Numerical Investigation of Strain Variations along Steel Pipelines in Four-Point Bending Tests

Abstract

Four-point bending tests have been widely applied for investigating flexural behavior of different materials. However, there are no guidelines or standards relating to four-point bending tests for pipes. A steel pipe with a diameter of 154 mm and 3.4-mm wall thickness was instrumented with distributed fiber-optic strain sensors and tested in four-point bending. The measured strains at the crown, springlines, and invert deviated from results calculated using beam theory. This strain deviation is investigated using numerical analyses, and it is found that local deformations along the length of the pipe due to concentrated loads at load and support locations contributed to the deviation. Parametric studies are conducted using different geometries of wood support blocks, specimen lengths, and pipe thicknesses to investigate their impact on the strain distribution with the pipe. Recommendations for reducing the strain deviation at the midspan of the specimen are given for four-point bending tests carried out on the steel pipes.