Thin-Walled Steel Fiber Reinforced Concrete Pipes Performance under Three-Edge Bearing Load

Steel fibers have been used recently in concrete pipe mix in attempt to reduce or eliminate the need for steel reinforced cage, which could reduce the production cost significantly and enhance the concrete pipe resistance for shear and radial failures. However, producing pipe with wall thickness specified by ASTM C76 may not be practical as buried pipes could carry more loads through soil structure interaction. The objective of this study is to evaluate the performance of concrete pipe with diameter of 1200 mm and reduced thickness to 50% of that specified by ASTM standard. The pipe was reinforced using hooked end steel fibers with a dosage of 9 kg/m³. The pipe was instrumented using string transducers to measure the horizontal and vertical deflections. Also, strain gauges mounted on the inner crown, inner springline, outer springline, and inner invert were used to monitor the strain response. The pipe was tested under three-edge bearing load in accordance with ASTM standard. The tested pipe experienced flexural failure as the cracks propagated longitudinally at the high-tension zones. Other failure modes such as radial and shear associated with large pipe diameters were not observed. Also, the tested pipe surpassed the minimum deflection ratio specified for the flexible pipe, which is 2% of the internal diameter. The presence of steel fiber increased the strain capacity of the concrete pipe prior to cracks appearing on pipe wall surface. The tested pipe could be used for the gravity pipe applications.