Monitoring and Assessment of Prestress Losses of Post-Tensioning Precast Segmental Bridges Pier

• Main Authors: YuhLin, 林郁
• Other Authors: I-Kuang Fang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/90246665558752562804

碩士 === 國立成功大學 === 土木工程學系碩博士班 === 101 === Precast segmental construction method is often used in bridge construction, but it’s more common in the box girder in Taiwan. This thesis aims at studying the prestress losses of segmental pier columns in the viaduct connecting Kaohsiung Harbor and First Freeway. In experimental study, the monitoring of concrete strain variations in pier segments and the material tests of concrete cylinder were conducted. The assessment of prestress losses was carried out based on the measured strains and design codes. The measured shrinkage strain of segmental bridges piers was 260×10^(-6) after 270 days of casting and the rate of increase in strain was not pronounced. Using the related parameters for the prediction of creep strain by ACI-209 methods for the concrete cylinder specimen and the piers, a proportion ξ between them can be found. The creep strain of pier column can be predicted by multiplying ξ to that of concrete cylinder. Therefore, we can estimate the creep strain of pier column based on the creep test of concrete cylinder. According to the currently measured concrete strain and prediction equation of the long-term prestress losses, the effective prestress of the piers, after 50 years of applied prestress, for P13~P15 is estimated as 13,420 kg⁄cm^2 , which is 93.5% of the initial prestress; while for the pier P16, the effective prestress is 13,639 kg⁄cm^2 , which is 95.1% of the initial prestress. The estimated effective prestress is greater than the design value of 10,000 kg⁄cm^2 .