To find and evaluate the tightness of the connection between the results of different methods, a nonparametric method for small samples with the Spearman rank correlation was used. It is established that the values of the Spearman's correlation coefficients for the piezoquartz microweighting and the peak optical density present in all gasoline samples at the characteristic wavelength have a direct and strong tightness of the connection. The dependence of the signs is statistically significant, there is a close linear relationship between the parameters. The possibility of applying the piezoquartz micro-weighting method to develop an express method for estimating the non-volatile residue of gasoline was positively evaluated.

Symmetry aspects in stability investigations for thin membranes

Modelling of structural instability problems is considered for thin square membranes subjected to hydrostatic pressure, with a focus on the effects from symmetry conditions considered or neglected in the model. An analysis is performed through group-theoretical concepts of the symmetry aspects present in a flat membrane with one-sided pressure loading. The response of the membrane is described by its inherent differential eigensolutions, which are shown to be of five different types with respect to symmetry. A discussion is given on how boundary conditions must be introduced in order to catch all types of eigensolutions when modelling only a subdomain of the whole. Lacking symmetry in a FEM model of the whole domain is seen as a perturbation to the problem, and is shown to affect the calculated instability response, hiding or modifying instability modes. Numerical simulations verify and illustrate the analytical results, and further show the convergence with mesh fineness of different aspects of instability results.

Comprehensive Fall-Risk Assessment of Construction Workers Using Inertial Measurement Units: Validation of the Gait-Stability Metric to Assess the Fall Risk of Iron Workers

In construction worksites, slips, trips, and falls are major causes of fatal injuries. This fact demonstrates the need for a safety assessment method that provides a comprehensive fall-risk analysis inclusive of the effects of physiological characteristics of construction workers. In this context, this research tests the usefulness of the maximum Lyapunov exponents (Max LE) as a metric to assess construction workers’ comprehensive fall risk. Max LE, one of the gait-stability metrics established in clinical settings, estimates how the stability of a construction worker reacts to very small disruptions. In order to validate the use of Max LE, a laboratory experiment that asked a group of subjects to simulate iron workers’ walking tasks on an I-beam was designed and conducted. These tasks were designed to showcase various fall-risk profiles: walking with a comfortable walking speed presented a low fall-risk profile; carrying a one-sided load and walking at a faster speed on the I-beam both presented high fall-risk profiles. Inertial measurement unit (IMU) sensors were attached to the right ankle of participants’ bodies to collect kinematic data for the calculation of Max LE. The results showed that Max LE offers adequate distinguishing power for characterizing the fall risk of various construction workers’ tasks, and the introduced approach to compute the gait stability from IMU sensor data captured from human bodies could provide a valuable analysis of the safety-related risks present in construction workers’ motions.

Stiffness of dowel-type timber connections under pre-yield oscillating loads

The dynamic behaviour of timber structures in service is becoming a more important consideration in design as modern engineered wood products allow longer spans and taller timber buildings, which can be sensitive to dynamic loading such as that from wind or footfall. Connections in timber structures have a pronounced effect on their structural behaviour. In dowel-type connections, the fasteners bend under load and embed into the surrounding timber and, since embedment is a nonlinear process, the stiffness of those connections varies depending on the nature of the applied load. Here, single-dowel connections are tested under cyclic loads representative of in-service vibration. One-sided and reversed cyclic loads are applied. The specimen stiffness is observed to reduce with the amplitude of one-sided cyclic load. For small-amplitude one-sided load, the specimen stiffness is seen to tend towards that predicted by an elastic model, and an analytical elastic model is presented to represent the embedment resistance of the timber and the behaviour of the connector.

