輸油氣鋼管撓曲強度之研究

Abstract

本研究係探討輸油氣鋼管在承受高內壓與撓曲作用下之撓曲強度與韌性行為，並針對輸油氣鋼管之修補與接合的方式，探討其行為。研究方法以試驗與理論解析兩方面進行，試驗方面製作十二組實尺寸鋼管試體進行撓曲試驗，試驗結果顯示：鋼管對銲接合提供管線穩定之撓曲強度與優良之韌性行為，且採用全圓周套管銲接修補之方式，能夠有效維持鋼管之撓曲強度與變形能力。解析方面以材料力學原理推導出鋼管在承受高內壓與撓曲作用下的側向力與側向變位關係，並對鋼管內壓、外徑及厚度三項變數進行探討，比較試驗與解析之結果發現，Tresca Criterion較von Mises Criterion更能準確的代表鋼管在承受高內壓與撓曲作用時之降伏狀態；變數探討結果顯示：鋼管內壓的存在會降低鋼管之撓曲強度，鋼管外徑及厚度的提高則有助於鋼管撓曲強度的提昇。

This research was conducted experimentally and analytically to investigate the flexural strength and deformation capacity of the pressurized steel pipelines. Twelve full-scale specimens, including the type of butt-weld steel pipes and full encirclement welded split sleeve repaired steel pipes, were fabricated and radiographically tested for the weld. Each specimen was subjected to a lateral deformation of a four-point bending test to study the flexural behavior of a buried pipeline. Test results showed that the API 5L steel pipes with butt-weld joint have significant ultimate strength and ductility. The full encirclement welded split sleeve provides an excellent repair procedure for steel pipelines to resist the flexural bending and lateral deformation. To study analytically, the relationship between lateral force and lateral deformation of pressurized steel pipes were derived that based on the theories of mechanics of materials. The parameters such as the pipe’s inner pressure, outer diameter and thickness were studied. Comparing the result of test and analysis showed that the Tresca Criterion can be more effective to represent the yielding state of the pressurized steel pipelines than the von Mises Criterion. The results of parameters studying showed that the existence of pipe’s inner pressure will reduce the flexural strength of steel pipelines. The increase of pipe’s outer diameter and thickness will raise the flexural strength of steel pipelines.