Now showing 1 - 4 of 4
  • Publication
    The Effect of Traffic Growth on Characteristic Bridge Load Effects
    Freight traffic in the European Union is increasing with time. This paper describes a method for considering this growth when assessing traffic loading on bridges and examines the effect of this growth on characteristic load effects. The Eurocode Load Model 1 is used for the design of new bridges. As this model can be overly conservative for the assessment of existing bridges, a scaled down version can be used by applying a–factors to the load model. This is usually done by modelling the traffic loading on the bridge using site-specific weigh-in-motion data and calculating the a–factors in accordance with the results. In this paper, weigh-in-motion data from a site in the Netherlands is used to demonstrate the proposed approach. 40-year simulations of traffic loading are performed on various bridges. The simulations consider year-on-year growth in both the volume and weight of trucks. Time-varying generalized extreme value distributions are then fitted to the simulated data and used to calculate the characteristic load effects. The results are then compared with the load effects generated by Load Model 1 in order to calculate the associated factors. It is found that an increase in truck weights has the most significant influence on the factors but that increased flow also has a significant effect.
    Scopus© Citations 27  304
  • Publication
    Traffic load modelling and factors influencing the accuracy of predicted extremes
    (NRC Research Press, 2005-02) ;
    Design and assessment of highway bridge structures requires accurate prediction of the maximum load effects, i.e. shear forces and bending moments etc., which may be expected during the proposed or remaining life of the structure. Traditionally these effects are calculated using conservative deterministic loading models prescribed by codes of practice. The inherent conservatism of these models lies in their need to be widely applicable. While this conservatism is relatively insignificant in design, it may be critical in assessment. In recent years advances in Weigh-in-Motion (WIM) technology have led to the increased availability of accurate and unbiased site-specific traffic records. These records have been successfully employed in the derivation of site-specific loading models and in calculation of load effects in assessment of bridge structures. The results of these assessments are accepted to be less conservative than those performed using generalised codified loading models. Given this reduction in the conservatism of the calculation it is important to quantify the implication of factors such as data inaccuracy or traffic growth on the calculated maximum load effects. This paper briefly describes the mathematical modelling involved in traffic simulation using WIM statistics. The results of direct simulations performed using WIM data are compared with those obtained through the statistical simulation technique termed Monte Carlo simulation, which is regularly employed where insufficient measured data exists. The implications of the accuracy of the recorded WIM data and the duration of recording on the predicted load effect are assessed along with the sensitivity of the extreme to the method of prediction. The effect of traffic evolution with time in terms of increased volumes of flow and weight limits are also explored.
    Scopus© Citations 116  985
  • Publication
    Considering Traffic Growth in Characteristic Bridge Load Effect Calculations
    Traffic volumes and weights increase with time. This is an important consideration in order toaccurately calculate characteristic load effects for the design and assessment of bridges. A modeling approach is presented which can allow for future growth of truck weights and volumes when assessing truck loading on bridges. Weigh-in-motion data from a site in the Netherlands is used as an example to demonstrate traffic growth at that site. In assessing the effect of growth on characteristic load effects, different growth rates for both truck volumes and truck weights are considered. It is found that growth of truck weights has considerablymore influence although growth in truck volumes also has a significant effect.
      322
  • Publication
    Traffic Load Effect Forecasting for Bridges
    (International Association for Bridge and Structural Engineering, 2015-09-23) ; ;
    Traffic flows, as well as truck weights, increase with time. This must be taken into account in order to accurately assess traffic loading on bridges. The Eurocode Load Model 1 is used for the design of new bridges but a scaled down version of the model can be used for the assessment of existing bridges. This scaling is usually done by applying α–factors to the load model. The effect of traffic growth on these α–factors is assessed in this paper. Weigh-in-motion data from the Netherlands is used as the basis for traffic models which simulate year-on-year growth of both traffic flow and truck weights. A time-varying generalised extreme value distribution is then used to calculate the characteristic load effects and determine the α–factors. The effect of different traffic growth rates on these α–factors is then examined. It is found that an increase in truck weights has the most influence on the α–factors but that increased flow also has a significant effect.
      369