Investigation of fatigue performance of welded details in long-span steel bridges using long-term monitoring strain data

Abstract

SUMMARYMonitoring strain data provides possibilities for the fatigue assessment of the critical components in real structures under the operational conditions. This paper presents a case study on the investigation of fatigue performance of welded details. Long-term monitoring strain data of 4 years between 2006 and 2009 collected by the structural health monitoring system mounted on the Runyang Suspension Bridge and Runyang Cable-stayed Bridge are utilized. The study focuses on two aspects: (i) the effects of different strain components in the raw strain data on the fatigue damage assessment and (ii) the necessity of long-term strain measurement for fatigue evaluation. The results indicate that temperature effect on the stress range spectrum is negligible. The enormous low-level stress cycles caused by random interference would result in erroneous equivalent stress ranges and number of cycles, and thus should be eliminated from the stress range spectrum. Through in-depth analysis of monitoring strain data in three special months and in 3 years, respectively, it is revealed that short-term data monitored in a few days and medium-term data monitored in a few months are not adequate enough to reveal the actual fatigue behaviors of steel bridges and would give inaccurate fatigue life prediction. Finally, the fatigue life predictions of two types of welded details by considering traffic flow growth are carried out. Lessons learned from the long-term monitoring are expected to enhance our understanding in fatigue performances of steel bridges.

Fatigue Stress Spectra and Reliability Evaluation of Short- to Medium-Span Bridges under Stochastic and Dynamic Traffic Loads

“…Fatigue stress spectra are essential for fatigue reliability evaluations and fatigue life prediction for existing bridges. Since the stress spectrum is sensitive to site-specific traffic loads, a numerical simulation based on weigh-in-motion (WIM) measurements is an effective method for simulating the stress spectra for an extensive range of bridges, in addition to the structural health monitoring (SHM) approach (Chen et al 2012;Deng et al 2015). In this regard, numerous studies have been conducted to develop fatigue truck-load models based on site-specific WIM measurements (Wang et al 2005;Chen et al 2015).…”

Fatigue Property and Improvement of a Rounded Welding Region between the Diaphragm Plate and Closed Rib of an Orthotropic Steel Bridge Deck

“…Owing to the cyclic load stress caused by a high number of vehicles, fatigue cracks in orthotropic steel bridges significantly occur at partial-penetration fillet-welded connections [1][2][3][4][5][6][7]. Usually, enhancing the fatigue strength of welded joints, such as the rib-to-rib welded details, rib-to-crossbeam welded joints, and field splice joints of longitudinal ribs [3,[8][9][10] is an effective method to improve the fatigue resistance of the orthotropic steel decks.…”

Seismic response of a suspension bridge: Insights from long-term full-scale seismic monitoring system

“…The objectives of structural monitoring of these bridges are various depending on the specific concerns of the structure, operational condition, and the potential hazard of the bridge location. Long‐term monitoring data, which typically consist of structural static and dynamic response, temperature, strain, and wind, have been used extensively and proven useful to evaluate global structural performance and to evaluate performance of specific structural components such as suspender of suspension bridge, expansion joints, fatigue performance of welded structure, and temperature effects on structure …”