Muscle Imbalance and Body Composition of Elite Junior Female Volleyball Players

This study presents the state of a muscular apparatus of junior female volleyball players and the impact of one-sided sport on their bodies. A group of 12 female volleyball players aged 15−16 were examined by a complex kinesiologic analysis and anthropological tests by the InBody 3.0 instrument. The early specialization as well as the one-sided load can lead to muscle imbalance, deficient posture and further problems with a muscle apparatus. The aim of this study is to point out the situation in the group of examined volleyball players and also to show the necessity of an interventional compensating programme to counterbalance the lateral asymmetries

Evaluation of the effect of rolling correction of double-o-tunnel shields via one-side loading

During construction of a double-o-tunnel (DOT), rolling will inevitably occur due to the following: (i) nonuniformity of subsoil condition, (ii) manufacturing errors in the DOT shield machine, (iii) different pulling forces at two sides of the DOT, (iv) effect of assembled segments, (v) loss of grout, and (vi) inappropriate operation. In engineering practice, rolling correction using a one-side load at the elevated side is a cost-effective method. The weight of the one-side load is determined by the experience of the engineers and (or) through observation of the returned rolling angle. However, these methods cannot predict the value of the one-side load before applying it. This paper presents a series of finite element analyses that was performed to investigate the relationship among the one-side load, rolling angle, and subsoil deformation. The analytical results show that the proposed approach can predict field-observed data well. It is concluded that analytical results can be used as guidance for DOT construction.

Circular crack in a transversely isotropic piezoelectric space under point forces and point charges

In this paper, two kinds of circular crack including external circular crack and penny-shaped crack in a transversely isotropic piezoelectric space are considered. Firstly, we obtain the solution to the problem of an external circular crack in a transversely isotropic piezoelectric space subjected to antisymmetric normal point forces and point charges. Based on this, the solution of one-sided loading of an external circular crack is constructed. Secondly, the real shape of an external circular crack and the opening displacement of a penny-shaped crack under an arbitrary point force and point charge are further obtained. At last, the results are presented in a graphical form.

Research of porous coating influence on heat exchange crisis in circular cooling channels at one-sided loading

Abstract Test data on the Ultimate Heat Flux investigation at a heat loading typical for the ITER Divertor are presented. It is determined that using of technology of the Porous Coating deposiiion to the cooling channel surface leads to a significant increase of the Ultimate Heat Flux value. Before-crisis and pre-crisis temperature state calculation results for one-sided loaded rectangular mock-ups with tubular cooling channels are given. Two alternative conceptions (optimistic and pessimistic) were used in the calculations. Water flow rate influence on the mock-up temperature level was investigated.

Two Scholte–Stoneley waves on doubly fluid-loaded plates and shells

Previous theoretical and experimental studies of sound scattering from plates and from evacuated cylindrical or spherical shells with one-sided water loading have demonstrated the existence of a water-borne Scholte–Stoneley wave, and its acoustic excitation, in addition to that of the Lamb-type plate or shell wave modes. For two-sided water loading two Scholte–Stoneley waves, of symmetric (S) and antisymmetric (A) nature, were predicted on plates, with only the A wave surviving for the case of one-sided loading, while for loading with two different fluids, again two such waves have been demonstrated theoretically. In the present investigation, these two Scholte–Stoneley waves are studied experimentally via short-pulse scattering from water-immersed, thin-walled cylindrical shells filled alternatingly with air, water, and alcohol, and a theoretical analysis of their dispersion curves is presented.

FINITE ELEMENT ANALYSIS ON SHEAR RESISTING MECHANISM OF CONCRETE BEAMS WITH SHEAR REINFORCEMENT

The nonlinear finite element analysis program for reinforced concrete planar member subjected to reversed cyclic loading is expanded to analyze reinforced and prestressed concrete linear members with shear reinforcement subjected to one-sided cyclic loading. It is found that the predicted strains of shear reinforcement can be made much closer to the experimental ones by considering reduction of concrete tension stiffness due to slip of shear reinforcement at its lower bent. The ultimate strengths of beams are also predicted reasonably. Based on the analysis, a new truss model is presented to explain shear resisting mechanism of beams with shear reinforcement.

Multispan Stayed Girder Bridges

In stayed girder bridges with two or three spans the horizontal displacement of pylon tops is prevented by the so-called fix-cables, i.e., upper end span cables. If stayed girder bridges are constructed with several equal main spans the intermediate pylons will tend to move horizontally under one-sided loading. This induces a rotation of the entire cable system giving unacceptable vertical deflections of the stiffening girder. To obtain the necessary stiffness two measures might be taken, either application of triangular pylon structures with sufficient horizontal rigidity at the top, or introduction of a horizontal fix-cable (tie) connecting all pylon tops.