ABSTRACT
Bridge performance is affected by bridge material, bridge system, loading type and other internal and external factors. A moving truck generates a dynamic response which is greater than static because of the interaction between the moving vehicle and bridge structure hence it can accelerate deterioration process of the bridge.
The dynamic load is time varying and depend on various criteria like: vehicle type, vehicle weight, axle configuration, bridge material, bridge span length, road roughness and transverse position of the truck on the bridge.
Dynamic force induced by the vehicle-bridge interaction plays a significant role in the design of a bridge. Dynamic loading results in an increase of the bridge deformations that are described by DAF, it shows how many times static load should be increased to cover additional dynamic effects was studied by Fryba (1996).
Dynamic vehicle load on a bridge depend on the dynamic properties of the vehicle, dynamic properties of the bridge, vehicle speed and bridge surface roughness. Although additional dynamic load usually does not lead to major bridge failures, dynamic vehicle load can cause problems that later contribute to fatigue, surface wear rapid deterioration and cracking of concrete that leads to reinforcement corrosion was studied by Cebon (1999). It decreases bridge lifetime and increase the maintenance cost of the structure.
EN 1991–2 (2003) do not exactly indicate how dynamic load should be evaluated in the design, but there dynamic effect is accounted by multiplying the static live load by DAF or are a built-in value of a live load model. In general, in codes, the DAF is given as a function of the bridge span length. However, the obtained load test results showed DAF dependence on the road surface conditions and passing speed. DAF dependence on span length. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig327_1.tif"/>
This paper presents results of 3 bridge dynamic load tests performed from 2009 to 2012.
Results show that for bridge dynamic response carriageway surface condition is a very important factor. Deteriorated bridge surface and heavy vehicles can significantly increase DAF values hence accelerating deterioration process of the structure.
Results also show that natural frequency correlated with DAF – for higher natural frequency values DAF values increased for vehicle speed 20 km/h over uneven pavement surface.
Overall DAF values for even pavement were within 1.0 and 1.4 and are in the range proposed in the EN 1991–2 (2003). Hence proposed values are reasonable for good pavement condition.
