Mechanical properties and microstructure Characterization of on-line heat-treated rebars after fire exposure to different fire damage temperatures

• Main Authors: Chih-Cheng-Lin, 林志政
• Other Authors: Tzong-Tzeng Lin
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/82185216173805041481

碩士 === 國立高雄應用科技大學 === 土木工程與防災科技研究所 === 97 === Abstract This study is focused on the relationship between mechanical behavior and microstructural characterization for the fire-damaged controlled rolling rebar. Consequently、it will be helpful to the identification of the fire-damaged building for structural safety assessment. The research was used a series of heat-treated processes to simulate fire-damaging temperature and duration in situ、and analyzed the effect of various temperatures on mechanical strength and crystalline microstructure. Based on the results、the conclusion is summarized as follows: 1. Based on the relation of fire-damaging temperature and mechanical property. The result indicated that the strength of the fire-damaged rebar at fire-damaging temperature treated lower than 500℃ is not remarkable reduction. When the temperature was up to 700℃、the strength (about 17% reduction) shows a marked tendency to decrease. The strength has above 32% reduction at 800℃、and the yield strength of the contolled rolling rebar has been unable to conform to the requirement of CNS 560 standard. 2. Based on the relation of fire-damaging temperature and microstructural characterization. The result showed that the external structure of tempered martensite will form the spheroidized carbide gradually. Then、the cementite existed in pearlite will transfer from coarse to spheroid at the increase of fire-damaging temperature. When the temperature was up to 800℃、the grain boundary of martensite will be gradually replaced by ferrite and pearlite due to recrystallization. Moreover、the external structure of tempered martensite will not be observed. Thus、this infers that there is an evident relationship between the external mcrostructural change of tempered martensite and the reduction of mechanical strength for the fire-damaged rebar. Keywords: fire-damaged、microstructure、controlled rolling rebar、martensite