<![CDATA[Natural gas transmission pipelines are susceptible to deflection due to ground settlement, heavy traffic loads, and surrounding construction activities. This study evaluates the structural response of a 6-inch API 5L X52 gas pipeline experiencing a vertical deflection of 9 cm over a chord length of 370 cm at KP.03+500. The assessment uses the sagitta-based radius of curvature together with a strain-based framework. The revised calculation separates longitudinal bending strain from extensional strain. The measured geometry gives a radius of curvature of 1905.9 cm and a deflection angle of 11.12°. The longitudinal bending strain is 0.0186%, the extensional strain is 0.0296%, and the combined longitudinal strain is 0.0482%, below the material yield strain of 0.1760% and the adopted 0.25% normal-operation criterion. The elastic bending stress is 37.9 MPa, while the hoop stress due to MAOP is 36.77 MPa. Sensitivity analysis indicates that the yield-strain threshold is reached at approximately 19.3 cm and the 0.25% strain criterion at approximately 23.5 cm. The measured 9 cm deflection therefore retains a calculated yield-strain margin of approximately 10.3 cm. The assessment provides an analytical screening framework for field integrity evaluation while recognizing limitations associated with single-point measurement and simplified pipe-soil interaction.]]>
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