Application of new materials and innovative detailing for reinforced concrete structures

摘要

Confinement enhances mechanical properties of concrete sections specifically its strain capacity thus results is higher displacement capacity for reinforced concrete members. Even though the behavior of concrete confined with external jackets has been extensively investigated in previous studies, the use of rubber-based material as an external confinement is new, and was investigated for the first time in the present study. Thirty concrete cylinders were tested under uniaxial compression to investigate mechanical properties of rubber confined concrete. It was found that rubber does not increase the strength of confined concrete. However, the strain capacity of rubber confined concrete was more than 10%, equal to or higher than reinforcing steel bar tensile strain capacity. This unique property may make this type of confinement a viable retrofit or rehabilitation method to increase the ductility of low ductile members and structures in high seismic regions.;Repair of ductile components is often inevitable under strong earthquakes mainly because of concrete failure, significant yielding of reinforcement, or large residual lateral deformations. In this case, the structure needs to be demolished and reconstructed as the repair of reinforced concrete (RC) structures is complex when longitudinal reinforcement of ductile member fractures. External reinforcing bars are capable to increase energy dissipation of rocking columns and frames. Deformed reinforcing steel bars without any reduction of the section enclosed in steel pipes was proposed as external energy dissipaters, entitled as buckling restrained reinforcement (BRR) in the present study. The test results showed that the compressive strain of BRR at the peak stress can exceed 5%, which will be sufficient in most practical cases since the strain of compressive reinforcement in a concrete section is usually controlled by the core concrete strains.;Experimental and analytical investigations were carried out on RC beam-column specimen under cyclic loading. A nine-story RC building was analyzed and designed as special moment resisting frame (SMRF). A half-scale exterior beam-column joint of the first floor of the prototype frame was tested to investigate the seismic behavior of the specimen. The test result showed that the column longitudinal and transverse reinforcement did not yield under the cyclic loading and the damage of column was insignificant. Almost all cracks were formed in the beam and more cracks were observed after drift ratio of 1.46%. The beam longitudinal reinforcing bars yielded then fractured at a high drift ratio (3.5%). The beam-column specimen showed 75% higher lateral drift capacity than the ASCE allowable drift ratio, which was 2% for this building. The test results confirmed that the modern seismic design codes ensure large displacement capacities for SMRF without any premature failure.