High modulus carbon fiber materials for retrofit of steel structures and bridges
This paper summarizes the research work dealing with the use of high modulus carbon fiber reinforced polymer (HM CFRP) materials for the retrofit of steel structures and bridges. The research work included selection of an appropriate adhesive for bonding HM CFRP materials to steel and the performance of Large-scale steel-concrete composite beams tested to examine the behavior of different strengthening schemes. The research findings demonstrate the effectiveness of the proposed HM CFRP strengthening system.
BOND AND SPLICE BEHAVIOR OF HIGH MODULUS CFRP MATERIALS BONDED TO STEEL STRUCTURES
Research on the use of CFRP materials for retrofit and strengthening of steel bridges and structures has increased in recent years. In order to implement these types of strengthening systems to longer span members, it is important to establish an effective method to splice adjacent lengths of CFRP laminates. This paper describes an experimental program to investigate the bond behavior of carbon fiber reinforced polymer (CFRP) laminates with the objective of developing an effective bonded splice joint. The experimental program was conducted in two phases. In the first phase, the effectiveness of three different CFRP splice joint configurations was evaluated using double lap shear coupon tests. In the second phase, steel beams were strengthened with CFRP laminates which incorporated a bonded splice joint located at the midspan of each of the beams. The test results demonstrate that debonding of the CFRP splice plate was the primary mode of failure for the tested joints. The research also indicated that the use of a reverse tapered joint configuration can significantly increase the splice joint capacity. The findings indicate that careful detailing can significantly increase the capacity of bonded CFRP splice joints.
Structural behavior of composite steel beams strengthened/repaired with carbon fi ber reinforced polymer plates
Of the approximately 600,000 bridges in the United States, more than 110,000 are either structurally deficient or functionally obsolete. Causes of deterioration are attributed to the age of the structure, steady increase in legal load limits, increase in traffic density, deterioration due to environmental attack, and the lack of proper maintenance. A large number of these bridges are constructed out of structural steel. One significant cause of deterioration in these structures is corrosion due to extensive use of de-icing salts in severe winter weather. These bridges either have to be replaced or strengthened to extend their service life. In most cases, strengthening of these structures is more cost effective than replacement. Among the popular strengthening methods used in the past on steel bridges are post-tensioning and the bonding of steel plates to the tension flange of the girders. However, these methods are labor intensive and disturbance to the traffic flow is inevitable. This investigation focused on the behavior of steel composite beams strengthened with carbon fiber reinforced polymer (CFRP) plates attached to their tension side. In the experimental part of this study, a total of ten beams were tested under a four-point bending; six of the beams were in the undamaged state (two control beams and four strengthened), while the remaining four beams were damaged and repaired (one control beam and three repaired). Since this technique depends on the shear strength of the adhesive, extensive instrumentation was utilized to measure shear stresses along the CFRP plate in all load ranges (i.e. elastic and inelastic); this is something that was not emphasized in the previous research available. Another contribution of this work was the study of the effect of damage on the stiffness and strength of the section as well as the effect of repair schemes in restoring both the lost