ABSTRACTEFFECT OF TEMPERATURE ON THERMAL AND MECHANICAL PROPERTIES OF HIGH STRENGTH A325 AND A490 BOLTSBySonali S. KandBolted connection is a very popular connection type as it is the most economical, versatile, and reliable method of connection. Although, these bolted connections are effectively designed to withstand various loads under ambient conditions, there is a lack of specific methodology for fire design. Limited information is available on high temperature properties of steel bolts. The heat treatment and metallurgical composition of high strength steel used in bolts governs the material properties of these bolts. Thus an experimental study is carried out on high strength steel bolts to evaluate high temperature thermal and mechanical properties. Thermal conductivity and specific heat tests in 20 to 735°C temperature range and thermal expansion tests on 20 to 1000°C range were conducted on A36, A325 and A490 steel in heating as well as cooling phase. Result from these tests indicates that chemical composition and phase transition that occurs in steel has significant influence on its thermal properties. For mechanical property characterization, high temperature steady state single shear and tension tests were carried out on A325 and A490 bolts in the temperature range of 20 to 800°C. Data from these tests were utilized to deduce high temperature stress-strain curve, strength and stiffness reduction factors. Test results indicate that the strength and stiffness properties of A325 and A490 bolts are more temperature sensitive than conventional steel. Also A490 bolts maintain higher strength and stiffness properties than A325 bolts throughout 20 to 700°C temperature range. Data from property tests was utilized to develop high temperature relations for thermal and mechanical properties of A325 and A490 steel in 20 - 800°C temperature range.
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