Dynamic Behavior of Pedestrian Bridges
Footbridges are now becoming an integral part of a modern city infrastructure. These bridges allow safe transfer of pedestrians over the urban roads, city waterways or highways by providing a segregated grade separated transportation facility in walking mode. Furthermore, in some applications, the bridges of this class also connect urban installations at different elevations.
In the current trend, the architects, in the design process carefully consider the aesthetic appeal of these bridges to maintain a harmony with the surrounding infrastructure. The structural engineers follow the current design codes to ensure the stability, safety and durability of such facilities.
The construction of 332m long three-span Millennium bridge having a notable architectural appearance built over the Thames at London is a recent example. However, on the eventful opening day of the bridge with a large crowd trying to use it, the Millennium Bridge oscillated significantly due to vibration. It was induced due to pedestrian movement. On the eve of a new millennium, the event made the scientific and engineering community over the world realize the necessity to further sharpen their views about the nature that interacts with our built environment. The dynamic stability of the structures due to human movement induced vibration came into focus. Following that event, several studies have been carried out. These studies led to significant modifications of the code provisions for the footbridges.
Nevertheless, the efforts of the architects and structural engineers in coming up with new and innovative designs have not ceased in the recent days. In 2004, a similar footbridge has been designed and constructed over the Crescent Lake at Dhaka, Bangladesh by considering the recently improved code provisions. We compared and reappraised the code provisions as of today for foot bridges, the newly proposed dynamic loads in different codes and the responses for different bridge forms obtained from dynamic analysis.