David Schnerch

Bond Behavior of CFRP Strengthened Steel Structures

Recent research has focused on rehabilitation and strengthening of steel structures and bridges using fiber reinforced polymer (FRP) materials. The bond behavior of FRP materials to steel structures is quite different from that of concrete structures. Preliminary test results showed the occurrence of very high bond stresses for most strengthening applications due to the amount of strengthening required for steel structures and bridges. In this paper, surface preparation methods and means of preventing galvanic corrosion are discussed. The results of an experimental program for selection of suitable adhesives through determination of the development length is discussed as well as preliminary testing showing the importance of proper detailing of the ends of the FRP strips. The shear stress distribution determined in the experimental program is compared to analytical models using a stress-based approach. The remainder of the paper focuses on the current methods for determining bond stresses and their use for the design of FRP strengthening system for steel structures.

Strengthening Steel Structures and Bridges with High-Modulus Carbon Fiber-Reinforced Polymers Resin Selection and Scaled Monopole Behavior

Cost-effective solutions for the rehabilitation and strengthening of steel structures, including bridges and monopole towers, are greatly needed. Rehabilitation is often required because of cross-section losses occurring as a result of corrosion; strengthening may also be required because of changes in the use of a structure. Current techniques for strengthening steel structures have several drawbacks, including their fatigue performance and the need for ongoing maintenance owing to continued corrosion attack. The current research program makes use of a high-modulus carbon fiber for the strengthening of steel structures. This program, currently in progress, includes phases for the resin and adhesive selection for wet layup of carbon fiber sheets and bonding of precured laminate plates. Test results of the first scaled monopole tower showed a 25% increase in stiffness in the elastic range compared with the same monopole before strengthening.

RECTANGULAR FRP TUBES FILLED WITH CONCRETE FOR BEAM AND COLUMN APPLICATIONS

This paper introduces an innovative concept of FRP/concrete hybrid structural member. This concept includes rectangular filament-wound glass fiber reinforced polymer (GFRP) tubes, totally or partially filled with concrete, and used as beams and/or columns. The paper presents the experimental program and results of three beams and five short columns tested with different eccentricities. Two of the beams were completely filled with concrete, while the third beam was partially filled to minimize the self-weight of the beam. This beam had a void within the cross-section, eccentric towards the tension side of the beam such that the remaining concrete was used to resist the internal compression and shear forces. Two of the columns were subject to zero eccentricity and the other three were subjected to various levels of eccentricity to study the combined effect of axial and flexural loading.