Papers by Keyword: Tendon

Abstract: The paper deals with the design and development of a new and progressive structural types of footbridges with an external tendon used as a main load bearing member. Main goals of the paper are checking the possibilities of using such structures for many different spatial arrangements and especially identifying the problematic aspects of the design. Using the results of research conducted in previous years, the procedure for finding the optimal shape of the cable was described in detail. For specific examples the process of cable shape optimizations is shown. In the next part the influence of various boundary conditions is discussed. The structures were also checked in terms of ULS and SLS limit states. Particular attention is paid to the buckling analysis of the struts and stress distribution in the deck part. The structures were modeled using FEM software Midas Civil. The models used for basic analysis consist of beam and truss elements. For precise analysis the shell models were used. Finally the dynamic behavior analysis was performed according to SÉTRA methodology. The results and outputs of the research should be used by designers who have to deal with similar structural types and they shall hopefully help to identify the most problematic features.

Abstract: Tendons and ligaments injuries have become more and more common due to the increase of the general populations interest in sports and physical activities. Beginning with the 1970s many researchers have tried to reconstruct the torn ligaments and tendons, at first using products such as Polyflex and Proplast ligaments, with poor results. In recent years the use LARS ligament has been researched. The Ligament Augmentation and Reconstruction System, now at its 3^rd generation, is an artificial ligament made out of polyethylene terephthalate (PET) that over time allows tissue ingrowth, recreating the natural orientation of anatomical ligament and tendon fibers.

Abstract: Despite of their outstanding axial strength, CFRP tendons necessitate special anchorage due to their low lateral shear strength. In order to cope with such CFRP tendon, the conventional bond type anchor needs to be improved. The results of bond tests executed on 10-mm diameter CFRP tendons coated with sand and oxide revealed that, even if the average bond strength increases by 3 times compared to the non-coated bare tendon, the coated CFRP tendon still requires excessively long anchored length for bonding. Therefore, this study applies a method enabling to shorten the bonded length and improving further the bond performance compared to sand or oxide coating. The improvement of the bond characteristics is achieved by splitting the ends of the CFRP tendon so as to widen the bonded area by 3.5 times. The test results showed that the anchor performance of the CFRP tendon reaches 95% of its tensile strength making it applicable for the bond type anchor.

Abstract: The anchoring of CFRP tendon can be performed by wedging, bonding or compressing. The wedge type anchor, used for PS steel tendon, is inappropriate for direct application to the CFRP tendon due to its low lateral stiffness. Since the bond performance of the CFRP tendon depends on the anchor performance, the bond type anchor presents the problem of requiring long steel sleeve in case of low bond performance or high tensile performance. Compared to the bond type anchor, the compressing type anchor offers better applicability but necessitates the development of a sleeve fitted to the dimensions of each CFRP tendon. This study intends to examine the anchoring characteristics of the compressed sleeve for the temporary anchorage of a CFRP tendon with diameter of 10 mm. To that goal, the properties of the 10 mm-diameter CFRP tendon were assessed using the bond type anchor and the corresponding anchor performance is compared to that of the compressed anchor. The test results revealed that the use of spacers in the compressed anchor provided lower anchor performance due to the characteristics of the spacers. For the specimen without spacer, the micro-deformations formed inside the sleeve were seen to compress the CFRP tendon by gearing directly the tendon and to provide anchor performance reaching about 72% of the tensile strength of the CFRP tendon. Further study shall develop a sleeve with increased compress force on the CFRP tendon so as to improve the anchor performance of the compressed sleeve. Moreover, solution shall also be provided to introduce a uniform compress force.

Abstract: Deep-sea offshore wind resources are extremely abundant. Large offshore wind turbine is the future trend to utilize of deep-sea offshore wind resources. Because of excellent heaving, pitching and rolling performances, tension-leg platform ( TLP ) is one of best floating support structures for large wind turbine. However, under extreme environment condition, the large tendons which are required for large offshore wind turbine TLP platform will meet extreme response, even lead to damage. Extreme response of tendon of a 10 MW offshore wind turbine TLP platform ( an improved MOSES TLP ) in the extreme environment condition is studied here. It is showed that the global motions can meet the basic requirements for 10 MW floating wind turbine, where the maximum angle of TLP is less than 10⁰. Meanwhile, the maximum tendon tension of the TLP in the simulation is less than the breaking force, which meets the requirements of API rules on tendon of TLP.

