Initial Tensile Force Research Articles

Experimental study on flexural performance of prestressed concrete beams strengthened by Fe-SMA plates

Shape memory alloy (SMA) is an innovative intelligent material, capable of restoring its shape before deformation upon reaching the critical activation temperature. This property promotes its promising applications in civil engineering. This paper proposes a novel reinforcement method and aims to investigate the reinforcing effect of iron-based shape memory alloy (Fe-SMA) plates on prestressed concrete (PC) beams through four-point bending tests on one reference beam without reinforcement and three Fe-SMA reinforced beams, as well as with three beams reinforced by carbon fiber-reinforced polymer (CFRP). The results show that Fe-SMA can effectively reduce concrete cracks, and improve stiffness and characteristic loads of beams without negative effects. Under the same loading conditions, new cracks of Fe-SMA reinforced beams were relatively fewer than those of CFRP reinforced beams. Besides, Fe-SMA exhibited superior performance when utilizing the same cross-sectional reinforcement material to enhance the bending capacity of beam, and proved more advantageous for improving stiffness and characteristic loads of beam under the identical initial tensile force. Furthermore, the reinforcing effectiveness of Fe-SMA positively correlates with the cross-sectional area (thickness) and recovery stress (pre-stretch level and activation temperature) of Fe-SMA. Increasing the thickness of Fe-SMA plates by 100%, while maintaining other parameters constant, resulted in a 33% increase in cracking load. Similarly, elevating the recovery stress from 314 MPa to 340 MPa led to a 12.5% rise in cracking load. This paper investigates the reinforcement effect of Fe-SMA plates on PC beams, and provides a reference for the application of Fe-SMA in PC beam reinforcement, laying a foundation for promoting the utilization of Fe-SMA in civil engineering.

A Multi-Segment Expanded Anchor for Landslide Emergency Management

Conventional mortar cemented anchors cannot meet the needs for landslide emergency management, as they can withstand loads only after mortar curing for 14–28 days. This study developed a multi-segment expanded anchor (MSEA) that expands using a sliding mechanism and rapidly bears loads using multiple load-bearing bodies by the frictional drag along the perforated wall, and the reaction force of the underreams’ platforms. Field tensile tests without grouting and the secondary tensile tests of six MSEAs, each with a length of 23 m, were carried out. The field tests show that the installed load-bearing bodies expanded steadily when the MSEAs were tensioned without grouting. In hard sandstones, the initial tensile force of each load-bearing body exceeded its design value of 150 kN, and the initial bearing capacity of each MSEA was greater than 300 kN, which exceeded the bearing capacity of the existing anchors regardless of grouting. The secondary tensile tests of the MSEAs were conducted after they were grouted for three days, and their lock-off load was greater than their design value of 600 kN. Based on the elastic mechanics and the stress process of the MSEAs, this study derived the theoretical equations of the ultimate bearing capacity of the MSEAs without grouting. The results calculated using the theoretical equations were roughly consistent with the field test results of the ultimate bearing capacity.

Supraspinatus tendon reconstruction using open infraspinatus tendon shift and autologous biceps tendon interposition grafts

IntroductionInferior tendon quality, wide retraction, and tendon stumps that cannot be mobilized define the limits of what is technically feasible for open and arthroscopic rotator cuff reconstruction. The aim of this study was to develop a procedure that enables the open reconstruction of otherwise non-reconstructable rotator cuff tears.MethodsFrom 2014 to 2018, 23 operations were performed on 21 patients (mean age 63) using open procedure involving separating the infraspinatus tendon from the point of insertion on the greater tubercle and mobilizing it proximally and ventrally into the defective area. Any remaining defects were augmented using an autologous biceps tendon interposition graft. This augmentation was performed to achieve complete closure of the defect. Furthermore, the augmentation of the rupture zone was intended to strengthen the tendon stumps of the SSP and ISP to better neutralize the initial tensile forces. After a postoperative period of 12 months–4 years, clinical examination and functional tests were carried out, the Constant score was determined, and radiological and magnetic resonance imaging check-up examinations were performed.ResultsThe technique resulted in a low-tension closure of an otherwise “non-repairable” superior rotator cuff defect. All patients experienced a significant functional improvement, a reduction in pain, and an increase in muscle strength. An improvement in the Constant score from 48 points preoperatively to 87 points postoperatively (p < 0.05) was observed. In 19 patients (90%), the magnetic resonance image showed an intact reconstruction. Re-rupture was seen in three patients (14%).ConclusionThe surgical procedure using infraspinatus tendon shift and autologous biceps tendon interposition grafts resulted in the successful reconstruction of otherwise non-reconstructable massive rotator cuff lesions. The complete closure of the defect was observed.

