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RISS 인기검색어
- 검색키워드
- 저자 : Mostafa Fakharifar (검색결과 2 건)
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Mostafa Fakharifar,Genda Chen,Ahmad Dalvand,Anoosh Shamsabadi 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.3
Past earthquakes have signaled the increased collapse vulnerability of mainshock damaged bridge piers and urgent need of repair interventions prior to subsequent cascading hazard events, such as aftershocks, triggered by the mainshock (MS). The overarching goal of this study is to quantify the collapse vulnerability of mainshock damaged substandard RC bridge piers rehabilitated with different repair jackets (FRP, conventional thick steel and hybrid jacket) under aftershock (AS) attacks of various intensities. The efficacy of repair jackets on post MS resilience of repaired bridges is quantified for a prototype two span single column bridge bent with lap splice deficiency at column footing interface. Extensive number of incremental dynamic time history analyses on numerical finite element bridge models with deteriorating properties under back to back MS AS sequences were utilized to evaluate the efficacy of different repair jackets on the post repair behavior of RC bridges subjected to AS attacks. Results indicate the dramatic impact of repair jacket application on post MS resilience of damaged bridge piers up to 45.5 % increase of structural collapse capacity subjected to aftershocks of multiple intensities. Besides, the efficacy of repair jackets is found to be proportionate to the intensity of AS attacks. Moreover, the steel jacket exhibited to be the most vulnerable repair intervention compared to CFRP, irrespective of the seismic sequence (severe MS severe or moderate AS) or earthquake type (near fault or far fault).
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Reza Hassanli,Osama Youssf,Julie Mills,Mostafa Fakharifar 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.3
In this study the behavior of unbonded post-tensioned segmental columns (UPTSCs) was investigated and expressions were proposed to estimate their ductility and neutral axis (NA) depth at ultimate strength. An analytical method was first employed to predict the lateral force-displacement, and its accuracy was verified against experimental results of eight columns. Two stages of parametric study were then performed to investigate the effect of different parameters on the behavior of such columns, including concrete compressive strength, axial stress ratio, diameter and height of the column, axial stress level, duct size, stress ratio of the PT bars, and thickness and ultimate tensile strain of fiber reinforced polymer wraps. It was found that the column’s aspect ratio and axial stress ratio were the most influential factors contributing to the ductility, and axial stress ratio and column diameter were the main factors contributing to the NA depth of self-centering columns. While at aspect ratios of less than ten, as the axial stress ratio increased, the ductility increased; at aspect ratios higher than ten, the ductility tended to decrease when the axial stress ratio increased. Using the results of parametric study, nonlinear multivariate regression analyses were performed and new expressions were developed to predict the ductility and NA depth of UPTSCs.
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