Vibration control of an inclined sagged cable using two different passive systems, a comparative study

Cables are widely used in different structures such as cable stayed bridges, suspension bridges, and other cable structures. The dynamic behavior of an inclined sagged cable as an individual structural element, is highly complicated due to its high tension and geometrical nonlinearity. Moreover, the high flexibility and low inherent structural damping of stay cables, intensify their vulnerability to seismic support excitations as well as rain-wind induced vibrations. For vibration mitigation of cables, two different major systems are commonly used: first, transversely attached mechanical dampers, with one end connected to the cable and the other end to the ground; and second, tuned mass dampers (TMDs) which can be installed along the cable without position limitations. In this study the structural behavior of a three dimensional (3-D) nonlinear inclined stay cable with sag is simulated in OpenSees software with finite element method. The two aforementioned major kinds of control systems are applied to the cable. The control systems are subjected to different support excitations, and their efficiency is calculated based on three performance criteria. Then, the efficiency of each control system is examined and compared with others’. The results show that the both kinds of control systems are capable of making remarkable reductions in seismic response of the inclined sagged cable. The normed value of cable displacement can be suppressed by up to 79 and 74 percent using TMD systems and fixed transversely attached dampers, respectively. However, the latter system exhibits a relatively lower efficiency. In other words, in order to achieve an equal efficiency, an excessively much higher damping coefficient is needed in fixed transversely attached dampers compared to TMD systems.

Keywords:

Passive control , Inclined cables , Fixed damper , Tuned mass damper