Experimental and numerical study on seismic performance of deficient interior RC joints retrofitted with prestressed high-strength steel strips.

• Two innovative retrofit methods are presented in this paper. • Pre-stressed steel strapping technique is applied to retrofit deficient RC joint. • A numerical model is proposed to simulate the cyclic behaviors of specimens. • Softened strut and tie model is applied to obtain the shear capacity of specimens. This paper presents the results of an experimental and numerical study on strapping method for retrofitting deficient interior RC beam-column joints, which do not meet the requirements of current seismic design codes due to some deficiencies including low strength of concrete, inadequate transverse reinforcements, and low construction quality. In order to explore the seismic behavior of the retrofitted RC joints, six interior joint specimens, including two deficient RC joints with inadequate transverse rebar, three RC joints retrofitted with prestressed high-strength steel strips and one RC joint retrofitted with adhesively-bonded steel and prestressed high-strength steel strips, were designed and tested under cyclic loading. The main variables included the retrofit methods, axial compression ratio and volume of steel strips. The test results indicated that the prestressed steel strips worked together well with the deficient RC joints, and the retrofitted specimens exhibited better seismic behavior than the deficient control specimens, especially in deformability and energy dissipation. On the basis of the experimental study, the corresponding numerical model was established using the Open System for Earthquake Engineering Simulation (OpenSEES) and then verified to be valid. Finally, the modified softened strut and tie model was proposed in this paper to calculate the shear capacities of the specimens, and the calculated results agreed well with the test results. [ABSTRACT FROM AUTHOR]