Pre-study of Dynamic Amplification Factor for Existing Road Bridges
Rapport, 2022

The Swedish Road network has, since 2018, been divided into four bearing capacity classes (BKs)—BK1–BK4. The heaviest allowed gross vehicle weight increased when BK4 was introduced, from 64 tonnes (BK1) to 74 tonnes (BK4). The Swedish Transport Administration aims, by 2025, to classify 60 % of the strategic road network for the heavy transport industry as BK4, increasing to 70–80 % by 2029. However, to reach these goals, it is estimated that over 700 bridges will need to be strengthened or replaced.
This study, using a site-specific investigation to calculate the assessment dynamic ratio (ADR), showed that some of these bridges could be upgraded to BK4. A review of the literature indicated that light vehicles tend to have high dynamic amplification factors (DAFs), but light vehicles do not have critical load effects and are therefore not relevant from a design perspective. Instead, heavy vehicles are critical for the design. Both experimental and analytical investigations have shown that heavy gross vehicle weights result in low DAF values.
This report proposes effective ways to collect site-specific dynamic traffic load information and a methodology to produce site-specific dynamic allowances using both experimental measurements and numeric models. It also explains how this methodology can be adopted by transportation agencies to study bridges along transport corridors.
Findings from the pre-study have resulted in the following research proposals: sitespecific field measurements to quantify DAFs, guidelines for numerical modelling of vehicle–bridge interactions (VBIs), DAF for each limit state, three–dimensional analysis of VBIs, the introduction of gross vehicle weight into DAF equations, and pilot tests of proposed frameworks for transport corridors. The authors believe that several topics can be covered within the framework of a PhD project.

Gross Vehicle Weight

Load-Carrying Capacity Assessment

Assessment Dynamic Ratio

Heavy Transport

Transport Corridor

Dynamic Amplification Factor

Site-Specific Dynamic Allowance


Christoffer Svedholm

Elu Konsult

Viktor Eriksson

Elu Konsult

Mario Plos

Chalmers, Arkitektur och samhällsbyggnadsteknik, Konstruktionsteknik

Mats Karlsson

Chalmers, Arkitektur och samhällsbyggnadsteknik, Konstruktionsteknik

Förstudie: Ökad kapacitet för tunga fordon hos befintliga vägbroar - Förfinad modell för att beräkna fordonsdynamiska effekter

Trafikverket (TRV2020/36935), 2020-04-01 -- 2021-06-30.


Hållbar utveckling



Building Futures (2010-2018)


Transportteknik och logistik


Rapport ACE / Institutionen för arkitektur och samhällsbyggnadsteknik, Chalmers tekniska högskola: 2022:1



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