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Asymptotic formulas for vibration-based cable tension identification accounting for uncertain boundary conditions
Published in Hiroshi Yokota, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 2021
X.L. Le, H. Katsuchi, H. Yamada
Identifying accurately the forces in cable stays is paramount important during the construction stage or health monitoring of structure to evaluate the serviceability of bridge (Casas 1994). Tension force, currently, can be determined by either direct or indirect measurement methods. In detail, by direct measurement, tensions are commonly measured with oriented load measurement devices (e.g. hydraulic jacks, pressure and displacement meters). A report presented by Cho et al. (2012) shown that the values of cable tension extracted from the lift-off test are highly convergent to the design (less than 2 % difference). Direct measurement, however, would cost a colossal amount of money because of employing not only advanced instruments but also skillful labors. Practical implementations of the direct assessments, in addition to high cost, might cope with on-site installed challenges, poor endurance of sensors and so on. To alleviate this, the vibration-based approach, one of the indirect measurement methods, is becoming alternatively prioritized to practical engineers owing to its simplicity, speediness and economic efficiency (Fang & Wang 2012). In term of vibration-based cable tension estimation method, tensions are commonly deduced through field measured natural frequencies along with geometrical and mechanical parameters of the cable.
Mechanics
Published in W. David Yates, Safety Professional’s, 2015
Contact forces include the following: Frictional force is a force that resists the relative motion of objects that are in contact with each other.Tension force is the force required to pull an object (opposite of compression).Normal force is the force on an object caused by the normal interaction between two objects.Air resistance force is the force between an object traveling through air and the contact with the air. As with all forces, air resistance force opposes the motion of the object.Applied force is the force applied to an object by a person or another object.Spring force is the force exerted by a compressed or stretched spring.
Preload Control
Published in John H. Bickford, An Introduction to the Design and Bchavior of Bolted Joints, 2018
In most applications the answer is “No.” But a number of techniques are emerging which come close to tension control, and which are usually claimed to be such. For example, there are “tension control” systems which are based on the measurement of torque and turn, or on the measurement of strain. We looked at the torque-turn techniques in Chap. 8 and will now look at some of the strain measurement techniques—many of which are useful in special situations—and then we’ll look at some as-yet-unavailable ways in which actual stress could, theoretically, be measured. Finally, we’ll look at a useful device that is widely, but erroneously, believed to be a tension-control device: the hydraulic tensioner.
Tensile strength and elongation of selected Kenaf fibres of Ghana
Published in Cogent Engineering, 2023
George Ansong, Yesuenyeagbe A.K. Fiagbe, Antonia Y. Tetteh, Francis Davis
The tensile strength can be defined as the maximum stress that a material can bear before breaking when it is allowed to be stretched or pulled. The tensile strength of the fibre strand was obtained from the test result and found to range from 734.53 MPa for EB31 to 1365.14 MPa for HN11. For the genotypes, the tensile strengths are found to be 734.53 MPa (EB31), 1292.37 MPa (TN11), 1241.53 MPa (EN31), 979.35 MPa (PN11) and 1365.14MPa (HN11). The tensile strength for the EB31 genotype ranges from 242.03 MPa to 1450.27 MPa; that of TN11 ranges from 630.28 to 2300.95 MPa; EN31 from 912.47 MPa to 2076.63 MPa; PN11 from 388.25 MPa to 2302.48 MPa and for the HN11 genotype, it ranges from 405.03 MPa to 2624.89 MPa. The tensile strength result is presented in Figure 5.
Optimization of an angle between the deflector plates and its orientation to enhance the energy efficiency of Savonius hydrokinetic turbine for dual rotor configuration
Published in International Journal of Green Energy, 2022
Figure 4 indicates the photograph of the experimental setup used for the present experimental analysis. The design parameters used for the rotor are shown in Table 2, and the detailed nomenclatures used in the rotor design are shown in Figure 5. The torque on the turbine shaft is applied by winding the cord on the turbine shaft. The tension on the cord has been altered using different loads on the end of the cord. The tension is measured using load cells attached at both ends of the cord. The torque is calculated using applied tensions on the cord and measured shaft radius. The turbine rotor’s angular velocity is calculated by measuring the time for 15 revolutions of the turbine shaft. The time is measured using a stopwatch with an accuracy of 0.01 s. The experiments are extended to turbine rotor stops by gradually applied to the load. The obtained values of torque, power output from the turbine, and angular velocity of the rotor are presented as the coefficient of torque (Ct), co-efficient of power (Cp), and Tip Speed Ratio (TSR), respectively. The results obtained from the experimental analysis are shown in Figure 7. The maximum coefficient of power of 0.112 at a tip speed ratio of 0.55 is recorded from the experiments.
An activity theory perspective on contradictions in flipped mathematics classrooms at the university level
Published in International Journal of Mathematical Education in Science and Technology, 2020
Helge Fredriksen, Said Hadjerrouit
According to Engeström et al. [39], contradictions cannot be observed directly, they can only be identified through their manifestations. Tensions or similar terms such as disturbances are the visible manifestations of underlying contradictions [40, p. 302]. We agree and thus consider that contradictions must be identified through their manifestations. They become recognized when participants express them in words and actions, but they cannot be reduced to subjective experiences or situational articulations [20, p. 371]. In other words, contradictions cannot be identified directly without their manifestations that would qualify them as contradictions [20, p. 372]. Some indicators for tensions are then necessary to identify contradictions in AS. In this work, the term ‘tension’ is not used in its everyday sense. Instead, tensions are defined and expressed as forces pulling in opposite directions [41], imbalance of participation or divergent objectives among participants [42], disagreement among participants, disagreement between a participant and an external source (e.g. curricular material), or apparent incompatibilities between different utterances made by a single participant [1]. Other similar indicators are proposed by Engeström and Sannino [20, p. 373]: incompatible evaluations (dilemma), conflict in the form of resistance, disagreement, or argument; critical conflict facing contradictory motives, and double bind, that is facing pressing and equally unacceptable alternatives.