Recent research by Matthews et al. at the Louisiana Tech University Trenchless Technology Center (TTC) regarding styrene emissions produced during steam-cured, styrene-based cured-in-place pipe (CIPP) installation was compared to data from six relevant, independent studies. As part of this analysis, data in the reviewed studies were compared to exposure guidelines published by the Environmental Protection Agency (EPA), National Institute of Occupational Safety and Health (NIOSH), and Occupational Health and Safety Administration (OSHA). Measurement methodology and goals were considered and briefly described in the analysis. Finally, this paper highlights differences and similarities in the conclusions and measurements of the reviewed studies while searching for and identifying conclusions and trends that are common across the reviewed studies.

This paper introduces a new shear reinforcement beam-column joint mechanism—the twisted opposing rectangular spiral—and carries out numerical and experimental investigates. Converting the conventional discontinuous shear reinforcement system into a continuous system in different reinforced concrete structural elements improves energy dissipation capacity and ductility. The proposed reinforcement has an inclined characteristic that intersects shear cracks at a more favorable angle. In addition, the reinforcement considerably eliminates slip observable at the hooks of conventional stirrups, resulting in the reduction of shear resistance. The seismic performance of the reinforcement is compared to conventional shear reinforcement and normal rectangular spiral systems. Six full-scale beam-column joint mechanisms were designed per Eurocode CEN-EC8 for low- and high-ductility modules. Quasi-static cyclic loads are used to simulate seismic loads as recommended by a widely used building code. In this paper, the experimental results of the six specimens are compared with the numerical results of finite-element analysis. The investigation concludes with the introduction of a newly proposed connection, resulting in the improvement of its capacity to dissipate energy, lateral strength, and ductility.

Despite the significant investments made in the use of cured-in-place pipe (CIPP) rehabilitation technologies, quality assurance (QA) and quality control (QC) practices can vary widely among municipalities, and CIPP liner evaluations are mostly restricted to periodic CCTV inspections. The information in this paper is derived from a multi-year project funded by the U.S. Environmental Protection Agency (US EPA). The study included a first of its kind retrospective evaluation of retrieved CIPP liners that were in service between 5 and 34 years at 18 different locations. This paper focuses on an assessment of the types of testing that were used during a pilot study to perform the CIPP retrospective evaluation. After performing the suite of tests, both visual inspection and flexural testing were found to be the key QA/QC assessment techniques. However, liners’ specific gravity was also found as a useful QA/QC tool and pursuing several other possibilities for non-destructive or minimally-invasive testing for measuring in situ physical properties of liners appeared feasible.

Cured-in-place pipe (CIPP) is one of the most popular in situ rehabilitation techniques to repair sewer and water pipes. While there are multiple approaches to curing CIPP, steam-curing of styrene-based resins has been found to be associated with air-borne chemical emissions. Health officials, utilities and industry representatives have recognized the need to know more about these emissions, especially styrene. Such concern has led to multiple studies investigating the concentrations of volatile organic compounds on CIPP installation sites. This study expands upon previous effort by modeling worst-case, steam-cured CIPP emissions over a 5-year weather record. The effort also includes calibration of the model to emissions averages over the work day rather than instantaneous field measurements. Dispersion modelling software, AERMOD, was utilized to model the styrene component of CIPP emissions on two CIPP installation sites in the US. Based on the analysis results, it was found that the styrene emitted from stacks dissipates rapidly with styrene concentrations only exceeding minimum health and safety threshold levels at distances close to the stack (2 m or less). The values predicted by the model analysis are comparable with the field measured styrene concentrations from other studies. Current safety guidelines in the US recommend a 4.6-m (15-ft) safety perimeter for stack emission points. The results of this study indicate that significant and lasting health impacts are unlikely outside recommended safety perimeter. The results also validate the importance of enforcing recommended safety guidance on steam-cured CIPP sites.