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RISS 인기검색어
- 검색키워드
- 저자 : Ahmad Dalvand (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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Denise-Penelope N. Kontoni,Behnaz Jahangiri,Ahmad Dalvand,Mozafar Shokri-Rad Techno-Press 2023 Advances in concrete construction Vol.15 No.1
One of the important problems of concrete placing is the concrete compaction, which can affect the strength, durability and apparent quality of the hardened concrete. Therefore, vibrating operations might be accompanied by much noise and the need for training the involved workers, while inappropriate functioning can result in many problems. One of the most important methods to solve these problems is to utilize self-compacting cementitious composites instead of the normal concrete. Due to their benefits of these new materials, such as high tensile, compressive, and flexural strength, have drawn the researchers' attention to this type of cementitious composite more than ever. In this experimental investigation, six mixing designs were selected as a base to acquire the best mechanical properties. Moreover, forty-eight rectangular composite panels with dimensions of 300 mm × 400 mm and two thickness values of 30 mm and 50 mm were cast and tested to compare the flexural and impact energy absorption. Steel fibers with volume fractions of 0%, 0.5% and 1% and with lengths of 25 mm and 50 mm were imposed in order to prepare the required cement composites. In this research, the composite panels with two thicknesses of 30 mm and 50 mm, classified into 12 different groups, were cast and tested under three-point flexural bending and repeated drop weight impact test, respectively. Also, the examination and comparison of flexural energy absorption with impact energy absorption were one of the other aims of this research. The obtained results showed that the addition of fibers of longer length improved the mechanical properties of specimens. On the other hand, the findings of the flexural and impact test on the self-compacting composite panels indicated a stronger influence of the long-length fibers.
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