Keywords: bridge, load, assessment, simulation, traffic, weigh-in-motion, extreme value, long combination vehicles.

This paper investigates the potential effects on European bridges of the introduction of long combination vehicles (LCVs) into Europe's truck population. Measurements from truck traffic have been collected at a number of sites throughout Europe using weigh-in-motion (WIM) technology. With knowledge of the traffic at a site, a traffic loading model can be tailored for a bridge at that site. With the possible introduction of LCVs the loading model will change, and this paper examines the resulting effects on the lifetime loading on bridges.

The demand for freight transport in Europe has led innovators to develop alternative methods of transporting freight. One method of tackling this issue is the use of long combination vehicles (LCVs).

In this research, lifetime bridge load effects are calculated for three possible scenarios:

Scenario 1:

Current traffic with no LCVs

Scenario 2:

50% road freight shift from heavy goods vehicles (HGVs) to LCVs

Scenario 3:

50% road freight shift from HGVs to LCVs plus a 50% modal shift from rail to road.

From the WIM data recorded onsite macroscopic traffic flow properties such as gap distributions and flow-rates can be calculated [1]. Monte Carlo simulation [2] is used to model truck weights, axle configurations, and general traffic characteristics: speed and inter-vehicle gaps. The simulation program described here is written in C++ and uses parallel processing to generate lanes of traffic and to pass the traffic over bridges of different spans. This use of parallel processing makes it possible to model traffic for the complete return period of the bridge: a 1000-year traffic stream. The output from a typical simulation gives annual maximum load effects for each bridge span together with details of the loading events which produce these annual maxima and this allows the effects of the introduction of LCVs to be assessed.

For the spans considered, the lifetime loading of a bridge does not vary much between the three traffic scenarios. This suggests that the characteristic load will not be significantly affected by the introduction of LCVs to Europe's truck population. However, the average daily maximum load effect that a bridge may be subjected to may increase significantly. The implications of such an increase in average daily load effect warrant further investigation into the effects on fatigue loading and the service life of European bridges.

1

E.J. O'Brien, C.C. Caprani, "Headway modelling for traffic load assessment of short- to medium-span bridges", The Structural Engineer, 83(16), 33-6, 2005.

2

R.Y. Rubenstein, "Simulation and the Monte Carlo Method", John Wiley and Sons, 1981.

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