Novel Approaches for Fracture Detection in Steel Girder Bridges

Abstract

The bottom flanges of steel plate girder bridges can be considered fracture-critical elements depending on the number of girders and bridge configuration. For such cases, it is required that inspection of these bridges be carried out using costly “arms-length” approach. New techniques in structural health monitoring (SHM) that use non-contact sensors and self-powered wireless sensors present alternative approach for inspection. Application of such techniques would allow timely detection and application of repair and strengthening, in other word, providing for more resilient bridges. This paper investigates the feasibility of using a handful of self-powered wireless or non-contact sensors for continuous or periodic monitoring and detection of fracture in steel plate girder bridges. To validate this concept, vibration measurements were performed on an actual bridge in the field, and detailed finite element analyses were carried out on a multi-girder bridge. The records obtained show that vibration amplitude was significantly increased for fractured girder, and a distinct pattern of strain variation was registered in the vicinity of fracture, all of which can be detected effectively with relevant sensors. Moreover, the amplitude and frequency of the vibration was shown to be significant enough for providing the required power for typical sensor(s).

Synthesis of Repair Materials and Methods for Reinforced Concrete and Prestressed Bridge Girders

“…This may be performed on a periodic or usage basis, or motivated by reports of damage or extreme loading to determine the severity of the damage, cause, and prognosis [22,23]. The existing load-carrying capacity of the structure should be determined.…”

Effect of Cross-Frames on Load Distribution of Steel Bridges with Fractured Girder

“…The first stage was used as initial stage for starting the second stage. Details of this modeling process can be found in the work by Abedin and Mehrabi [3]. The FE model was analyzed for the construction stage and subsequent point loading as reported for the laboratory tests on the University of Nebraska-Lincoln Bridge experiments.…”

“…It is critical to assure that the bridge will have adequate capacity to prevent collapse until the next cycle of inspection discovers the damage. The fracture can also be detected through instrumentation at the onset of fracture or by periodic vibration measurements at inspection intervals or earlier [3] and different strategies can be used to repair and retrofit the damaged bridge [4,5]. It is realized that once one of the bridge girders is fractured, vertical dead and live loads need to be distributed through an alternative path to the intact girder(s) which could occur through the deck or girder cross-frames.…”

Shear Lag Effects in Angles Welded at Both Legs

“…By converting the engineering stress-strain into true stress-strain and extrapolation by the use of power law, the true stress-strain diagram for steel and weld metal is obtained, as shown in Figure 3. e ductile damage fracture criterion of ABAQUS has been used for more accurate modeling of the materials and better observation of the specimen's fracture location in the finite element model [18,19]. Figure 4 illustrates a typical FE model of a tension member with tensile fracture at the critical section.…”