Alexander G. Tsonos

Seismic Resistance of Type 2 Exterior Beam-Column Joints Reinforced With Inclined Bars

An experimental investigation of the behavior of external beam-column joints with inclined reinforcing bars under seismic conditions is presented. A simple technique to prevent these elements from falling in premature, explosive cleavage shear fracture was implemented for the first time. Twenty full-scale reinforced concrete exterior beam-column subassemblies were tested. The primary variables were the amount of inclined bars, the ratio of the column-to-beam flexural capacity, and the joint shear stress. Test results showed that use of crossed inclined bars in the joint region is one of the most effective ways to improve the seismic resistance of exterior reinforced concrete beam-column joints.

Lateral Load Response of Strengthened Reinforced Concrete Beam-to-Column Joints

Two test series were conducted to determine the effectiveness of the United Nations Industrial Development Organization (UNIDO) Manual guidelines for the repair and strengthening of beam column joints damaged by severe earthquakes. Two exterior reinforced concrete subassemblages (M1 and M2) were subjected to a series of cyclic lateral loads to simulate severe earthquake damage. The specimens were then repaired and strengthened by jacketing according to UNIDO Manual guidelines. The strengthened specimens RM1 and RM2 were then subjected to the same load history as was imposed on the original test specimens M1 and M2.The repaired and strengthened specimens exhibited higher strength, greater stiffness, and better energy dissipation capacity than the original specimens.

Ultra-high-performance fiber reinforced concrete: an innovative solution for strengthening old R/C structures and for improving the FRP strengthening method

In this study a new innovative method of earthquake-resistant strengthening of reinforced concrete (R/C) structures is presented for the first time. Strengthening according to this new method consists of the construction of steel fiber ultra-high-strength concrete jackets without conventional reinforcement, which is usually applied in the construction of conventional reinforced concrete jackets. An innovative solution is also proposed for the first time that ensures a satisfactory seismic performance of existing reinforced concrete structures, strengthened by using composite materials. The weak point of the use of such materials in repairing and strengthening old R/C structures is the area of beam-column joints. According to the proposed solution, the joints can be strengthened with a steel fiber ultra-high-strength concrete jacket, while strengthening of columns can be achieved by using CFRPs. The experimental results showed that the performance of the subassemblage strengthened with the proposed mixed solution was much better than that of the subassemblage retrofitted completely with CFRPs.

Steel fiber high-strength reinforced concrete: a new solution for earthquake strengthening of old R/C structures

In this study a new innovative method of earthquake-resistant strengthening of reinforced concrete structures is presented for the first time. Strengthening according to this new method consists of the construction of steel fiber highstrength concrete jackets without conventional reinforcement, which is usually, applied in the construction of conventional reinforced concrete jackets (i.e. longitudinal reinforcement, stirrups, hoops). The proposed in this study new innovative steel fiber high-strength or ultra high-strength concrete jackets were proved to be much more effective than the reinforced concrete jackets and the FRP-jackets when used for the earthquake-resistant strengthening of reinforced concrete structural members.