Bridge structures

Bridges and other large civil structures are the biggest candidate for SHM as safety, reliability and operational availability with lowest possible maintenance cost are very important for such structures. Since these structures are designed for a greater life span and are subjected to the vagaries of nature, the implementation and successful operation of appropriate SHM system is more challenging. In this case, not only the structures but the sensors required to extract data should be robust enough to survive for the planned life of the civil structure. This becomes very crucial in cases where the sensors are to be embedded in the structure at the time of construction of the structure itself. Some of the important works available in literature are being presented here.

Brownjohn et al [2002] have reviewed ongoing project in Singapore in which an expressway viaduct is instrumented using conventional static sensors as well as Fiber Bragg Grating (FBG) arrays and data are managed by wireless and internet. The two technologies of wireless internet access and fiber optic sensors are believed to be central to future developments in sensing and data management for structural health monitoring of civil structures. DeWolf et al [2002] have reported their experience in non-destructive field monitoring to evaluate the health of a variety of existing bridges and shown the need and benefits in using non-destructive evaluation to determine the state of structural health.  Moyo and Brownjohn [2005] have analyzed in-service civil infrastructure based on strain data recorded by a SHM system installed in the bridge at construction stage. Bridge instrumentation and monitoring for structural diagnostics has also been done by Farhey [2005]. The strain-time histories at critical locations of long-span bridges during a typhoon passing the bridge area are investigated by Li et al [2002] using on-line strain data acquired from the SHM system permanently installed on the bridge. Ko and Ni [2005] have explored the technology developments in the field of long term SHM and their application to large-scale bridge projects in order to secure structural and operational safety and issue early warnings on damage or deterioration prior to costly repair or even catastrophic collapse. Tennyson et al [2001] have described the design, development and application of fiber optic sensors for monitoring of bridge structures. It has been observed that in most of these applications, the sensory network is considered to be of fiber-optic systems. The penetration of other smart materials like piezoelectric and magnetostrictive materials is still quite low in this field.