Abstract: The exploitation of FRP tendon necessitates not only to improve the performances of the FRP tendon and anchoring device but also to examine its structural performances by applying it to various structures like concrete structures. This study applies CFRP tendon on internally and externally post-tensioned concrete specimens so as to observe their flexural performance considering the number of tendons and jacking force as test variables. The tests show that the externally post-tensioned specimens undergo lesser cracks with wider distribution of the cracks than the internally post-tensioned specimens with similar jacking force. In addition, the externally post-tensioned specimens with larger number of saddles experience smaller number of cracks with larger distribution. The specimens without saddle and the internally post-tensioned specimens with the same jacking force exhibit similar behavior until the yielding of the reinforcement to show different behaviors from the time at which the eccentricities of the tendons start to vary after yielding. The externally post-tensioned specimens with saddle provide increased crack load compared to the specimens without saddle, with an increase of approximately 25% of the ultimate load.

Abstract: Many post-tensioned concrete bridges have been reported to have ruptured tendons due to corrosion [1] and the assessment of their residual structural capacity has to account for the possibility of re-anchorage of failed tendons. This paper presents an experimental programme to validate a numerical model developed by the authors for the re-anchorage of a ruptured tendon in post-tensioned concrete [2]. The experimental programme considered 33 post-tensioned concrete prisms, in which the rupture of tendon was simulated by releasing the tendon at one end. The full field displacement at concrete surface after release was measured using 3D Electronic Speckle Pattern Interferometry (ESPI). A wide range of parameters: tendon diameter, duct material, grout strength, concrete strength and shear reinforcement were investigated to validate the proposed model, which is found to be suitable for use in assessing post-tensioned concrete bridges with damaged tendons.

Abstract: With the rapid development of hydraulic technology, pressure-driven piston pump, the output pressure, simple structure, in the field of mechanical engineering and field engineering work has been widely used. For existing pneumatic piston existence of a functional insufficiency, poor technical performance, the irrational structure, and high-pressure areas, especially in high pressure areas occupy an irreplaceable position in the axial and radial piston pumps, there are also complex, expensive, traffic pulse rate not ideal and other indicators of disadvantage. In this paper, the normal replacement method for flexible-rigid pneumatic cylinder replacement tendons, structural design, light weight, is able to adapt to harsh environments tendon type pneumatic piston. Practical results shows that the design of the pneumatic piston in the wild-type tendon in applied engineering work obtains good results.

Abstract: Prestressed concrete beams with vertically distributed FRP tendons possess some flexural performance obviously different from prestressed concrete beams with steel tendons. This paper provides a complete theoretical approach to analyze and evaluate the flexural behavior of prestressed concrete beams with FRP tendons. Calculation and analysis results show that a prestressed concrete beam with FRP tendons designed at balanced ratio reaches the maximum of its deformability. The increase of prestressing ratio and number of reinforcement layer will increase, respectively, its moment capacity but simultaneously decrease its deformability.

Abstract: This paper demonstrates, theoretically and experimentally, the feasibility of utilizing Shape Memory Alloy (SMA) as an actuator in controlling the flexural vibrations of a flexible cantilevered beam. The shape memory alloy used in this study is merely a straight wire which is made of nickel titanium alloy called Nitinol. Acting as tendons, these SMAs undergo phase transformation, to the austenitic phase, producing significant forces and displacement capabilities as well as low power consumption. This actuator unit is composed of a SMA wire attached to a spring in series. After being set-up with a load cell the transfer functions of the actuator are measured. Considering the uncertainty of the actuator unit performance the H-infinity optimal controllers are designed and installed into the control system. By integrating the thermal and dynamic characteristics of the SMA into beam dynamical model the composite beam-actuators system can now be developed. The robust stability performance of the designed controller is evaluated through vibrational test on the cantilever and the result is shown to be adequately attenuated.