The seismic performance of reinforced concrete (RC) columns retrofitted using the steel plate sandwich method bonded with prestressed PC bars was compared in both in-plane and out-of-plane ...directions. Therefore, in-plane and out-of-plane bending strength, initial horizontal rigidity, and cumulative energy absorption improved.
The seismic performance of reinforced concrete (RC) columns retrofitted using the steel plate sandwich method bonded with prestressed PC bars was compared in both in-plane and out-of-plane ...directions. Therefore, in-plane and out-of-plane bending strength, initial horizontal rigidity, and cumulative energy absorption improved.
The current practice in Japan for most driven pre-stressed high strength concrete (PHC) piling sites utilizes an ″energy formula″ approach involving the ″set-penetration test.″ In its current state, ...driven PHC piles in the Japanese construction industry are at increased risk of being damaged due to inferior driveability evaluation procedures leading to an increased probability of damaged piles remaining undetected after installation. This study presents two case studies in Okinawa, Japan which utilized dynamic analysis as the primary piling quality acceptance criteria and compares results to the energy formula approach which is more common to Japanese construction sites. Based on the observations of these two case studies, the applicability of dynamic testing, particularly the high-strain dynamic test, the low-strain integrity test, and wave equation analyses is analyzed. In conclusion, a case is presented that Japan′s over reliance on an energy formula approach should be augmented by additional QC procedures. A combination of wave equation analysis, dynamic testing and simple visual inspection of post-driven PHC pile conditions is recommended to better protect the integrity of driven PHC piles throughout Japan.
A strength–ductility type seismic retrofit technique for soft first-story reinforced concrete (RC) buildings via adding wing-walls to the existing RC columns is called thick hybrid wall (THW) ...technique. In this technique, the additional wing-wall does not require longitudinal, transverse and anchor reinforcements; therefore, its construction is easy and cost-effective. In this study, THW technique was applied to an existing pilotis RC building in Okinawa. The objectives of this study were (1) to compare the advantages of THW and conventional retrofit techniques applied to this pilotis building, and (2) to assess the future retrofitting activities through this study.
This study explores a seismic retrofit method for existing RC columns using a cast-in-site partial thick hybrid wing-wall (THW) technique. The THW technique plays two important roles: (1) to enable ...easy and cost-effective construction and (2) to considerably increase lateral strength and ductility. The aim of this study is to experimentally determine the shear resistance (truss and arch mechanism) and shear strength of the columns retrofitted using the THW technique. Based on the analytical assessment of the THW technique, design equations of ultimate shear strength and steel plate thickness are proposed.
This study proposes a rehabilitation method (emergency retrofitting) to restore the axial compression capacity and shear resistance mechanism of shear-damaged reinforced concrete (RC) columns. For ...the emergency retrofitting of shear-damaged RC columns, coupler and aramid fiber belts are used. The key concept of this approach is to provide active confinement to firmly confine damaged RC columns externally. The active confinement is used to close cracks in damaged RC columns and to recover their vertical and lateral load-carrying capacities and ductility. To investigate the rehabilitation capacity using fiber-belt prestressing, axial compression and cyclic loading tests were conducted in this study.
This study proposes a rehabilitation method (emergency retrofitting) to restore the axial compression capacity and shear resistance mechanism of shear-damaged reinforced concrete (RC) columns. For ...the emergency retrofitting of shear-damaged RC columns, coupler and aramid fiber belts are used. The key concept of this approach is to provide active confinement to firmly confine damaged RC columns externally. The active confinement is used to close cracks in damaged RC columns and to recover their vertical and lateral load-carrying capacities and ductility. To investigate the rehabilitation capacity using fiber-belt prestressing, axial compression and cyclic loading tests were conducted in this study.
•The interaction between the URM infill wall and the surrounding RC frame members was investigated in the non-retrofitted specimen and the specimens retrofitted by the thick hybrid wing-walls.•The ...ability of the thick hybrid walls in increasing the lateral strength, stiffness, and ductility of URM-infilled non-ductile RC frames was assessed.•The steel-jacketed non-reinforced hybrid walls were used to retrofit the URM-infilled non-ductile RC frames.•The RC column with URM wing-wall was tested under cyclic horizontal loading and a constant axial force.
The present study aims at using the hybrid wall technique to prevent the occurrence of shear failure of the reinforced concrete (RC) columns in the unreinforced masonry walls (URMs) infilled in the RC frames and to increase their lateral strength, stiffness, and ductility. The hybrid wall integrates a boundary RC column with its adjacent URM infill with the help of jacketing steel plates, to make them perform as a unified member. Two series of experimental tests, including one element test (RC column with URM wing-wall) and five frame tests (one-bay one-story RC frames with URM infills), were conducted under reversed cyclic loading. The interaction between the masonry infill wall and the boundary RC columns before and after retrofitting by the hybrid wall technique is studied, and a corresponding design framework is suggested. The experimental results of the retrofitted frames demonstrated not only enhancing lateral strength, stiffness, and ductility of the URM-infilled RC frames but also the prevention of the shear failure of the boundary RC columns and postponement of the occurrence of the URM infills’ failure to larger drifts. The columns’ shear failure is a significant concern due to infill-column interaction in URM-infilled RC frames. However, one of the important impacts of the thick hybrid walls is that the boundary RC columns remained undamaged even in large lateral drifts due to flexural behavior. From the viewpoint of applicability, the thick hybrid walls technique does not require relocation of occupants and does not disturb RC buildings’ operations during construction. Moreover, it is not a labor-intensive technique.
This study investigated the flexural strengthening effect of the Thick Hybrid Wall (THW) technique as a seismic retrofit approach for Unreinforced Masonry Wall (URM)-infilled Reinforced Concrete (RC) ...frames. THW is a strength–ductility-type seismic retrofit technique, which was developed for pilotis-type RC buildings. In this study, the flexural strength and failure mechanisms of URM-infilled RC frames retrofitted using the THW technique were investigated. Consequently, a comprehensive theoretical model was developed to measure the flexural strength, and a previously proposed equation was modified. Additionally, an equation was developed to determine the minimum additional-wall length, and another equation was developed to determine the demand length of the additional wall to obtain the demand flexural strength. These equations enhance the cost-efficiency and reduce the irregularities risks. The interaction between the URM infill and surrounding RC columns was modeled, and a cyclic loading test was performed under the influence of a constant axial force on the four specimens. The results indicate that THW technique changes the failure mechanism of URM-infilled RC frames from shear to flexure and that the retrofitted URM acts as part of the lateral resisting system owing to the active lateral confinement pressure. The accuracy of the analytical models was confirmed via experimental results, and the developed models facilitate the practical implementation of the THW technique on intended frames.
•Flexural strength and failure mode of retrofitted URM-infilled RC frames were investigated.•A comprehensive flexural-strength calculation model was developed.•Equations for minimum and demand additional wall lengths were developed.•The interaction between the URM infill and the surrounding RC columns was defined.•The accuracy of the proposed analytical model was examined using the test results.
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