Theoretical model for variable helical angle of tensile armour wires in bent flexible pipes

This paper systematically addresses a theoretical model to account for the variation of the initial helical lay angle of the tensile armour wires in flexible pipes during bending condition. Based on differential geometrical discussion and curved beam theory, a non-linear differential equation system which contains the unknown variable helical angle is established. Moreover, different expressions of wires’ strain before and after wires’ slip are included in the paper to underline the discrepancy between scenarios in non-slippage and slippage regions. The variation of the armour wires helical angles, which are usually implicit in previous work, can be obtained numerically, revealing potential application in global bending problem. Case studies compared with results obtained through analytical and numerical models available in the literature as well as parametric analyses corresponding to original helical angle, initial tensile force, friction coefficient and bending curvature are performed to verify the feasibility of the proposed theoretical method.

Initial Tensile and Residual Forces of Pigmented Elastomeric Ligatures from Various Brands

This study aimed to investigate the initial tensile and residual forces of pigmented elastomeric ligatures (clear, pink, and metallic) from three commercial brands – Brand 1 (USA), Brand 2 (USA), and Brand 3(China). Twelve elastomeric ligatures of each brand and color were evaluated for initial tensile and residual forces after stretching for 28 days at 37°C by a Universal Testing Machine. The results showed that the highest initial tensile force was 14.78 N, 20.71 N, and 15.1 N for the metallic color of Brand-1, pink color of Brand -2, and metallic color of Brand -3, respectively. There were significant (p<0.05) differences in the initial tensile force of each brand, except clear and metallic color of Brand-1 & 3 and pink color of Brand-2 & 3. Similarly, among the pigmented ligatures from each brand, significant (p<0.05) differences were observed in the initial tensile force, except metallic color of Brand-1 & 3. Brand-3 had the highest residual force after 28 days, whereas the loss of force was 80-90% in Brand-1 & 2 and 20-30% in Brand-3. There were also significant (p<0.05) differences in the residual forces in each color and brand, except metallic color of Brand-1. In conclusion, there were significant differences in the initial tensile and residual forces among the three pigmented elastomeric ligatures of the three commercial brands.

The Vibration of a Linear Carbon Chain in Carbon Nanotubes.

An explicit solution for the vibration of a carbon chain inside carbon nanotubes (CNTs) was obtained using continuum modeling of the van der Waals (vdW) interactions between them. The effect of the initial tensile force and the amplitude of the carbon chain as well as the radii of the CNTs on the vibration frequency were analyzed in detail, respectively. Our analytical results show that the vibration frequency of the carbon chain in a (5,5) CNT could be around two orders of magnitude higher than that of an independent carbon chain without initial tensile force. For a given CNT radius, the vibration frequency nonlinearly increases with increasing amplitude and initial tensile force. The obtained analytical cohesive energy and vibration frequency are reasonable by comparison of present molecular dynamics (MD) simulations. These findings will be a great help towards understanding the vibration property of a nanowire in nanotubes, and designing nanoelectromechanical devices.

