Field testing of a 30-year-old composite Preflex railway bridge

Abstract

Within the framework of the French National Research Project MIKTI dealing with 'composite steel-concrete footbridges and bridges for tomorrow', a loading test was performed in Belgium on a railway bridge deck consisting of simply supported composite 'Preflex' beams. The bridge was 30 years old at the time of the test so the timedependent stress redistribution between the steel of the girders and the concrete was almost stabilised. The bridge deck was loaded progressively by two heavy diesel-electric locomotives. A 4 m long zone situated at the mid-span of the deck was instrumented and monitored during the loading test. The following measurements were taken: the mid-span deflection; the slopes in five locations; the length variations of 16 extensometers of 250 mm length situated near the bottom fibre of the beam and acoustic emission. All of the measurements showed that the behaviour of the bridge deck under the test load was linear elastic, the concrete was not cracked before the test and no cracking appeared in the concrete during the test. The concrete part of the cross-section fully contributed to the stiffness of the beam, confirming the excellent long-term behaviour of this kind of railway bridge, even after a very large number of live load-cycles applied on them during more than 30 years of service. These observations are in very good agreement with the values of stresses computed by a step-by-step method, applying the principle of superposition of linear viscoelasticity for modelling the time-dependent stress redistribution in these composite beams.

Categories of SHM Deployments: Technologies and Capabilities

“…Nowak and Tharmabala (1988) use bridge test data in conjunction with load-rating models to estimate what they refer to as safetyreserve. Similar studies were reported by Jáuregui and Barr (2004) and Staquet et al (2007).…”

“…This category is a completely model-free approach to SHM investigation. Examples of SHM deployments with anomaly detection components have been reported in Chang and Im (2000); ; Staquet et al (2007); Koo et al (2013); Roberts et al (2006Roberts et al ( , 2012; and Minardo et al (2012). Chandola et al (2009) give a detailed treatise on the fundamentals of detecting anomalies in data sets.…”

A case study of replacement of external post-tensioning cables

“…For small spans (below 25 m), the choice was precast girders or pre-bent composite girders of the Preflex type patented by the Belgian engineer A. Lipski in 1950 (e.g. Staquet et al, 2007). For medium-sized spans (25-60 m), prestressed concrete bridges would be cast in place with hollow box beams supporting tracks instead of composite steel-concrete structures.…”