Bernard Jacob

Report of current studies performed on normal load model of EC1. Part 2. Traffic loads on bridges

ABSTRACT This report gives results of some new studies performed to validate the european road traffic load model proposed by the Eurocode EC1. Weight in motion has developed greatly in the last ten years and confidence in the accuracy of recorded data has increased significantly. Traffic data recently obtained from a number of representative European sites are used to re-calibrate the codified main load model of the European bridge loading code, Eurocode 1 Part 3. A wide range of real and virtual bridge forms were chosen for the study. Simulations were performed using free-flowing and jammed traffic. Load effects generated were determined and statistical extrapolations were performed, where appropriate, to determine characteristic values for the load effects. Some of the assumptions used in the derivation of the original loading model were re-assessed.

ASSESSMENT OF THE ACCURACY AND CLASSIFICATION OF WEIGH-IN-MOTION SYSTEMS: PART 2 EUROPEAN SPECIFICATION

This is the second part of a two-part paper which addresses the issue of accuracy in weigh-in-motion (WIM) systems. The first part develops the statistical background necessary for any system of accuracy classification applied to a WIM system. This second part describes a draft European specification for the weigh-in-motion (WIM) of road vehicles, prepared by the COST 323 management committee. The philosophy behind the specification is outlined and the basic structure detailed. The specification gives an indication of what WIM accuracy might be achievable from sites with particular characteristics. There is a comprehensive review of methods of calibrating and testing WIM systems. Four types of calibration/test condition are described for tests using statically pre- or post-weighed vehicles. Accuracy classes are defined on the basis of the width of the confidence interval within which the measured results lie. Confidence interval widths arc specified for gross weights and weights of individual axles among other things. The percentage of test results which are required to fall within the confidence intervals is a function of the test conditions and the number of test runs. Examples using real WIM data illustrate the use of the specification.

ASSESSMENT OF THE ACCURACY AND CLASSIFICATION OF WEIGH-IN-MOTION SYSTEMS: PART 1 STATISTICAL BACKGROUND

This is the first part of a two-part paper which addresses the issue of accuracy in weigh-in-motion (WIM) systems. This part describes, and where necessary develops, the background necessary for any system of accuracy classification applied to a WIM system. The second part describes a draft European specification for WIM of road vehicles, prepared by the COST 323 management committee. The system of accuracy classification used in the specification is based on the principles described in this part. The common metrological definitions of accuracy are not applicable to WIM systems because the measured quantities are not traceable. Moreover, many WIM sensors may not be used to weigh static loads and/or cannot be checked with calibration masses. The WIM operations are not fully repeatable. Therefore particular definitions, sound reference values and statistical tools of which users should be reminded, are presented. Relevant formulas and methodology are developed and illustrated with numerical examples.

AN EXPERIMENTAL INVESTIGATION OF SPATIAL REPEATABILITY.

The results of an experimental road research project are presented which demonstrate the existence of spatial repeatability and show patterns of axle impact forces along a pavement. As part of the project, a section of highway near Paris, France, was instrumented with 18 weigh-in-motion sensors. Data was collected for a large number of vehicles over fourteen days between June 1994 and May 1995. For all the vehicles the impact factors were calculated, and typical graphs are presented which show the variation of impact factor with distance along the sensor array. Mean impact factors and coefficients of variation are also presented and differences between steel and air suspensions are highlighted. The influence of vehicle speed on maximum impact factor is also considered. Language: en

Report of Current Studies Performed on Normal Load Model of EC1

ABSTRACT This report gives results of some new studies performed to validate the european road traffic load model proposed by the Eurocode EC1. Weight in motion has developed greatly in the last ten years and confidence in the accuracy of recorded data has increased significantly. Traffic data recently obtained from a number of representative European sites are used to re-calibrate the codified main load model of the European bridge loading code, Eurocode 1 Part 3. A wide range of real and virtual bridge forms were chosen for the study. Simulations were performed using free-flowing and jammed traffic. Load effects generated were determined and statistical extrapolations were performed, where appropriate, to determine characteristic values for the load effects. Some of the assumptions used in the derivation of the original loading model were re-assessed.

Test of WIM sensors and systems on an urban road

This paper describes a large-scale test of six WIM systems and four additional sensors on an urban roadway in Zurich, Switzerland. Gross weights from some thousands of statically weighed vehicles were used to determine the levels of accuracy for each system, with reference to the new draft of the European specification on WIM (C0ST323). The accuracy of axle weights was not tested. The WIM sensors, which included one prototype, were tested with the assistance of a recording and processing device supplied by the organiser. Most systems encountered some problems, failures and faults, under the carefully controlled conditions of the 30-month test. However, these were generally solved by the suppliers after some delay. Statistics are provided on overall levels of accuracy and on trends with season and time. In addition, a brief history of system malfunctions and failures is provided. Nevertheless the scope of the conclusions is limited by the traffic conditions and the test plan.

TEST OF A MULTIPLE SENSOR AND FOUR PORTABLE WIM SYSTEMS

In June 1996, a trial of four portable WIM (weigh-in-motion) systems was performed on a heavily trafficked highway near Trappes. France. This site was equipped with a multiple sensor (MS-WIM) array consisting of 24 piezoceramic strip sensors built in the road at non-uniform spacing. Within three days, 116 runs were made with two pre-weighed test vehicles. Moreover 92 trucks in the traffic flow were stopped randomly and statically weighed on a weighing area upstream of the test site. They were used to check the accuracy of the MS-WIM and the four portable WIM systems, using the criteria of the draft European WIM Specifications. Furthermore, the axle loads and gross weights of almost 4,000 trucks were recorded in the traffic flow by the MS-WIM system. This large sample of data was used as a reference to assess the accuracy of the portable WIM systems.

Report of Current Studies Performed on Normal Load Model of EC1-Part 2. Traffic Loads on Bridges, 5(4),

ABSTRACT This report gives results of some new studies performed to validate the european road traffic load model proposed by the Eurocode EC1. Weight in motion has developed greatly in the last ten years and confidence in the accuracy of recorded data has increased significantly. Traffic data recently obtained from a number of representative European sites are used to re-calibrate the codified main load model of the European bridge loading code, Eurocode 1 Part 3. A wide range of real and virtual bridge forms were chosen for the study. Simulations were performed using free-flowing and jammed traffic. Load effects generated were determined and statistical extrapolations were performed, where appropriate, to determine characteristic values for the load effects. Some of the assumptions used in the derivation of the original loading model were re-assessed.

International Conference on Heavy Vehicles HVParis 2008: Weigh-In-Motion (ICWIM 5)

The conference addresses the broad range of technical issues related to heavy vehicles, surface transport technology, safety and weight measurement systems. It provides access to current research, best practice and related policy issues. It is a multi-disciplinary, inter-agency supported event.