Effect of Bridge-Pier Differential Settlement on the Dynamic Response of a High-Speed Railway Train-Track-Bridge System

A model based on the theory of train-track-bridge coupling dynamics is built in the article to investigate how high-speed railway bridge pier differential settlement can affect various railway performance-related criteria. The performance of the model compares favorably with that of a 3D finite element model and train-track-bridge numerical model. The analysis of the study demonstrates that all the dynamic response for a span of 24 m is slightly larger than that for a span of 32 m. The wheel unloading rate increases with pier differential settlement for all of the calculation conditions considered, and its maximum value of 0.695 is well below the allowable limit. Meanwhile, the vertical acceleration increases with pier differential settlement and train speed, respectively, and the values for a pier differential settlement of 10 mm and speed of 350 km/h exceed the maximum allowable limit stipulated in the Chinese standards. On this basis, a speed limit for the exceeding pier differential settlement is determined for comfort consideration. Fasteners that had an initial tensile force due to pier differential settlement experience both compressive and tensile forces as the train passes through and are likely to have a lower service life than those which solely experience compressive forces.

Vibrations and instability of double-nanowire-systems as electric current carriers

Current-carrying nanowires are expected to be building blocks of the upcoming micro-nano-electromechanical devices, however, little is known on their dynamic interactions in a bundle. As a pivotal step towards realizing such a crucial mechanism, this work is devoted to vibrations and instability of a double-nanowire-system as an electric current carrier. Using Biot–Savart law, the Lorentz interactional forces between doubly parallel current-carrying nanowires are evaluated. Accounting for the surface elastic energy, equations of motion pertinent to the in-plane and out-of-plane vibrations are established. Using analytical techniques, the explicit expressions of both static and purely dynamic parts of the nanowires’ displacements are obtained. For each component of the transverse displacement field, two major vibration modes are observed: in-phase and out-of-phase modes. The frequencies associated with these vibration modes are analytically calculated. Further, the condition corresponds to the dynamic instability of the system is discovered, and the roles of initial tensile force, electric current, and interwire distance on frequencies and stability of the system are addressed.

Vibrations and instability of pretensioned current-carrying nanowires acted upon by a suddenly applied three-dimensional magnetic field

Longitudinal and transverse vibrations of a pretensioned current-carrying nanowire subjected to a suddenly exerted three-dimensional magnetic field are of concern. Using an elastic string model by considering the surface effect, the equations of motion of the nanostructure are established. By employing admissible mode shapes and Laplace transform approach, an analytical solution is proposed to determine the nanowire's elastic field. The explicit expressions of the longitudinal and transverse displacements of the nanowire are derived. The conditions that lead to the dynamic instability of the nanostructure are also discussed. The influences of the initial tensile force, electric current, and the components of the magnetic field on the dynamic displacements are comprehensively addressed.

Necessity of transient-state unwinding equation of motion for analyzing unwinding motion of a thin cable

When a thin cable is unwound from a spool dispenser, factors that influence balloon shapes are initial tensile force, unwinding velocity, balloon height, package radius, and fluid condition. Historically, a thin cable’s unwinding motion has been analyzed using transient- and steady-state unwinding equations of motion. The transient-state unwinding equation of motion can be derived by using Hamilton’s principle for an open system in which mass can change within a control volume. In the process of solving the transient-state unwinding equation of motion, two-point boundary conditions are exactly adopted for each time step. The steady-state unwinding equation of motion can be derived by using a perturbation scheme from the transient-state unwinding equation of motion. To find a solution for the steady-state unwinding equation of motion, the shooting method is utilized, but due to insufficient boundary conditions at the lift-off point, finding a unique solution is impossible. Therefore, analysis of the unwinding motion of a thin cable should be performed using the transient-state unwinding equation of motion.

Stability and vibrations of doubly parallel current-carrying nanowires immersed in a longitudinal magnetic field

Abstract This paper deals with dynamic interactions of two parallel nanowires carrying electric currents in the presence of a longitudinal magnetic field. Using Biot–Savart law and a surface elasticity model, the equations of motion are obtained. Accounting for both Lorentz and gravity forces, the static and the purely dynamic parts of the total displacements of the nanosystem are explicitly expressed. Two crucial modes of vibration, synchronous and asynchronous patterns, are identified and their characteristics are inclusively explained. It is shown that the nanosystem becomes dynamically unstable under certain conditions in the asynchronous mode. The minimum initial tensile force as well as the maximum values of the electric current and the magnetic field strength corresponding to the dynamic instability are derived. The roles of the crucial factors on the lowest asynchronous frequencies are also addressed and discussed.

