Observed Dynamic Characteristics during Progressive Damage Test of a Flyover Bridge December 4, 2008
Posted by dionsiringo in Bridge Engineering, Destructive Test of Bridge, Structural Monitoring, Vibration, mechanical vibration, paper work.add a comment
Progressive destructive test of a structure is an important and rare opportunity to observe the change in structural characteristics. During the step-by-step demolition process, we can measure structural response and learn how the dynamic characteristics evolve. This insight is valuable in evaluating structural performance and in setting the benchmark for typical deterioration of structure. In this paper, we discuss the evolution of dynamic characteristics of a reinforced concrete bridge during a destructive test.
An instrumented box girder flyover bridge is sequentially damaged by cutting the tendons of its main span. Ambient vibration measurement was performed during destructive test and dynamic characteristics of the bridge were evaluated in each damage stage. The results show the change of natural frequencies is clearly visible as an indicator of global damage presence, while the change in damping distribution may be used as the local damage indicator.
Structures with Human-Induced Vibration – How Serviceability Requirement Improves Vibration Design Concept July 25, 2007
Posted by dionsiringo in Vibration, mechanical vibration, opinion, paper work.1 comment so far
In the past few years, human body motions have quite often caused serious structural vibration problems. We have seen several excessive vibration problems caused by human motion during the service of structures. Human-induced vibrations were sometimes not considered in vibration suppression design due to the fact that the problem itself is primarily serviceability problem. Main considerations for structural dynamic design are safety against the occurrence of major vibration impact to the structures such as: earthquake, wind-induced vibration, traffic-induced vibration or/and impact-induced that might lead to structural failure at a catastrophic level. Human-induced vibrations, which were perceived only as serviceability problem in term of annoyance and disturbance to the users, accordingly have not been addressed properly in design code.
Several latest reports on cases, where human-induced vibrations were found excessive and annoying, however, have changed the common perspective on this problem. The closing of Millenium Bridge in London right after its completion due to excessive human-induced lateral vibration is one major case that took public attention. Thus following this report and some other previous cases, researcher, structural engineers and building authority have work together to accommodate users convenience requirements (serviceability) to provide better structures that suppress the anticipated human-induced vibration.
