Prestressed CFRP-strengthening and long-term wireless monitoring of an old roadway metallic bridge

Abstract

This paper presents an application of prestressed carbon fiber-reinforced polymer (CFRP) plates for the strengthening of metallic girders of a roadway bridge in Melbourne, Australia. The study also describes the application of a wireless sensor network (WSN) system for longterm structural monitoring of the retrofitted bridge girders. A flat prestressed unbonded retrofit (FPUR) system was developed to apply prestressed CFRP plates to the steel girders of the Diamond Creek Bridge (122 years old), which is subjected to daily passenger and heavy vehicles. The first section explains the results of sets of static and fatigue tests performed in the laboratory to examine the efficiency of the proposed FPUR system prior to its installation on the bridge. The second section presents details of different aspects of the CFRP strengthening of the bridge girders, fatigue design criteria, and layouts for short-and longterm monitoring. For the short-term measurements, the bridge was loaded with a 42.5-ton semi-trailer before and after strengthening. The CFRP plates were prestressed up to approximately 980 MPa (≈38% of the CFRP ultimate tensile strength), which resulted in about 50% reduction in the maximum tensile stress in the bridge girders. The third section discusses the development, installation, and preliminary results of the WSN system used to monitor the pre-stress level in the CFRP plates. The results of the short-and long-term measurements in this study show that the FPUR system is very effective for flexural and

Mixed mode I/II fatigue crack arrest in steel members using prestressed CFRP reinforcement

“…As mentioned earlier, the only intention for FE modeling was to determine the maximum fatigue precracking loads (T max ) for the 850.0 × 450.0 mm ( Figure A2a) and 700 × 700 mm ( Figure A2b [38,43,45,46]).…”

“…The reason is attributed to the relatively low bond capacity of prestressed bonded reinforcements (PBRs) prior to their debonding failure, as well as certain concerns that are associated with the durability and fatigue performance of adhesively bonded CFRP-to-steel joints [40,41]. Consequently, various prestressed unbonded retrofit (PUR) solutions were introduced [42,43], and their excellent performance has been demonstrated for the fatigue strengthening of metallic bridge girders in Switzerland [44] and Australia [45,46].…”

“…, except for the beach marking cycles, where a fatigue load ratio of R = 0.6 was considered, a constant R = 0.2 was incorporated in all other fatigue cycles, which is deemed to fairly represent the practical load ratio that is experienced by most of the fatigue-prone details in existing metallic members[43,45,56]. All the fatigue tests were performed under load-controlled conditions with sine-wave cycles, while the dynamic performance of the servo-hydraulic actuator imposed a constant frequency limit of 15 Hz.…”

Innovative prestressing method for externally bonded CFRP laminates without mechanical anchorage

“…Since the mid-1980s, fiber-reinforced polymer (FRP) composites have been used for external strengthening of concrete [1], steel [2,3] and timber structures [4] and a great deal of research work has been devoted to different aspects of this technology in the past four decades [5][6][7]. Currently, FRP bonding has been widely accepted as an effective and cost-efficient upgrading technique in structural engineering.…”

“…As summarized in the review Aslam et al [12], using prestressed CFRP laminates, instead of passive (non-prestressed) ones, can result in: (1) enhancing utilization of the strengthening laminate; (2) improving the fatigue strength of the strengthened structure; (3) enhancing the flexural capacity; and (4) improving the behavior of the strengthened member in serviceability limit state, such as delaying the initiation of cracks, increasing bending stiffness, and reducing crack width. There are mainly three alternatives to apply prestressed CFRP laminates as EBR: (1) introducing the prestress by cambering the structural member before bonding, (2) prestressing against an independent element, and (3) prestressing against the element to be retrofitted. The latter is the most practical to apply prestressing force.…”