Unwinding motion of cable by taking into consideration effect of bending on cable

One of the most important factors influencing the performance of wire-guided missiles is the ability to exchange information through a connected cable. Some of the problems that occur during the process of unwinding the cable from the spool package are tangling of the cable because of low tensile force at the guide-eyelet point and cutting of the cable because of high tensile force. Therefore, it is important to analyze the transient motion of the unwinding cable withdrawn from the spool package, while considering the effect of flexural rigidity on the cable. The unwinding system is defined with cylindrical coordinates, and Hamilton׳s principle in an open system is introduced to represent the mass change of the cable in the control volume. Using Hamilton׳s principle, which takes into consideration the Lagrangian, virtual work, and virtual momentum transport, the unwinding equation with high non-linearity can be derived using boundary conditions. Further, by assuming inextensibility, the tensile force can be derived for the spatial variable. To solve the unwinding equation numerically, Newmark implicit integration is utilized with the central finite-difference approximation for spatial variables. The motions of the cable can be ascertained on the basis of various initial tensile forces by considering the constant unwinding velocity at the guide-eyelet point in air and water. It can be concluded from these motions that fluid resistance is the dominant force on the cable when it is unwound in the water, and, in contrast, centrifugal force is dominant in the air. Further, it can be observed that the initial tensile force required when the cable is unwound in water is greater than that required in air, to avoid unwinding problems such as tangling and cutting of the cable.

Surface effect on free transverse vibrations and dynamic instability of current-carrying nanowires in the presence of a longitudinal magnetic field

Abstract Free transverse vibration and instability of current-carrying nanowires immersed in a longitudinal magnetic field are of concern. On the basis of the surface elasticity theory, a model is developed to investigate the problem. The analytical expressions of dynamic transverse displacements as well as natural frequencies of the magnetically affected nanowire for carrying electric current are obtained. The influences of the surface effect, initial tensile force within the nanowire, strength of the longitudinal magnetic field, and electric current on the natural frequencies as well as dynamic displacements are examined. The obtained results reveal that the transverse stiffness of the nanostructure is enhanced by the surface effect and the initial tensile force, while electric current or longitudinal magnetic field reduces the nanowire's stiffness. The condition which leads to the dynamic instability of the nanostructure is obtained. Further, the roles of the influential parameters on its stability are inclusively discussed.

