Vibrations of a cable-stayed bridge due to vehicle moving over rough surface | |
| Author | Indrawan, Benjamin |
| Call Number | AIT Thesis no. ST-89-3 |
| Subject(s) | Bridges, Cable-stayed Bridges--Vibration Bridges--Live loads |
| Note | A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | The dynamic behaviour of Rama IX c~ble-stayed bridge in Bangkok caused by an idealized single axle vehicle travelling over the bridge at constant speed is investigated. The bridge is modelled as a plane frame system with the girder and towers represented by beam elements and the stay cables by truss elements. The lumped mass approach is used. The cable mass is concentrated at the cable supports. The dynamic response is determined using the concept of generalized coordinates. The deflection of the girder, tower displacement, cable forces and cable deflection are computed for different types of vehicle models moving on a smooth surface, a rough surface and a bumpy surface, at speeds of 10 to 150 m/s. The single axle vehicle is modelled as a force, an unsprung mass, and a sprung mass (single-degree-of-freedom system). Since Rama IX bridge is equipped with tuned mass dampers to suppress windinduced flexural and torsional oscillations, a comparison is made between the dynamic response with and without the presence of tuned mass dampers. The tuned mass damper is tuned to the first flexural mode of vibration which has a frequency of 0.325 Hz. Results show that the impact factors for the deflection of the girder and cable force increase with increasing vehicle speed. In the case of a force moving over smooth surface at a speed of 20 m/s, the impact factors for midspan deflection and the cable force of the shortest cable in the backspan are 5.2% and 11.2%, respectively. For a sprung mass moving over rough surface, the impact factor for the cable force of the shortest cable reaches a value of 51.8% which is about ten times as high as in the case of an unsprung mass. For a bumpy surface the impact factors for midspan deflection and cable force due to a sprung mass are 20.l %and 57.8%, and for an unsprung mass 20.1%and23.3% respectively. It is observed that the tuned mass damper is very effective in reducing vibrations of cables located near midspan. The clamper is most effective for suppressing the free vibration response of the bridge, therefore it can greatly reduce the dynamic response when a large number of vehicles is crossing the bridge. |
| Year | 1989 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Wireland, Martin |
| Examination Committee(s) | Worsak Kanok-Nukulchai ;Gupta, Satyendra P. ;Jain, Sudhir K. |
| Scholarship Donor(s) | The Royal Netherlands Government |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1989 |