Change search
ReferencesLink to record
Permanent link

Direct link
Dynamics of thick bridge beams and its influence on fatigue life predictions
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.ORCID iD: 0000-0002-2833-4585
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.ORCID iD: 0000-0002-5447-2068
2013 (English)In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 89, 262-271 p.Article in journal (Refereed) Published
Abstract [en]

An analytical model for moving load analysis is derived based on the Timoshenko beam theory. The model enables rapid and reliable analyses of the influence of dynamics on the fatigue life prediction of thick beams. This type of beams is typical for open deck railway bridges. The number of modes required in a modal superpositioning is studied as well as the influence of damping and support stiffness. A total of 22 bridge beams from open deck bridges presented in the literature is included in the study. The results clearly show a fundamental difference in the behaviour of one span beams and continuous beams. Especially in the case of assessment of existing bridges, the quasi static model of the Eurocode renders an excessive safety margin. For the majority of continuous beams studied, the dynamic response is lower than the static response resulting in no dynamic amplification. Such an outcome can have a substantial influence on the remaining fatigue life prediction due to the exponential relation between the stress range and the fatigue life.

Place, publisher, year, edition, pages
2013. Vol. 89, 262-271 p.
Keyword [en]
Dynamics, Fatigue, Timoshenko beam theory, Railway bridge, Moving loads
National Category
Infrastructure Engineering
URN: urn:nbn:se:kth:diva-126020DOI: 10.1016/j.jcsr.2013.07.012ISI: 000326206800023ScopusID: 2-s2.0-84881268458OAI: diva2:641591

QC 20130820

Available from: 2013-08-18 Created: 2013-08-18 Last updated: 2013-11-27Bibliographically approved
In thesis
1. Refining the fatigue assessment procedure of existing steel bridges
Open this publication in new window or tab >>Refining the fatigue assessment procedure of existing steel bridges
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis treats the fatigue assessment process of steel bridges. The purpose is to identify areas with potential of enhancement with an overall aim of attaining a longer service life. The aging bridge stock in Sweden and in many other developed countries is an impending economical burden. Many bridges have reached their expected service life and increased axle loads, speeds, and traffic intensity further accelerate the deterioration. An immediate replacement of all our bridges approaching their expected service life will not be possible. For economical and environmental reasons, effort should be put on extending the theoretically safe service life as far as possible.

 Fatigue is one of the major reasons limiting the service life of steel bridges .A specific example is the Söderström Bridge in Stockholm, Sweden. Fatigue cracks have been found in the webs of the main beams and theoretical assessments have shown an exhausted service life. As a mean to reduce the uncertainties in the theoretical assessments a monitoring campaign was started in 2008 and continued in periods until 2011. The first continuous period of 43 days of measurements in 2008 forms the experimental foundation for this thesis.

A fatigue life prediction involves (i) an estimation of the load effect, (ii) an estimation of the resistance, and (iii) the selection of a prediction model. This thesis treats in some sense all three of them. Considering part (i), the load effect, a theoretical study on the influence of dynamics has been performed. The quasi static approach suggested in the standards does not necessarily reflect the true dynamic behavior of the structure. Performing a dynamic moving load analysis gives for all cases studied a more favorable fatigue life. A further enhancement of the assessment is to perform in situ measurements. The uncertainties related to dynamics, loads, and structural behavior are thereby captured in the response. Routines for processing the measured response and performing life predictions are treated, moreover the quality of the measured response.

The resistance, part (ii), in form of the fatigue endurance has a funda- mental influence on the fatigue life. As an attempt to reach a more adequate fatigue endurance a refined assessment of a typical joint is performed using linear elastic fracture mechanics (LEFM). A descriptive detail category is suggested which renders a somewhat more favorable resistance.

Part (iii), the prediction model, is treated considering the safety format. A reliability-based model is suggested which enables a consideration of the uncertainties in each stochastic variable. Thereby, all aforementioned parts and uncertainties can be combined within the same prediction. The reliability-based model is used for a code calibration of partial safety factors to be used in semi-probabilistic assessments according to the standards.

The implementation of the suggested procedures is shown with a numerical example. The outcome should not be generalized but the example clearly shows an increase in fatigue life with the proposed enhancements of the assessment procedure.




Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013
Trita-BKN. Bulletin, ISSN 1103-4270 ; 118
Fatigue, Steel bridges, Assessment, Reliability, Monitoring, Utmattning, stålbroar, bärighetsberäkning, tillförlitlighet, mätningar, Söderström, getingmidjan
National Category
Civil Engineering
urn:nbn:se:kth:diva-127707 (URN)
Public defence
2013-10-11, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)

QC 20130917

Available from: 2013-09-17 Created: 2013-09-04 Last updated: 2013-09-17Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Leander, JohnKaroumi, Raid
By organisation
Structural Engineering and Bridges
In the same journal
Journal of constructional steel research
Infrastructure Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 163 hits
ReferencesLink to record
Permanent link

Direct link