The Test Mechanisms for Long-term Pipe Stiffness of Plastics Pipe

• Main Authors: Jaubih Wang, 王昭弼
• Other Authors: Chiwan Hsieh
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/18664274002572593688

碩士 === 國立屏東科技大學 === 土木工程系碩士班 === 93 === Plastic pipes are flexible and consist of good corrosion resistance. Pipe stiffness is an important design factor for predicting its deflection under long term loading. The convention and accelerated long-term pipe stiffness of PVC, ABS, HDPE pipes under parallel-plate loading mechanism was investigated. The nominal inside diameter of the test pipes are 300 and 400mm. Initial pipe stiffness is proportional to its young’s modulus and inverse proportional to its SDR three-degree power ratio. In general, the initial pipe stiffness of PVC pipe is greater than that associated with ABS and HDPE pipe under same geometry condition. Since the test 300 and 400 mm PVC pipes consisted similar SDR values, they consisted similar pipe stiffness values. It would take about 10000 hours to reach 5% deflection for 400 mm PVC pipe under 80% initial pipe stiffness loading. Slightly reduce pipe loading could significantly increase the time to reach 5% deflection for 400 mm PVC pipe. However, it is almost impossible to reach 5% deflection for 300 mm PVC pipe under 80% initial pipe stiffness loading. Therefore, long-term pipe deflection would decrease as decreasing its diameter. The pipe stiffness of 300 mm PVC pipe is about 2.5 times higher than that for 300 mm ABS pipe; however, the deflection of ABS pipe is only about 30% higher than that for PVC pipe. Long-term pipe stiffness value can be approximated as a reverse S-curve on a semi-log coordinate system. Moreover, the elevated temperature process was used to accelerate the long-term pipe stiffness test for HDPE pipes. The preliminary test results can be fitted into Bragaw’s formulation to predict the long-term pipe stiffness of the test HDPE pipes. The use of this process for PVC and ABS pipes needs further investigation.