Getachew, Abraham

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Getachew, Abraham
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Getachew, Abraham

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  • Publication
    Sensitivity of predicted bridge traffic load effects to the tails of truck weight distributions
    (Thomas Telford, 2005-04-13)
    Getachew, Abraham 
    ;
    O'Brien, Eugene J. 
    In the last two decades, simulations have been used to predict the characteristic traffic load effects on bridges using Weigh-In-Motion (WIM) data. The recorded Gross Vehicle Weight (GVW) is usually modelled by multimodal distributions. The parameters for these distributions are generally obtained by using different goodness-of-fit tests where the entire recorded data is considered. These parameters are then used as the basis for the simulations. In this work, the sensitivity of the predicted traffic load effects to these fittings is investigated. Generally, moment at mid-span for different return periods can be determined from simulations based on three different assumptions. The first approach is to use empirical distribution functions, i.e., direct simulations using the recorded GVW data. The second approach is to use parametric distribution functions to represent GVW from the recorded data. In the third approach, developed here, semi-parametric distribution functions are used to model the distributions of GVW. From these, load effects corresponding to different return periods are calculated and compared. The results are shown to be highly sensitive to the assumption adopted.
      77
  • Publication
    Simplifed site-Specific traffic load models for bridge assessment
    (Taylor & Francis, 2007-12)
    Getachew, Abraham 
    ;
    O'Brien, Eugene J. 
    Traffic load is identified as one of the greatest sources of uncertainty in the assessment of bridges. In recent years, simulation techniques, using measured traffic data, have been used to predict the characteristic traffic load effects on bridges. However, the techniques are complex, sensitive to the assumptions adopted and require specialist statistical expertise. This work presents a simplified site-specific traffic load model that generates comparable load effects to the corresponding results from a full simulation. While the simplified model is still sensitive to the underlying assumptions, these can be carefully reviewed prior to the method being approved. Further, the simplified method can be employed by practicing engineers for bridge assessment.
      1467Scopus© Citations 57
  • Publication
    Importance of the tail in truck weight modeling for bridge assessment
    (American Society of Civil Engineering (ASCE), 2010-03)
    O'Brien, Eugene J. 
    ;
    Enright, Bernard 
    ;
    Getachew, Abraham 
    To predict characteristic extreme traffic load effects, simulations are sometimes performed of bridge loading events. To generalize the truck weight data, statistical distributions are fitted to histograms of weight measurements. This paper is based on extensive weigh-in-motion measurements from two European sites and shows the sensitivity of the characteristic traffic load effects to the fitting process. A semiparametric fitting procedure is proposed: direct use of the measured histogram where there are sufficient data for this to be reliable and parametric fitting to a statistical distribution in the tail region where there are less data. Calculated characteristic load effects are shown to be highly sensitive to the fit in the tail region of the histogram.
      832Scopus© Citations 56