수치해석을 통한 앵커의 긴장력과 사면 안전율의 상관관계 도출

최근 기후변화로 발생하는 이상강우에 의한 지하수위의 상승은 사면보강을 위해 설치한 앵커의 초기 긴장력의 증가를 유발시킬 수 있다. 한편 사면의 국부적 파괴나 낙석 등으로 인한 앵커 두부(head)의 예기치 못한 손상은 긴장력 상실로 이어져 앵커로 보강된 사면의 안정성을 저하시키는 주된 요인이 될 수 있다. 이와 같은 앵커 긴장력의 변화는 사면의 안정성에 매우 직접적으로 영향을 미치지만 현재의 기술은 앵커 긴장력의 존재 유무만을 간단히 확인하거나 단기간의 긴장력 변화를 측정할 수 있는 기술만이 있을 뿐 영구사면과 같이 장기간 앵커의 긴장력 변화와 사면의 안정성에 대한 직접적이고 효과적인 모니터링 방법은 찾아보기 어렵다. 본 연구에서는 장기간의 앵커 긴장력 모니터링이 가능하도록 개발된 광섬유 센서 내장형 텐던을 이용하여 사면의 안정성을 직접 평가할 수 있도록 초기 긴장력 감소 및 증가와 사면 안전율의 상관관계에 대하여 수치해석적 검토를 수행하였다. 앵커가 시공되어 있는 실제 사면의 사례에 대한 한계평형해석 및 3차원 유한요소해석을 실시하여 사면에 설치된 앵커의 긴장력 변화와 사면 안전율(factor of safety) 변화에 대한 검토를 수행한 결과, 지하수위 상승으로 인한 앵커 긴장력의 증가는 사면 안전율의 비선형적 감소를 동반하며 일정 수준 이하의 앵커 긴장력 감소는 선형적 사면 안전율 감소를 동반하는 것으로 나타났다. Main reasons making the slope reinforced with anchors unsafe are rise of ground water table due to heavy rainfall and sudden reduction of initial tensile force due to damage of anchor head. In this research, numerical analysis was carried out to evaluate the safety of slope reinforced by anchors from the monitoring result of tensile force. Limit equilibrium analysis and 3D finite element analysis were carried out to model the sudden reduction of initial tensile force and increase of tensile force due to soil movement, which was caused by rise of ground water table. From the numerical analysis, it was found that the increase of tensile force due to rise of ground water table comes with nonlinear decrease of safety factor and reduction of initial tensile force due to damage of anchor head accompanied with linear decrease of safety factor. From the results, it can be concluded that safety of the slope can be evaluated indirectly by monitoring the tensile force of anchor using FBG sensor embedded tendon.

Unwinding characteristics of thin cables for inner and outer dispensers

When thin cables of materials such as yarn and tether are unwound from a spool dispenser, various balloon shapes are generated depending on the initial tensile force at the guide-eyelet point. The shapes are dependent on the properties of the cable because the point of unwinding depends on the thickness of the cable. In this paper, the unwinding characteristics are analyzed for inner and outer dispensers by using three types of thin cable. The dimensionless steady-state equation of motion is first derived from Hamilton’s principle for an open system and the perturbation scheme. The second-order differential equation is then solved by means of shooting method because the boundary conditions at the lift-off point are not fully sufficient. Several parameters such as cable diameter and initial tensile force are checked to study their effects on the balloon shapes. For a given material, the larger is the diameter of the cable, the higher is the air-drag coefficient on the cable, and the effect of the centrifugal force is weaker than that of the fluid resistance. Moreover, the maximum radius of the balloon and the total length of the control volume are small when the cable is thick.

Field measurements of anchored flexible systems for slope stabilisation: Evidence of passive behaviour

Flexible systems anchored to the ground constitute a technique for slope surface stabilisation. They are formed by membranes (cable nets, wire mesh, ring net), reinforcement cables and bolts tightly anchored to the ground forming regular patterns. Most manufacturers and independent researchers assume active behaviour of these systems when they propose their design models, which means that the system avoids occurrence of instability. To consider active behaviour, two conditions have to be fulfilled: the membrane has to be initially prestressed and the slope must present a convex shape. Neither of these two conditions has been verified so far, therefore, there are no guarantees that current design methods are adequate. Review of the technical brochures of manufacturers shows that applied prestress force on membranes and reinforcement cables is nonexistent or very low.In this paper, three field systems in north Spain with cable nets anchored to the ground have been instrumented. Net cables, reinforcement cables and bolt heads have been instrumented by using sensors based on electrical extensometry. Tensile forces on cables and compression forces on bolt heads have been monitored for more than a year from the beginning of installation. Initial tensile forces in net and reinforcement cables induced an average value of 0.7% and 2.1%, respectively, of the ultimate strength of each component. In relation to bolts, average compression force on bolt heads was 5.3% of their ultimate strength.These measurements demonstrate that prestress force on flexible systems is very low, and nearly negligible. Therefore, flexible systems anchored to the ground cannot be considered as active, but passive, which means that most current design methods are not adequate.

