Date of Award

Fall 2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

First Advisor

Erez N. Allouche

Abstract

Some of the older cities across North America and Europe had been using steam driven HVAC systems since beginning of the last century. Consolidated Edison (Con Ed.) of New York operates the New York City steam system, the largest commercial district heating system in the world, with more than 100 miles of transmission and distribution pipes serving Manhattan Island. Other steam district systems exist in San Francisco, Harrisburg, Minneapolis, Pittsburgh, San Diego, and Detroit, some dating back to 1903. In those cities the sewer pipes are used as venues for discharging the waste steam condensate from the HVAC system.

The city of New York is considering the rehabilitation of the Time Square, including the near-by sewer pipes which pass beneath the subway station and/or along the concrete wall. Rehabilitation of these sewer pipes requires trenchless technique, installation of CIPP liners. Therefore, in the event of a malfunction of the aging steam system and failed steam trap, the sewer pipes lined with CIPP liners might be subjected to direct steam injection and the temperature may soar as high as 212°F. The presence of steam and the associated elevated temperature inside the lined pipe could result in an environment, incompatible with standard CIPP lining products.

The main objective achieved within the first phase of the research was to experimentally determine the thermal effects on the aging of resin used in CIPP liner. Therefore, the resins expected to perform well under prolonged exposure to elevated temperature (up to 212°F) were identified first. Total 1890 specimens (ASTM D638 and ASTM D790) were prepared using epoxy, vinyl ester and polyester resin which were subjected to cyclic thermal loading (maximum 540 cycles intermittently changing between 90°F and 212°F). Next the specimens were tested to obtain the modulus of elasticity value and stress-strain curve; thus to indentify the best resin to serve at elevated cyclic temperature. Raman spectroscopy, a technique used for studying the chemical composition and chemical bonds of materials, was also used to provide more fundamental understanding of the degradation of the resin materials at the molecular level. It was found that vinyl ester and epoxy resin performs better at elevated temperature application than polyester resin, although polyester resin is used in more than 90 percent of the CIPP projects as it is economical.

Another objective completed at the second phase was to evaluate the stresses generated due to the thermal strain on the full scale specimens. At this phase CIPP liners were impregnated using the best two resin types performed at elevated cyclic temperature in the phase one and full scale specimens were prepared by lining steel host pipe. The full scale specimens were kept inside custom built oven and cyclic thermal load was applied. Stresses generated on the specimen due to thermal loading were observed by analyzing strain gage data. It was found that stresses developed in the liners impregnated with vinyl ester resin were significantly lower in comparison to the liners impregnated with the epoxy resin.

In the third phase, numerical simulation of the effect of high temperature on a CIPP liner was performed and parametric study was carried out to compare and validate the results obtained in the second phase.

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