ASU will provide the services of Sam Ariaratnam and others in support of Project 4473 the Assessand- Fix Approach: Using NDE to Help Select Pipe Renewal Methods. Specific tasks to be completed by both participants are: 1. Structural analysis, as described below. 2. Review draft report sections and provide comments. 3. Help arrange and participate in Expert Workshop, to be held in conjunction with the NASTT No-Dig Conference 2013 in Sacramento. 4. Participate in up to 3 other meetings and technical conversations, via phone conference and email, when available. Structural Analysis Structural analysis, using finite element analysis and other methods, will be performed at Arizona State University, under the supervision of Dr. Sam Ariaratnam. Three modes of corrosion-related failure will be analyzed: Failure Mode 1: Rust-hole. This failure entails a corrosion pit that penetrates the pipe. Although graphite, scale (tuberculation), and lining material will often plug the hole and delay leakage, it will be assumed that any new lining material must span the hole unaided by these unreliable materials. Both punching shear and flexural membrane failures will be analyzed, for various thicknesses of lining spanning various diameters of holes, subjected to various internal water pressures. Formulae for selecting a lining thickness will be developed. Variables are: internal pressure, long-term lining strength, factor of safety, and (future) diameter of hole. Failure Mode 2: Longitudinal split. This failure method entails corrosion loss over a large-enough area such that the hoop strength of the pipe is insufficient to contain the internal pressure. The corrosion loss may result from a general loss of metal over a large area, or from a series of closely spaced corrosion pits. The ability of various thicknesses of lining to span across longitudinal splits of finite lengths will be analyzed, subjected to various internal water pressures. Failure Mode 3: Circumferential crack. Small-diameter mains in particular are susceptible to cracks circling the pipe barrel. These cracks occur due to some combination of corrosion weakening, bending of the pipe from ground movement, and axial contraction due to temperature changes. For cast-iron mains, where ductile bending and elongation are not possible, a pipes ability to resist circumferential cracking will be directly related to its section modulus and cross-sectional area. These loses can be calculated for pipes of various conditions and a qualitative ranking of resistance to circumferential cracking will be provided. Subconsultant Agreement 8 Rev. 1 - 2011 Lining material strengths. For these analyses, the strength of the lining materials will be based on projections of long-term strengths, using engineering and material science principals found in industry-accepted standards, as adopted by AWWA, ANSI, and ASTM for other plastic pipe materials.
|Effective start/end date||3/13/13 → 6/30/14|
- US Environmental Protection Agency (EPA): $30,000.00
Finite element method