Failure Behavior and Separation Criterion for Strengthened Concrete Members with Steel Plates

The purpose of the present study is to identify the local failure of strengthened plates and to derive a separation criterion at the interface between concrete and steel plates. To this end, a comprehensive experimental program has been set up. Double lap pull-out tests that take into consideration pure shear force and half-beam tests that consider combined flexure-shear force were performed. The main experimental parameters include the plate thickness, adhesive thickness, and plate end arrangement. The strain along the longitudinal direction of the steel plates was measured, and the shear stress was calculated from the strain measured. The effects of the plate thickness, bonded length, and plate end treatment are also clarified by the present test results. Nonlinear finite-element analyses were performed and compared with the test results. The interface properties were also modeled to identify the separation failure behavior of strengthened members. The cracking patterns as well as maximum failure loads agree well with test data within error of 1%. The relationship between maximum shear and normal stress at the interface was derived to propose a criterion for separation failure of strengthened members. This study allows more realistic analysis and design of externally strengthened flexural members with steel plates.