ABSTRACT
The dynamic component of bridge traffic loading is commonly taken into account with a Dynamic Amplification Factor (DAF) – the ratio between the dynamic and static load effects on a bridge
The FP6 ARCHES project (Gonzalez et al. 2009) went into some detail of the dynamic effects of traffic on bridges. It provided an overview of the current building code recommendations for dynamic allowances and compared those with the simulations and with the measured allowances obtained using bridge weigh-in-motion (Moses 1979) measurements on several bridges. One of the more important conclusions was that the design code recommendations are generally conservative with respect to true dynamic allowance values, especially at higher (extreme) traffic loads. For assessing of existing bridges, and in many cases extending their lifetime, it is thus beneficial to apply more accurate methods of estimating dynamic allowances.
The SiWIM® system is a commercial bridge weigh-in-motion system (B-WIM) co-developed by the Slovenian National Building and Civil Engineering Institute and Cestel d.o.o. The system is currently the only B-WIM system capable of calculating dynamic allowance from measurements of the bridge response to the passing vehicles. However, the methods of obtaining the dynamic allowance were, until recently, limited. Recently a new method of calculating dynamic allowance has been developed with data from one bridge (Kalin et al. 2015). Data from several other bridges had been analysed since then. This paper presents the results of this analysis.
The background for B-WIM is presented and the new method briefly described. The sites from which the data originated are presented and the selection of data discussed. The results of the analysis are presented and discussed and, finally some examples of DAF calculations are shown.
The results obtained from data from suitable sites, shown on Figure 1, are in accordance with the observations of the ARCHES project, where it was shown that DAF decreases for larger axle loads. Mean values of DAF for vehicles above a range of GVW limits. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig32_1.tif"/>
