Bridge Monitoring/ Jembatan
A SUCCESSFUL BRIDGE-MONITORING PROGRAM REQUIRES APPROPRIATE PLANNING, DESIGN AND EXECUTION. TO FULLY MEET THE OBJECTIVES OF SUCH A PROGRAM, SPECIAL ATTENTION MUST BE GIVEN TO THE SPECIFICITIES OF EACH BRIDGE THROUGHOUT THIS PROCESS.
The primary function of monitoring is to ensure the longevity and safety of a bridge. To implement corrective measures, monitoring must enable the timely detection of any conditions or behavior that could deteriorate the bridge, deem it unsafe or potentially result in its failure. The monitoring program plays a fundamental role during the construction phase as it enables the verification of design hypotheses and construction processes, affecting, in some cases, the construction rate of the bridge. Monitoring also allows performance evaluation of new materials and technologies used in bridge construction and rehabilitation. This objective is easily achieved with fi ber optic sensors, since these sensors effectively integrate in new materials such as fi berreinforced polymer composite. Furthermore, fi ber optic sensors adapt perfectly to long-term monitoring of bridges behavior as well as short-term monitoring of the bridges dynamic behavior under traffic load.
Bridge Instrumentation – Canada
The Joffre Bridge located in Sherbrooke was initially built in 1950. The bridge experienced severe deck slab and main girders degradation. The City of Sherbrooke and the “Ministère des transports du Québec”, decided to reconstruct the bridge deck in 1997. The main objective was the restoration of the bridge deck but also to demonstrate the usefulness of fi ber optic sensors (FOS) for local and remote strain monitoring, to implement the technology of fiber reinforced polymer (FRP) composite reinforcements in bridges and to demonstrate the possibility of fi ber optic sensor integration. This part is a collaborative effort with ISIS-Sherbrooke. The Joffre Bridge has a large transverse span of 3.7 m and different types of FRP were used to reinforce the concrete deck slab, the sidewalk and the traffi c barrier. Fabry-Perot fi ber optic temperature sensors were installed to monitor concrete curing. In addition, Fabry-Perot strain sensors installed in FRP grid and on steel girders provide a complete understanding of FRP reinforcement under traffic loading and environmental conditions. Calibrated load test results indicated that the bridge superstructure defl ections and FRP reinforcement stresses are well within their allowable limits. Measured girder steel strains resulting from static tests are less than 120 microstrains and measured strains in concrete and FRP reinforcements resulting from static tests are very low (less than 20 micro-strains). Dynamic response of FRP grid in the bridge deck was recorded with FOS using a portable readout unit. Currently, a 32-channels fi ber optic data acquisition system allows continuous monitoring of the long term behavior of this structure. This fi eld application demonstrates that Fabry-Perot fiber optic sensors are suitable for the short and long-term monitoring of bridge performance. With this new generation of sensors, Smart Structures are now arrived.
Bridge Rehabilitation Monitoring – Singapore
CASE STUDYComposite materials are making great inroads in civil engineering structures. Fiber optic strain gauges are ideally suited for measuring strain in composite column wrappings and other concrete struc ture rehabilitation systems. The FOS-B long base fiber optic strain gauge is now installed in an overpass rehabilitation projectin Singapore and data monitoring is going on; results of this application will be soon available. Because of the small size of the fiber optic strain gauge, usually 0.30 mm in diameter, the resulting instrumented product will behave identically to the conventional Fiber Reinforced Polymer (FRP) product used for the rehabilitation. Also, as the host material is identical to the FOS-B it is easy to install between composite material sheets. At this time, laboratory testing of the FOS-B bonded on concrete cylinders have been performed and have demonstrated that it is possible to monitor concrete strains with this sensor