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- 저자 : Sajad Heydari (검색결과 2 건)
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Fatemeh Heydari,Amir Maghsoudipour,Mohsen Ostad Shabani,Zohreh Hamnabard,Sajad Farhangdoust 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.1
The objective of the present work is to study properties of a composite material consisting of zirconia nanoparticles in a glass matrix based on the system of BaO-CaO-SiO2-B2O3-Al2O3. Zirconia nanoparticles are added by 0-20 vol.% into the glass matrix to prepare the glass composites. Coefficient of thermal expansion, glass transition temperature and dilatometric softening point temperature of specimens are determined by means of dilatometry analysis. Coefficient of thermal expansion of base glass is 10.38 × 10−6 k−1 and by increasing zirconia content to 10, 15, and 20 vol.%, coefficient of thermal expansion reduces down to 9.88 × 10−6 , 9.84 × 10−6 and 9.76 × 10−6 k−1 respectively. Sinterability of different specimens is studied by increasing zirconia nanoparticles. Electrical properties are measured in different temperatures, and results show that with increment of zirconia nanoparticles, temperature resistivity of specimens has been decreased. Microstructural investigation reveals a well-adhered bonding between the sealants and electrolyte.
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Farzad Raeesi,Sajad Heydari,Hedayat Veladi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.5
Environmental thermal loads such as vertical and lateral temperature gradients are significant factors that must be taken into account when designing the bridge. Different models have been developed and used by countries for simulating thermal gradients in bridge codes. In most of the codes only vertical temperature gradients are considered, such as Iranian Standard Loads for Bridge code (ISLB), which only considers the vertical gradient for bridge design proposes. On the other hand, the vertical gradient profile specified in ISLB, has many lacks due to the diversity of climate in Iran, and only one vertical gradient profile is defined for whole Iran. This paper aims to get the both vertical and lateral gradient loads for the concrete box girder using experimental analysis in the capital of Iran, Tehran. To fulfill this aim, thermocouples are installed in experimental concrete segment and temperatures in different location of the segment are recorded. A three dimensional finite element model of concrete box-girder bridge is constructed to study the effects of thermal loads. Results of investigation proved that the effects of thermal loads are not negligible, and must be considered in design processes. Moreover, a solution for reducing the negative effects of thermal gradients in bridges is proposed. Results of the simulation show that using one layer polyurethane insulation can significantly reduce the thermal gradients and thermal stresses.
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