ABSTRACT
The undesirable perceptible vibration of the composite steel girder bridge under live loads is one of the most important problems in the bridge industry especially with current trend towards longer span and lighter deck system which combined with limited damping due to nature of the system. Because of their structural form, being wide but shallow in depth, bridges are predominantly susceptible to vertical vibration. Although the strength design and the deflection control criteria of these bridges are done fairly well in accordance with the bridge design codes, the vehicles movement on the bridge may still cause vibrations that would seem undesirable from the viewpoint of the pedestrians walking or standing on the footpath. Essentially, the bridge vibration under the effect of traffic movement should be limited to satisfy two basic purposes. First, reducing ratio of dynamic stresses to static stresses (this feature be considered in static design by dynamic load factor or dynamic load allowance). The second reason is that too much vibration may cause fear to those who use the bridge and undermine confidence in the structure.
