Assessment of the bond strength of concrete structures after fire using Stress Wave Method

• Main Authors: Shih-Kai Hung, 洪士凱
• Other Authors: Chia-Chi Cheng
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/97383961848716990296

碩士 === 朝陽科技大學 === 營建工程系碩士班 === 96 === The aim of the present research is to evaluate the degree of deterioration of concrete after fire by means of stress waves, bond strength using pullout test. In the study, a steel ball is used as the impactor and the frequency of the principal response obtained by a receiver 20 cm away is used for concrete evaluation. Two types of specimens were investigated. One is the large concrete plate with the size 240×100×18 cm3. These specimens were heated by oven with the temperatures 500, 600, and 800℃. The others are the small specimens with the size 40×40×20 cm3 and 40×40×30 cm3. These specimens were heated by oven with the temperatures 600 and 800℃. The frequencies of the principle responses of the large specimens were compared to the depth of concrete deterioration obtained from drilled core. The cores were sliced into disks and the depth of the deterioration was evaluated by the dynamic elastic modulus of the disks. It was found the lowest primary frequency is linearly decreased with the depth of deterioration. A formula between the depth of deterioration and the lowest primary frequency is developed based on the experimental results obtained from these big concrete plates and small specimens constructed in previous study. It was also found that the pull-out strength of the steel reinforcement is lower when the calculated depth of deterioration is larger than the cover thickness. The results of the small specimens show the lowest primary frequency is similar for specimens withstanding the same high temperature but with different thickness.