Probabilistic optimal safety valuation based on stochastic finite element analysis of steel cable-stayed bridges

This study was intended to efficiently perform the probabilistic optimal safety assessment of steel cable-stayed bridges (SCS bridges) using stochastic finite element analysis (SFEA) and expected life-cycle cost (LCC) concept. To that end, advanced probabilistic finite element algorithm (APFEA) which enables to execute the static and dynamic SFEA considering aleatory uncertainties contained in random variable was developed. APFEA is the useful analytical means enabling to conduct the reliability assessment (RA) in a systematic way by considering the result of SFEA based on linearity and nonlinearity of before or after introducing initial tensile force. The appropriateness of APFEA was verified in such a way of comparing the result of SFEA and that of Monte Carlo Simulation (MCS). The probabilistic method was set taking into account of analytical parameters. The dynamic response characteristic by probabilistic method was evaluated using ASFEA, and RA was carried out using analysis results, thereby quantitatively calculating the probabilistic safety. The optimal design was determined based on the expected LCC according to the results of SFEA and RA of alternative designs. Moreover, given the potential epistemic uncertainty contained in safety index, failure probability and minimum LCC, the sensitivity analysis was conducted and as a result, a critical distribution phase was illustrated using a cumulative-percentile.

Probabilistic optimal safety with minimum life-cycle cost based on stochastic finite element analysis of steel cable-stayed bridges

This study was intended to efficiently perform the probabilistic safety and optimal design assessment of steel cable-stayed bridges (SCS bridges) using stochastic finite element analysis (SFEA) and expected life-cycle cost (LCC) concept. To that end, advanced probabilistic finite element algorithm (APFEA) which enables to execute the static and dynamic SFEA considering aleatory uncertainties contained in random variable was developed. APFEA is the useful analytical means enabling to conduct the reliability assessment (RA) in a systematic way by considering the result of SFEA based on linearity and nonlinearity of before or after introducing initial tensile force. Appropriateness of APFEA was verified in such a way of comparing the result of SFEA of a simple structure and the result of numerical analysis using Monte Carlo Simulation (MCS) program. The probabilistic method of SCS bridges was set, taking into account of analytical parameters. The dynamic response characteristic by probabilistic method was evaluated using ASFEA, and RA was carried out based on analysis result, thereby quantitatively calculating the probabilistic safety. The optimal design of SCS bridges was determined based on the expected LCC according to the results of SFEA and RA of alternative designs. Moreover, given the potential epistemic uncertainty contained in safety index, failure probability and minimum LCC, the sensitivity analysis was conducted and as a result, a critical distribution phase was illustrated using a cumulative-percentile.

Theoretical-experimental static and dynamic analysis of double layered catenary

The paper presents the results of static and dynamic tests of double layered catenary of the swimming pool building roof in Leskovac. By the comparison of measured and calculated values, a potential was created to correct the mathematical model, and to verify it. Only then, the calculation model for all sorts of static and dynamic load was able to simulate the realistic behavior of the structure. In this paper, the authors presented the basic recommendations in terms of what initial tensile force should be adopted in order to control the stability of such very cost-effective girders.

Stiffness matrices of thin-walled composite beam with mono-symmetric I- and channel-sections on two-parameter elastic foundation

For the coupled analysis of thin-walled composite beam under the initial axial force and on two-parameter elastic foundation with mono-symmetric I- and channel-sections, the stiffness matrices are derived. The stiffness matrices developed by this study are based on the homogeneous forms of simultaneous ordinary differential equations using the eigen-problem. For this, from the elastic strain energy, the potential energy due to the initial axial force and the strain energy considering the foundation effects, the equilibrium equations and force–displacement relationships are derived. The exact displacement functions for displacement parameters are evaluated by determining the eigenmodes corresponding to multiple non-zero and zero eigenvalues. Then the element stiffness matrix is determined using the force–displacement relationships. For the purpose of comparison, the finite element model based on the classical Hermitian interpolation polynomial is presented. In order to verify the accuracy and the superiority of the beam elements developed herein, the numerical solutions are presented and compared with results from the Hermitian beam elements and the ABAQUS’s shell elements. Particularly, the influence of the initial compressive and tensile forces, the fiber orientation, and the boundary conditions on the coupled behavior of composite beam with mono-symmetric I- and channel-sections is parametrically investigated.