KAZUYOSHI IKEDA

Research on CFRP Reinforcement of Rectangular Section Steel Members.

TAKESHI MIYASITA

Following the Hanshin-Awaji earthquake, the road bridge design guidelines were revised. Steel truss bridges constructed before 1995, particularly the lower chord near the beam ends designed with minimum plate thickness, were deemed insufficient in load-bearing capacity, necessitating seismic reinforcement. The commonly used method, plate bonding, raises concerns such as increased dead load and perforation of the base material. In contrast, CFRP adhesive bonding method offers many advantages, being lightweight, causing minimal increase in dead load, and allowing construction without perforating the base material. This study aims to assess the applicability of CFRP adhesive bonding for seismic reinforcement, focusing on rectangular section members. In previous years, research targeted H-shaped section members. However, this study focuses on rectangular sections, conducting compressive loading experiments on short-column specimens, compressive loading experiments, and alternating loading experiments on long-column specimens to evaluate the reinforcing effects of CFRP adhesive bonding. Experimental results showed that cases with an equal number of vertical sheets (fiber direction aligned with the loading axis) and horizontal sheets (fiber direction perpendicular to the loading axis) demonstrated the maximum reinforcement effect on compressive load-bearing capacity. While horizontal sheets did not reduce stress, they exhibited stiffness against out-of-plane deformation, suggesting an improvement in out-of-plane bending stiffness of the reinforced surface. Evaluations using conventional load formulas and a coupled buckling strength formula, both with an equal number of vertical and horizontal sheets, resulted in conservative assessments of load-bearing capacity. Furthermore, in alternating loading experiments, even if CFRP suffered partial damage during compressive loading, it demonstrated reinforcing effects against tensile loads, and CFRP bonding increased the cumulative energy absorption even when partial damage occurred.