Recommendations on dynamic amplification allowance

Abstract

The ARCHES (Assessment and Rehabilitation of Central European Highway Structures) project (2006-09) involved partners from Belgium, Croatia, Czech Republic, Ireland, Italy, Poland, Slovenia, Spain, Switzerland and The Netherlands. The overall goal of the project is to reduce any gaps in the standard of highway infrastructure between Central and Eastern European Countries, particularly New Member States and the rest of the EU. Deliverable D10 is within WP2: optimise the use of existing infrastructure through better safety assessment and monitoring procedures which will avoid interventions, i.e., avoid unnecessary replacing or improving structures that are in fact perfectly safe. In particular, D10 provides a more realistic site-specific dynamic allowance for traffic loading than those genral values recommended in bridge codes.Correct evaluation of the behaviour of highway bridges under heavy traffic loading is extremely important both for the enhancement of design techniques, and also for the assessment of existing infrastructure. It is widely accepted that shortfalls exist in the determination of the traffic load which the bridge may be required to support during its expected lifetime due to inadequate consideration of amongst other factors, the dynamic interaction between the bridge structure and the heavy vehicles crossing it. Since it is the overall objective of this deliverable to combine lifetime static load effect values, with realistic dynamic amplification factors (to obtain an overall total lifetime load effect) there are two distinct parts:1) The calculation of bridge static load effect due to site-specific traffic flow, which is discussed in subtask 2.1.1 (Deliverable D08) along with the resultant assessment of bridge lifetime static load effect, and the selection of those loading events that are deemed critical (statically).Examples on how to determine these bridge traffic load models using Weigh-In-Motion (WIM) data and their configuration when using data from Central European countries are provided in subtask 2.1.1 on bridge traffic load monitoring. This subtask has also compared results between data from Western and Central European countries.2) Deliverable D10 focuses on the assessment of the levels of dynamic interaction occurring between a bridge and its associated vehicular traffic. This analysis incorporates a review of those recommendations given in current design/assessment codes for dynamic allowance.Then, the procedure to obtain a site-specific dynamic amplification factor using theoretical simulations and available experimental data is described. Some specific issues concerning the dynamic allowance associated to: (a) deteriorated bridges; (b) pre-existing bridge vibrations; (c) maximum total effects developing in sections different from midspan, (d) the existence of a bump prior to the bridge, or (e) critical loading cases such as cranes, are also discussed. Finally,general recommendations on dynamic allowance are provided.